Primitive Archer
Main Discussion Area => Bows => Topic started by: GraemeK on November 25, 2008, 02:53:17 am
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Hi All
Have for quite a while thought we might be using the bamboo on laminated wood bows the wrong way around so I decided to give it a go the other way . I realised that people were going to say it was back to front so I built it as a backwards bow.
It seems to prove that bamboo as a belly and Osage as the back works fine -- the bow has taken no set which has always been a problem the other way around.
The bow is 68" ntn and 48# @ 28"
Graeme
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Couple of extra photos
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Way to think out of the box :) Curious to see how this works in the long run.
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Me too....I tried a Backwards Hedge Bow once.....and the Handle Popped Off!!!
Nice Bow Graeme..........and please keep Us posted.....this will be most intereting to keep tabs on.....and watch it break-in
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Ooooo... that just looks so backwards, doesn't it? Can't argue with results, however. Way to think outside the box! Nice tiller.
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very interesting, and good looking. When it takes set, string it the other way around, and so on :D Nice workmanship.
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That is a neat idea. The bow looks really cool. I love the osage and boo combo.
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If that doesn't beat all. Good for you for thinking outside of the box. Looking forward to seeing how this one stacks >:D up for November Laminate Bow of the Month.
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Interesting. Did you temper the boo ? My brother and a few other guys have been making tri-lam boo backed and bellied bows for quite a while now with good success. So I guess its no suprise it works but I still think you'd be better off with the boo on the back. Bamboo isn't all that great in compression but its extremely tough in tension. Tempering the bamboo will help its compression property's though. ;)
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Interesting Idea. Pat
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COOL 8)
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Now that's different. I assume you pre-tillered that Osage slat before glue-up?
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Can you string it the other way too ;) ;)
Looks great.
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Cool looking bow... Are you sure you didn't just glue the tip overlays on the wrong side? >:D ;)
John
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Hi Guys
Its true that boo is not as strong in compression as tension but this is the same for most woods. I finally found some decent test data for boo that was done on wall sections not whole sticks and the result is that boo is as good in compression as most woods so I figured it was worth a try since the boo is so much stronger in tension than almost all woods that I get heaps of set unless I trap the back. So far I have no set and the bow is quite fast -- shoot 175 fps out of my shooting machine drawn 26 1/4" from the rear of the handle with 10 grains per pound.
The way I made it was to tiller the boo then glue on a osage slat about 3/16" with a taper to glue up the handle slope then re tiller the back which works fine since the osage has the grain on edge.
Graeme
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Good looking bow, but I can't get over how it looks like it's strung backwards! ;D As already said, you'll have to keep us posted to see how it's doing after a lot of shooting time. Congrats on accomplishing this design successfully!
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Thanks Greg
I think it should be fine in the long run, the only thing I think might happen is it may take set with a lot of use -- Graeme
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That's awesome, never woulda thunk it. :)
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Hi Hillbilly
It just goes to show you that a lot of what we think of as fact and set in stone is just our way of making the world seem safe and predictable.
I think of it like my experience with limb tips -- over time I have made them smaller and smaller and and now they seem to be scary small and I think it is just not possible to make them any smaller but the fact is that I have never had one break so so they must still be strong enough but I just can not bring my self to make them thinner than about 4mm wide.
Graeme
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It is not a backwards bow. It is bamboo belly bow.
Bamboo skin as belly is not a new idea. It has been used as sinew backed in horn bow substitute, where hornbows have been norm. It has also used as self bows in Bhutan.
I think Osage should be ALSO strong enough to work well as backed with bamboo.
(I'll add some links.)
I would reinforce the fades by wrapping with linnen and wood glue, I see potenttial for splintter in the area.
____________
______---- ----____
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....<-wrap->........<-wrap->
Asian hornbow like bows made with bamboo belly.
http://www.atarn.org/FAQ/bamboo_composite.htm
http://atarn.net/phpBB2/viewtopic.php?t=123&highlight=bamboo+belly
http://www.hornbow.com/mokgoong.html
I could not find article about Bhutanese
bamboo selfbow made from 2 pices and joined at handle.
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I think the point here was to try something new for the bow maker him self. Still, a really nice bow.
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Graeme, this is an interesting idea and interesting looking bow. Osage is definitely strong enough to be a backing and bamboo will work for the belly. One way to increase the compression strength of the boo, and allow for less set is by tempering the boo before glue up. I watched James Parker temper boo for one of his short, highly stressed recurve bows and you would have thought it was toast when he was done. :o
Experimentation is what keep primitive archery alive. It always has. Nice work. Pat
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That's a great lookin' bow,and it sounds like it's performing well.I hope it'll keep sound for you. Good work. God Bless
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Hi Pat
I have seen boo heat treated to increase the compression strength and it seems to work well but I have been skeptical about how the heat effects the bow over its working life -- obviously it makes the cells harder and more brittle so I can not help but wonder it they break down with lots of use. I guess I am going to try it if i make an all boo bow but with the current osage / boo bow it has not taken any set as yet so I guess the boo is stronger than people think in compression and only needs to be improved if you put boo on the back as well since it like most bow woods is stronger in tension than compression.
Graeme
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If heat treating a bamboo belly,I would be adding the heat only to straight parts and not to the node areas.
Hmmm... No, since I think this would add more compression to the nodes, and I assume they are weaker spots.
Hmmm. Are bamboo nodes weak sponts in compression too, or just in tenssion side?
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Did not want to discourage the author for trying to invent anything new, the fact that has been invented allready,
means it is a good idea, and most usefull things in this hobby just have been invented allready...
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Hi Jkekoni
From the work I have already done with boo it does not seem that the nodes are a weak spot in compression.
There are some commercially available all boo bows that have the nodes removed on the belly and this does not give any problem.
I think it works a bit like short pieces of horn glued on the belly and butted up to one another -- even thought they are not connected they can resist the compression by pushing on one another.
Graeme
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Nice experiment,Graeme.
I myself, made a bamboo belly bow with hickory back and maple core . It was a sort of english longbow at the handle but with a little arrow rest cut in it and the limbs were rectangular in cross section like an american longbow. So there was no glue-up handle. After a fews hundred arrows trough it ,it took more than one inch of set but remained a fast shooter. Maybee the set came from the hickory being too spongy ( in humid Belgium) and thus too soft for the bamboo belly. I had made before another longbow with bamboo belly and back and it takes about 2 inches of string follow after unstringing. IMO its a good design (been used for centuries on the japanese yumi ) but the belly should be heat treated.
By the way ,Graeme, I like your bows very much , especially your recurve, hope some day I can do as good as you.
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Hi b
I have the same trouble with Hickory, just too humid here to get good results so I gave up trying. At 12 or 13% MC which is what we normally have the stuff is like a limp noodle.
I am going to try an all boo pyramid next and attempt to tiller the belly even though it will remove the nodes since I have seen this done successfully, I will probably temper the belly as well since this will help to reduce the amount I have to remove by tillering.
Surprised you are familiar with my recurves -- I dont really remember posting them?
Graeme
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Very nice looking bow,great job on that one. :)
Pappy
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GraemeK
I think hickory works well as backing even in humid weater, It just does not work as belly.
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Graeme, sorry I have mistaken you for the australian guy of Araucaria archery, LOL. In any case we are waiting for your recurve's pictures.
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Hi b
I manufacture modern take down recurves ( Downunder Bows) so they are not appropriate on this site -- thats why I was surprised you mentioned them.
I may well make a boo d/r next so you never know.
Graeme