Primitive Archer
Main Discussion Area => Bows => Topic started by: bubbles on May 20, 2016, 03:54:32 pm
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Getting a bit frustrated with limb twist lately. It is a problem I deal with on most of my bows, both backed and stave. Same problem. Top limb twisting towards the camera(I think) and probably the bottom doing the opposite. I posted something similar on the "mechanics of limb twist" sticky, but there was no replies. I've been over that thread dozens of times and I think I'm understanding it correctly, but i just never seem to be able to get a limb from twisting on me. It seems to be getting real bad on this guy, so I'm reaching out. Which side is the weak side? I'm kind of at a loss.
I've been scraping what I believe to be the strong side, but it just doesn't seem to be getting worse or better. There is twist on the tree as well as in the hand and There is some grain runoff, so maybe that is making the problem worse. I don't want to make it worse at this point. Let me know your thoughts.
(http://i357.photobucket.com/albums/oo19/mikemeusel/website%20pics/Screenshot_2016-05-20-14-30-15_zps5gxlktng.png) (http://s357.photobucket.com/user/mikemeusel/media/website%20pics/Screenshot_2016-05-20-14-30-15_zps5gxlktng.png.html)
(http://i357.photobucket.com/albums/oo19/mikemeusel/website%20pics/20160520_151926_zps2kpqqikg.jpg) (http://s357.photobucket.com/user/mikemeusel/media/website%20pics/20160520_151926_zps2kpqqikg.jpg.html)
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i have read that thread too, I think I am dyslexic about that twist thing,, I am looking at your bow,, if it is twisting to the weak side, that would be the left side in the photo,, so taking off wood in the right strong side would bring the string to center ????? I am hoping someone definitive will post,,,, but thats my guess,,
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Like you I've read that post many times and walk away scratching my head. There are two main posters there and to me it seems like they are saying opposite things. I'm probably wrong. I've had a few that, like Bubbles, just did not seem to respond. All they did was get weaker. Wizardgoat set me on the road. For that bow I would heat it at the base of the recurve and bend it to the right to bring it into line. Pretty much ignore what it looks like unbraced. Marc St Louis also told me to just grab it by the handle in the vice, pull it to about 20", and manually twist it, no heat, in the desired direction. It's kind of scary but it works.. I think the bottom line is if it dosen't seem to respond to a few scrapes then just be the boss and twist the damn thing ;)
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Go manual on it. Clamp the handle and wrench the recurve past straight. You have to train it a bit
The scraping of the opposite side it is twisting toward is pretty straightforward but you still have to educate the wood after it's had it's own way for a while.
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The twist increases as its drawn though. Is that just a result of the recurve being slightly out of line?
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Yes, the recurve gains mechanical advantage on the twist as the limb advances.
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i have to admit,, I have usually gone manual,, heating and twisting into line,,, I have never tried without heat,, but good to know that is an option,,
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Yep the little I know and have had success with is that your alignment is just off a little bit but know that's the trouble here.You got opposing tip alignment there and maybe each might have to be tweaked just a little.Your very close though.
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I guess I was trying to fix it by scraping when I should have fixed the alignment from the get-go.
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You fell into the same trap I did. Every time you open the "Bows" page there it is, top of the page, "Mechanics of Bow Twisting". So where you going to go when your bow is twisted? It's subliminal advertising at work ;D ;D ;D ;D
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Why do you scrape to correct string alignment or lever offset?
I wouldn't do that, take the heat gun and correct your stave! scraping only on one side of the belly produces a 'trapezoid' shaped cross section with different amount of stress on the left and the right side.
I have made lots of statics and most of them have a lever offset when first bracing. I do immediately unbrace and go to correct with heatgun or steam.
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The limb twist 4est explained was not a recurve but a flatbow with one side thicker than the other if i remember right
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Right. I'm in the process of getting them in line through gentle use of heat as well as brute manipulation. Its a backed bow so I need to be careful with my heating. Is it possible that recurves might be a different beast that the "mechanics of limb twisting explained" thread would not apply to? Maybe I should get a pine slat, recurve it and try it out myself.
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You got some funky grain there in the foreground.
That grain would cause twist that may never come out.
Regarding twist...the weak sides is the side closest to the string at brace. Remove wood from the other side. Use a scraper. Take a few passes...say 10. Take some really short draws and continue.
More on my site.
http://traditionalarchery101.com/
Jawge
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I feel like the limb closest the to string at brace is the strong side, at least that's what I understand from the limb twist thread. Am I wrong on that? It twists towards the weak side bringing the strong side closer to the string?
Anyways, here is the alignment now and a draw pic. No real improvement on the twist.
(http://i357.photobucket.com/albums/oo19/mikemeusel/website%20pics/20160521_161050_zpsqdh3it6n.jpg) (http://s357.photobucket.com/user/mikemeusel/media/website%20pics/20160521_161050_zpsqdh3it6n.jpg.html)
(http://i357.photobucket.com/albums/oo19/mikemeusel/website%20pics/Screenshot_2016-05-21-16-15-37_zps5onvppgk.png) (http://s357.photobucket.com/user/mikemeusel/media/website%20pics/Screenshot_2016-05-21-16-15-37_zps5onvppgk.png.html)
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Is the twist affecting the bow, string coming off or something?
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Yes, it twists towards the weak side. Weak side is closest to the string. Jawge
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Not yet, but I'm afraid it will in the next 5-6 inches. Or the limb will just twist off or something.
I've taken the tip a bit to the left of center and that seems to help a bit. We'll see.
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Sorry I really did'nt realize that your bow was a backed bow.Thought it was a stave bow.Your alignment looks good on the last pic now.I will say this though.I had an extreme static that was throwing the string off at 20 to 22 inches on the tree.I fixed that by lining up the tips better with heat.It was a stave bow though.Good luck.
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I try deepening the knock (side needed). that may help some. Or unback it then fix my heating and bending the handle to where its needed.
Short limbs narrow limbs, steep curves you'll always get twists. Or learn about alignment your tips and handles. All that built up pressure has to go somewhere.
Try widening your limbs a 1/8 inch. If keep failing with alignment.
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Allright, update, with gentle heating of the limb to correct alignment(even put it a bit past center on the other side) and deepening of the nocks to move the string over a bit, the situation seems to be improved.
A few important lessons I've learned:
1. Camera placement: I've been placing my camera below the center line of the bow, and slightly behind the riser. This led to a great straight on shot of my bottom limb but my top limb always looked like it was twisting, even when it wasn't.
2. Recurve limb twist is best dealt with by tweaking string alignment, instead to trying to scrape the strong side of the limb (right?)
Here it is now, let me know how the tiller is looking. Its 60# at 22", going for 26.
(http://i357.photobucket.com/albums/oo19/mikemeusel/website%20pics/Screenshot_2016-05-22-13-54-51_zpspt242psb.png) (http://s357.photobucket.com/user/mikemeusel/media/website%20pics/Screenshot_2016-05-22-13-54-51_zpspt242psb.png.html)
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Yes, but you mean scrape the strong side. ;)
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Haha, yes. Let me fix that.
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If you do that again can you tell me it's one frame of a video. I tried a bunch of times to get it to play ;D ;D ;D ;D ;D
I think there is a time and place for scraping to eliminate twist but with a recurve after a couple of battles like you've had it's heat and/or twist first for me from now on.
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Yeah, nobody wants a wedge shaped limb. If the wood is even and the limb is twisting because of internal differences in the wood it gets worse if you don't nip it on the bud and makes you think the wood is half as strong on one side.
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Here's the full draw. Limb twist started creeping back as I removed some of the previously heat corrected belly, but some more gentle heat seemed to fix it right up. Here it is, 60#@25. I've got a bit of weight to play with. What are the opinions on the tiller?(it's a screen shot, not a video )(http://i357.photobucket.com/albums/oo19/mikemeusel/Hickory%20Backed%20Osage%20Recurve/Screenshot_2016-05-26-19-25-09_zpsbmnxxqss.png) (http://s357.photobucket.com/user/mikemeusel/media/Hickory%20Backed%20Osage%20Recurve/Screenshot_2016-05-26-19-25-09_zpsbmnxxqss.png.html)?
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Looks really good to my eyes. How does it shoot?
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I'll start shooting it tomorrow and report. Need to shape the handle and make it a bit less square before arrows start flying.
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Looks spot on to me! Great looking tiller!
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Shooting pretty sweet. I'm liking it.
I made a small dent in the belly on the top outer limb from a clamp (my leather pad was too small) when I was removing twist. Is this anything to be concerned about?(http://i357.photobucket.com/albums/oo19/mikemeusel/Hickory%20Backed%20Osage%20Recurve/20160527_103230_zpsffnkrccm.jpg) (http://s357.photobucket.com/user/mikemeusel/media/Hickory%20Backed%20Osage%20Recurve/20160527_103230_zpsffnkrccm.jpg.html)
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If its on the belly i wouldnt worry about it. Just something cosmetic that will annoy you.
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Try a wet rag and a steam iron. Del talks about using a hot spoon on his blog.
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bubbles.....I made a sharply bent static the would throw the string at around 22" or so on the tillering tree.Did'nt hurt the limbs or tips any but it is unsettling.Aligned the tips and the issued stopped.Good to hear your progressing there.Tiller looks fine.You've got a tillering tree?I mean one with a pulley & rope.
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That was on a self bow though.Now I've seen on here before an issue people have glueing the laminations together not lined up correctly with string not across the handle,or putting a twist on them from wrapping one direction with inner tubes or something.Don't know if this is a case of that or not.
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Yep. I've got a tillering tree. Its been shooting good so far, so I'm pretty happy. Starting to add brush nocks