Hinges in a Bamboo Rod Taper

[Canewrap]

I saw a post where someone was assuring people that a certain taper did not have any hinges. I know what people are calling hinges. Does the average user understand what the concept of 'hinges' means? They're not bad.

[3creeks]

I think this might be the thread you're referring to. viewtopic.php?f=64&t=119475&hilit=Dickerson+hinge

I kind of understand the hinge concept but I will defer to those more knowledgeable to explain it. I have heard that the Sir D is a great roll caster due to the hinge in the taper. Coincidentally I just glued one up a few hours ago and I glued up a Dickerson 8013 yesterday.


Jeff

[Canewrap]

Ok, the question was a little leading. I purposely asked it that way to see if any rodmakers, besides myself, would weigh in. Hinges are simply a reduction in the rate of increase for a taper. A short (5 to 10 inch) section in a tip where the increase is less than the section in front of it and the section behind it, allows that part of the tip to flex sooner than the area behind, facilitating shorter casts to load sooner. This does not weaken the rod or affect how long a cast you can make. Likewise, a similar section in the butt allows a rollcast to form with less line out. Again, it doesn't weaken the rod, just allows a rod to be designed with a fast action and yet work well in close. Designed right, you likely won't feel it as a negative.

[PT48]

What about a hinge in a progressive action? Say half way along the tip section of a 7' 6" two piece rod. Will that prove to be a weak spot and a potential breaking point because it detracts from the ability of the full progressive action to absorb the pressure?

[Shrimpman]

I can't see hinges being at all positive. Most of them are pretty heavy, especially the brass ones, and the screws would definitely weaken the cane. I would just stick with ferrules.


Sorry, I couldn't resist. Things are getting squirrely in confinement!

[LeeO]

Hinge is probably not the best description. May taper transition? I would describe PHY tapers as “hingey”

[mer]

"Hinges are simply a reduction in the rate of increase for a taper."
Basically the opposite of a swell, no?

If the word offends or has negative connotations (like calling something parabolic or semi-parabolic), describe it differently. Lee has it right in my mind, call it a transition in the taper or just say "it's the taper".

I think hinge is better used in the context of doors (chapeau bas to Shrimpman) or making a self bow. Bowyers seem to see it as a discontinuity in the desired bend of the limb, which it is.

[Canewrap]

I agree completely, that the word has a negative connotation. I would love to find a way to rename that effect and while taper transition gets it partly right, it doesn't completely describe what is happening. Mer - uh, no it is not the opposite of a swell, that would be a regression. PT48, what you describe is exactly what I was talking about with how you get a tip to load better in short. It doesn't weaken the tip at all, since there is still an increase in the taper. It is a slowing of the taper increase over a short distance. I have to mull this over, since there has to be a better label to slap on this, so other rodmakers know what you're talking about.

Good one Shrimpman; first time I heard the term a lot of years ago I was like - what does a hinge have to do with a bamboo rod?

[quashnet]

I have measured a number of Paul H. Young rods inch by inch, often taking three cross-sectional measurements at each location. I have found that many of PHY's parabolic rods have a hinge just forward of the cork grip. It is consistently placed in that position, and is actually a regression in the taper.

The photo shows Bob Summers casting a nine-foot, parabolic Nymph Special that Paul H. Young built in 1949 for his best friend, Paul Cardell of Birmingham, Michigan. Note the overall slight S-curve in the shape of the rod. My interpretation is that we are seeing the "double action" (as PHY termed it) of a full parabolic fly rod. Near the grip, the cane is flexing with the parabolic "kick" created by the extremely flat butt section. The effect is further enhanced when a butt section is built with a "hinge," or a reduction of several thousandths-of-an-inch that begins about two inches forward of the grip, and extends for about three inches.



To the left of the photo, you can see that the tip section is about to catch up and form the loop of line that propels the fly to its target. Per Brandin once told me that these rods may feel slower in the hand, but due to the kick the tip actually moves faster and throws the line farther than you'd expect, with less perception of effort on the part of the caster. The deliberate casting stroke of the angler plus the kick of the hinge creates Young's "double action." Finding the appropriately deliberate, focused rhythm in any individual Young parabolic rod is key to speeding up the rod tip and benefiting from the rod's parabolic action. I'm not a rod builder, but that's what a "hinge" means to one who has studied Mr. Young's tapers. I have no problem with using the word "hinge" for this point at which the rod is designed to flex in a particular way.

[stoneflyer]

I find a hinge or flat spot when properly accounted for can be a performance-enhancing feature of a taper. The performance-enhancing feature will not be detected when lawn casting and certainly not while trying to hit a double haul out of the park. Rather it will be appreciated streamside with a lightbulb moment of "damn this thing can roll cast" or a "little flick of the wrist and my fly gets under the branch with ease."

I have built rods that had flat spots in the wrong position (or too severely flat) and it will make the rod a dud. One rod, in particular, will catapult a whole fly line while lawn casting. It really does catapult line and not cast it. Other than that feat, it will not do anything else with merit.

A step in a taper at the ferrule can be a good feature in my opinion. Not all tapers need them. To me, a step helps support the weight of the ferrules reducing the swing weight effect. It also pushes the action towards the tip while fishing in close. When casting further distances, the caster can modify their stroke to engage the power reserve in the butt section.

[Gnome]

Quash,

that is the same drop / hinge that is exhibited by the John Enright Castle Connell Trout rod that is in the GTRS and you literally can see the drop and it is in the same place as what you are describing. Further evidence that the parabolic did start at Castle Connell. And then was continued on by Enright and later by Charles Ritz and Paul Young. Good stuff!!!

Jeff

[quashnet]

I learned about the Castle Connell rods from you years ago, Jeff - in 2008! This thread on the early origins of parabolic rod action may be of interest to all.

[Jim Curlee]

A hinge in a self bow is a weak spot, that's because the material is thinner there than the material on both side's of the hinge.
This is a big no-no in the self-bow world.
Guaranteed she'll either break there, or take a major set.
If she's made from yew/juniper she will eventually blow-up, where as a bow made from a hardwood like osage, or hickory, will just take a set.

It might be different with a bamboo flyrod because you are not thinning/weakening the belly side, and you still have the power fibers to support the rod, but still can't believe it would help in the longevity of the rod, your just forcing all of the stress of bending into one small area.
To me the worst area to "put" a hinge would be at the handle.

Just a bow-builders, 2 cents.

Jim

[stoneflyer]

A hinge in a tip would look something like this, from tip top down:

.065", .075", .095", .112", .122", .138", .153"... The change of taper is
.010" , .020", .017", .010", .016", .015"

In tip sections, I would advise against putting a regression in the taper. In other words, the bamboo should always be getting thicker. What we are talking about is how much thicker it gets determines where and how it flexes, and whether or not it is a good or a bad thing. Your Bow example suggests that the taper slope becomes negative. I wouldn't like this in a tip section.

The .010" would represent a flattening of the taper and would promote more bending at that station when the rod is loaded. If .010" became .005" it would perform significantly differently and would obviously be weaker. Bamboo is a very strong material and can be pushed.

[Canewrap]

A hinge in a self bow is a weak spot, that's because the material is thinner there than the material on both side's of the hinge.
This is a big no-no in the self-bow world.
Guaranteed she'll either break there, or take a major set.
If she's made from yew/juniper she will eventually blow-up, where as a bow made from a hardwood like osage, or hickory, will just take a set.

It might be different with a bamboo flyrod because you are not thinning/weakening the belly side, and you still have the power fibers to support the rod, but still can't believe it would help in the longevity of the rod, your just forcing all of the stress of bending into one small area.
To me the worst area to "put" a hinge would be at the handle.

Just a bow-builders, 2 cents.

Jim

Jim, that's why when I modify a taper or design one I put the hinge at about 10 to 15 inches up from the grip. But, none-the-less you can't argue with the Young rods that have lasted for over 60 years with a hinge or even a regression that is not far up from the grip. IMHO, the stress distribution on a hex bamboo rod are quite a bit different than an archery bow. Also, sounds like a hinge in a bow is different than the hinge we're talking about. What you describe is more like a regression - with the material being thinner in that spot than on either side. A hinge in a bamboo rod is not thinner than the material in front of it, it just doesn't increase in thickness as fast as the material in front of it. A bamboo rodmaker that is using regressions in his taper has to be especially careful because it can result in a weak spot that will break, but it is also a useful design feature, just tricky to implement successfully.

[quashnet]

Jim: You are right that the hinge in a Young rod is an area that's a few thousandths of an inch thinner than the cane both before and behind. I believe that Paul H. Young was most concerned about the possible problem you raised in his 8'6" Parabolic 16 rod model. Young called it an "unusual" rod that "has the most line casting power per weight of bamboo of any rod in our line." In the catalog description, Young cautioned buyers that "the butt is only .305" in diameter. so we want you to hold the rod at not greater than 60 degrees to the strain when it is greatest." Not many Para 16s were built, and those few that I have measured are thicker everywhere in the butt than 0.305" cross-sectional, indicating that perhaps Young gave up some of the radically parabolic effect in exchange for less risk of breakage. I have fished some strongly parabolic Young rods like the Para 15 and the Driggs for many years, without babying them, and not had any problems. I will say, though, that when I find the right casting stroke for a parabolic rod, and the double action kicks in with a regular rhythm so that the rod itself seems to be doing all the work, then I find that I can often use a lighter-than-expected line weight with good immediate results and surely less risk of stress breakage at the hinge in the future. For example, I have a PHY Bob Doerr salmon rod. A previous owner marked on the tube that the rod takes a nine or ten-weight line - but it's an eight-weight rod if the caster doesn't force it, and just lets the rod shoot the line.

[mer]

Ok, maybe I'm being pendantic here, but Canewrap you said this:
"Hinges are simply a reduction in the rate of increase for a taper"

From what I've seen in actual rods,
a swell is very much an increase in the rate of increase for a taper.

Is not an "increase in the rate of increase for a taper" the opposite of a "reduction in the rate of increase for a taper"?

[PT48]

Very interesting and edifying discussion. No doubt that the great makers were able to deliberately build hinge points into their rods to effect a certain type of performance characteristic. In bad tapers I agree with you Jim, the hinge point takes too much pressure and eventually splinters or breaks - that has been my experience with one rod.

[Canewrap]

Mer, now I understand what you're thinking. A swell is not what I am referring to when I talk about a 'hinge'. A swell interrupts the flow of energy and is not something desirable when it's a sudden jump. But, I suppose a sudden increase in taper could be looked at as a hinge. That's why I am trying to come up with a different term for what I am talking about. There are useful swells, like a swelled butt that stops the action. Also, a gradual increase in taper halfway down the butt can expand the useful line weight range. But, it can be tricky to introduce a swell, since it can turn a good rod into a dog with just a few thousands of an inch.

No, what I am talking about is a flatter increase in the taper, which is pretty much the opposite of a swell.

[Don Andersen]

John Bokstrom and I pondered the hinge thing many years. John called these rods “butt swingers”.
I believe that the taper rather than growing towards the butt at 0.013”/5” of rod length, the droop may be 0.002” and I avoid a negative droop although I’ve seen some droops very close to 0.000”
I use a stable of Para 15’s for my lake fishing casting 5>7 weight lines. I found the tips tend to set about 25” off the tip. Mind you, these rods land a lot of 5+lb. fish each summer.
In Marinaro’s book in the Ring of the Rise, he details a double hinge effect over the ferrule section which appear very close to zero.

Don