Double and triple building of rods

[mrampant]

I have known of rods designed for mainly salt water in the distant past had used the double or triple building techniques to get more strength out of the cane rods.
My question is has anyone recently employed these techniques and how did it go? what sort of line weights for fly rods did you achieve or for boat rods?
I have thought about this and figure that utilizing the power fibers of about 70 thou it may require 2 laminations and having a hollow rod to minimize weight to achieve rod weights of 12 weight and above comfortably. I have done an 11 weight using solid cane and it gets uncomfortable casting after a while.
I am open to suggestions and input from others.
Cheers,
Mark

[carl otto]

Mark:

I would of thought some answers would have shown up by now. Let me take a stab at this.

A fly rod is a dynamic structural cantilever, being loaded and deflected by a weight (the line and the rod) to do a certain amount of work. There are all sorts of structures in various disciplines these principles apply to. In simplistic terms one finds that you get the most bang for the buck out of a hollow tube. One finds that if we dealt with a solid round bar the closer to the center of the bar you go the less and less the material affects the structural outcome of the rod working to perform its task. Once this was known, tubular cross sections came into use to solve structural problems, because they were the most efficient in material used, to size and weight, to do the work they could do.

Now the load on a tube can reach a point where it can collapse, so to compensate for this one makes the tube wall thicker, place spaced reinforcing wraps around it or add internal bracing.

The double build technique was developed in early rod building to compensate for this collapse. The pithy portion of bamboo at the interior of a solid built rod had little to no structural cohesion such that under a heavy load the rod would fail. By removing the pith and substituting the stronger power fibers of additional bamboo sections in its place one created a stronger rod cross section with an associated increase in weight and stiffness. This is how these heavier weight and lined rods came about. In the same vein, since early glues were suspect to failure intermediate wraps were employed to add to the structural integrity of the rod shaft. When folks like E. C. Powell came along he removed the pith and substituted the stronger Port Orford Cedar, as well as increased the butt diameter of his rods to compensate for the greater loads his rods incurred while fishing for salmon and steelhead on the west coast. Some builders deployed graphite or fiberglass laminated to the interior of their strips to keep a rod lighter but stronger. I believe in the 40' and 50's, Orvis, Young and some others showed that a proper built rod could handle larger ocean fishing situations without the need to double build. So double building disappeared.

I believe the need to double build is a historical artifact and that materials and construction techniques have pre-empted the need to do so in today's world.

As always, I look forward to the collective unleashing other points of views and/or amplification to my view.

Best,

Carl

[mrampant]

Thanks for the reply Carl,
I thought I might get more response maybe from some who had done something like this.
I figured that with the introduction of graphite and glass rod building went away from bamboo and therefore the larger weighted rods were no longer relevant due to the heavier makeup of bamboo. I have considered the making of a 13 or larger rod for some time and thought that the relatively thin power fiber walls of tonkin would not be sufficient as a single layer even if the diameter was increased; larger diameter also has the problem of small radius.
The idea of an internal core of cedar may be able to increase stiffness although I'd like to use only bamboo; that is why I suggested just using the power fibers of about 70 - 90 thou in laminations and still hollowing. Using intermediate wraps with Kevlar thread or power silk definitely is an asset to added strength with minimal weight.
Just seeing the thread that Jan96 did on bamboo reel seats shows the small section of power fibers relative to the total thickness.
I am still open to any other thoughts out there. An 8' 13 or 14 weight rod would only have probably a half inch butt section?

[Canewrap]

Mark, I have entertained doing what you suggest and the real weakness is the lack of hoop support. As you increase the mass of a rod, the shear forces increase. I've toyed with the idea of using a graphite tip section that is waxed and wrapping thin silk thread the length of it (tied off at the tip, in tight coils, then insert into the freshly glued and hollowed (fluted from top to bottom) tip section. Once the glued section has cured for a few days, pull out the graphite inner. The rod section glue should have soaked into the silk thread and provided the necessary hoop strength. So, if I was building an 8ft 13wt, I would find a culm with the deepest powerfibers I could find and then try this. Just a wild thought.

[mrampant]

Canewrap, As I understand what you are saying is essentially having a silk thread coil inside the rod? Novel idea. How much added strength would this supply as to intermediate wraps? I would have thought intermediate wraps would supply more strength than internal coils.
Cheers,
Mark

[Canewrap]

The internal coils are to provide a cross-grained support effect (like the cross-graining in plywood). The intermediate wraps would certainly tighten up the rod, just don't know how many you would need to support the hollowed section. Do you think that the intermediates would help prevent splitting? Maybe double build one as a medium-action rod, hollow it and then add the intermediates to get it to a medium/fast action. The internal coils idea was a result of my experience with composites when I worked for an R&D company a lot of years ago. If you did pretty aggressive hollowing and then added an internal coil like that it, it would stiffen up the action a bit - of that I am sure. I need to try that with an 8ft 9wt, just to see how much of a difference it does make.

[oddsnrods]

I am not convinced that intermediate wraps affect the rod action at all to stiffen it up, having added them to a few of my rods for decorative purposes only.

A friend of mine, who frequents these pages, double built a fly rod specifically to boat a Costa Rican black marlin, which he succeeded in doing- to the tune of 100 lbs plus. I remember him telling me how much work was involved and quite some waste. I have seen the rod- it's a beast.

Having made a few very 'big' and long double handed rods, both hollow and solid, I don't feel there is any need to increase so called 'hoop strength'. Even if there was, I don't think the strongest thread would be beneficial- either inside or out. Bamboo rods give of their best if held low when fighting large fish, the higher the rod is (greater the hoop) the less 'command' it will have.

My view is that, if a rod is not excessively hollowed and retains 1/4" dams along it's length for inner support, it will be strong enough for any fresh- water application and probably many in the salt as well. Close examination will reveal that there are some power fibres which are sanded/ cut through when hollowing, that in itself will affect the rods strength. Striving to remove mass may make the rod feel lighter in the hand, but may not make a better fishing rod.

I do however double build under the corks of all of my rods these days, by adding 1/16" thick strips of surface bamboo, glued face down on the blank; which is then turned round on the lathe prior to the corks being added to reduce the flex lower down, which I much prefer.

Malcolm

[mrampant]

Thanks for adding in on the conversation Malcolm, I have seen some posts where you have made some double handers and figured that you may have contemplated double building at some point.
I have used the hollow build technique as you have shown and it is very apparent when you hit the main power fibers. On some rods I have hollowed from 20 thou at the tip to 60 thou at the butt end on a 7'6" rod. Varying the depth minimizes the loss of power fibers and takes out most of the pith. I had thought of using the intermediate wraps as a support over the hollowed sections to reduce the ovaling of the section; with the hollowed sections ranging from 15mm to 60mm and the dams kept to a minimum.
In the pic of the handle have you laminated the pith side to the rind side? For something like that where you are not reducing the internal side, laminating rind to rind would be more effective? Another thing I thought of; I have done plenty of thinking, and need to applying !
Cheers,
Mark

[mrampant]

Canewrap, I have used the Moser power silk for bamboo ferrules to hold them together. It is obvious that is supports the thin bamboo laminations, as I have tested it and have broken the spigot before the ferule split apart. I don't know if it will increase the stiffness of the rod much but it should definitely support the hollowed section of the rod. For the bamboo ferrules the laminations were from 50 to 70 thou. This would also be the thickness that I would opt for in double building; the double built section would be for the mid and butt sections of a 8' rod. I don't think a longer rod would be required for that weight range.
As Malcolm mentioned I was looking to use it for Bill fish and tuna, from a boat.
Cheers,
Mark

[RScottFlyRods]

. This is how these heavier weight and lined rods came about. In the same vein, since early glues were suspect to failure intermediate wraps were employed to add to the structural integrity of the rod shaft. When folks like E. C. Powell came along he removed the pith and substituted the stronger Port Orford Cedar, as well as increased the butt diameter of his rods to compensate for the greater loads his rods incurred while fishing for salmon and steelhead on the west coast. Some builders deployed graphite or fiberglass laminated to the interior of their strips to keep a rod lighter but stronger.

Best,

Carl

Hi Carl,

Very interesting. So are you saying that the interior of the rod has a significant structural significance? In other words, you are saying that Powel replaced the softer weaker bamboo pitch with stronger cedar because that made the rod stronger? So both pith and cedar would be stronger than a completely hollow rod? And an even stronger material if used in the center, like graphite, will strengthen the rod even more. Is this because the hollow tube will collapse under stress but a solid rod will not? Or do you think the interior material, when glued to the exterior material, helps hold the exterior material together in the same way that intermediate wraps do? Intuitively it seems to me that the outside of the tube would have the greatest effect on the overall strength and the the interior would have very little effect, unless if it somehow helps to hold the outside material together (like intermediate wraps do). What percentage of the overall strength do you think comes from the makeup of the interior material and is this additional strength due to the strength of the material in and of itself or is it due to the effect it has on supporting the exterior material?

Thanks,

Ron

[Canewrap]

Thanks for replying Mark. I have been toying with that idea for a while.

[carl otto]

Ron:

Please read my entire reply.

I believe Powell in perfecting his rods found substituting the cedar for the bamboo pith yielded a stronger rod. The next step was to hollow, which was easy to do with the cedar and it yielded dams of a stronger material. The cedar also worked with his double building two strips over the cedar core then resawing to the taper and then hollowing. These are all pieces to complete a whole.

Carl

[RScottFlyRods]

I believe Powell in perfecting his rods found substituting the cedar for the bamboo pith yielded a stronger rod. The next step was to hollow, which was easy to do with the cedar and it yielded dams of a stronger material. The cedar also worked with his double building two strips over the cedar core then resawing to the taper and then hollowing. These are all pieces to complete a whole.

Carl

Carl:

I see it quite differently.

Powell's Patent Letter states:

"Occasionally a cane is found with a thin rind of very dense fibers that break off suddenly into pith. This latter form of growth gives the desired results as to a combination of strength and great lightness, but such canes are so few that they cannot be depended on as a source of supply for the manufacture of fishing rods. I have therefore reconstructed the bamboo so that I obtain artificially, and in any quantity, rods having a combination of strength and lightness substantially equivalent to that found in the last mentioned type of bamboo."

He obviously thought the pith to be a good thing -- it being light made it desirable. The outer thin rind of dense fibers provided the strength. He was NOT trying to add strength by adding a stronger inner material -- he was trying to find something that was light knowing that the outer rind provided adequate strength. The fact that modern graphite rods are completely hollow support this position. The addition of a light weight material on the inside of a bamboo rod provides a means of obtaining adequate gluing surfaces but in an by itself it provides little additional strength.

Ron

[bluesjay]

Hi Guys, What about Hexagraph rods? I alays thought it was interesting, though NOT bamboo. There are double built rods, I'm thinking of the South Bend double builts, but there are others. The topic on surf rod tapers didn't, for me, turn up anything but Herters', but it seems like there should be something in the Herter's tapers, but no....

Jay Edwards

[mrampant]

I am assuming the purpose of double building is to achieve a greater wall thickness of power fibers; dense power fibers. this will also give a greater weight, unavoidable. Maximizing the dense power fibers by thinning the outer layer of the bamboo and repeating this should give a wall thickness of a size to use for the heavy rods. The only issue is with the larger diameter the rounder the outer face.
The question is how thick does the wall need to be to achieve a 13wt rod? Strength can be increased by increasing the diameter of the rod and allowing a relatively thinner wall (hollowing). The trade off to the larger diameter and thin wall is lack of hoop strength or ovaling of the profile, maybe the best outcome is to use the "Clover Leaf" profile from Mduval's ""Different profile" thread.
Any thoughts? I would be interested on what Mduval's thoughts were on this as he has made this type of rod maybe compared the hollow hex profile to the clover with the same size of wall thickness.
Cheers,
Mark