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Rod Design - Stress Curves

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In it's most basic use a stress curve shows you how close a split cane rod is to breaking with the weight and length of line you specified. Garrison believed 200,000 ounces per square inch was a good, safe upper level.  In reality  you can  go up to 220,000 or 230,000 without  any  problems.  Garrison  himself  went  up to 220,000 on his lighter rods.  Garrison  believed  that  below the 140,000 point the bamboo stopped flexing.

Some basic information on stress curves:

The X axis is rod length, with the tip on the left and the handle on the right.

The Y axis is ounces per square inch. This sounds like a pressure, as in PSI, but it is really a stress measurement.  The square inch refers to the area of the cross section of the rod at that point.

The higher the stress curve goes, the more the rod will bend, taking the curve as a whole.  I  say  this  because  a  reading of 200,000 near the tip, where the rod is thin in diameter is going  to bend more than a reading of 200,000 near the handle where the bamboo is thicker. But, if you compare a whole stress curve of one rod to the whole stress curve of another rod, the rod with a higher reading at the same point along the length will bend more at that point.

A stress curve means nothing if you can't relate it to something. The only way you can start to see how a stress curve can help you is to graph up the stress curves of real rods and cast them. In my case I didn't have a bunch of rods to try. I had to make them. I now have a bunch of experimental rods lying around, but fortunately I was able to sell a few of the better experiments. I was also lucky in accidentally making a rod I really like (a Cattanach taper) on my third attempt, and being able to contrast that to a rod I really didn't like (a Garrison taper).

As you get deeper into stress curves you can begin to pick out certain  characteristics that tell  you what kind of action the rod has, or will have if it hasn't been made yet. A Garrison rod, which I consider to be slow, has a well rounded "hump" near the tip and a fairly slow drop off as it goes towards the handle. Let's see if I can do this with ASCII art.

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The rod that I'm always raving about, the Cattanach 7' 0" 4 wt, I consider to be fairly fast. It has a stress curve like this:

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The blip near the handle is the Cattanach hinge, and it greatly enhances roll casting. Don't forget to put it in. I did and the rod I made was a terrible roll caster. It isn't as necessary on longer rods, but on shorter rods it's definitely needed.

A Paul Young Para 15, what is described as a parabolic action looks like this:

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Looking at this rod, and never having cast one, I would guess that it would feel fairly slow, due to the enhanced bending near the handle, but able to throw a lot of line, due to the stiff mid section. I would also guess that it could roll cast really well.

There are as many variations of stress curves as there are rodmakers. This covers the slow, fast and parabolic actions.  (Darryl Hayashida)

I was working on wrapping the guides on a rod and looking at the stress curve. Some rod curves have several peaks of higher stress areas in one taper. I can almost see how guide placement can effect the curve. Is this possible? I've read where makers tape guides on so they can be moved around. Is this the reason. Does anyone place guides according to the stress curve or where the "hinges" are in the taper? I can see the math calculations for guide placement works for straight or progressive tapers, but question the accuracy on tapers with hinges.  (David Dziadosz)

Yes, I tape my guides on, then put a bow in the rod.   I examine the greatest distance the line is from the rod between every set of guides.  If one set of guides has a large bow in it and the adjoining guides aren't bowed as much, I adjust.

It sure will help fighting a fish and I believe it helps with casting too.  (Terry Kirkpatrick)

Have you ever measured the guides so you can duplicate the spacing on rods with the same taper? Also, If you have measured them, have you compared the spacing with the stress curve? I haven't tried this yet, but seems it could make a difference.  (David Dziadosz)

I believe it's useful when thinking about stress curves and rod design to answer the question frequently asked at presentations I've done which is this: Why not design a rod that has a constant stress curve so that all parts of the rod are stressed equally? In doing so consider what happens when the stress curve value is high and what happens when the stress curve value is low? The outcome of this exercise leads one into understanding the variable stress curves and why they are valuable especially for those folks just starting in rod building.  (Ray Gould)

Designing rods considering a constant stress all along the rod is very popular here in France. A rodmaker named Daniel Bremond has developed tapers using this technique. Those tapers are well known in 'Le Club Francais du Refendu' which is a French rodmakers association.  (Jean Claude LeBraud)

Garrison designed his rods to hold the stresses constant throughout their length (excluding the slightly fudged tip).  I for one think Garrison tapers are solid, smooth, good all around tapers  (though less exciting in certain areas than some specialty tapers).  (Chris Obuchowski)

I'm translating what "constant" stress means is that the plot of stress Vs position along the rod results in a horizontal line. Garrison designed his rods with what he called a "progressive action" which essentially is a uniform taper (that is a taper where the plot of thickness Vs  position along the rod is a straight line not a curved line). To get this kind of taper the stress curve is not horizontal (constant) but it is a straight line from tip to butt starting with a high stress at the tip and a lower stress at the butt.  (Ray Gould)

Thank you Mr. Gould and also to Chris Carlin

Thank you Ray for your persistence in trying to explain Mr. G's intended stress curve. I have looked for years now at the stress's posted at various sites, including mine and it has been my assumption that G was trying to derive a flat across the top stress curve. Due to your persistence I went back and reevaluated my premise and found that most of the line lengths proposed were not sufficient enough to load the rod. When loaded properly the stress curve that you (he) define leaped of the page. A straight stress curve from the tip to the butt. Thanks again.

This was also reinforced by the graphic representation that Chris presented. Namely a multiple set of stress curves that show the stresses for 20 line to cast situations, It takes only a little imagination to project this into a active range of performance distances for the rod.

Not dynamic, but good enough, I think.

The subtlety of stress curves that I have been trying to evaluate over the last couple of years is the one of the anomalous little bumps that appear in many if not most of the stress curves. Other than Wayne’s Roll Casting hinge i'm not sure if these were intended or just the resultant of some friend that asked the maker to make some portion of the rod a little stiffer, softer, etc. They may be a product of 5 in stations in the planing bars. They certainly appear at those locations generally. Or they could be an artifact of G's math always trying to derive the taper based on a linearity.

Whether these are good or bad is another subject, 'cause in the end the rod is what it is.

My question would be, are any of these Weighting methods able to detect these abrupt changes in flow.  (Jerry Foster)

I think the question you ask as to whether those little bumps in the stress curves are good or bad is a really good question. I certainly don't understand them. If you accept Mr G's stress formulations and use the stress graphs generated by the application of his formulations to try to design or tweak rods, rather than faithfully reproduce them, then surely you have to consider whether those bumps serve a good purpose.

As I understand it the bumps are the results of changes in the taper. Other than in the case of 1)Wayne's roll casting argument, 2)changes that occur at the tip, 3)changes/swells  at the butt and 4) changes at the ferrule, I can't imagine any logical reason for introducing other bumps.  If you smooth over the bumps what effect does this have? I would really be interested to hear a rational argument as to why the bumps are there.

The more I hear about it the more convinced I am  by the logic of the Powell A, B, C approach to design, although that said I have to admit to having never cast a Powell. (Stephen Dugmore)

There are two more possibilities for the bumps that I neglected to mention. Thanks again to Larry and others.

Measurement techniques, and manufacturing tolerances (poor execution, or tooling that will not allow the taper to be cut as designed)

My Mantra has been: if you are going to reproduce an existing rod then the bumps should be faithfully reproduced, because that's the rod that is. Unless you have access to that makers notes, or forms, templates, platens, pattern boards, etc.

If you attempt to smooth the bumps then you have either made the rod better or worse from an internal perspective (inside the rod). It is not the same rod anymore, close, but not the same.

We are probably talking 10ths of thousands here, and most will scoff, but the rod is  an accumulation  of these fractions so I think it matters .

This all goes back to building the best rod you can from the bamboo's perspective.

People like these rods as they exist, so the bumps are necessary to get the same result  Many also appear to be in conflict so they may, set up little micro resonance's help which achieve the desired action.

Indeed one of my testing goals is to see if there is a better rod without these bumps. Perhaps the rod will cast 3 more feet with the same amount of applied power, or is a little bit lighter, or the swing weight

feels smoother. Who knows. Well maybe someone does, and they just want me, (us) to figure it out for myself (ourselves).

As to the Powell ABC. Applying these principles will produce beautiful stress curves. It's the math progressions. If you like this particular rod action then it probably can't be improved on. You must remember that many of his rods were hollow built.

But this method strictly adheres to a particular design philosophy and is not relevant for more exotic structures that need changes in ramp formation in different parts of the rod. Again, double paras and the like.  (Jerry Foster)

The bumps just indicate a compound taper. I think they need to be there, unless they are the result of a mistake. I have cast a known taper that was "smoothed". Blah... 

Now, that is not to say it would happen every time, but eliminating them without knowing the why, or without being able to predict the result strikes me as no different than adding one "just because".  (Larry Blan)

Here is an example of stress bumps I don't understand. Can anyone explain what purpose 'the waves' in the butt of this rod serve?

....to build in 'wave action'  :)

But seriously, I can't see any reason for them and would have to be working on blind faith if I were to build them into a rod. I don't buy the blind faith argument. I think they are most likely measuring or manufacturing errors. Are those who advocating that tapers be strictly copied and not tweaked seriously going to work hard at building in each of these bumps?  (Stephen Dugmore)

I think that measuring errors are pretty common, and that could certainly account for some of them. Compare this taper to the one posted by Dennis. It lacks some of the bumps. You really don't have to work at putting them in, set the forms to the dimensions given and they will be there. If you change it, you won't be building the rod listed. It might be better, it might be worse. We can't answer that. Not to speak for Jerry, but I think this is one of the points he has been digging for, what happens if a given dimension is changed.  (Larry Blan)

My argument is really that I think tapers should not be copied religiously unless they make theoretical sense and the final rods can then serve as physical tests for that theory. How else does one learn from existing tapers?

True! it is not really hard work to achieve  the bumps....but I still don't know why one would want to, or more importantly, whether one should even try to. ...and True! by changing the taper you won't be building the rod listed... but then again should you build it as listed?

The taper posted by Dennis makes much more sense to me. The bumps are mostly located in places where I can see that they could meaningfully influence the rod's action. An argument, right or wrong, could be made for each one. e.g.. the bump at 25 could be seen as creating a shoulder for the tip, the bump at the ferrule takes into account the ferrule itself, the bump at 50 stiffens the middle of the butt and the bump at 60 imparts more of the rod action to the front of the grip. This taper is probably a much 'truer' one - taken from a better manufactured and/or mic'ed rod and as such is probably truer to the original design intentions. I think it's very existence makes a good argument for not religiously copying the other one. I certainly would not want to build a taper like the other one unless I had personally cast and liked the rod and then personally measured it very carefully. Even then I would be skeptical of the contribution made by bumps to my enjoyment of the rod. For all I know omitting those bumps might make it even more enjoyable to cast. I can't see how omitting them would make it less so.

On the other hand I would feel much more confident building Dennis's one without even trying the rod first. It simply makes more sense  to me.  (Stephen Dugmore)

Another possible explanation for bumps in taper graphs may involve our use of stations 5" or so apart.  It's likely that the original designers used a different spacing, whether 1", 3", or 6".  It's also likely that their numbers did not start and stop at the ends of each section but allowed for some overlap.  And heck, they may well have measured from the big end to the little end rather than the way so many of us do things.

How we account for these factors, I haven't a clue.  I do know that these days I'm more and more skeptical of taper numbers about which I know nothing else.  I trust those measured by Dennis, etc. but those numbers that just "float around" really don't tell us all we need to know.   (Harry Boyd)

I wish to make an apology to all Powell fans..

The Powell tapers which appear on my page and the one on Franks may have been measured from actual rods..which might say something about sawing final tapers, but they bear no resemblance to the ABC tapers (an assumption) which they started as.

So those of you who own, have built, or have cast these rods, are they the rod they would be if they conformed to the intended taper?  (Jerry Foster)

The one Powell taper in the Hexrod archives is pretty darn close to a straight taper; maybe as close as a beveling saw (have you ever seen the Powell saw? scary thing; I'm surprised no one lost any fingers operating it).

It actually looks like a B-9 taper (.299-.061)/80" x 6" = .01785/6" slope of the built rod, or .009/6" per spline. you can compare the two in Hexrod (the straight taper is stored under B9co, use the compare function to superimpose the graphs).

As for the bumps, i suspect that they are the result of the tapering process, not a purposeful product of the design phase.  looking at the Powell taper, the variation from straight occurs mainly on either side of the ferrule, so maybe the intention was to flatten out the slope slightly thru the ferrule station.  (Chris Obuchowski)

While we are talking to avoid power  fibers to be cut, aren't we strange to implement bumps on the rod? All such bumps and hinges would weaken that part while long use of the rod and if heavy load (fish, tree) is experienced?

Just a thought.  (Max Satoh)

Bumps are just a way of describing high points in the taper.  In practice, no more fibers are removed from the outer surface of the bamboo in any one place.  If there is more material at the "bumps", it is on the interior surfaces.  (Harry Boyd)

I think the little bumps are the results of several things. One is that a "shoulder" or rapid increase in taper will tend to stop flex at that point until it is overcome by more force, read also, weight of line. You can design in these places to make a rod work off the section in front of the first shoulder at close range, the next at a longer distance, etc. I'm sure some of these "bumps" were done on purpose. Another way to get these is to leave the enamel on the rod surface until after it is glued up and then remove it and the glue residue with a file, as did all the production makers great and small that I can find out anything about. One further comment, when you generate a stress curve it seems to me that it magnifies very small change in dimension to a much larger "swoop", for lack of a better word, than is apparent in a taper graph of the same rod.  (John Channer)

Good point John.  The stress graphs are very compressed, so much so, that it is also necessary to have them pretty close in scale before they are of any value for comparison.  (Larry Blan)

Stress curve is very likely to the trend line of stock price.  It goes up and down, bumping, flattening.

By making the trend in rolling average, a week rolling average for instance, will show smoother line.   That's interesting.

A stress curve will surely pick up any up and down of slope of dimension. Especially around 15 pt, most rods have a stand up of slope. Someone designs its taper by digging some dimples from a drawn straight line.

While the stress curve is made with Garrison's 4, it is not so obvious, just looks like there are bumps or hinges.  But When the rod is loaded like a quarter circle, the even small bumps will grow up to a big gap of stress value. It is when any fiber problem will happen.

With whatever reason, if it is because of the station of PF, if it is for hinge, the big gap of the stress will become a  weak point for the continuous bamboo fibers.  This may be the fact. The rod with hinge is good while casting it by wrist but,  may not endure with the full line cast.  (some one might say that I can do it.)  The hinge point will have the most stress at that time.

So it can be said that, while the rod is being used under a certain load, the bump, hinge would work as the designer expected.  But once the rod get into the situation where it is overloaded than expected, it may easily become a weak point for fibers.

Nevertheless, these are  all  in logic and theory, or things happened in PC. In actual world, there may be more bumps on a rod which are made by planing.  (Max Satoh)

Since before Garrison makers were probably oblivious to stress curves, I would guess that all the bumps in classic tapers were not consciously designed into the rod. Would Leonard have looked at a stress curve for one of his rods and said:  "Jeez guys, I need to remove some cane at this station"?

That being said, I do like to see a smooth curve, though I still need to work on execution before I try to improve design.  (Henry Mitchell)

I have no way of knowing, but I'm sure you're correct in how most of the old classic tapers came about. Old Hiram would have said, "Let's whack off a little here and add a little there, and see how she goes."

Engineers are interested their discipline, understandably, and they're eager to discuss how various principles may apply to rod design. I really do think that's great, and I also think their lack of consensus increases our appreciation of the "simplicity" of the bamboo fly rod.

I'm not in a position to chime-in on the debates because I have no knowledge of these things and usually cannot follow the discussions. But, in between understanding and not-understanding, I do appreciate the wonderful irony of it all.

Think about it: Here we have all these dozens of excellent fly rod tapers from various makers -- past and present -- most of which evolved through trial and error, and yet our best mathematical minds can't quite agree on how to account for why our rod tapers work as they do -- or how to go forth and do likewise.

For myself, I really do want these guys to keep slugging it out, because when they finally arrive at some common understandings -- which I expect they will do  -- we'll all benefit from the results. That is, once we find someone to translate it all back into English.

Meantime, it's nice for some of us older duffers to know that ol' Hiram's design methods also work just fine.   (Bill Harms)

I (or we) are not blaming anything else, especially I think we are just the follower of old great rodmakers. I know a good rod does not always comes out of  a computer, too.

I seem to have larked around too much.  It would be a time for me to get back to workshop.  (Max Satoh)

It's nice to be hearing from you again. I surely remember the wonderful time we all had at "Whispering Pines" on the Manistee River a few years ago, and I hope we can capture those days again.

I know that none of the folks who are trying to account for rod design in terms of engineering principles and software programs would wish to discredit any of the old makers in any way. And I really do support the current efforts undertaken by you and the others who understand such things. I meant no criticism of any sort in my comments before.

I just wanted to offer some encouragement for the other poor slobs who, like me, can only do things the old-fashioned way - just a reminder for those who don't understand computers and mathematics that there are other ways to design good rods.  (Bill Harms)

I have one final issue in regards to Mr. Milward’s book:

I wish he would have given a little more info. what does the the illustration on pg 99 represent. If it is the terminus of the forward cast, at the completion of the wrist action, and I waited a few more milliseconds would I see a flex in the rod that would appear to load the tip only, which would not bear out his point. He also expresses a load due a double haul, the ultimate extreme in loading (except a tree).

Feed his dimensions into Hexrod and see if it resembles his Garrison predicted results. You will have to pick a tip dimension as this appears to be a tipless rod.

This is cherry picking in it's the highest form.

By the way it appears this rod would throw a MINIMUM 3' 1" loop with a perfect motion. Which is fine for the kind of fishing it was intended.

If you just dismiss Garrison based on this work, you are left with nothing.

Go For it Max!  (Jerry Foster)

I personally think that Bob does make a point in his discussion of Garrison's math, but misses a bigger one. I think he is right that Garrison's math has nothing to do with the actual stresses in play when the rod is used. Intuitively, I think we all know that if you stress a rod to the breaking point, it's going to break in the middle, just as Bob's stress diagrams and calculations predict. What he misses is that it does not matter. Garrison's math is a way of designing and modifying tapers, and it works fine, it seems to me, in the normal size range of trout rods.

Where he also falls down, I think, is using his example of building a noodley spey rod as an example of Garrison's method being flawed. The problem is not with the math, it's a problem with how he applied it.  The last paragraph of the Math chapter in "The Book" says that as rods get longer you have to develop a stress curve with lower values.  It is not explained, and few seem to take notice of it. My theory is  that it's because the density of the rod section changes in larger diameters due to additional pith, and you have to compensate. If you could find a way to accurately vary the density value in Garrison's formula, you could do it that way, but it's a lot easier just to change the stress curve. If Bob had based his stress curve on other  spey rods, and not a trout rod curve, he would have been fine, IMHO.

Don't get me wrong, I think Bob's book is very worthwhile and very important, but I think he missed the boat in this section.  (Tom Smithwick)

My sense of stress,

I think of stress curves as a magnifying glass with which I can see where the rod wants to bend.  Importantly,  it also takes into account the summed masses (moments) along the rod as well as from the tip load. We need to keep this in mind because everywhere we add or take away material to resist or promote bending we change the distribution of moments. The stress curve ALA Garrison takes this into account. The graphite guys don't need to worry about this much because the mass to modulus ratio of graphite is such that the mass of the rod doesn't have near the effect that it does for bamboo. Since bamboo rods are self-loading and have a feel that is as much a result of the rod's own moments as of the line load, we cast both the rod and the line.  That is one of the special characteristics of bamboo rods. To me the stress curve is the only way I know to get some insight into the effects that various design changes will have on how a rod feels and casts. When designing rods; put the bumps where you want them. When copying; try to measure as many stations as possible as well as possible and let the shavings fall where they may.  (Doug Easton)

What I found in the book after the discussion of bamboo was disjointed, conflicting information. Others will have to generate the coherency for me.

Robert, tell me where in the book he explains how to put the dynamic MOE or whatever to work to design a rod.

Robin, I couldn't disagree more about the margin of error, the premise is false and the reverse engineering to arrive at stress values is dripping with venom. If the stresses he derived  were real the rod would be useless.

His Garrison derived stress value is totally wrong and just propaganda to exploit his agenda. That is not what the new tools, Hexrod and others derive.

He flames Garrison for treating the tip section as he does and praises Mr. Bokstrom for doing the same.

Throw you computers away he declares.

He finds Garrison inadequate because he declares the rod maker must make some decisions and then leaves the entire design process up to you with his rod examples to modify.

All rods built using stress analysis are junk.

This is not the objective enlightenment I was hoping for. I think has generated a cult. This is an anti- thing and has no positive virtue, until someone like Max does do something with it.

This is only my opinion of course.

It is thought provoking I will give you that.

Send me your P Young's... or I guess Larry already has them.  (Jerry Foster)

Since here is the opposite side of the earth, my response would delay for about 12-14 hours than your place.

You fired me up again, I may not stop any more...<g>

I put my thoughts between your statements below;

I have one final issue in regards to Mr. Milward’s book

I wish he would have given a little more info. What does the the illustration on page 99 represent. If it is the terminus of the forward cast, at the completion of the wrist action, and i waited a few more milliseconds would I see an flex in the rod that would appear to load the tip only, which would not bear out his point. He also expresses a load due a double haul, the ultimate extreme in loading. (except a tree)

Feed his dimensions into Hexrod and see if it resembles his garrison predicted results. You will have to pick a  tip dimension as this appears to be a tipless rod.

This is cherry picking in it's the highest form.

The stress curve comparison on page 99 is a fake.

Milward’s stress curve like a mountain, never happens when a rod is cast in a shorter distance.  It seems just under the maximum load of full casting.

In my moving dynamic stress calculation (that is in a moving rod gadget), that shape (like a mountain) happens in such situation; a rod is enough loaded, a rod angle (grip angle) is leaned over to front, line is pulling a rod back, a rod well bent at the middle like a crescent.

The peak stress value of 40,000 PSI (=640,000 oz/sq in) is very high. Since the break even  point  of  bamboo  (Tonkin) is from 50,000 to 65,000 PSI, averaged as 60,000 PSI, for close-to-skin section of bamboo, based on his experimentation.  (see page 53, tensile strength) The rod is loaded close to breaking point.  If you shave out the enamel(closed to skin)  too much, the rod would break under this stress situation.

It is not fair to compare with Garrison's flat stress curve.

If you just dismiss Garrison based on this work, you are left with nothing.

This is the most influencing part of the book, but toward misleading direction.  We have to know this correctly

Go For it Max!

Thanks,

I am not denying a whole things that Mr. Milward says in his book. I just cannot forgive him saying that Garrison's math is outdated, since it is not true.

On other parts like MOE, or Young's Rate, testing, I think it is a great job.

To get MOE value of bamboo, it is not difficult for everybody to do it yourself. The resulted MOE is almost equal to what Mr. Milward did in laboratory facilities. For the verification of it, his book is valuable.

Prepare three hexagonal sections with diameter of tip (1 mm), mid (3 mm), butt (7 mm). maybe 1 feet is enough.  If you like, prepare several length of them. Hold them horizontally, like Robin makes quarter circle, fix it as if a certain length of bamboo is out of the table.  Hang a certain known weight at the top and measure the vertical drop down.

drop down = PL2/EI

reform this to:

E=PL2/ (I x drop down)

I value is known from the dimension, 0.06 x Dimension4

P is the weight

L is the length

Taking 3 E values per section  by changing weight and average them. The E (MOE) value is around 5 to 6 million PSI, doesn't so much matter if E is 5 or 6 MPSI. The thicker the dimension, the lower the value, like Garrison's bamboo weight/cubic inch. graph. You can plot averaged E values (as x) and dimension (as y) on a graph and draw a trend line, that is E graph. (Max Satoh)

In my recent communications with Dr. Wolfram Schott, who wrote the treatise "Bamboo Under the Microscope," I was referred to the web site of a retired Danish engineer, Falka Gregersen, who did a study of Garrison's stress curve analysis. I thought those of you who use the Garrison method for designing new rods, and those of you who might like to do so might find it interesting.  (Wayne Kifer)

Interesting. His opening paragraph looks like it basically says Garrison was hiding information from other people on purpose and that the stress curves are "not complete".

Now I'm not above trashing someone, even after they  are gone, but I just find it hard to believe this statement.  (Martin Jensen)

Actually no, don't come to any hasty conclusions here. According to Dr. Schott, Gregersen was a fan of Garrison.  After you read Gregersen, go back and read the section in Garrison's book where he discusses Modulus of Elasticity. Gregersen agrees with Garrison that calculating MOE on a curve is extremely complex. You'll note that while Gregersen, like Garrison, calculates a standard for MOE, he doesn't display his calculations and states there wasn't room on one page to display them. Garrison states pretty much the same thing in his book. Gregersen also states that in examining some of Garrison's tapers he concludes that Garrison also used a standard for MOE. He simply omitted it from his calculations due to the extreme complexity of attempting to calculate it even as a standard. Gregersen has just taken Garrison's work a step further by including a standard for MOE in his programs. I though you might find it interesting to run the same design figures through both Garrison's calculations and Gregersen's program and compare results.   (Wayne Kifer)

Yep, these are the statements of a true fan.

"We have the stories of how rod makers guarded their rod tapers, as were they the Holy Grail. Garrison continued that tradition in a very sophisticated way."

"It seems like Garrison used the stress curve as a red herring; he obviously did not want to share his knowledge of rod calculations with his fellow rod builders. "

"When   Garrison   used   words   as   'progressive   action'   and 'semi-parabolic' it was not to enlighten us but to lead us astray. "

"Withholding that information and presenting the stress curve as a starting point for rod design, Garrison put an effective brake on the study of the theory of rod design."  (Larry Blan)

Well, here we are again, my third favorite subject.

I read the paper and will try the programs. I wish Gregersen had  become a little more involved in actually making a rod than just  being interested in the math. The valuable part of stress curves is  the visualization. Without that it is just another pile of numbers.  The graph is the picture of the linkages between the numbers. The  graph is the portrait of the rod. It's power range and its action.

Yes stress is a tool, a design tool. Where I differ from most is I  believe it should be used for design and not just limited to looking  at your clone. That is a starting point, but it should also be a  point of departure. As a maker of rods, the primary quest should be  to do the best we can with all phases. If you get all hung up on the  artistry during the process then you are not concentrating on the job  at hand.

The other point of Gregerson's work was the hang-up with Garrisons  rods and verbiage. That was just the way Garrison wanted his rods to  act, it was not meant to limit the uses of the math.

The quest continues...

By the way, thousands of an inch may not matter, but, if they don't,  then why bother at all.  (Jerry Foster)

Yep, Dr. Schott stated that Gregersen, a personal friend of his, was NOT a rodmaker. One of the things I found interesting was  when Dr. Schott presented Gregersen with a program developed by Donald Barrer who was a good friend of Tim Bedford, (bought LL Dickerson's shop) Gregersen didn't think much of Barrer's program being a fan of Garrison. Dr. Schott had received permission from Barrer's widow to use the program and still has it and uses it in his own rodmaking. Schott, in addition to compiling years of research, is a veteran rodmaker of some twenty years himself. You might send him an email. He stated he would welcome a few questions and I think you would enjoy his correspondence.  (Wayne Kifer)

By the way, thousands of an inch may not matter, but, if they don't, then why bother at all.

Well our measuring tools are calibrated this way so we have to measure things this way. I do believe that (thousands) matter very much, I just don't think that "one thousand" matters very much, or two, or three.  (Martin Jensen)

You get to decide, the beauty of being a maker.  If you  don't mind, where is the limit 5,6 10 15 thousandths?  Seems like if you try to hit the numbers you are better off than  starting with a fudge factor built in.  I agree when the rod is completed, it is the way it is.  (Jerry Foster)

Oh I really agree. I honestly set my sights on perfection and really try for "spot on"*. I have just learned (unfortunately with age) to not fall apart if I don't meet them. (I used to be a perfectionist. After years of fighting, I finally ground that guy down into submission). I do have a minimum I have to meet. I guess you could call me a "realistic optimist".

* That's actually not true. When I started rod building I had a lot to think about as far as tolerances were. EVERYTHING was difficult. The first thing I had to get was a decent equal lateral triangle out of the spline. That was tough. I finally gave up actively trying to force myself to make the perfect triangle and figured out that it's just a matter of practice. I have build about 20 rods and now without really trying, my tolerances are within .003 most of the time. this is setting the form, planing down to the form, then measuring. I am developing my system that works for me and I just need to keep planing away. I really like planing and finally the tedious jobs which I used to hate, (node preparation and spline straightening) don't seem so bad anymore. Don't know why, they just don't bother me any more.  (Martin Jensen)

"As a maker of rods, the primary quest should be to do the best we can with ALL (sic) phases."

Jerry, that really says it all.  As a lover of great art, one of the things that has always annoyed me a lot is the so-called artist who decides to do "modern" art, but without first taking the trouble and applying the necessary discipline  to master the rigors of conventional drawing.  If you can draw like Picasso, you are able to produce a "Guernica".  If you cannot draw, you produce badly done rubbish.

When we set out to build rods, I think we ought first get the basic skills right.  That takes time and effort - "paying your dues", I think you Yanks put it.  When the mechanical production is  under control, it is time to try for better rods through design innovation.

It is here that tools like Hexrod are so valuable, but as you say, they will not do the job for us.  It is quite possible to do the same thing using empirical changes, but when you think how long it takes to produce a rod to try, any tool that will speed the design process is welcome, properly used.

All through this thread we are seeing reference to helping our novices; it is my opinion that the above quote from your last post is the best advice we can possibly give our novices - take care, become skillful, become thoughtful, and do it ALL well.

There is no magic potion, just Tincture of Time.  (Peter McKean)

I have a very specific question for all of you rodmakers, and it will affect the way you do your rod design.

Question:  How many of you actually use a Stress curve program to do all or part of your rod design ?  (Bob Norwood)

As far as the use of stress curves. Yes, I try to get as much information as I can get even if I don't understand it at the moment.  (Ren Monllor)

I use stress curves to design rods. Problem is, what looks good on paper doesn't always make a good rod. After over ten years of using stress curves and evaluating the resulting rod, I think I have a good feel for what works and what doesn't. So I suppose you would say I use stress curves for part of my rod design, unless it is a type of rod I know well, then it is for most of the design.  (Darryl Hayashida)

I may have asked this question before, but since I sometimes suffer from CRS I'll ask again.  Can I, in a generally way, tell how fast or slow the action of a taper is from it's stress graph?  I know this is not a science and there are so many variables, but I'm trying to figure out a way to narrow the choices when I'm trying to build a rod with certain characteristics. I thank you for your help in advance.

P.S.  This is not the time for opinions - I want to know the science without having to be an engineer.  Is this an impossible request.  (Tom Key)

Yes you can but I would also look at the rise of the rod taper. Fast tip action rods will usually have maximum stress at the tips.  (Gary Nicholson)

If the line weight and line length to fish is fixed, you may generally understand like below;

1. assume the line of 140,000 oz/sq. inch level as flex line.  (adjust this level by trial and error by/for yourself).

2. the rod part under the flex line is rather stiffer and above is softer.

3. find how much part of the rod is above or under the flex line.

This is only for a general quick view of stress curve.  Many other variable exists like, if a different line weight, or line to fish, rod length, used top guide, from here, my opinion.

Stress curve is considered as a substitutional factor of deflection curve.  (though Garrison uses static model). In deflection consideration, fastness or slowness is understood by the depth of deflection of the entire rod.  It is not possible to understand the entire deflection by the Garrison's stress curve by a glance.  But the steps above are generally true.

If you are interested in the deflection curve (or rod action), visit my site.  (Max Satoh)

Generally, "fast or slow" is used interchangeably to refer to how much the rod bends (stiffness) and line speed.  Those two characteristics of a bamboo rod are not synonymous as is generally the case with graphite rods.  A graphite rod has very little swing weight and is less elastic (springy) than bamboo.  A stiffer (tip flex) graphite rod will in fact throw a faster line than a soft (full flex) graphite.  Fast and stiff are interchangeable terms in that case.

That's not necessarily the case with bamboo.  Depending on the taper design, a bamboo rod can capitalize on swing weight and elasticity to increase line speed with a deeper bend.  I realize that's not what you asked, but I think it's an important distinction to make.  Bamboo rods with a deeper bend are commonly referred to as "slow" (the graphite term).  But the line speed may be faster than a stiffer taper depending on the taper design.

So, all things being equal (IE: rod length, line weight, etc...) you can generally tell how stiff the taper will be relative to another similar taper by plotting both stress curves on a single chart.  The stiffer rod will have consistently lower stress values.  But you can't tell which rod will throw a faster line by comparing stress curves.  You're going to have to cast a lot of tapers and get familiar with how different tapers perform from butt to tip.  Reading stress curves is kinda like reading the water.  You can't see the fish but you've got a pretty good idea where they will be based on prior experience.  That's about the best you can do with a conventional stress curve.  Generally, it's an art not a science.

If you're determined to narrow your choices mathematically, take a few minutes to read through the taper research posts on my blog.  Click on the "taper research" label in the left frame and scroll down to "taper research #1".  Read back up through all four posts sequentially.  Double click the slides to view them like a picture.  I can tell you from personal experience, it's more fun to cast a bunch of rods than to do the math.  (David Bolin)

The first few rods I’ve made were slow to medium slow actions for fishing wets and subsurface.

I’ve just begun cutting the tip sections for the modified Sir D.

I’ve a tendency to flex the individual strips as I cut them. I look at the stress curves in between alternating strip sides.

Well I’ve cut my second strip and I can’t believe the tip section on this baby. I just received an entirely new lesson without having to ask the teacher. I guess if I pay attention there’s probably a whole new world about to unfold with the making of this rod.

It’s awesome….

Someone said to me last week that “if you love what you do, you’ll never work again”; truer words have never been spoken.  (Ren Monllor)

I am trying to understand what an ideal stress curve should look like, any suggestions as to where to look to get educated. Is there a rod in Hexrod that you think come close to being ideal?  (Don Green)

When it comes to the ideal rod (and stress curve) beauty lies in the eyes of the beholder -- so it all lies in what YOU are consider to be ideal in a rod's performance. You need to test cast a bunch of rods, make notes on what you like and don't like about them, then look at their stress curves. Rods that have light tip action will have higher stresses in the tip. Rods that roll cast well will likely have some kind of hinge in the mid-lower section like the Cattanach "Sir D". Rods with a stiff backbone will have lower stresses there. I've never seen a comprehensive list of these kinds of generalizations but they do pop up piecemeal in discussions on the lists and forums.  (Larry Puckett)

So far I have learned that a "rod with a light tip will have a higher stress in the tip" (as reflected in the chart) and "that rods that cast well will have some kind of hinge ( does that look like a "v" ?) in the mid-lower section like the Cattanach "Sir D" and  Rods with a stiff backbone will have lower stresses there"  This is what I was hoping to get a grasp on from looking at the charts, or in other words how can I tell if a rod has certain characteristics (from the graphs) that I may or may not like. If the graphs are a representation of how a rod feels, how do I interpret that.   (Don Green)

That's really a very good question and I've had just enough beer to try and answer.

The answer is...it depends on you!

What type of rod are you most comfortable with now? Fast-ish, Garrison-ish, parabolic-ish, some other type of ish? Do you like the tip stresses high at a certain point in the tip section? (do you like to feel the tip bend at say five inches from the tip top or twelve?) Do you like the mid stiff or do you like a rod that flexes more in the center? Stiff butt or soft butt? Do you like the highest tip stress to be 180,000 or 220,000? Where do you like that stress? Do you like rods with a stress of 140,000 in the butt or 160,000 or what ever?

You know, I knew what type of rod I liked to cast and fish, but it took a gentleman and curmudgeon, Jerry Foster, to open my crusted over eyes! Jerry spent a considerable amount of time making 8 rods. I hope he makes a gathering near you so you can have the same experience I got to enjoy at Dunsmuir this past fall. All the rods were 8 footers for a five. 3 of the rods all had the same tip stresses but 'broke' at different points in the tip.  The mids and butts were the same. 3 of the rods all had different ranges of tip stress from 180,000 to 220,000 all breaking at the same place on the tip. 3 of the rods (yes, I know that's 9 rods, one did double duty) all had the same tip stresses breaking at the same point but had different mid and tip stresses, ALA Dickerson, Garrison, Parabolic (sort of).

All of the lines were the same manufacturer DT5, all the reels were the same. The demo was simply an eye opener!

So as Larry before me says, cast as many rods as you can. Find out what type of rod you like, then start digging for what floats your boat.  (Mike Shay)

Were these all the same lines?  (Anonymous)

Yes, they were all the same line, same manufacturer, and yes the line out the tip was all the same. In this case it might have been 35 feet. Maybe 30 sorry. And I didn't speak of curves directly, only how X amount of weight affects a particular rod with stress points placed a different places and ranges.  (Mike Shay)

Did you weigh the lines?  (Anonymous)

No we didn't weigh them. I didn't anyway. Maybe Jerry did but I doubt it. They were all the same maker, same ol' same ol'. Cortland if you want to know. Same brand/type. We were just standing on the grass in the afternoon, casting. I think we all understand that there are differences in line weights among makers line to line. They were close I'm sure. Maybe not LOL

In any event, the difference was noticeable, to me anyway. And I'm a shit caster as anyone will tell you! There was at the least one caster who was having a rough time that got the feel for the different rods. He got it.  It took a bit of switching back and forth, but he got it. I think that was more to Jerry's effort than the casters. Jerry diligently explained the difference in the rod the guy had in his hands at the time he was casting. It's really quite noticeable even in an inexperienced casters hands, let alone my fumbling fingers!

I think the key thing is what Jerry did. Take the time to make the amount of rods that as a minimum, it takes to show the difference. He (Jerry) could have broken it down even farther. But if you put these 8 rods in a customers hands, watched him cast and asked a few questions, you would be easily able to make a rod that would make that guy happy.

Of course, that's only my opinion.  To those who know me, you know what that's worth!  (Mike Shay)

Mike's telling the truth.  I've cast Jerry's series of rods, and an experienced caster can very definitely tell the difference in the actions, though sometimes, between certain rods, it's very slight.

As a tool to help define what works "best" for an individual angler/caster, the series is a great idea, and like Mike said, put the rods into an individual's hands, give him/her a little coaching, and you'll be able to find the one that works best for said individual.  (Chris Obuchowski)

There was at the least one caster who was having a rough time that got the  feel for the different rods. He got it. It took a bit of switching back and forth, but he got it.

Was that me? Sounds like me as I think I spent the most time with the rods. It wasn't so much that I was a having a rough time. The differences were pretty apparent straight away. It was more that I was trying to determine which rod I liked throwing a bunch of different casts (tip, curve, distance, slack leader) and casting styles ("eastern" v. "western"). And I'd rather spend the day casting than talking to you folks. :)  (Just kidding.)

The 185 was immediately attractive but after casting for a while, I settled on the 200 at 10 inches and the 220 (or was it 225?), with the 220 being just a bit soft for all round trout work but if I was fishing a dry fly within 35 feet in windless condition, it would be hard to beat. 

The result of which is that I'm going to make a rod at 210 with a 10 inch break point and think that should be just about perfect.

The thing that blew my mind was that the flat line rod felt so much lighter than the 5wt that it was.  (Jim Lowe)

LOL No Jim, it wasn't you!  You are one of the smoothest casters I've ever had the pleasure of watching!  (Mike Shay)

Now, if we just had any idea what a 185, 200, 210 or 220 rod was!  (Ralph Tuttle)

Like Mike said, Jerry had 3 rods with a progressive taper which topped out at 185, 200 and 220 on the Garrison stress curve and also had rods with different break points (ie. where that highest point was experienced on the tip).

The first 3 rods (185, 200, 220) had a break point at 18 inches from the tip (or close to it.) Lets call them, 185 at 18 inches, 200 at 18 inches and 220 at 18 inches.

The next set all had 200 as their highest stress value but the break points were at 5, 10 and he used the 200 rod from the first set to complete the second set. Lets call this set 200 at 5 inches, 200 at 10 inches and 200 at 18 inches.

Personally, my favorites were the 200 at 10, 220 at 18. I figure a rod with the best of both would be 210 at 10 inches. Why not 220 at 10? I think the 220 rod needed a little more wood to handle the wind.  (It was a fairly windy day early on.)

Now everything is clear. LOL.  (Jim Lowe)

We do; those are the maximum stress values from the stress curves.

If you want to play, go to Hexrod online and create a rod with an average stress of 150K. For 50’ of line (you can use 40 ft if you're going to routinely cast shorter distances) then set your peak to 200K where ever you want it to be (I use somewhere between 180 and 200K for rods I design).

I don't recall the line length that Jerry selected to generate his rods (he also designed them on Max Satoh's software, not Hexrod, but Hexrod works fine and is free to play with).

For instance,  input 0 150000, 20 180000, 35 150000, 96 150000 for an 8’ 5wt, then use the "edit stress curve function" to smooth out the curve to your liking (or do a relatively flat stress curve like Garrison).

Now compare the dimensions you've generated to the dimensions and stress curve of a rod you know well and are intimately aware of the casting characteristics.

I've never used RodDNA, but it might also let you do similar exercises.  (Chris Obuchowski)

Rods have different characteristics, feels and handling. A stress curve only relates to the specific rod and what you’re looking for in the design.  (Ren Monllor)

To those of you who design rods, or evaluate them using stress. How do assess the line to cast Vs how the rod really works? Can you feel the difference in rod action at 20' Vs 50'? If a 3 wt. is stressed at 200k at 50' is it really a 3 wt?  (Jerry Foster)

I am going to step out on a limb, and say no. But if it cast well at 20' with 3 wt. and still cast well at 50' with the same line, the builder built one hell'ava good rod.  (David Roberts)

That sort of begs the question " what's the maximum performance or presentation distance for each line weight, rod length combination?"

I regularly fish 4s and expect an 8’ 4 wt to cast out to a least 60 feet, but I'd be OK with a 7 feet 4 casting out to 45 feet.  (Jim Lowe)

If you think of carbon rods they have been exploiting this for some time.  (Gary Nicholson)

Great response Jim..

I guess I was begging the question. I got caught up in my narrow minded thinking.. I kind of look at line wts in groups of usage and not necessarily power. I haven't really equated rod length to that much more distance. But alas it is true. I think of 4's as medium to shorter casting distances 10-50'. Of course most rods will reach farther, it's that search for the sweet spot (band) at the distance I normally fish with a given line wt. that makes a rod sweet to me. And then there's always wind to consider. When the wind comes up on the Klamath it's time to ditch the 7 wt. and grab a 9. Of course my casting skills are not equal to yours so that part's not fair. Rod design is really interesting. Do you have a ratio of length of rod to distance? Anyone?  (Jerry Foster)

I guess I was begging the question. I got caught up in my narrow minded thinking.. I kind of look at line wts in groups of usage and not necessarily power. I haven't really equated rod length to that much more distance.

I do not necessarily equate rod length to distance/power but  equate length and distance to use. I'm a small stream and high country lake guy so I'm usually using shorter rods on small meadow streams were mending isn't that important or brushy creeks were space is at a premium. I use longer rods on larger streams and on lakes where the length will help with mending and casting over brush.

So I think of it more as rod weight/ length/ function. These days I fish 4s and 5s in different configurations. I've never thought of 3 wts as particularly functional, but I am building one now and I'm sure they have their place; I just haven't found it. If were building or buying an 8’ 3 wt graphite rod,  I probably would want it to cast 50 - 60  feet or more because that's the way the graphite boys seem to fish them. I see a 3 wt graphite rod as about equal performance wise to a 4 or 4/5 cane rod.  If I see a guy fishing a 3 wt graphite rod on Hot Creek, I've got to imagine that the thing can punch out 60 feet in normal conditions. (For those not in Ca. Hot Creek is a small to medium sized spring creek which can get very, very windy.

Of course most rods will reach farther, it's that search for the sweet spot (band) at the distance I normally fish with a given line wt. that makes a rod sweet to me. And then there's always wind to consider. When the wind comes up on the Klamath it's time to ditch the 7 wt. and grab a 9. Of course my casting skills are not equal to yours so that part's not fair.

HA! Thanks but if I were half the caster folks seem to remember me being,  I'd be happy and less self conscience too. Perhaps a faster 7 would suffice. That was one of the great things about your rods. After casting at the specified distance, you could play around and see that both the 200 and 225 would make great 5 wts at 20’ with no wind, in fact I would prefer the 225 because it really would cast itself with the right timing but if I were expecting a lot of wind I'd pick up the 200. The 185 delt with wind the best but it was a little stiff for fishing IMHO and the 200 was the better all around rod.  Does that make the 225 a 4.5  the 200  a 5  and the  225 a 5.5? I guess to some folks it would. It doesn't to me, just 3 different 5s with different core applications.

Rod design is really interesting. Do you have a ratio of length of rod to distance?

I think the way people approach  rod design is more interesting. Everyone seems to have their ideas but bottom line we're all making fishing rods and we all seem to come to a point and way that works for us.  Nope don't have a ratio of length of rod to distance. Here's that memory thing at work again. Haven't you ever noticed, I try to cast EVERY rod 100 feet? :)

I think in terms of function and distance......and as long as I can cast every rod 60 feet I'm happy. LOL. (Jim Lowe)

Do you have a ratio of length of rod to distance? Anyone?

I have always used the rule of thumb that in the hands of a competent caster, a rod of normal design should cast 10 times its length without taxing the caster. Normal design means 4 weights of about 7 foot length, 5 weights about 7.5 feet, 6 weights about 8 feet etc.  (Tom Smithwick)

There's a statistically significant correlation between line weight and rod length.  I believe there is a direct relationship between line weight and distance.  I use 10’ of distance times the line weight to compare tapers on paper.  There's nothing scientific about that.  I just picked a factor to be consistent and reasonably relevant.  I suppose you could draw a correlation between rod length and distance by inference, but I think that's a stretch.  A 9’ 4 wt couldn't possibly cast 80’ of line as efficiently as an 9’ 8 wt.  Not to say it couldn't be done.  It just couldn't be done as efficiently.  FWIW, here's some hex rod line weight and rod length stats from the RodDNA database:

Line	Number	Rod Length	Tip Diameter
Weight	of Tapers	(ft)	(in)
2	9	5.9	.057
3	62	6.2	.064
4	120	7.1	.068
5	136	7.7	.070
6	84	8.2	.076
7	28	8.6	.081
8	5	8.9	.094
	444

(David Bolin)

How do you define efficiency in this case?  (Jim Lowe)

If we could agree on a metric for the strength to weight ratio, we would have a proxy for efficiency.  I don't think anyone has nailed that ratio yet.  I've played around with several scenarios in FlexRod but haven't been comfortable with the results.  A 9’ 4 wt bamboo rod would probably fall way outside the normal limits of a strength to weight metric.  But if weight doesn't matter, I suppose we could put a 4 wt tip on an 8 wt butt and call it a 9’ 4 wt that will cast 80’ of line.  There's nothing wrong with that if there's  a fishing application for the rod.  (David Bolin)

Wouldn't that be hard to do. Wouldn't the strength to weight decrease as you go up in line weight and introduce more pith?

It seems to me its all well and good to take something like roddna and crunch all the tapers but aren't you really looking at apples and  oranges. By this I mean, do we know enough about each makers intent to be able to say one 7.5ft 5 compares to another because they were both made to perform the same function?

I would think you'd need to take something more consistent, like Bob Norwoods SLT or a Powell taper to have something meaningful. Don't you need a consistent base from which to build on?  (Jim Lowe)

My last question wasn't meant to read " Do you have a favorite rod length for line weight" but. " For each of inch of  rod length you add to a given taper (assuming we could make the equivalent taper in any length ) for the same line wt., would you expect to gain more distance." How much?  (Jerry Foster)

For me, given same line weight, distance is not a noticeable function of rod length.  (Steve Dugmore)

Good questions.  I chose to take a different approach than Bob.  But we almost always arrive at the same conclusions about a given taper.  I think that's a good thing.  By no means do I put all 7.5’ 5 wts in the same category as it relates to action.  But they do seem to have a common casting range.  It takes about the same amount of bamboo to hold 50 feet of line in the air no matter how you configure the taper, that is if your goal is to maintain a functional strength to weight ratio.

Regarding a consistent base.  I prefer to analyze a taper based on a combination of several metrics (e.g. diagonal values, deflection, effective length, etc...).  I need all of those factors to analyze a taper.  They're not very meaningful on a stand alone basis, but together they say a lot about a taper.  That's a consistent approach based on factors derived from hundreds of tapers.  For example, I know that a functional taper should have an effective length between 80% and 90% of the length of the rod using 10 feet of line for every incremental line weight.  An 80% effective length will load deeper than a 90% taper.  Diagonal values reveal the action of a rod.  An average value greater than 5% would generally be considered a parabolic.  Most tapers fall in the -5% to 5% range and less than -5% is generally a swelled butt rod.  There are probably very few folks in the rod making community that would give a plug nickel for that approach because it's way too detailed and there are too many moving parts.  I've been using financial statistics to analyze banks for 20 years.  I'm very comfortable applying a statistical approach to taper analysis.

Bob can analyze a taper by simply comparing it to a standard straight taper with a taper and stress chart.  He knows those standard straight tapers like the back of his hand.  That's a very effective approach.  Others can just look at a stress curve and tell you all kinds of cool details about that taper without comparing it to anything.  But that requires a lot of experience on the water with lots of tapers.  Beginners would probably get up to speed on taper design with Bob's program easier than some of the others.  It's a very straight forward approach to taper analysis.  RodDNA and DynaRod are robust design tools for more experienced users.  FlexRod is tooled up more for gear heads like me that love to crunch numbers on lots of tapers.  And there's absolutely nothing wrong with just making a classic and leave the number crunching to the gear heads.  It doesn't matter if you give them away or sell them for $5,000 a piece.  They're just fishing sticks at the end of the day.  (David Bolin)

Would you explain effective length.. is that similar to the action length?

Diagonals?  (Jerry Foster)

I'll give it a shot:

Effective Length - The straight line distance from the butt of the rod to the tip top when the rod is bent.  I divide that by the length of the rod to create a metric that I can use to compare any rod length.  The ratio will vary significantly throughout the casting stroke.  For simplicity, I calculate the ratio with a static load on the rod in FlexRod.  The only variable that changes is the line length.  As previously mentioned, I use 10’ of line for each respective line weight (e.g. 5 wt at 50’).  The ratio is statistically significant for the 400+ RodDNA hex tapers that I'm using.

Diagonal Values - The taper deviation as a percentage of the straight line taper diameter from the tip top to 10 inches from the butt (IE the trend line is based on the action length).  I use average diagonal values to put tapers in common design categories based on both full length  and sectional averages.  Again, the results are statistically significant for hundreds of tapers.

I would be glad to publish FlexRod with all the tapers so folks could browse through the statistics, but I'm hesitant to do that without Larry's permission.  I realize the tapers are in the public domain, but I don't think it would be appropriate for me to publish tapers from the RodDNA database without permission.  (David Bolin)

I think I will have to disagree with you on this one. Rods of one line size can be designed to cast 20 feet or +65 ft. depending on the designers intentions. I think this goes for all line lengths lengths. Your method of design, seems very dependent on how you define each of the parameters you have listed. For me, I am not as comfortable using and understanding your terms as you. I think if would take me a while to get as comfortable with it as you are. I'm sure you do get similar results as most other programs, I just find it difficult and have not spent the time I should learning what you are doing.

I would guess your background is in statistics maybe? Oh you said it's in Banking, I could use any extra money you don't need: Mine isn't, and maybe that’s much of my problem. For example you use terms like 80% and 90% deflection and I don't know exactly what that means, but I do feel that you have to look at the whole rod or there is a great chance you will miss something that has  been done at either end.

Just my thoughts David and You can see my lack of understanding showing in all my comments. That's why I have tried to stick to a method that is simple and easy to use for design and Taper understanding for all folks, yet also very accurate.

But I very much agree with your analysis of rod programs, right on the money, Joke Joke.  (Bob Norwood)

For what it is worth, I wanted to see how a change in one dimension would affect the stress curve model. I chose to add .010 to station 25. Everything else being the same here is the resulting curve.

Observations are that "in this model" the stations act independently . The change at station 25 has no influence on the stress profile at other stations other than to raise the levels of all proportionately. But the relative profile remains the same. I am suspicous that this is not an accurate "real life" portrayal but a result of math in the model. Question to the group is: how do you think that this change in the taper (adding .010 to station 25) affect the real life action and feel of the rod? (Ken Weymouth)

Wow Ken, good for you, you seem to be several steps ahead of me. But a quick answer is, it depends on your individual sense of feel. And the real loading factor which this graph does not show yet. (Jerry Foster)

Sorry for so many posts this morning. I guess I mixed my morning coffee too strong. I certainly don't want to interfere with what you are doing for the list here. I am excited to be a part of it. I just find that I get older if I don't ask a question when I think of it - I forget (-: (Ken Weymouth)

OK, that's very interesting. I am very surprised to see the magnitude of change as reflected in the curve.  Hadn't thought about it before, I guess.Jerry, when does the "real load factor" raise its head? (Peter McKean)

Ok, Maybe some of you have done the exorcize by now..Maybe.

But this is how you personalize the graphs. If you cast your 5wt and its sweet spot is 47 ft for you then thats the number you use on all 5 wts. All rods are not equal so this is not a hard and fast rule but you can see how the new rod deviates from the one you like.

There is also a shape to the graph, character. And an implied speed. You have to learn to denote the difference liking a rod just because it's speed matches your natural rhythm and one where the speed and the shape of the curve are both sympathetic to you. This is the rod you don't have to think about while fishing. Your target shooting rod. Thats why I'm pretty emphatic about not recommending a rod to anyone based on what you (I) like. You may prefer Powell B' or Garrisons and the other guy has a hitch in his stroke that requires some other shape to compensate. I don't know the answer but I do know through my test rods that different people prefer different tapers. You do have to aware that the line wt entered was a WF when you are going to use a DT. You, I mean each of you, have to decide how you are going to use a given rod in terms of loading distances Remember that those upper and lower stress numbers kind of set up your range. And, if you did the tests you can see that if a rod is down in the 140ks or below with the appropriate distance to cast you have a real broom on your hands. If you play with the line weights and distances, you will also see why rods can handle multiple line wts. Some better than others but... I'm sorry there is no universal rod. So. Questions? (Jerry Foster)

I am curious to read some responses to your question. I have an idea in my mind of what I think the change in feel may be. To me, I would think that the overall rod may feel somewhat stiffer due to less bending at the 25" mark. Am I way off base here? I'm curious if there are small dimension variances that are only noticeable when the rod is actually loaded while fighting a fish versus the amount of load applied while casting? (John Smith)

From casting and then measuring and graphing the dimensions and stress curves of a dozen drive river rods in the collection of a friend (nearly twenty years ago when i first started making cane rods) I can say that the rods varied as much as .012" for any given station, and yet the "averaged" dimension very around a taper curve representative of all. No taper was consistently larger or smaller than the others, ie. each varied randomly above or below the average. The rods were produced by the goings over a twenty or so year period. All took the same five weight line, and all felt similar in the hand, though some definitely were "sweeter" than others. My impression is that being "off" up to .012" (two line weights) at any given station will not change to overall bending/casting characteristics of the rod, but CONSISTENTLY being large or small will (I have built identical rods on the MHM, the anvil unchanged between them, the only difference between the three rods is a consistent .006" over and under "target", and as expected they take sequential Line weights, though because proportionally the incremental increase is greater at the tip, adding .006 to the tip makes a slightly slower action, subtracting .006 a slightly faster or more tip action rod, and using the same taper/anvil to build straight across as a quad jumps up a line weight AND makes a significantly faster action, but that's another story).Long response and doesn't directly answer your question. My guess is that the single station increase would be a slightly perceptible difference, bringing the action/feel slightly lower toward the hand, but not affect the line weight or overall "power" of the rod.  (Chris Obuchowski)

But its very interesting, nonetheless.

Once, it was necessary to cobble up a new tip, in a fearful hurry, because I had broken the tip on the original Superfast (by stupidity) and someone wanted to evaluate it at some cost in terms of time, travel and inconvenience.

It took me 48 hours to produce a new tip, and, no, pretty it wasn’t, made on a wood form and rather arbitrarily planed to boot.

I intended to scrape the worst excesses off it, but was so knackered I forgot............Anyway, all went well.Until the photos of the curve of it when playing a fish were uploaded, you could actually see the dodgy bits!

When I measured it the result was truly embarassing, I can tell you.

So I made another one, properly, I can do this, when I try, but I mutter a lot.........And carted the now proper rod off to the same place to fish for the same fish.

I really could'nt tell the difference, in the hand, but the curve was lovely, again.

So I put the cobbled tip back on, then I chucked it to my boat partner and asked what he thought, he thought it looked much worse than it was. When I tell you that the crap version was 20 thou oversize between 20 and 30 inches from the tip you may either deduce that we worry too much about minor differences, or that perhaps I should have designed the thing that way in the first place, in fact, now I've said that. (Robin Haywood)

You are correct, the change at 25" only affects that one station, however the curves you show differ all along their length therefore you must have changed something else also. Maybe the line length or size. If you are showing a graph of what you have said, only changing the one station, the graphs would be exactly the same except at 25" where the stress will be less because of the station increase of .010". I personally don't think a change at just one station will affect the overall rod taper very much if any. I think you need a change over 2 or 3 consecutive stations to cause a difference in the overall taper. By the way the Granger-Goodwin Victory 8'6" stress curve is much like the one for the snake rod, as are the following:

• Dickerson 7613 "1952 Ver"
• Leonard 50 df tip #1
• Cattanach 7'6" 3pc 5wt
• Richard Walker 9' 2pc 4wt
• Payne 214 7'9" 6/7wt (this one has a much stronger tip section
• And lastly Bob Nunley 9' 2pc 10wt.

I obtained the above by comparing Stress Curves, it took about 10 minutes. It would seem that quite a few of the well known rod makers like this style of taper; strong tip, drop off at/through the ferrule area and softer butt which looks like it is 1 or 2 sizes too small for the tip. A somewhat different taper style but it must work.  (Bob Norwood)

Ok, let's see.. Oh yes, this one just drives me crazy but that's just me.

Garrison had some rough approximate guidelines for his rods and for the most part they are close enough until you develop your own sense of where they should be. If I remember properly I think he didn't want his tips to go over 220K and he thought anything under 140k was unyielding. This works out to be approx 1 deg and .5 deg of bend angle which is about where my sense of feel is. Bob Norwood, who has a taper design program knows a lot more about Garrison than I do, should correct me if this is not correct. Now for the TRAVESTY. For some reason (I really know what it is, but I'm not saying) Frank saw fit to post the majority of postings at 30' of line to fish. This is flat out misleading. I believe Garrisons (and my) intention is to see the rod (stresses) at nominal fishing lengths. Personally, I use 10' of line per line weight. Now if you look at the granger with 30' of line it is a board. Now if you Jack the line to cast out to 50' you see the stress of a properly loaded rod. You just have to be ware and change each rod you look at to some appropriate fishing distance for that weight of rod. Ok now, most of you have been through this with me but for those that haven't you must do this. This is the one step that will make stress graphs make sense. You MUST take a rod that you like out to the yard (right now) and cast it till you find the sweet spot. The place where the rod talks to you. Take a tape measure, don't guess, lay the rod down and measure the amount of line, not line and leader, out beyond the tip top. When you go back inside enter this number in the line to fish. Now you have an exact picture (profile) of that rod. You can more or less use the max and min rages based on that as your baseline for further evaluation of rods. But while your out there do a couple of more tests. By the way, while you are doing these tests, please don't haul. There is nothing wrong with hauling it's just that it the stress curves don"t accommodate turbocharging. If you are an incessant hauler, stick your hand in your pocket. The reason I say this is also I think you should have your entire attention on your casting hand. Feel the feedback...close your eyes. Now for the next stage... and this is a little dodgier see if you can find the max and min ranges for your feel system... start with a min amount of line out and let line out and in until you can feel the point where the butt starts or stops bending. this will set your personal min stress range.  Same thing on the other end, find the point under normal casting where you can feel the tip start to give out.  Max range. Note these numbers and substitute them in the line to fish and see what the graph does. These numbers will not be universal but they will put you in the ball park to begin evaluating stress curves... Without this step this is all academic. You must set a sense of feel to what you see on the graph. Don't worry right now about the curves of the rod you choose. That is rod character and the next stage. (Jerry Foster)

Great idea and explanation for the stress curve to make sense for me. I understand the graphs BUT never figured out how it applied to what I liked. (Gordon Koppin)

The 30' number comes from the AFTMA standard weight which is based on the first 30' of the fly line. But you already know that, Jerry. (Chris Obuchowski)

I've been "out of the office" for a couple days, so I'm just catching up on this discussion.

A few points:

In online Hexrod I tried to use 30ft for 5wt and under and 40ft for 6wt and over for the rods in the archive.  It wasn't the AFTMA measurement; that's just what seemed reasonable, given where and how I tend to fish.  As Jerry says you should change it to suit yourself.  There are so many line tapers on the market now, its hard to really know how to handle it.  Your rod may have a sweet spot at 45ft with one line and at 35 with another, supposedly the same weight.  For Hexrod, its only the weight of the line that enters into the calculation, not the taper.  I'm using weights from the Cortland website, extracted and organized by Chris Carlin.

The way stress calculations work, adding 0.010 to the 25 inch station will affect (increase) the stresses from that point back toward the butt.  But not toward the tip. (If you are starting from 5 inch stations, the .010 will get spread back starting at 21 inches).  So this makes me question Ken's graph.

Robin, as a few rods in the Commons area of Hexrod, including his "Superfast," if you want to check them out. Its possible he will comment. (Frank Stetzer, Hexrod, Taper Archive, Rodmakers Archive)

Just as a random finding...I have found that each of the hex type programs will yield slightly different results, not enough to matter but noticeable. not only that, but I have even found slight differences using the same program from one  computer to another.. This isn't important, it's just I makes it hard to make picky little comparisons. So give it a little slack.Does anyone want the hear about deflection or have you had enough? (Jerry Foster)

Bob, I went back and reran the change being careful that only station 25 changed in dimensions .010. I did get a different result. Must have changed something else before. Can't get away with anything in this group! Anyway here is the new stress graph. (Key Weymouth)

Ken this still isn't right. There should be no difference between the stress curves until you get to 20" where the tapers diverge. When the tapers come back together, there will be very slightly greater stress all along the rest of the rod due to the load of the extra bamboo added between 20" and 30".(Insert McGuire_Mike_Stress.jpg)I ran it in my own stress analysis spreadsheet and above is what I got. You can see how the red line of the altered taper is just a bit above the original after 30". (Mike McGuire)

Unlike Mike, my eyes glaze over when I see "x = ..." so I am certainly in the "ordinary" class.

When I look at a stress curve I get a pretty good sense of how the rod will feel upon completion. When I look at a deflection curve I see that rod A bends more or less deeply than rod B but I get no sense of what the will feel like.

The hinge at 70” provides a definite kick but that feel doesn’t show up on the deflection chart so I don’t see its value as a design tool except when comparing two different rods. How should deflection charts be used in rod design?  (JW Healy)

If the upper chart is indeed a stress chart, at 100,00 you are showing me a picture of  rod with very little stress at the given load. I could only guess at what the rod would look like if properly loaded. But I'm am not familiar with the software you are showing so there may be a lot here that I don't understand. (Jerry Foster)

I appreciate all the helpful info you guys shared with me on building my heat gun oven. I bought a 6" piece of round duct and a 3" piece of duct, both 5'-0" long. Based on some instructions I found on the web, I raised the 3" duct up about 3" off the bottom and left 1" sticking out of the top cap. I got a tip from a list member about ensuring the direction of the heat gun was pointing down and not angled toward the 3" duct. To help keep the direction of the heat downward, I included a second piece of 3" duct about 12" long extending down from the heat gun opening. I mashed this piece of duct to more of an oval shape so it wouldn't be resting against the side of the main 3" duct. Once I got my heat gun in the cap plate, it sounded kinda weak. I took the heat gun out and once it was upright; the power was normal. Pointed downward, the heat gun power reduces significantly. My particular heat gun is an 11amp Ryobi I bought from the big box store about 2 years ago. After 15 minutes of running, my thermometer read 325 degrees 6" down from the top and 275 degress at the middle. I didn't check the bottom. Some things I believe may be affecting the 50-degree temperature difference are, the heat gun, my 3" duct needs to be further up than 3" from the bottom, and possibly my additional 3" duct needs to be longer in order to get the heat down further. Any thoughts?BTW...I insulated the exterior with some foiled backed 2" hvac duct insulation wrap. (John Smith)

Try turning your oven on its side and run it. (Joe Hudock)

It sounds like your heat gun is not up to the task.  I use a Steinel and my oven has the usual 6" duct with a 3" "oven"-duct riveted to one side.  The whole thing is inside an 8" duct with 1" of insulation (fiberglass batt without any foil or paper) in between. Essentially the same as what Rick Hodges suggested.  I made the hole for the heat gun a good fit, so no extra ducting is necessary where the gun blows in. Despite Mark Wendt's lack of belief in years past, the oven part varies in temperature only a few degrees from top to bottom (yes, it is vertical).  I credit the uniform heat to the high air throughput of the Steinel heat gun and to the insulation. (Tim Anderson)

I second the Steinel gun. Went through three big box units in a little over a year.  (Jim Miller)

Not sure what you mean by my lack of belief.  I have a conviction about convection... I have a lack of belief in strip heater ovens, since they have hot and cold spots.  I'm a firm believer in moving air through the heat treating chamber to help keep the temperature constant, and any effort to do that is in my mind, a good thing.  Some convection oven designs are better than others, but pretty much any convection oven beats a strip heater oven hands down if you want better overall temperature control throughout the oven.

My oven, which is based on M-D's design, which was based on I think Don Andersen's design, holds its temperature within + or - 1 deg F through the entire length of the cane chamber.  One of the benefits of keeping the heated air completely contained inside the oven rather than a pass through is better temperature control throughout, but as I said, any moving air is better than having no moving air. (Mark Wendt)

Sorry, I was not trying to offend you. It is just, every time I use my oven, I remember (with amusement) some past post of yours where you expressed doubt about the ability of a heat-gun oven to achieve uniform temperatures along its length. Why am I amused? Well, my thermometers (placed at different points along the oven) show temps within 4° F of each other while heating up or in a steady state. Most of the time the variation is not more than 2° F, which I think is pretty darn good. Perfect? No, but then neither is my rod building.

Of course, there are those who think my memory isn't all it should be …. (Tim Anderson)

If I start with a rod of a known stress curve, can I use that stress curve to calculate the dimensions of the new rod? Got the stress curve of a 7'0" 5 wt. 2 pc. and want to go to a 6'6" 3 wt. 3 pc.

Worked through the stress curves and got a stress "footprint" for the 6'6" rod that looks very close to the 7'0" rod.

Will they "feel" the same? (Don Anderson)

Will they "feel" the same?

They won’t feel exactly the same, Don, but they should feel related. You are changing the line weight, length, and number of ferrules. I don’t think you can make the two rods feel the same no matter what you do. I think the best you can hope for is the feel you get when casting different rods in the Garrison series. You can tell they were designed by the same guy because the actions are similar, but you can certainly feel the difference in weight and length. FWIW, if I were doing it, I would do exactly what you are doing and tell the customer in advance what to expect. What he wants is not realistic.  (Tom Smithwick)

This fellow is a friend. We fish together some. He wanted to try this so I'll give it a shot. He's made it clear that he has no interest in how I get there, just get there. He also expressed the thought of trying for a 3 1/2 wt. line taper.

And I agree with Tom, with linear tapers similar to Garrison's this would be fairly easy but I'm working with a Orvis 7'0" rod that has more whoops and hollows than a hilly road. Does make life interesting though. (Don Anderson)

Just guessing but sounds like you haven't used that particular feature on Hexrod.  Apologize if wrong, but if not (and for benefit of others) here's the procedure:  Call up the model you are using for the stress model for this shorter rod--Modify Rod Design--Fundamentals--Enter new rod info, then at bottom: Hold Constant--Stresses.  The new rod will come up with the same stress curves applied, flavor to taste.  What I've found, and for what it's worth, is that moving from a long rod of, say, over 8ft, to a much shorter rod requires the stresses to be relocated or otherwise modified to approximate similar feels in casting.  But this will get you reasonably close most of the time, and Tom is right, I believe, that similar is about the best we can ever do in this case.  (Bob Brockett)