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Light fast rods = "brittle" rods?
Posted by: George Hancock (---.lightspeed.hstntx.sbcglobal.net)
Date: October 11, 2010 04:34PM

Hello,
I posted the following to another flyfishing site, and one of the replies said, "Ask Tom Kirkman @ [rodbuilding.org]. This topic would be right up his alley." So, here it is:
I have a beautiful custom-made rod on a Sage Z-axis blank, 5 weight, 4 piece. I was roll-casting with it, perhaps 25 to 30 feet of line off the reel, 5 weight floating weight forward line, a size 10 or 12 light weight floating fly on the tippet. As I roll-cast forward, the distal (the smallest) piece of the rod snapped completely in two, about 2 inches above the ferrule.
The rod maker has a "You break it, I repair it" policy, and when I phoned him to tell him about it, he said he was convinced a lot of breakage of light weight rods was due to rough handling of the package containing the rod during shipping, i.e., the rod would be cracked or etc. during shipping and then the strain on the rod during fishing would complete the job.
Which got me to wondering (always weird, sometimes dangerous). In order to make the rod as light as possible, the rods are made with thinner walls, and if it is a fast rod, then would that make the rod more "brittle"? So would a fast light rod (like the Sage Z-axis or Orvis Helios tip flex, etc.) be more apt to snap than a heavier medium or medium flex rod? Or am I a million miles off the mark? What do you engineers out there think? Just wondering.
Another thought: maybe if a more durable or sturdy rod is desired rather than an obsession with lightness, what rod blanks would any of your readers suggest (especially if looking for a medium or medium-fast action)?
Many thanks to any who have an opinion or suggestion.

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Re: Light fast rods = "brittle" rods?
Posted by: Andrew Metzger (199.117.182.---)
Date: October 11, 2010 04:43PM

I'm not so sure I buy the broke in shipping statements....that sounds like a manufacturer defect or a builder roughing the blank(flag on the play) during the build.....someone can correct me if I'm wrong.

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Re: Light fast rods = "brittle" rods?
Posted by: Tom Kirkman (Moderator)
Date: October 11, 2010 04:50PM

No, they are not more "brittle" but they are less substantial. I would suggest you read the article in RodMaker Volume 12 #6 that addressed the issue of rod failure and how to identify the various causes. There are any number of reasons your rod may have failed. Some tell-tale signs generally lurk in the broken ends. It would be impossible to offer a cause for the breakage without seeing the actual break.

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Re: Light fast rods = "brittle" rods?
Posted by: tony ertola (---.dyn.optonline.net)
Date: October 11, 2010 04:55PM

It shouldn't have broke. Had to be a defect or damaged. Get it fixed and it will not likely happen again with reasonable care in handling. Anything more durable isn't going to cast like a z-axis.

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Re: Light fast rods = "brittle" rods?
Posted by: George Hancock (---.lightspeed.hstntx.sbcglobal.net)
Date: October 11, 2010 05:53PM

Ahhh. There is the question. What is "reasonable care in handling"? Unfortunately, I'm not the best caster in the world, and although I haven't done it yet, I can easily imagine myself accidentally whacking the rod with a misplaced clouser or similar weighted fly, which I have been told will do bad things to a rod, weakening the wall and acting as a "starter" for a broken rod.
Thanks to all for the ideas. Anyone else want to chime in?

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Re: Light fast rods = "brittle" rods?
Posted by: Duane Richards (---.ronkva.east.verizon.net)
Date: October 11, 2010 06:16PM

George,

All it takes on a high end rod is one nice little dent in the graphite. Failure will come later.

DR

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Re: Light fast rods = "brittle" rods?
Posted by: Russell Brunt (---.fort-lauderdale-04rh15-16rt.fl.dial-access.att.net)
Date: October 11, 2010 06:21PM

Would reasonable care (and usage) for an off road truck be the same as a high end euro street machine? What would be right for one would be abusive for the other.

I have lots of friends I'd consider building something for. They are nice guys that share the same passion. Then I take one look at how they strore, fish, and handle their rods.

Russ in Hollywood, FL.

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Re: Light fast rods = "brittle" rods?
Posted by: Eugene Moore (---.244.219.153.Dial1.StLouis1.Level3.net)
Date: October 11, 2010 08:53PM

Genarally I've seen many more "cheap" blanks failed than expensive blanks.
All blanks are subject to abuse if they are in fact being fished.
I've had reasonably priced blanks take years of abuse from novice casters. My self included.
We all learn over time. My 8'6" 5 weight has been dinged many times with weighted flys by numerous rookies, and at 20 years old still hasn't failed. I do store my rods in a rod sock and case between outings.
Maybe you did have shipping damage, maybe a weighted nymph caught the wrong place, maybe a cheaper rod would have withstood the damage, maybe not. An infinite number of possibilities.
A more durable rod is also heavier and less enjoyable to fish. They to are subject to failure but more likely require a higher level of impact. Performance does come with some penalty. Stiffer materials due tend to be more brittle. Lighter weights mean thinner walls and greater damage potential due to contact stress. Higher rod tip velocity creates more potential for increased impact damage. Higher line velocity allows tighter loops which reduce margin for error as the fly passes the rod.
Sage has a very high standing in fly rod construction and your failure is more the exception than the rule.
If you require a more durable rod you can switch back to "glass". You may also choose a thicker walled and heavier IM6 blank. You will also have to give back some of the performance you may have acquired.

Eugene Moore

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Re: Light fast rods = "brittle" rods?
Posted by: Bob Balcombe (---.rb.gh.centurytel.net)
Date: October 12, 2010 03:51PM

First of all the only party that can determine the cause of the breakage is Sage. Many things that are not obvious to the average cast can cause a breakage. From carrying a unprotected rod in a gun rack in the back of a Pick Up. just dropping, a hook scratch. manufacture defect an of course the designer/builder could have nick it there is always a situation of having a bad guide prep. but these issues can only be addressed by the builder or the manufacture

Good Wraps Bob

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Re: Light fast rods = "brittle" rods?
Posted by: Emory Harry (---.hsd1.wa.comcast.net)
Date: October 12, 2010 07:33PM

Eugene,
I agree with your post but there are a couple of things that I would add. Higher modulus material is more brittle. It is due to the material itself having a lower strain energy but about the same tensile and compression strength. And also due to the fact that less material for a given stiffness is required with a higher modulus material. I know that you are an mechanical engineer but if you have forgotten strain energy is the area under the stress/ strain curve. Blank manufactures partly offset the loss in strain enery and lower wall thickness for a given blank stiffness by reducing the blanks diameter to increse the stiffness and this also increases the hoop strength but incresing the wall thickness adds mass and unfortuntely when wall thickness is increased the mass increases faster than the stiffness increases. But you use the high modulus material to increase the stiffness and reduce the mass. In other words there is no free lunch.
There is one other issue. Roger said that his rod broke a couple of inches above the ferrule. Though Tom does not agree with this there is a well know phenomina called "stress concentration" that increases the stress where there is an increase in stiffness in a tubular of conical structure. They are much better now than they were in the past but blanks have a slight stiffening in the area of the ferrule that usually starts just in front of the ferrule due to the additional material used to strengthen the blanks ferrule. This slight stiffening results is a slight increase or concentration of stress and will therfore result in the blank being slightly more susceptical to breakage in the area a few inches in front of the ferrule. Anyone that does not believe this can flex a blank, it is easiest to see with a long two piece, and carefully look for the stiffness in the blanks natural curve to increase slightly in the area of the ferrule.

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Re: Light fast rods = "brittle" rods?
Posted by: Tom Kirkman (Moderator)
Date: October 12, 2010 07:58PM

I do agree - it's a matter of fact. But rods are designed to withstand such stress (if they're not, you have a very poor rod design) and the better ferrules are designed to minimize this stress (if they're not, you have a very poor ferrule design). This isn't something that any competent designer can't overcome.

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Re: Light fast rods = "brittle" rods?
Posted by: Emory Harry (---.hsd1.wa.comcast.net)
Date: October 12, 2010 09:20PM

Rods are not designed "to withstand such stress" they are only designed to minumize the effect. I agree that a competent designer can minimize but cannot eliminate it.
Every rod builder that builds a significant number of rods gets a few back that were over stressed and broke a few inches in front of the ferrule due to stress concentration.

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Re: Light fast rods = "brittle" rods?
Posted by: Tom Kirkman (Moderator)
Date: October 12, 2010 09:48PM

If they're breaking due to stress concentration in front of the ferrule - they're junk. I've built many ferrules in my time and those rods which employed them have never failed in front of the ferrule due to stress concentration. Nor will they. Not unless they're improperly used.

During the rod breakages performed for the article on rod failure causes, we broke 40 multi-piece rods (St. Croix and North Fork) by deadlifting them to failure. Not a single one broke anywhere near the ferrules. All broke within 2 feet of the butt end.

The idea that multi-piece rods are in any way problematic due to stress concentration in front of the ferrule is simply not in any way true. It's a non-issue. And George's rod most definitely did not break due to such stress in front of the ferrule - Jerry does a better design job than that.

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Re: Light fast rods = "brittle" rods?
Posted by: Emory Harry (---.hsd1.wa.comcast.net)
Date: October 12, 2010 11:38PM

Tom,
When I read your article about all of the blanks that you broke I remember thinking that it was a very limited experiment and I was not sure that it proved very much. I am quite confident because you say they all broke near the butt of the blank that you were mounting them all so that the angle between the load and the butt of the blank was 90 degrees or not much less than 90 degrees. In this case I would agree that most blanks would break close to the butt because this would put the maximun stress on the blank down near the butt. Where a rod breaks is very much a function of this angle. If you would have varied this angle and lifted the tip of the blank up so that the angle was higher, which is the case the way most rods are normally used, the maximun stress point and the breakages would have moved up toward the rod tip with this increased angle.
There will be a lot of heavy boat rods that will break toward the butt of the rod just as with your testing because of the way they are used and the typical angle between the load and the butt of the rod. However, most other types of rods when over stressed will break in the tip section. And I am referring to rods that are over stressed but otherwise properly used, not increasing the angle so as to high stick the rod. Many will break just in front of the ferrule if the angle is about right. With a well designed ferrule the stress concentration will be small. And though it may be small it does exist and increses in the area just in front of the ferrule which will result in more breakage in this area.

If you remember five or six years ago I corresponded with you about breaking, as I remember, 30 or 40 blanks that cost me nothing. I could make the blank break anywhere along the blanks length that I wanted it to break by varing the angle between the load and the butt of the blank. By the way the blanks I used were from one of the best known and highly thought of manufacturers in the world. They were not junk as you suggest. In fact, I get a few rods back that are made from Lamiglas, Rainshadow and I used to get a few back from Loomis that were broken just in front ot the ferrule. I do not get a lot back broken in front of the ferrule but I get back a lot more that are broken in the tip section than are broken near the butt.

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Re: Light fast rods = "brittle" rods?
Posted by: Tom Kirkman (Moderator)
Date: October 13, 2010 09:41AM

Emory,

What you say is just not the norm for multi-piece rods. They are not prone to failure due to the ferrule.

Plenty of rods break in the tip area, both multi-piece and single-piece models. It's rarely a question of the ferrule - it's much more a question of improper use that overloads a section of the blank not designed to handle that amount of load. The article covered all that. Most of the time when you high stick a blank the break will occur just behind the apex of the curve. This holds true whether the rod is a multi-piece or a one-piece model. Most likely the multi-piece rods you had returned would have broken in exactly the same place even if they had been one-piece models. You're seeing a ferrule and deciding that it must be the problem, when in reality the rods broke where they did because of an overload in that area.


...............

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Re: Light fast rods = "brittle" rods?
Posted by: Bill Napier (---.208.88.219.rdns.vpslime.com)
Date: October 13, 2010 09:48AM

This is an interesting conversation.I have a lot of older rods and some newer bamboo models that all have stiff metal ferrules. I would think these would be the world's worst when it came to having a bad situation just in front or even to the rear of these stiff metal ferrules. But none of mine, knock on wood, have ever broken. In fact going back to my younger days when all two piece rods had stiff metal ferrules I can't recall ever seeing one break right at the edge of the ferrule. Maybe this is due to the heavy glass construction. And maybe bamboo is a different animal altogether?

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Re: Light fast rods = "brittle" rods?
Posted by: Tom Kirkman (Moderator)
Date: October 13, 2010 10:25AM

Putting a stiff, nearly rigid metal ferrule into a rod blank creates about the worst situation you can possibly have. But it was done that way early on for lack of a better method.

The rods that metal ferrules were most often used on were pretty substantial. The beefy construction of those rods can handle the stress concentration created by that sudden and quite radical change in characteristics. But if you were to take one of those same metal ferrules and install it into a modern, high modulus, thin wall graphite blank, the outcome would likely be much different. In that case the ferrule could certainly be problematic.


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