Primitive Archer
Main Discussion Area => Bows => Topic started by: dwardo on December 29, 2011, 09:45:41 am
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Hi all,
I was wondering what kind of prop twist you have all had to deal with in the past?
What kind of degree will you just huff at and think "life is too short"
What are your tips for removing the twist or just living with it?
Just a general discussion point, cheers all :)
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I used to leave it in if stringing the bow wasnt a problem. I straighten every bow I build now. I want them flat when I tiller. I found it hard to keep my taper even when the limb twists. I would get thin spots here and there.
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Any limb twist is just another source of limb vibration/hand shock IMO. Don't much care for it myself..........Art
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A little bit of prop twist is no big deal. It looks abnormal, but doesn't affect how the bow shoots. A small amount is not worth correcting, as long as the string stays in the middle of the bow. Most prop twist only happens at max full draw. I haven't noticed any difference in hand shock.
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I used to leave it if it was less than 35 degrees or so with no problems. These days I've started heating it out. Like this. Just add water from another container. Jawge
(http://img.photobucket.com/albums/v331/Jawge/Fixing%20a%20twist/00small62434721.jpg)
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If there is more than 120 degrees of prop twist I am out the door with saw in hand hunting the next stave. I do have SOME standards, you know!
The stave with the 120 degrees of twist was a narrow osage stave with the twist distributed evenly from one end to the next, no knots, no pin knots. I chased a ring, found the center line, and drawknifed it into the profile of an ELB. I squared the belly with the sides and got ready to unscrew it. I started in the middle using a heat gun and a pipe wrench. I hung a weight off the end of the pipe wrench like George shows in his photo (all great minds think alike, and all fools fail in similar fashion). I unscrewed it one foot at a time over several days. I wound up with a little prop twist left in it but I was just happy I hadn't blown it.
Now 90 degrees of twist in just a foot of limb would be a challenge! Kinda like some of gstonebergs mutant osage! His stuff's so bent that if you was to burn it the heat would go sideways and the smoke would try to down thru the ground!
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much as described above. took this twisted piece o wood and got it flat.
did it over a week with numerous heatings.
(http://i878.photobucket.com/albums/ab346/sadiejane9/bowmaking/DSCN8273.jpg)
the eventual bow-it had numerous other issues to go along with the twist. but has held up so far....
(http://i878.photobucket.com/albums/ab346/sadiejane9/bowmaking/DSCN0038.jpg)
have only made a few bows, but all cept one needed some twist taken out with heat
this being the most extreme
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Thanks for the comments all.
My main reason for asking is I have a few twisty staves sat in the naughty corner which i just keep avoiding.
I have in the past taken out tiny amounts of twist but never gone the whole hog and takenout anything more than 30 deg or so of twist. In say a gentle 45 deg of twist over a full 60" would it be possible to just ignore the grain and make it flat or would that much run out just be gambling... I dunno but worthy of thought.
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This thread shows how I made a bow with a fair amount of twist and just worked with it. It's probably the best shooting bow I've made, fast and it groups nicely.
http://www.primitivearcher.com/smf/index.php/topic,28324.0.html (http://www.primitivearcher.com/smf/index.php/topic,28324.0.html)
Del
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I forgot that one had so much twist Del, thanks for posting it.
Well i have two almost identical staves from the same sapling, both with the same twist so in teh interest of experimentation i will completely ignore it on one and follow it on the other. Bout time i blew a bow anyways ;)
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keep a fair bit of width on the tips to start with so you can adjust the position of the knot/sting alignment as there is bound to be some lateral movement as you are tillering it.
Getting it to come back straight needs some patience/luck/skill/cussing.
Del
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dwardo
Just don't blow the wrong one and
prove us that like to take the twist out to be doing it wrong ! >:D
Guy
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Whoa, Del that bow is gorgeous. Where do you buy your horn?
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Whoa, Del that bow is gorgeous. Where do you buy your horn?
Highland Horn in the UK.
Del
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I heat twist out of virtually every bow I build. The only problems I have are when I want to make 2 corrections in the same spot, ie take out twist and flip the tip. In that case it's best to wait until you can do them both at the same time. A caul is helpful then.
George
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I take all the twist out of my staves.
Here are a few tips;
I use a piece of aluminum angle as a reflector for my heat gun. I get a more even heat distribution and can heat an area in a third the time. After I heat an area I wrap a rag around it and the reflector to hold the heat and let it penetrate deeper. The reflector will really hold the heat so keeping it close to the stave is like putting the stave on a low temperature stove eye.
(http://img.photobucket.com/albums/v181/ekrewson/bow%20making/insulatedaluminum.jpg)
I remove twist like George but us a pipe wrench and a 5 gal bucket to add weight to. I have 2, 25# bags of lead shot I put in the bucket plus an assortment of C clamps if I need more weight.
I have found if I put a piece of old sanding belt around my stave (rough side in) the pipe wrench won't slip or chew up the stave.
(http://img.photobucket.com/albums/v181/ekrewson/bow%20making/straighteningproptwist.jpg)
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Some great tips here thanks.