qestion aboute asiatic bow...

[akila]

HI....i know aboute Atarn forum...thats the place where i find themm talking aboute the good properties of bamboo, used for the belly of the bow..they warr saying that its better thenn most woods , for compresion... ..can you tell me plzz, how thick should be a siyah???thks a lot..

[tom sawyer]

Depends.  How long of a bow, what is draw length and how much poundage?  I made mine about 8" long and at a modest 30 degree angle.  They were about in inch deep, and about 1/2" wide.  At the joint I went from 1/2"x1" to 1"x1/2" and cut my v out of that.  Then I shaped the front to blend in from the wide/skinny to thin/deep.

[Bowclan]

Hey Tom,

I like that bow in your pics, simple design but looks good. Would you mind giving the deminsions?

Core lenght, width of limbs and pound pull etc

Thanks
Terry B.

[tom sawyer]

I should say right off that the bow deteriorated after a lot of shooting, the tiller is off now and needs to be rebalanced.  I basically fudged in a few areas and I think it came back to bite me.  Also, I initially shot it at 70lb and then worked it down to just over 60lb but this is probably still too much for the design.  I was just playing with it though, it was a first attempt.

Going from memory since I'm at work.  The bow is 48", limbs are about 1.5" wide.  Core is a flattened strip of bamboo (for low mass) that was about 36" long and maybe 1/4" thick (too thick as it turns out).  Roughly 8" siyahs and I did a 4" v-splice.  I glued horn on the belly and laid a thick layer of sinew on the back, sinew covered the splice and I wrapped sinew around the splice and the handle piece area.

If I did it again, I'd make the core quite a bit thinner.  I had to remove a fair amount of the horn to get the weight even down as much as it was.  I feel like the limbs were not too short, had they been making 50lb I believe the bow would have been fine.  I also should have used longer horn strips so they would cover the belly side of the siyah splice and butt against each other at the handle.  Mine didn't and I used wood in those places to reinforce things.  I used resorcinol for the horn/core bond, that worked well. 

http://groups.msn.com/LenniesBowPage/abcwannabes.msnw?Page=1

[akila]

Tom...i wass looking at your siyahs, and i notest that at the base, where you make the V splice , they are a little bit wider and thicker,,,can you plz. tell me how thick and wide should be a siyah at the base( where i make that V shape)....and btw. ....the bamboo bow is realy nice...so simple and perfect...how did you make it??? did you glue a fiew strips of bamboo together? or....? today i started to make the bow....i have started to straighten a little a hornbeam stave that i have...it wass a little twist, but nothing sever....ohhh...all most forgot??? how wide shoud be the tip of the bow, so that i can make the  V shape for the siyah to glue ..?thks a lot...

[Bowclan]

Thanks Tom.

[Far East Archer]

Hello Akila!
I don't know how ash and locust work and perform but I do know about bamboo. I know a lot of people think bamboo is not good in compression and very good in tension, but this is not 100% true. Bamboo is in fact very good in compression also, and I believe it is the closest "wood" comparable to horn. You could say," well ipe is closer because its stronger in compression than bamboo." True, but bamboo is more elastic than ipe and it is lighter than both materials. I think a close second would be yew but I've never worked with yew so I cannot compare. Yes, bamboo takes set, but if it is heat treated well and is good quality it takes considerably less set and holds its shape much better. I have made some "experiment" bows with C shape unstrung profiles and they did not break. Actually, the ones that broke, broke on the back before they broke on the belly and I think its because I didn't use sinew, which is a better backing than wood. Also, Some Korean horn bows were made with bamboo as the belly in place of horn and these bows still had about half-circle reflex in them. So, If you can get a hold of some good bamboo I'd try it out and you just might get a good bow, if not you can always try another as bamboo is considerably cheaper than horn and much more available. Good luck mate!

-Alex

[tom sawyer]

The other bow is a short bendy handle bamboo-backed osage bow.  Single strip of bamboo glued on an osage belly slat.

Alex, I don't deny that bamboo is decent in compression.  The widespread use of bamboo flooring boards as belly slats in backed bows, is a testimony to this fact.  I have worked with it myself and gotten good results.  Good bamboo isn't a lot lighter than several hardwoods.  I simply don't think it is any better than other woods, and probably not comparable to the best compression woods like osage or ipe.  If you have access to bamboo but not these other woods, then by all means it will make a good belly.

[Far East Archer]

Sorry, but I just want to make something clear. When you talk of bamboo do you mean these flooring slates or boards of bamboo as a belly material? If so, this is not what I meant as bamboo for belly, this is actually not good at all to me unless adding lots of reflex since these boards are mostly made from the inner, less dense part of the bamboo and not the wood right under the skin which is very dense. I have made bows with this material and was disappointed with the results until I knew it needed to be made with more reflex to counter the set. What I mean is to use the dense wood under the skin of raw bamboo as the belly, this way it takes very little set when heat treated correctly. The only reason I think bamboo is better than strong compression woods like osage and ipe is because its not as stiff but still has the compressive strength needed in these high stress designs and I think its advantage against horn is that its lighter. Stiff material like ipe just does not work well in these designs, it needs to be like horn, very flexible but also good in compression, thats why I think yew might be a good material as well. Osage might work, but I think because of its stiffness it would become too thin and chrysal unless the bow was made longer to compensate for this, same for ipe.

BTW Lennie, I would pick osage over bamboo every time if you mean using it as a self Asiatic bow,but as just a belly lamination for a short working limb Turk/Korean bow I'd have to go with the boo. This thread is about making it out of one piece of wood though so, I'd have to agree to you.

-Alex

[tom sawyer]

Alex, I was talking about using raw bamboo as a belly, as I think you were advocating.  I just used the flooring material as an example.  I'd agree that they have to flatten the boo first, and probably do plane off some of the best performing material that way.  It still has decent properties.

I am not that familiar with raw bamboo as a belly material, so I defer to your experience.  I was just going by its density which I have some experience with, as well as its structure of having the large bundles of fibers running its length.  The fibers do get smaller and more concentrated close to the surface.  I just don't see how they contribute to compression properties but they certainly might just by being solid and not having a great deal of pore space.  I also agree that bamboo can bend a long way when it is thin, so can some woods.  I don't know how elastic bamboo is relative to wood, I thought its utility as a backing came from the fact that it stretches less than wood in that application.  When you add a bamboo backing, you put most of the belly wood in compression.  Maybe this strength in tension is apart from its elasticity though.  Interesting stuff to ponder.  I have quite a bit of bamboo, maybe I'll have to give it a try as belly wood.  I've admired people's all-bamboo bows made from raw bamboo.  You have to get your tapers good though since there is only the opportunity to tiller from trhe sides after glueup.

[akila]

Hi...i have finaly make my decision...and i  use a ash board...i already cut the board, and its  66" long, i have cut the  V  shape( its 4" long), and the piece its 1,2" wide, and 2cm thick.The siyahs i made them 8" long, and i cut the V shape at 30 degrees angle.The siyah are a little bit thicker right now, but i will make themm tinner after i glue themm in place.I dont realy now how much to taper the belly.Right now its 2cm thick the hall length of the wood.I dont want to make a verry heavy bow...25# would be nice...the only problem is that my draw lenght it 29"..so i realy hope that  the belly of the bow will not chrisall.I think that i have sinew to put 3 layers on the back of the bow....you think its enugh???/, and do you think that i should have cut the wood a little more wider???...the wood is 1,2" wide , the hall lenght..

[tom sawyer]

It will be a pretty long bow, so it won't bend very hard that way which should help protect the belly from chrysalling.  And since it won't be bending hard, it will take more wood to make a given weight.

All I can say is, try this one and see how it goes, then use your experience in subsequent attempts.

[Badger]

It will be difficult to make such a low draw weight bow efficient with those syhas. They will just be too heavy on a 66" long 25# bow. If I were going to add sinew and syhas I would likley reduce the length to no more than about 56". Steve

[akila]

Hi guys...i wass just comming to say  that the bow  it seams to me to long right now.. all most 2 meters(80" )...so whenn i came to the computer, i just find your replays on me..so your right..its realy to long...o man...and i just work 2 hours to mate  the siyahs on the V shape..sanding and all the stuff.. ....how long do you think it should be with the siyah and all???

Here is the bow with the siyah just fixed a little to the wood( not glue yet)...the siyah will not remain so thick..i will reduce themm later...

[tom sawyer]

Looks like you did a pretty good job with the siyahs.  You might just make the bow without sinew and see how it performs.  Or you could cut it in half, reduce the length and resplice it together in the center with a z- or w-splice.  I'm with Badger, something under 60" (including the siyahs) would be better.