There have been several threads on the board lately about "composite" and multi modulus blank construction. After reading and trying desperately to put the information in a context that I can deal with in order to build a better rod, the following is bothering me.

About two years ago, a large commercial builder was almost wiped out when he released a rod that experienced an extremely high failure rate due to snapping of blanks in the lower section. The failure rate was almost 40% in a very short time. The story that hit the street was that they got a bad batch of blanks. At the time I had never thought about multi modulus and wonder if this had an effect. The following is an oversimplification but I hope that the thought process is not flawed.

1. I get returned bass casting rods that have snapped in front of the first double foot guide, normally a high V frame 12. The fishermen usually say something to the effect that the thing broke when I set the hook - usually Power Pro.

2. I don't have any real concept of how the blank was made and if there is a prepeg flag transition of different fibers in the area of failure or not. I am wondering if a custom builder needs more information on the construction of blanks such as the limits of fiber changes along the length of the blank.

3. The blank manufacturer has no idea of what kind of influence on the rigidity of the blank a builder adds to the blank with guide frame, thread and finish or the specific location of where these items are placed on the blank in relation to the fiber material changes within the blank.

4. I do know for a fact that the principles described by Ralph Oquin are valid when you repair a broken rod. The one that describes that internal posts need to be of a lower modulus that the original blank is mandatory if you want the repair to last. If this is violated the repair will quickly fail just above the bad splice.

5. Could the rigidity of guide frame coupled with the modulus transitions within the blank have a lot to do with the type of failure noted. When double foot guides are used there are a number of "flats" on the blank exterior that could influence the deflection profile.

6. If a blank designer sets up a blank for specific purposes with modulus changes should he also offer some advice as to the placement of things that will alter the applied forces. It may be that conventional guide spacing techniques need to be altered on multi modulus blanks.

Gon Fishn

Bill,
You make a couple of very good points. However, the wraps and epoxy materials tend to be plastic rather then elastic so they are not going to have a significant effect on either the stiffness or the hoop strength. As you probably know being plastic means that for small stress the strain will be high or in other words as you apply a force to them they tend to give or deform rather than resist the force. The guides though can tend to create areas on the rod that are stiffer so the stress will tend to be higher mainly just in front of the guide feet.

Actually all blanks are muti-modulus because the modulus of the scrim is different than the modulus of the fibers that run relatively straight up the blank. The spots on the blank where the flags of prepreg begin and stop will tend to create steps or transitions in the stiffness which may be where many rods tend to break. Also if, as you point out, multi-modulus graphite fibers that run straight up the blank are used where the different modulus fibers begin and end will tend to create steps or transisitions in the stiffness and toughness. Because the blank manufacturers, at least the ones that I am familiar with, use the higher modulus material toward the butt and the lower modulus toward the tip so the problem from this stand point is not as bad as it would be if the opposite were the case, because the tougher fibers are used on the part of the rod where the higher stress and strain will be.

Is this one builder or is it 40% of that blank model that were failing regardless of builder? Ed

Nope, one commercial production level builder using signature blanks all from the same source.

Bill,

On your bass rods that have failed, your first #12 is the butt guide (on top) and it failed in front, meaning toward the reel side, correct? How about the commercial builder...guides on top or bottom?

I have a couple of other thoughts on the subject, but typically the area of greatest risk from stress due to guide placement would be directly between two adjacent guides.

mark