Lee - Very informative thread.

For me, speed, w/i reason, is merely a number on paper. As long as my site picture remains unchanged out to 25 yards, I am satisfied.

My current and previous high end carbon long bows have performed equally or slightly better than my high end curves and equal to a previous high end carbon curve.

I certainly welcome the fact that these fast bows permit me to further optimize my personal arrow design.

Ive wonder if anyone has tried to build a carbon limb thats tubular?
All this compression and tension stuff.I would think a tubular design would give very good results.
Anyone!!!

Laurent yuor tests do not count since you are left handed.

Lee, If you build double carbons in the manner you are talking about you will blow the belly lam off. Carbon does not compress. When building double carbons I go 10 thousands lighter on the belly than on the back. I then trap the back to level the forces out and bring my negative plane to the center of the coreor preferably to me slightly below the core center.
Thse  cmpression forces cause the lam that is next to the belly carbon to literally explode . Glass on the other hand compresses more than carbon so it is not as major a deal but Technicaly the principal is still in play and that is that the belly should be slightly weaker than the back of the bow or equal to it. Thats my story and I'm sticking to it LOL.

God bless you all, Steve

Very informative post, thanks. Lee I sent you a pm.

I think it would be great to have a warehouse of comparable data, that not only includes materials and designs, but also bowyers experience so we could track their "curve" as their experience progresses. Maybe some of those speed deifferences could be measured as an experience difference?

Sixby, I don't make a double carbon. I only use carbon on the back and it too is then covered with 0.030" of ULZ (S-glass). I have heard a few bowyers had some problems with double carbon bows failing when carbon was on the belly. Gary Sentman taught me to only use it on the back as a tension material after speaking with Gordan glass. I have an idea that I want to experiment with at a later date (time permitting) with a double carbon bow, but I don't have the time right now.

The example I gave above could easily be misunderstood as to imply any material could be used on the belly...and that wasn't my intention. Thanks for bringing that up.

What I wanted to emphasize was an awareness of compression and tension forces and strength of the materials used as I believe the stats on the materials can tell use what is the best way to trap a limb.

Lee,
I got a Fredrick longbow that has 5 boo lams sandwhiched between very thin glass.Very agressively trapped for the back.
My question is?
Can one replace the glass and center boo core w/ carbon?So you would end up w/ 4 boo lams and 3 carbon lams.

I would keep glass on the exterior surfaces. Use carbon on the backside just underneith the glass on the back side. If the carbon is in the very center of the core, it doesn't utilize its tension strength...so I use it on the backside of the core.

If we look at the numbers, we see how the materials are best used...  http://www.gordoncomposites.com/products.htm

E-glass (ULS) - Tension strength of...152  /  compression strength of...111

S-glass (ULZ) - Tension strength of...243 / compression strength of...119

Carbon - Tension strength of...430  /  compression strength of...160

This is why I like to use the black S-glass over the carbon

I see Centaur has gone to a carbon/boo core w/ no glass(triple carbon limbs) as Chris Cox been building for that past couple years.
What makes their design different?

Last I heard, Chris was putting a VERY thin layer of wood and then glass over the carbon even in his triple carbon bows. I don't know the details on his methods, but I would say he and Jim are both excellent bowyers that produce state of the art quality.

I own a triple carbon Habu and there is no glass at all.He told me his finish is extremely durable and protects the bow.

I could have sworn that just about a year ago Chris told me he was using an extremely thin layer of glass in his triple carbon bows...very thin...so thin that he was putting a separate piece of wood on the belly at the string groove so he wouldn't have to file into the glass. He mentioned to me that he wasn't using fiberglass and that he wouldn't shoot a glass bow again, but in further conversation (IF I REMEMBER CORRECTLY ), he mentioned that "if we want to be technical about it"  that there was a still a very thin layer of glass covering the carbon in his bows. I want to say he said it was only 0.005" thick, which is so thin I don't know how someone could mill out glass that thin...but that is what I recall, but if anyone could do it I imagine Chris would be such a person. Maybe I am getting old and my memory is fading though. LOL. I hope I haven't misspoken on that issue.

I think the wood veneers in his bows are about 0.020-0.025", but I am not sure about that..but they are probably close to that regardless. I really can't say what he is doing because I don't really know.

I have owned a few of his bows and they shot very well (accurate and stable), but I did like his older Habu version bow over his newer Vyperkahn. Regardless...I do know Chris is a great bowyer and that he has made some of the nicest performing bows out there.

Gee thanks for making shooting a longbow complicated, lol

Very informative thread, I only understand about half of it but it may help to explain why I love longbows and never felt handicapped shooting one.

From D bows to R/D bows.....long live the Longbows.