Bamboo Tips - Tips Area
Rod Design - Material Data

< Home < Tips Area < Rod Design < Material Data

My new rod making neighbor Larry Lohkamp and I have been exchanging e-mails about MOE, heat treating, varnish viscosity and other deep subjects from my shallow well.  It occurred to me after reading Larry's last note on MOE that there are a few truths about Tonkin cane that are universal.  But that universe may not extend beyond the walls of my garage.  Here's the list I came up with so far:

Moisture:

• Wet bamboo is more elastic than dry bamboo.
• Heat treating temporarily reduces the moisture content of bamboo.
• Therefore, heat treating temporarily stiffens the bamboo.

Other Stuff:

• Over heating power fibers makes them brittle (e.g. flaming or excessive heat treating).
• Nodes are stiffer than internodal sections.
• A heavier culm does not equate to a stiffer rod.
• Higher density power fibers equates to a stiffer rod.
• Power fiber density varies significantly around the circumference of a culm.

Is there something on this list that fails the truth test?  What would you add to the list?  Please no technical terms like MOE or MOI.  Those are helpful when explaining why bamboo does what it does.  I'd like to build a list of what bamboo does.  Not why it does it.  Remember, my well is relatively shallow when it comes to physics.  (David Bolin)

Not certain about what the 'truth' is, but my understanding of elasticity is that an object which is more elastic will, under a specific load, return to its original shape more rapidly than one which is less elastic, and that the one with the lesser elasticity will reach an elastic limit (no longer able to return to its original shape) sooner than the one which is more elastic. Thus it would seem (to me) that a wet noodle would be less elastic than a dry noodle.  (Vince Brannick)

I agree.  I used the term "truth" incorrectly.  I was trying to avoid confusion created by MOE conversations and confused myself in the process.  Al suggested the term "plastic" might be more appropriate.  "Plastic" and "inelastic" would be synonymous terms in that case.  Maybe I should have said that lower moisture content produces a stiffer rod.

I didn't mean anything special by "truth".  Just that whatever it is is easily validated. There are several generally accepted "facts" that could be on this list that aren't easily validated...like cross linking.  That doesn't mean it's not true.  It's just difficult to validate in a way that's material to the performance of a bamboo fly rod.  So here's my modified list so far:

Moisture:

Other Stuff:

In physics the terms for the results for things that are stressed are: plastic deformation (bend it and it stays bent) and elastic deformation (bend it and it returns to it's unbent position). So hopefully your bamboo will only have elastic deformation. If your rod develops a set I guess that's a plastic deformation. So a truth is that heat treating can make a rod more elastic even though it also makes it stiffer.  (Ken Paterson)

Close.  "In physics, elasticity is the physical property of a material when it deforms under stress (e.g. external forces), but returns to its original shape when the stress is removed."

The real question is, how much stress can you place on a wet noodle.  (Mark Wendt)

Heat treating temporarily reduces the moisture content of bamboo.

Therefore, heat treating temporarily stiffens the bamboo.

Interesting speculation David, although I would have to seriously doubt the following assertions in particular the adjective "temporarily" I suggest that once the ambient moisture is driven out, there remains some moisture locked into the molecules.  It can regain the ambient moisture, but the locked in part is permanent and always stiffens the rod.  (Ralph Moon)

Dr. Schott's testing indicates that the permanent loss of locked in moisture is 1 to 2 percent by weight.  In other words, the bamboo will reacquire all but 1 to 2 percent of the moisture lost during the heat treating process.  The question as he put it is:  "is it noticeable in the finished rod?" (Bamboo Under a Microscope, page 16)  So if the rod is any stiffer due to lower moisture content, it will be less than one fourth the difference between the AFTM line weight of a 4 and 5 weight line.  I can't detect a difference that small on the water.  That's why I referred to stiffening due to lower moisture content as temporary.  I suppose it could take up to a year to reach equilibrium, but that's relatively temporary compared to the useful life of a bamboo rod.

My original post flamed out as soon as it hit the list server.  My intent was to compile a short list of bamboo specific things that are most important from a rod making perspective...and easily understood.  I suppose any bone head that's ever made a rod should know what's on that list.  I started out a few years ago with a long list of things I thought were required to make a quality rod.  But I’ve found that things I initially accepted as mandatory were nothing more than just another way to make a rod.

Thanks for commenting Ralph.  It means a lot to me, and many others I'm sure, that you continue to contribute to the List.  Maybe there's someone else here in your league, but no one else I know brings the years of practical experience to the table that you do.  I think it would be very cool to hear your list.  What do you consider to be the most important things to consider when selecting and preparing bamboo for a quality rod?  (David Bolin)

I am sorry to have delayed responding to your message, but I wanted to read Schott's papers again. I don't want to get into a sparring match, because my observations were subjective and I would lose the debate.  My list  of the most important things in building a rod (make that a good rod)  boils down to one comment.  Every phase of rod building is important Selecting cane, splitting heat treating planning, finishing.  None ranks higher than another.  (Ralph Moon)

A list of truths may be hard to find, although I too would like to hear what Ralph thinks. I can point to some things that don't seem to matter.

1. Making little strips out of big chunks of bamboo.  You can hand split using one of several methods; saw them on a band saw against a pin; sand the nodes sort of straight and saw them on a band saw against a pin; or saw them with a gang saw like Bellinger sells, or on a home made sled.

2. Removing nodes. You can smash them, displace them, or just sand them off... or build it the nodeless way and ignore them.

3. Moisture content and soaking. You can soak before straightening or not. You can soak before rough planing or not. You can soak after heat treating or not.  Tapering can be done wet, dry, or some combination.

4. Heat Treating the beveled strips. You can torch them in a pipe until they smell done. You can roast them in a precision oven at temperatures ranging from near 400F to the mid 200's for several minutes to several hours. There seems to be no particular correlation in the time-temperature ratio.

5. Gluing the blank. You can use a range of glues from hardware store wood glue to industrial heat setting adhesives.

Pick your process based on your beliefs and druthers from any of the above and you can produce a functional, hard fishing fly rod. It may not the prettiest in some peoples minds or the best that can humanly be made, but it will fish. Bamboo is a very forgiving and versatile material.

Of course it does have some limits. Cook it too long and it won't be bamboo any more. Screw up the angles too badly and it won't glue up right. Muck up the taper and you may still end up with a fly rod, but probably not the one you wanted.

Much of what we kick around on the list and in the rod building forums has more to do with the process of continuing improvement than  what you absolutely must do.  (Larry Lohkamp)