Primitive Archer
Main Discussion Area => Bows => Topic started by: DC on November 14, 2015, 08:00:13 pm
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Before I do something stupid can anyone see anything in the design or execution of this bow that would cause it to throw a string. I've been fighting it for seems like weeks of minor heat corrections back and forth and once or twice I think I got close, but no cigar. Maybe recurves too big, limbs too narrow, anything that will stop it from becoming a working bow. This is my 4th recurve and I haven't had this much trouble before. Any other pictures I can post to help just yell.
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With those big hooks maybe a stability issue, I've had some that until i get to full brace i glue on some string bridges and it helps a lot
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Oh yeah, it doesn't try to throw the string until almost full draw, depending on how successful the last heat tweak was. Right now I can pull it to string lift off and when I let off I can hear the string snap back into its groove. I'm pretty sure it's twisting( I think it must be) but is it because the large narrow tips are just so unstable or is it a tillering problem. Maybe too thin one side. It's usually the same limb although after one heat treatment the other limb popped off.
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I gave up on big recurves for just that reason. They just don't suit some of us.
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I can always flatten out the recurves and still make a good bow but I'd hate to admit that a piece of wood made a fool out of me. That might be a given though, or maybe the wood had nothing to do with that. ;D Would the narrow limbs be a major player? When I use OS the limb width is always going to be tight.
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A wider limb actually distorts easier if you think about it. Never could figure out why people say a wider limb is more stable.
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try trimming an inch or so off those big hooks and see what happens
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try trimming an inch or so off those big hooks and see what happens
Yeah, it's sounding like that. Thanks
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Play around with the string nocks, like a a steeper angle or vice/versa. Just maybe the last 6-7 inches of the tips is to stiff. I find that sometimes the last 3-3 1/2" is good enough.
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it looks super straight. great job on getting it where it's at right now.
you're probably just dealing with the grain variances.
as mentioned, if you removed a little from the hooks, you'll give it less leverage to be able to torque on itself.
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I took 1 1/2" off each end. It was way better but the same tip was twisting off slightly. I did one more heat tweak. Maybe it won't be so fussy with the shorter tips. We'll see tomorrow.
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I don't understand how the string groove would affect the limb twisting. What am I missing?
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The groove stops the string from being torqued across the recurve as you draw.
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Thanks Pat. Isn't that treating a symptom rather than the cause. If I could stop the twist there would be no torque.
I just checked it and it's still twisting a bit. I've taken some deflex out so I have a few spare pounds now. I can try tillering some of the twist out.
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Its an oceanspray? Every one I've tried with agressive reflex or recurves would throw the string around backwards and not hold brace. My issue was tip alignment. I don't know how anyone puts agressive recurve on a curvy character stave, but they do.
Depending on which side the string /nocks are thickest (more material between edge of bow and where the middle/string line is) will affect torque. T=FCos(theta) The further away one side of the string groove/nock is from the center of the bow , the greater the torque. Does that make sense? Like a torque wrench the longer the arm the greater the force. If you look up/down the bow you can see which way it is twisting.
Unless the grooves are pefectly equal then I dunno. I suppose you can watch which way it flips and remove wood on the side of the nock to reduce the torque on that side.
This is all theory of an amateur stick bender tho. String bridges would be my first attempt.
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Yes. it's OS. It's pretty straight though. When I string the bow I make sure the loop and bowyers knot are centered. It's the bottom limb(bowyers knot end) that's giving me grief. I don't like the look of string bridges so I won't go that route. If i have to I'll take some recurve out.
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Lose the knot. They tend to allow the string to twist off to one side.
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I made a little diagram. It looks a little, obscene..
Anyhow I over -emphasized the difference in the groove distance to show how the forces would work. It might not be your issue at all though.
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I don't have side nocks, just temp tips with back nocks.
I figured the knot would be a bit of an issue so I take extra care to make sure it's centered. I have grooved the tips from tip to string contact point so it's not to hard to center. I don't have a stockpile of strings with loops at both ends and I'm not settled on brace height yet so I'm kind of stuck with the knot. The one string I have with double loops gives me a brace height of about 7 1/2".
Right now I'm doing a few chores for winter.
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You need side nocks in order to get the string into the belly groove of the recurved portion. How is the loop riding from the back nock onto the belly?
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I agree with PatM side nocks are a good thing. :) and deep grooves in the back without compromising strength.
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I don't like cutting side nocks until I'm closer to finishing but I'll give it a try.
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I never have piked a bow. I feel like it is sacrificial and kind of dangerous. But thats me. Not sure if your outer 1/3 of the limb is bending or not. If not get it bending.
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I don't like cutting side nocks until I'm closer to finishing but I'll give it a try.
Why not? Bridges are also a help. You may need to separate your needs and wants.
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OK I cut side nocks on the offending limb. It didn't fix it but I do feel more confidant that it's on center. I shone a laser down the string and it looked like the string had a bit of a bend where it left the bow. One more heat tweak and now it seems good. It doesn't throw the string so I can at least continue tillering. I've got about 7-8 inches to go. As long as the alignment stays I should get that done tonight.
Bow101- I don't think that piking this made a lot of difference except in the string stability. The string still lifts of at the same draw so up to there nothing changes. After lift off the bow is shorter so it's harder to pull but since I haven't tillered that part yet it's kind of a non-issue. It's different than it would have been but it may have been too unstable to shoot.
Pat- I like to cut the whole nock at once so it all lines up nice. It just seems easier to me. Less chance for something to go west. I don't know why I dislike bridges so much, they're fine on horn bows. I guess if the design of a bow was deliberately such that there was no way the string would stay on without them I could do it. This was supposed to be a simple R/D bow. I started out with way to much D and when I took some of that out I had to much R. I know now that I want to keep the deflex down to 1 1/2 to maybe 2".
Thanks everyone that helped. I learned a few things on this one and that's what it's all about :D :D
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Well it's not a D/R it's a deflex recurve. A difference that matters in the big picture.
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True. I actually just figured that out the other day and it hasn't quite locked in yet. I thought anything that went back and then forward was an R/D. I was looking at some pictures and the light went on.