Primitive Archer
Main Discussion Area => Bows => Topic started by: YewArcher on August 19, 2008, 05:45:54 pm
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I tell ya, I am frustrated with a project that I have been working on. I started making a series of ipe backed iwth hickory ELB's. The problem is that the rate of sucsess is so low. I have made 8 in the last week with 4 failures. I am using 1/4" quarter sawn hickory backing on quarter sawn hickory. I am making deep section D elbs. They are so unpredictable. I am making them 40#-60# and none past 50# have made it. They get fully well tillered and about 20 arrows through and then BLAM they let go. Its real frustrating because they make it all the way through tiller and into shooting and it just does not seem like they should be breaking. I cannot tell if they are breaking on the back or belly.
Does anyone have any sugestions or thoughts on this problem? Is the D profile to much for IPE to take?I know that allot of the europen guys are making them in heavy weights so I cannot see why I cant get them past 50#.
Any thoughts would be apriciated,
Steve
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I'll be looking for the replies on this one for sure...
Are they breaking on the draw or on release? Are they delaminating? What kind if string are you using? A string with a bit of stretch might help....and a slight loss in arrow speed may be worth saving the bow from braking.
What is the arrow weight to draw weight ratio? How long are your bows? Are you trapping the bellies?
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With out the dementions its hard to say?? Pics would definetly help..With that said..The Ipe in the D belly could be over powering the hickory..
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These bows are 72" long and are typical elb diminsion 1" wide at center taper to 1/2" at tip. 7/8" deep taper to 1/2". They are not delaminating they are breaking at full draw.
Steve
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I have a hunch your bows are breaking mid to mid outer limb. Ipe hickory longbows can be good but they tend to get too narrow trying to keep the mass down, also bending them too much in the outer limbs is a common problem with lightweight elbs of this length and wood combo. Steve
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That is exacyly whre veryone has broken. What would be a better ELB wood combo in your experience?
Steve
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Hmmmm....IMO, the ipe must have some wild grain. It's hard to see the grain in most ipe and it might look straight for the most part. I've had ipe break at the slightest imperfection on the grain. Also, quatersawn ipe will not splinter as badly as plain sawn, but it will give you less warning before breaking. This is probably why you get through the tillering process without hearing the telltale "cracking" noises of a failing stave.
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My guess is your backing strips aren't running parallel to the grain. And being quartersawn, there's really no way for you to tell because the skinny dimension is the one you'd have to evaluate. Its either that or the stuff was kilned improperly or something like that. In any case, backings are generally the weak link in a backed bow. If you had belly problems you'd probably see chrysals first, or at least in some of the bows.
Grain on the belly is much less important, it will withstand compression OK. But try pulling a series of fibers apart that aren't completely connected to each other and bad things happen.
Certainly the ELB at the dimensions you describe, shouldn't be overly taxing any of the wood.
I think a lot of people have had trouble with hickory backings. Its why bamboo has become so popular, you have a better idea of what you're starting with. You know a slat of bamboo has continuous fibers.
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Does ipe even have normal growth rings? I don't think it is a ring porous wood is it? Being a tropical wood, I thought some of these trees sort of grow continuously. Ive never really been able to make out a distinct ring pattern on the massaranduba I've played around with.
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Tom, the ipe I have has distinct grain....but, of course, there are many varieties of ipe. Mine is a deep red with some black streaks. As far as massaranduba, I've never worked with it.
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ive used ipe,but only with boo backing
never had one fail yet
i love boo/ipe combo.
strong,fast and for me atleast they seem fairly indestructible. jmho
peace,
tim
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I've made three ELBs of ipe with bamboo backings. The first broke on the tiller (probably my inexperience at fault), the second worked well but chysalled almost as soon as I started using it and the third has been a great sucess so far. I suspect there are lots of subspecies sold as ipe and my first two bows (from the same plank) were made of wood much less dense than the last one. The ipe I've had lately is dark chocolate brown and HEAVY (it sinks in water). I was advised to check the density by seeing whether or not it floats - if it sinks and has reasonable grain then it ought to be good!
Not tried hick backing with ipe so no ideas about that.
Stan
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SORRY ABOUT YOUR FUSTRATION MY QUESTION IS I AM BUILDING AN ELB MADE FROM MASSARANDUBA W/ HICKORY BACKING AND (I BELEIVE ) AN IPE HANDLE DO YALL THINK THERE IS A POSSIBILTY THAT I WILL HAVE THIS SAME PROBLEM? I HAVE ONLY BEGAN SHAPING WITH A RASP AND HAND SANDER. I HAVE NOT TILLERERED IT YET. MY DIMINTIONS ARE 1-1/2 AT THE FADES GONING TO 3/8 AT THE TIPS.MY FLOOR TILLERING IS STILL VERY STIFF.
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TBB suggests that you always back a softer wood with a harder wood. I am not an expert on this, but I have had hickory backed red oak and locust bows blow up on me, and it was always the hickory that failed. I think hickory has great bending strength, but not very good tensile strength. When you put in on the Ipe, perhaps the Ipe overpowers the hickory backing at first, and when it blows, the whole thing goes (hey, that rhymed, didn't it?). Anyway, that is my two cents' worth.
Dan
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I think you are blowing out the backs as well. A few things to consider, first its the heavier bows that are blowing up, second if the back is failing then the back is failing and if the belly fails the back won't blow out in the same manner as it will collapse.
Good Ipe is stronger in compression than hickory is in tension, and personally I would only use a thicker1/4" flat sawn hickory backing on the heavier longbows..This is because there is so little wood, and its easier to see that you follow a ring down the back which really matters on these slender high strain bows.. But those dimensions should be good for 75-80#'s without being underbuilt..
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Thanks guys, Lots of good info here. I thought that 1/4 sawn hickory would be the way to go. It sounds like flat sawn is prefered with hickory backing?
That being said. bamboo sounds like a better option then the hickory.
Thanks for all the input. I think this all makes perfect sence.
SJM
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Is the hickory tried and true? Made other successful bows with it? I've had hickory lumber that had been outside or something and just fractured easily, even with absolute parellel ring lines running vertically. The break has the characteristics of a straight fracture, like a clay pipe stem break rather than a long splintery break more typical of a bow trension fracture break.
In fact I just cooked some hotdogs past weekend with the remnants of a piece of such.
Dave
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Its not that quartersawn is worse than plainsawn, its just that its hard to tell if the grain is running absolutely parallel over the length of the backing. Really, its just all-around tough to tell on hickory, you're at the mercy of whoever made the backings. And I'm sure they meant well but a log isn't totally square to begin with.
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Does ipe even have normal growth rings? I don't think it is a ring porous wood is it? Being a tropical wood, I thought some of these trees sort of grow continuously. Ive never really been able to make out a distinct ring pattern on the massaranduba I've played around with.
I never even thought about that Lennie. I have never seen a growth ring in Ipe either. It does have grain like Jackcrafty said, but that is entirely different than growth rings. What do you say Rich? Justin
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Some Ipe can be hard to read the grain, but almost all the Ipe I buy will look like normal boards. It's not ring porous. Often the black boards can be the hardest to read since the ring lines are black as well.. This is usually the heaviest Ipe.
I take the board outside in the sun and rub the edges with a wet cloth to highlight what grain there is.. Also if the face of the board is smooth its probably has very little violation or irregular grain as the planer will leave rough spots marking these irregularities.
I past out a few sticks of it at Mojam to guys who couldn't understand why I use Ipe since its so soft..and I find they got it from someone whose motive is to sell osage/cookie cutter bows..I put a stick of Ipe in their hands and they were saying..Whats this? ;D
Don't always believe its Ipe, until the green sawdust burns your nose, and it sinks like a rock in the pool...