Unconventional Rod Sections

[Bobinmich]

Has anyone ever cast a quad boo? I have not. But looking at a square or rectangular cross section from a mathematical point of view, it would tend to have a lower section modulus in a plane normal to the flat surface than diagonally across the corners. It would seem, then, to have a pronounced directional "spine." If that were true, then by alligning the rod seat and guides in the direction of this pronounced spine, the rod would have a definite self alligning effect - sort of like caster in automobile wheel allignment. I was wondering if any of you experts had experienced this and if, in fact, it were even noticable?

If that observation were true, or if true was even desirable, could a graphite rod be made in a similar fashon? Using a squared off mandrel and wrapping a uniform wall it might look like this.



No, I am not smoking anything strange, I just have a weird curiosity. Anybody else want to bite?

Godspeed,

Bob

[lestrout]

Bob - you have struck a different kind of chord with me. I have always liked to evaluate fly rods, and have ffished nearly a thousand of them and casted several thousands. I love to discuss the engineering and wave dynamics of these with rod makers, a few of which have scientific backgrounds but mostly don't.

Our own BillT is a cane maker who specializes in quads, because the fact that so few have been made in years past means that the design front is wide open. He terms the format 'liberating', since most of the successful hex tapers have already been established by Leonard, Payne, Garrison, Winston, Thomas and Paul Young (no relation). With the exception of the Sir D, the tapers are nearing the century mark. The great designs by Kusse, Aroner, John Channer, Marty Karstetter, Bob Sigman and others could be construed as tweaks on the core designs.

The same applies to pents, tho' probably not to 3 sideds. The one and only 3 sider I've casted was done by Bill Fink, and he will never do another. The assymmetry of the cross section means that the forward and back casts are way different, which is disconcerting to say the least.

Yes - the 4 and 5 sideds do lend them to directionality - but this is what all the plastic makers strive for. Gatti is most uniformly successful with this, but certainly the products by Sage and others that get to the fly shop are quite good. The non-pejorative term is tracking.

Hexagraph already does with plastic what you are suggesting - but with hexes (no surprise?). The original English designs were maybe suitable for wet casts on some English tidal rivers, but were not popular with dry fly anglers. When the great Walton Powell hooked up with them, he really advanced their castability and ffishability (not at all the same thing). I prefer using these to hollow plastic tubes when in boats (especially with metal gunwales) and when bushwhacking.

tl
les

[J Castwell]

http://www.ronkusse.com/quads.html
We have two of his quads, our favorites. Square, not a parallelogram. Far more power than a six strip rod.

[fishbum]

[quote=Bobinmich;247197]Has anyone ever cast a quad boo? I have not. But looking at a square or rectangular cross section from a mathematical point of view, it would tend to have a lower section modulus in a plane normal to the flat surface than diagonally across the corners. It would seem, then, to have a pronounced directional "spine." If that were true, then by alligning the rod seat and guides in the direction of this pronounced spine, the rod would have a definite self alligning effect - sort of like caster in automobile wheel allignment. I was wondering if any of you experts had experienced this and if, in fact, it were even noticable?


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Actually Bob, a rod with a square cross section bends equally in every plane. Any difference in bending is due to difference in the splines the section is made from and not the square cross section. There is a difference in stress from bending a square cross section from flat to flat and corner to corner. The corner to corner stress is higher than the flat to flat stress.

fishbum

[Bobinmich]

Hey, you're right. The moment of inertia does not change for a square rotated 90 degrees. Only the section modulus - and therefore the stress - changes.

But a rectangle, slightly wider horizontally, would change. Would this change tracking? Would it be a good thing?

Bob

[fishbum]

You got it!

Your rectangle would indeed bend more in one plane than another 90 degrees to it. I don't think I would like a rod like that but what the heck, to each his own.

Check this out.

http://www.overmywaders.com/index.php?Montagnespeaksout

Rectangular cross sections have been tried in the past. Never very popular.

[rizeye]

what would happen if you cast say 30 degrees to the horizontal plane of the sides? this is basicaslly an upstream flip.

[Bobinmich]

Now there's a thought. Intentionally rotate the rod out of verticle to get a sideways bent out of it. Got to build one - someway or another. Just to try it.

Bob