Glass or carbon ??

[mikkekeswick]

So i've been thinking about experimenting with carbon lams in my limbs for a while now. I've done a bit of reading on the subject but am still a little unclear of what the best way to use them is!
So what are the pros and cons to their usage in different configurations in the limb
- Back and belly lams instead of glass
- Single layer in the core only
- Back and belly and one layer in the core.
Then what are the advantages/disadvantages of uni-directional versus 'normal' woven carbon?
Thanks

[Jon in North Idaho]

Not being rude -- this has been discussed in depth many times...  I think you might be best to do some searching.

If you go to the pirates of archery .net site, under the bowyers section there is a carbon info page that has more info available than I have seen anywhere else.  You have to sign up in order to access it, as it's hidden to non-members, but it is more than worth your time.  Hope that helps.

[monterey]

I ve not used carbon at all, but just speculating on the possible performance improvements, I don't see using it as core material would add much.  The very cores of our bows do so little work that it seems that it would only help if it served to reduce overall mass.  Maybe it does.  What is the mass comparison for an equal thickness of carbon as opposed to maple or elm?

[Al Dean]

I put it on the back under glass.  It increased the noise of my bow, probably won't use again.  I only used .020 but performance increase was negligible in my opinion.  Maybe .030 would do more.

[jsweka]

In Jack Harrison's book, he says to use it on the back to get the most out of it.  In the core doesn't add anything.

I've never used the stuff, so I really don't have any first hand knowledge.  

[canopyboy]

Now y'all know I'm the first to over-engineer something. But from an engineering perspective, a material like carbon (or even glass) shines in tension and compression -- especially tension. A bow limb has maximum tension on the back, compression on the belly, and neither in the middle. In the middle what you have is maximum shear. Composites really don't do anything wood can't in sheer and weigh more. I know a couple of bowyers who swear by the stability that a carbon or glass lam adds in the middle of the limb, but I just can't reconcile that. It does kinda look cool, but that's about it as far as I can tell.

I think I'd consider it on the back, maybe the belly if I was trying to get a bit more performance. But I haven't heard of many carbon bows that shoot that smooth (kinda along Al's experience), so I'm a bit hesitant to venture there.

BTW, the POA site does have some good carbon info. Thanks for the pointer! Interesting reading even if I don't have plans for it in the near future.

[Pago]

I have been working/learning with a bowyer of 40+ years. A lot of the things I have read about carbon or lack of performance of carbon never made sense to me.  He uses carbon in all his bows, uses precise repeatable methods and uses a scientific approach. I think he is getting min 10fps kick from the carbon based on force draw and crono. I have shot his bows and am convinced of the benefit when incorporated into a design harmoniously (for lack of a better  descriptor).

[Nezwin]

Originally posted by canopyboy:
Now y'all know I'm the first to over-engineer something. But from an engineering perspective, a material like carbon (or even glass) shines in tension and compression -- especially tension. A bow limb has maximum tension on the back, compression on the belly, and neither in the middle. In the middle what you have is maximum shear. Composites really don't do anything wood can't in sheer and weigh more. I know a couple of bowyers who swear by the stability that a carbon or glass lam adds in the middle of the limb, but I just can't reconcile that. It does kinda look cool, but that's about it as far as I can tell.

Precisely this, except neither glass or carbon do well in compression. But the resin between the weave does    :D

Carbon on the back would add a little performance, but not an enormous amount. Anywhere else on the bow and it's a waste of time & money.

As far as uni. vs. weave, the unidirectional would be the best way to go - no internal shears with the weave and you're only pulling in one direction anyway. For recurves there's a justification for weave (lateral stability) but a really well made bow shouldn't need it. And if you're using carbon, you'd want to be a good bowyer!

[Roy from Pa]

I've read where it makes the bow noisy compared to wood core lams.

[canopyboy]

Originally posted by Roy from Pa:
I've read where it makes the bow noisy compared to wood core lams.

You can read?

 

[Roy from Pa]

Remind me to smack ya the next time you stop to visit me..  

[fujimo]

     
 great way to start the day- with wet pants   :D

[Roy from Pa]

Front or back?
LMAO

[BigJim]

Carbon in the zero plane works for performance 45+-degree or 90 degree as in woven works for stability  and looks in the case over woven. 45 is slightly beneficial in performance.
Carbon on the back is easy enough but carbon on the belly must be backed with the proper core so the core doesn't colapse. Carbon in core unless just inside thin back glass and then it's insignificant.
A properly built carbon belly and back bow could experience 10fps gains. But is it really worth it for the extra money and then having to live with ugly limbs  
Bigjim

[Pago]

All of the bows I have played with have the carbon under black glass on the back of the bow except one.  How much carbon you use and how long the working limb is make a big difference. Too little carbon or too short of working limb with carbon are a waste imho. I have seen one experimental bow with the carbon under the belly glass but the verdict is still out on that one. I have been looking all over for some triaxial 0/-45/+45 to try but can't find any. My understanding is that Hoyt uses this.  I have found 0/-60/+60 if anyone is interested I will post a link.

[BigJim]

I stock the 0/ -45/+45 * +45/-45/0 carbon and when I use carbon, that is what I use.

I have been able to talk most everyone out of carbon...oh yeah, there may be a tad of advantage, but it is more with lightening the limb and reducing hand shock than it is with speed.
But then I find black limbs to be ugly so I cover with snakes.
BigJim

[Pago]

That is good to know thanks.  What are the dimensions of that carbon? Do I need to call/email to buy some? There is more about this bow making that I don't know vs that I do, so I defer to yourself Jim, and other more experienced bowyers.  That said, untill I determine why the hard data I'm seeing is so different I can't ignore it.

[mikkekeswick]

Some interesting points raised. Thanks for all your thoughts fellas.  
I'll do a bit of experimenting and see what I come up with.

[BigJim]

Hey, if everyone went off the word of a couple of guys, we would only have a couple of bows out there. Experimentation can be fun...and or disappointing. Just because it didn't work for me doesn't mean it won't work for you.

I never claimed I knew what I was doing anyway...or did I. that's the crappy thing about memory, I can only seem to remember It the way I want too.  

BigJim

BTW, the dimensions of my carbon is about .040 unsanded and available in 1.5" x 72 and 1.75" by 72.
thanks, bigjim

[Jean-Luc Streff]

I am with BigJim on the part where he says that "carbon is about reducing handshock and lightening the limbs". Nevertheless that lightening the limbs obviously contributes to increasing speed, as a matter of known facts.

I am practically never posting in forums, but on the topic of the use of carbon, I guess I have to. Because (except what Jim said in the context) I can't disagree more on what is usually said about the use of carbon.

First of all, it seems to me that people have used a single or a similar type of carbon which you can't compare to others. The carbon I use on my bows now is MUCH thinner (.20 and even .15) and it is either HD carbon or explicitly a hybrid material made from carbon and glass fibres. There are a few other types available, but the one I am referring to plus the othermaterial is apparently not available in the US in retail.

When people say it increases speed by 10 fps, they are probably just repeating what they have heard before.

When people say it is not worth the money, they are referring to retail prices that are incredibly high, compared to what better and more performant material is traded in large and larger quantities elsewhere. To give you an idea, 5 times less expensive or less.

From my experience, which really seems to be unique (if not ending up sounding surreal at the end), After having build a number of bows now using different kinds of carbon (as described), a bow that is build from glass laminate, seems to have a tremendous handshock compared to the bows I have build with combined carbon materials, including using "archery foam" of various types. The difference is that much, (no kidding) that I would not even shoot any bows that are not made using this type and combination of carbon, because the handshock is too obvious and apparent in comparison.

As for the gain of speed, 10 fps is underrated or too conservative at best. I am not giving any numbers here, because that would only create conflictual reactions and put me in trouble. I am just saying that the gain in speed is obviously related to the initial performance of a bow design and also depends on other materials (laminates) used in combination and would make more sense if using increase in percent. Also, using a number now - if a bow would reach a 170 fps instead of 160, you would not find it a big improvement, but 205, (with a gain of 15 fps) instead of 190, really makes a difference.

In conclusion, I would highly recommend to all those who are interested in using carbon, to investigate further about which material (carbon), you would use for the purpose, before drawing any conclusions, or settling with the credo I have read over and over again… leaving me with that smile… well you know what I mean.