Primitive Archer
Main Discussion Area => Bows => Topic started by: DQ on February 05, 2013, 06:22:02 pm
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This is (was) the 57" ntn sinew backed HHB bow I had at Martyjam. I had the bow tillered to 45# @ 20" before adding the sinew.
After sinew it must have weighed 90#! 6" of reflex was a challenge for me to tiller. I sanded down the sinew and was slowly working it down to the 55# I wanted. Almost there. It was 57# @ 27" when it blew. (on the tillering tree) BANG! I hate short bows.
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:( I hate when that happens! At least it was on the tree and not in hand. Back to the drawing board.
Tracy
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Ouch! Terribly sorry for your loss Daryl. :'( Try again with osage. >:D
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i'm not saying nothing, I got my ishi bow out to 25, gotta start shooting in to get the rest of the draw, Bub
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Sorry for you pain, but don't give up on trying shorter bows. IMO 57" isn't really all that short. With a stiff handle like that the tillering is a little different than a bendy. I know you know all this so get back out there and whip me up another. :)
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Having not made any sinew backed bows yet, I was under the impression sinew was supposed to prevent tension failures like this, and that a bow would slowly failure under compression.
Hamish.
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Almost looks too dry? I seen the bow and flexed it some. It was done right and looking too good to blow??? Sorry Darryl. Im with Matt.
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Tiillering a sinew backed bow down should be done by width and then belly reduction. Sanding the sinew down is not the best idea.
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I feel your pain my friend I am part of the broken HHB sinew backed Club myself ;)
(http://i1082.photobucket.com/albums/j380/thadsoy/photobucket-28912-1349995045558.jpg)
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That sucks Darryl!! I've been there. I could never get a shorty to survive till I finally gave in to the bendy handle. Now I make nothing but bendy handles. Love me a short bow!!
Tattoo Dave
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PatM - I wasn't tillering by sanding the sinew. Only sanded it smooth before tillering.
Hamish - Yeah, that's what I thought too. I was surprised to see the tension failure. The belly was toased and it wasn't even damaged by the explosion.
soy - Kinda exciting club isn't it? :-[
PEARL - Too dry? Hmmm... maybe.
Mwirwicki - Yeah, that's your standard answer for everything. LOL >:D
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Sanding it in any way is still a potential problem. If the backing is not very thick in the first place just reducing it to smooth can be the tipping point.
How thick was your backing in the center? Looks like you can cut an actual cross section of the limb now. ;)
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Could have happened to anyone. In the first pic the left limb does look thin and I'm just curious what the thickness is there.?
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Well, maybe you're on to something, PatM. Since the bow gained so much weight, I thought the sinew was too thick. I sanded and scraped it down a bit. Maybe I over did it?
Guess I could cut a few cross sections now to see how thick (or thin) it was.
After the bow blew up I quit for the day. When I pulled the string to turn off the light, it broke! My nerves are shot! LOL :-\
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Time for a break Darryl. That sinew was is fine shape and your smoothing it wasnt the problem in my opinion. Just a tough break. You cant explain them all!
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I'm thinking the same thing as pearly in that it might have been too dry. Just a guess but it also looks like the inner limb is fairly thick and may not have been doing its fair share causing too much bend in that spot. Sorry to see it go. After just the first layer of sinew I've ever layed this weekend it stinks that so much work goes into it to see it break. :/
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Sorry for your bow
57" NTN with a 6=8" non bending handle was the most likely death of the bow. That is just to much bend for that little amount of working limb.
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Bummer - sorry to hear that Darryl ! Time to pick up the next piece and go to work. Bob
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Commisserations ... you obviously haven't read that bit that says sinew backing makes a bow virtually unbreakable! >:D
Smae happened to me on the only sinew backed bow I did >:(... lot of work for no reward. I daresay I'll have another go sometime.
Del
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Sorry about that DQ, What Keenan said,that is asking a lot from such a short piece of wood ,sinew will help hold one together but it ant the cure all. :)
Pappy
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Suck....that one was looking awesome.....I'm a lil baffled and I'm not 100% certain as to why it broke. Everything looked good design wise on it honestly IMO. I've made 55.5" stiff handled unbacked bows pull 26" with retained setback...but that was osage. Matts right..try osage ;)
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DQ I'm a shortie builder and just gotta say "been there done that". It happens occasionally. But, I have had tremendous results with sinew as well. Judging from the pics, it appears that was a lot of handle for that particular shortie IMHO. Try it again.
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DQ sorry to here about that it was a sweet looking bow it happens to all of us grab a nother stick and start another nother one take care
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Thanks for your condolances, guys. LOL Just another bump in the learning curve. :) I cut a cross section of the limb to see what I had. There is 1/16 inch of sinew at the place the limb blew up. This taperes to 1/32 inch at the limb tip. I don't have much experience with sinew but it looks good to me.
I agree that I was asking for too much bend in that limb length. Also, I checked the humidity in my shop. 38% @50 degrees. So, according to the chart, moisture content of the wood was about 7 1/2 percent. Pretty dry! That could be the problem too.
Anyway, onward and upward. I hope.
DQ
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Yep, too thin for the wood thickness and type. You're not moving the neutral plane much if any with a very thin layer.
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7 1/2 should be OK for IW. :) I just think it was asking to much for to little working limb. :)
Pappy
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For that length and a stiff handle, maybe a little wider limb would have helped.