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Rod Design - Converting Section Count

Anyone having experience with converting a 2 piece rod into a one piece?  Can I just use the numbers as is or should compensate....  (Danny Twang)

    It depends on what you want. If you absolutely want to preserve the original action, use Hexrod to compensate. If you don't, you will get some extra zip out of a rod that will still be lighter than the original. Personally, I would normally choose that option.

    If you have a step-down ferrule, that complicates things a bit. I would still use Hexrod to smooth things out in the center of the rod, but I would want to look at the stress curve and dimensions before commenting.  (Tom Smithwick)


I have some questions about converting tapers from two to three piece, two to one piece, etc.  What are the parameters some of you use when making such a conversion. 

For quite some time I thought the difference in dimension between similar tapers with different number of pieces was based on the stiffness of the ferrule either being added or removed.  The more I read though, I now think that its based more on the weight of the ferrule.  By adding in a ferrule you need to add more cane below the ferrule to carry the weight.  Or conversely, by removing a ferrule you can  remove more  material in the butt to compensate.

My question though is how do you decide how much to add or subtract.  I'll give you an example that most people should be familiar with.  Wayne's "Sir D" in his book is given in both two and three piece versions in various line weights and lengths.  I'll focus on the 7' 4 wt. (top of page 182 in my copy of his book).  The dimensions for both the two and three piece are identical for stations 0-25, which makes sense since there wouldn't be a ferrule encountered until 28 inches.  Starting at station 30 though the 3 piece begins to get progressively larger.  The dimensions for the two tapers are listed below.

station        2 piece            3 piece

30                .152                .154
35                .166                .171
40                .184                .191
45                .206                .213
50                .214                .220
55                .220                .225
60                .244                .250
65                .258                .266
70                .272                .282
75                .300                .311

The difference starts out small and gets bigger until the ferrule point of the two piece.  It slows down then (because there is no ferrule at 47 inches in the 3 piece) and picks up again after the final ferrule in the 3 piece.

Converting this rod is not a big deal because I have a book that lists the taper.  What if I didn't have a book?  I tried using hexrod to change the same 2 piece Sir D into a three piece and came up with different numbers.  Not vastly different, but still different.  What's more, when I told Hexrod to use truncated ferrules I got still different numbers.

One of the reasons I even bring this up is that this winter I want to try to make a longer 1 piece rod as well as a rod using a FIBH ferrule (integrated bamboo ferrules).  Lets say I want to make a 1 piece Sir D.  Should I just run the 2 piece through hexrod?  Or are there other factors I should keep in mind?  For rods with bamboo ferrules (which are substantially lighter than metal ferrules) what adjustments should I make?  Split the difference between a 1 and 2 piece taper?

Any help, insights, or discussion would be great.  I'd like to learn how to balance the use the a computer program with being able to use my head.  (Aaron Gaffney)

    When comparing Wayne's 3 piece taper with the 3 piece taper you get from Hexrod, make sure that the two are using the same size ferrules.  The Hexrod programs will make an assumption as to the proper size ferrules  but the builder must be the final judge.  The stress calculations that Hexrod performs depend on the weight of all the components (cane, ferrules, line, varnish & guides), so the sizes of the ferrules used will change the stress curve.  Going to truncated ferrules will also change things.  Going to cane ferrules, well you should try to find out their weight if you are going to use Hexrod to help build the taper.  I have no idea if cane ferrules are lighter  than a truncated NS ferrule or not.  (Frank Stetzer, Hexrod, Taper Archive, Rodmakers Archive)


I just finished Wayne C's 7042, but made it a 4 piece and impregnated it instead of varnish.  I test cast it with a regular 4 weight line (Orvis I believe), and it really didn't feel right (been thinking more about feel after Jerry's recent posts).  I then strung up a 5 weight line (Cortland Sylk), and that was much better.  The rod loaded more effectively, and I had tighter loops and hauling was a pleasure. 

My question is - why would my rod, which is slated to handle a 4 weight line just fine, need a 5 weight?  Was it the conversion to a 4 piece, or because it was impregnated, or maybe both?  Or was it the different line types? 

I don't know enough about lines to understand how rod design (besides taper manipulation) affect its ability to cast one line better than another (given the same caster of course).

Thanks for any thoughts you may have.  (Louis DeVos)

    Adding nickel silver ferrules will stiffen a rod, so that is a possible reason for the better casting with a 5-weight line.  The added weight further toward the tip also will change the casting characteristics.  Impregnating might have produced some swelling of the cane.  That, too, could change the casting properties.  I know what my solution would be:  just use a 5 weight line with the rod!  (Tim Anderson)

    You could have used RodDNA to convert the rod to a 4 piece and it would have recalculated the new dimensions while holding the stresses the same.  (Larry Tusoni)

    The Cattanach 7042 is a 'tippy rod'. The line weight designation relies to a large extent on that tippiness.

    I'd say the line weight change is almost certainly the result of adding the top ferrule. The stiffness of this ferrule would buttress, and thus reduce, the high stress point in the tip making the tip stiffer.  (Steve Dugmore)

    I’ve recently done some calculations that show that adding a ferrule increases the stiffness 3X over what it would be without any.  BUT that’s over only about 2” of rod length. My deflection program shows that extra stiffness to be the equivalent of a little less than 1/2 line wt increase. Adding the weight of 3 ferrules instead of one has the effect of reducing the stiffness by a little less than 1/2 line wt, so they about cancel out.

    I don’t have any information on the effect of impregnation on stiffness. Intuitively, you would say that adding material to the rod (impregnant) would stiffen it, but the added weight of the impregnant    would    tend   to   counteract   the   stiffness.  Non-reinforced plastic-like materials don’t have anywhere near the mechanical properties that bamboo has so the impregnant is unlikely to increase the stiffness much.

    I’ve measured enough difference in bamboo Modulus of Elasticity to say that you could easily find 1/2 line wt difference from one culm to another.

    Don’t be insulted:  Did you hit your numbers?  If you wound up oversized, that could make the difference.  (Al Baldauski)

      The answer... butt over tip, bamboo ferrules... simple and smooth, very slight increase in weight and moderate increase in stiffness. Makes the rod react closer to a one-piece and the sensitivity is amazing. Well, OK, just my humble opinion, but I am really sold on them.  (Mike St. Clair)

      Has anyone weighed the Cortland Sylk lines?  Just in terms of feel, I have always thought they were light for their line weight designation.  Again, only going by feel, I think of a 5 weight Sylk line as being a 4 1/2 weight.  (Dan Zimmerlin)

        Agreed.  I have a 5DT Sylk and does seem a tad light.  Definitely thinner diameter than usual modern lines.  I've not weighed it, only judging by feel.  Do like the way it shoots, good lack of memory right out of the box, and works well through smaller guides.  just my opinion.  Have no idea about durability yet, as the line is fairly new.  I'd also be interested in hearing from anyone who has actually weighed any of these lines.  (Bob Brockett)


 

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