Primitive Archer
Main Discussion Area => Bows => Topic started by: Mo_coon-catcher on November 23, 2013, 12:48:39 pm
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I see people getting nice smooth curves when they put recurves on their bows. I have tried several times and mine always seem to kink at one spot. It still ends up with the tip at the angle I want, but it's a harsh transition instead of a nice flowing one. The main wood I have been using is Black Locust with a couple of Osage thrown in using dry heat to bend them. The way I have been bending them is to clamp the tip on the form then start heating with the heat gun until the bow starts dropping on its own weight. Then I put a couple pounds more of down ward pressure until it fits the form. I try to concentrate the heat on the lowest part of the limb closest to the tip and work my way up the curve toward the handle, so the wood should be softening as I work my way up the form. But I still end up with a sharp bend. Does anyone have any advice for this?
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If you are getting a sharp bend that means the wood is collapsing under compression in a certain spot. Make sure to taper the thickness so that the tips can bend easily. Test the bending a little without heat at first. You should be able to see if the wood is bending in a gradual arc. If not, taper the tips more. Then take your time with the heating and clamping.
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In order to bend the wood does still have to collapse. I prefer sharp angled bends myself and get disappointed when the wood curves in a longer arc.
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I've used steam for all my big bends, then dry heated and bent most of them just a touch farther because I tell myself it'll be more permanent. Not sure it it actually works that way ::)
You might need to heat the wood more evenly and thoroughly before putting it in the form, don't give it one spot to bend at more than anywhere else.
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A strip of thin metal pulled down over the wood will help stop the kinking.
This entry in my blog shows what I mean.
http://bowyersdiary.blogspot.co.uk/2013/05/radical-recurve.html (http://bowyersdiary.blogspot.co.uk/2013/05/radical-recurve.html)
Del
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I've found that I have to heat and bend the curves slowly. I do a little section, let it cool and then bend some more. I also make sure it is close to 70% tillered with the limb thickness so I don't have to get it real hot.
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I don't start bending until I get the whole 'bend area' hot enough to bend... then just bend it in one smooth motion and clamp it. Never had a kink show up.
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If the curve of your form is smooth and you're getting a kink because it's lifting off the form in one spot, make sure to watch for that as you advance the bend and hit it with a clamp right where it tries to lift. You may have to add a couple clamps like this as you go depending how long a curve you're putting in.
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I'd say the biggest cause of kinks is prob' impatience and insufficient heat.
Del
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Does a sharp angle have any real difference over a smooth arc in any way besides ascetics? I mean of course everything being equal.
I steam tips, run outside and either wedge it in the crotch of a tree and tie it in place for a bit or I clamp it in a form attached to my fence posts (4x4). I made one sharp angle recurve with a small pipe tied to a board and just cranked it down fast. wasnt as big a fan as the slow curves on my more recent bows.
Easiest steam method for me is boiling a pot of water with a big piece of tinfoil over it that I form to the size and area of the bow I want to bend. works great and fast, and also is great for adding reflex to a handle without heating and warpping the limbs.
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Does a sharp angle have any real difference over a smooth arc in any way besides ascetics? I mean of course everything being equal.
I steam tips, run outside and either wedge it in the crotch of a tree and tie it in place for a bit or I clamp it in a form attached to my fence posts (4x4). I made one sharp angle recurve with a small pipe tied to a board and just cranked it down fast. wasnt as big a fan as the slow curves on my more recent bows.
Easiest steam method for me is boiling a pot of water with a big piece of tinfoil over it that I form to the size and area of the bow I want to bend. works great and fast, and also is great for adding reflex to a handle without heating and warpping the limbs.
Not that I know but I like the looks and it would make sense that it is just for looks. Longbows and recurves only have a couple fps difference and I'm sure if they are different, you are splitting fps
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I do like BL and usually don't have a problem,and like Eddie said have them close to finish dimensions. :) I use dry heat most of the time. :)
Pappy
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I prefer a round bend over an abrupt bend. All the pressure is on one small area with abrupt bends rather than spread out over the whole bend, similar to a hinge in a working section of limb.
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I use steam when I bend the tips of BL. Dry heat to bend the limbs a little to line up the string, but the tips gets steamed for abt 45 minutes and then bent in one smooth motion over a form. Done one at time and allowed to cool for an evening.
Russ
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So it sounds like I need to get the tips a little thinner, and mostly take a little more time bending them. I've been trying to bend them at around 1/2" thick so I can go a little thinner. The bows with the sharp bends still seem to shoot good to me, but I don't like the look of the sharp bend and would rather it be nice and smooth.
Thanks for the tips everyone.
Kyle
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I bend mine at abt 1/2 inch thick or bigger. I expect them to split a little at the grain line, but plan to thin the tips after the bend so it does not matter.