Hi,
just received a Lamiglas FL904-3 blank and inspecting the female ferrules I noticed how thin the walls are - much much thinner than any of the graphite blanks I have seen - it looks very brittle to me.

Is fiberglass really so much stronger than graphite ?

I also noticed that on the end with the male spigot you can actually see how far into the blank the spigot is inserted - the blank is somewhat transparent - just an observation that I'm sure wont surprise most of you - I just found it to be interesting.

Thanks
Peter

Stronger? No, it's actually weaker. But you'd have to define those terms a bit more to make sure we're all speaking about the same strength attributes.

The blank and ferrules are fine. If they weren't, Lamiglas couldn't continue to make them and stay in business. And yes, the honey or gold colored glass blanks do pass light pretty well. They are somewhat translucent.

And keep in mind that the blank you mention is light line model - it's not expected to carry extremely high loads. What you have there is more than sufficient for what the blank designer intended that blank to do.

...........

Peter - whatever you do, do not forget to thread-wrap the outer barrel of both the female end AND the male end (with the spigot) of the ferrule before you start flexing the blank when joined. In fact, there is no reason not to wrap both these barrels before you even find the blank's spine. It is, of course, uncommon for an un-wrapped ferrule to fail under the moderate stressing of static-deflection and test-casting. But you don't want to discover thru carelessness just how common it can be, either !

Use a wrap that is at least as wide as the blank's diameter.
Up to two blank widths is often used.

My personal opinion is to use a wrap which extends beyond the depth of insertion of the spigot (internal plug) by about one-half to one-full blank diameter. This approach, I believe, provides reinforcement at the far & internal end of the ferrule. I believe Mr. Tom Kirkman has stated that the forward end of the ferrule is the only place where propagation of a split / failure can occur.

It is my opinion, however, that once the mouth of the ferrule is re-inforced by our user-applied wrap, that the NEXT structural location where a split-failure is likely to occur is where the next discontinuity in wall thickness and blank flexibilty-rigidity occurs. And that is at the far end of the ferrule, where the ferruled blank suddenly jumps from double-walled back to single-walled. Using a continuous thread wrap that starts at the forward end of the ferrule and extends out beyond the end of the inserted plug, up to one-full blank diameter, helps smooth out the abrupt change in the magnitude of flexibility in this overlap zone.
(How abrupt is that change in magnitude? I am unable to quantify it.)

Again, that's my postulation on the subject. While I did get as far as a course in Statics while in my undergraduate studies in Engineering, I did not get as far as a course in Strengths & Materials before adjusting my college major. But that view is sufficient to present the argument as I have just done.

There are, of course many rod builders who can unequivocally say that they have never had such a problem and that they use a wrap width of only one blank diameter and only use a wrap at the mouth of the female end(s) of the ferrule (both sides for a plug-spigot style, like Lamiglas). Amen.

I'm thinking more toward the extreme set of stress conditions and designing accordingly. And some would sigh, "Over-kill". But it does point out that there are a wide range of solutions to a problem within which stress to the point of failure is never reached. And within which
a builder can apply his (own) understanding of a satisfactory design and prove the quality of it's performance. And that's why we are all here at RodBuilding.Org.

Happy rod building & Merry Xmas! -Cliff Hall, Gainesville, FL-

Peter,
I think that the answer to your question about the relative strength of fiberglas and graphite is yes and no. I think that Tom is right that the modern graphite ferrules are a big improvement over the older glass ferrules and stronger in the sense that they are less likely to break but I think that most of this improvement is in the design rather than the material.
Glass is harder than graphite and less subject to being damaged by impact.
Glass is tougher than graphite or has higher strain energy. Graphite has roughly 4 times the modulus of elasticity of glass(depending upon which graphite and which glass) but when the modulus goes up the strain energy or toughness goes down in direct proportion to the increase in modulus. The tensile strength, where the two will give under tension, is in the same ball park.
Glass blanks are usually all glass while the vast majority of what we call graphite blanks are actually a combination of glass and graphite. Every other layer of material in most graphite blanks is called scrim and is glass. It is there mainly to increase the strength of the blank against shear and torsional stress, or increase the twist and crush strength.

I hope that helps to answer your question but is probably more than you really wanted to know.

Peter,
I just looked it up and I was wrong in the post above about the tensile strength of glass and graphite being in the same ball park. S Glass has about one half of the tensile strength of graphite, E glass is a little lower than S glass.

Peter, Emory and Tom are both correct in the information given. The one thing about an "E-Glass" or "S-Glass" material is that the fibers are not oriented in the same manner as the carbon fibers. Fiberglass is a woven cloth with approximately 30% of the fibers off axis which provides a greater degree of hoop strength that help to keep the parts from splitting at cut areas of the blank. I do however strongly recommend a ferrule wrap at the female ferrule and on the male end where the spigot exits the blank.

Todd

Hello everyone, Have just built a lamiglas GFW842M an didn't know the male end of the ferrule needed to be wrapped too. I do have a guide wrapped within a Quarter inch of the male end where it meets the female end of the ferrule, well this be close enought to support the male end?

thanks for your help, I just love this sight Steve.

Interesting about wrapping the male end of the ferrule. I've been doing that anyway to provide a "balanced look" to the rod (even when separated) and also so I can insert an alignment thread to mark where they sections should be joined to align the guides. Now I'll feel even better about having done that - Thanks Todd.

For the record: On page 33 of his book, "ROD-BUILDING GUIDE", Mr. Tom Kirkman says that he "settled on a formula that sets the wrap length at TWICE the outside diameter of the ferrule" at the female opening (or on BOTH sides of a spigot ferrule.) He continues, saying: "In almost 20 years, I have not had a single ferrule failure, and feel that this amount of re-inforcement is quite sufficient." Lots of other important advice is included in that section on page 33 for those wanting more.

Hi,
thanks for some interesting answers - I have wrapped spigot ferrules before and if I remember correctly, on both sections, I placed wraps near the edge and where the spigot ends inside the blank - I used to make the edge wrap first then spiral the thread to a half centimeter before the end of the spigot then make a wraps covering the end of the spigot extending about a half centimer beyond the end.
I questioned the wall thiknes - and I know that ist strong enough otherwise they would change the design - out of simple curiosity/amazement (?) - the walls are very thin I think.

But I got some good replies about the strength of fiberglass - thank you.


Peter