What is the different in grades of Bamboo and Carbon?

[ken denton]

As a buyer of tradional bows,I am wondering what the difference is in Bamboo used in the limbs. I know there is tempered,tonkin,actionboo, and some others.I read some noted bowyer said that only actionboo was consistant and some of the others had more elasticicy than others.I notice that a lot of major bowyers use actionboo!Can anyone help me understand Bamboo?     Also does Carbon have different grades like Bamboo? I know there is a Natural and a tempered actionboo! Thanks, Ken

[John Havard]

Ken, you'll probably get some other opinions and input but FWIW here's mine:  bamboo is a wonderful core material but it can vary a lot too.  Over the years I have determined the mass weight per unit volume of quite a few samples of bamboo.  Depending on whether you have mostly power fibers or mostly pith you can find bamboo lams that weigh almost 250 grains per cubic inch (very similar to osage) all the way down to 125 grains per cubic inch.  How dry the bamboo sample is certainly impacts these values.  Actionboo weighs a very consistent 145 grains per cubic inch.  Neither material makes a perfect lamination but both have their pluses and minuses.

I know very little about other bamboos such as Tonkin bamboo.  Hopefully someone more knowledgeable than I am can chime in.  True Tonkin bamboo grows in such small diameters that it is not useable for making bow laminations.  It's great for fly rods. But if the largest diameter is perhaps 1.5"-2" then it cannot be turned into laminations that are wide enough for bows.  

There are as many variations on carbon laminations as you can possibly imagine.  Everything from all uni-directional (longitudinally aligned with the long axis of the limb) to multi-layered with offset bias plys.  With layers that are not aligned with the axis of the limb you only get the longitudinal vector of the carbon when determining the stiffness per unit thickness.  In other words, it's entirely possible to make a carbon lamination that's not any more stiff than fiberglass.  And since a carbon lamination weighs almost as much as a fiberglass lamination some people have correctly concluded that (using those wimpy carbon laminations in certain bow designs) carbon adds very little performance.  On the other hand, if a bow is designed around the use of carbon and if top-quality carbon is used in that bow, it can add a material amount to a bow's performance over fiberglass.  The right carbon must be used in a bow design that's developed from scratch to make the most of carbon for that to happen.  

Another thing to remember is that a carbon lamination is a combination of carbon fibers (or hairs) held together with (typically)some type of epoxy resin.  You can have the best carbon fibers in the world but if the resin system is too flexible or too stiff or present in a less-than-optimum percentage of the total weight (or volume) of the finished lamination, then utility of the lamination for use in a bow may be diminished by any non-optimal parameter.

[ken denton]

John, thanks for the excellent info!Anyone else?

[woodenwonder]

Since Tonkin bamboo is small diameter, I've always wondered if it could be cut into strips and glued flat to make a wide enough backing. Any thoughs from anyone on that?

[Java Man]

Woodenwonder,

Jack Harrison talked about that in his book.  Said something like it would cost a couple hundred $ or more per bow, just to make the laminations.  Might have been more than that.  

Hard to beat actionboo.

[Foxtail]

Two of the most knowledgeable people in the world who know about the use of carbon in limb technology are Sid from Border, and Arvid from Black Swan. You can find a number of conversations on the use of carbon on one of the other trad friendly sites, and also check the Border Forum at Archery Interchange- all good stuff!

[snag]

Woodenwonder, I think it is possible to do as you suggest. You would have to have like material weight and density so the flex and strength were equal.  They do this for making spruce soundboards in pianos. If you know anything about piano construction you know that the board is crowned like the back of a violin. Then on the other side is the 250+ strings pushing against this crown. The glue joints are stronger than the wood itself. Yeah, I would think it would be possible to lay them out and glue them side by side.

[ken denton]

Anyone know the diff. in Tempered Actionboo and Natural Actionboo?