Primitive Archer
Main Discussion Area => Bows => Topic started by: Crogacht on June 18, 2014, 06:51:27 pm
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What is the best way to straighten a stave that needs deflex removed, lateral straightening and prop twist corrected?
Can you do the deflex and lateral straightening and then deal with the prop twist?
The stave is 60 inches of Elm.
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Do it all in one shot on a caul with a back. Start at one fade work towards the tip. Repeat on the other side. Watch you don't scorch the back.
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Thanks Pearl Drums, how would you attack the prop twist in that sort of setup? Can you do the wrench and bucket thing, or do you use clamps on one side of the limb?
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All in one swipe. I use little thin pieces of craft leather tucked up under the low side of the limb. when it's clamped flat it takes it a little past flat to compensate for some return. Then like PD said, just clamp and heat from fade to tip. Heat will get in underneath the areas where the leather props it up so just use some caution. I don't like the bucket, but that's just me, it will work, I just find this easier.
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I use clamps and wood wedges for twists and try to do it all at once but sometimes it takes 2 or 3 tries to get it right if the twist is severe.
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I dont mean to swipe your post but I have some hackberry that has a slight prop twist...can someone explain the bucket thing? The twist is not severe.
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I dont mean to swipe your post but I have some hackberry that has a slight prop twist...can someone explain the bucket thing? The twist is not severe.
Haha, no problem, we need all the help we can get.
Exhibit A, from George:
http://georgeandjoni.home.comcast.net/~georgeandjoni/fixtwist.html
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All in one swipe. I use little thin pieces of craft leather tucked up under the low side of the limb. when it's clamped flat it takes it a little past flat to compensate for some return. Then like PD said, just clamp and heat from fade to tip. Heat will get in underneath the areas where the leather props it up so just use some caution. I don't like the bucket, but that's just me, it will work, I just find this easier.
Exactly how Id do it. Leather or wood wedges to allow for over bend wherever needed. The bucket deal works, but a symmetrical caul makes a symmetrical bow makes an easier tiller job. But Im picky.
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Great advice, thanks PearlDrums, Slimbob and Pat B.
I think I'll have to get a bunch of clamps and build a jig for 3 way bending. Should be fun.
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Ok.
So, it's "best" to do all 3 at once, but what if you
can't? I've got a nice BL stave down to near final
dimensions that needs twist removal, lateral
correction, and then reflexing of the tips....
I took care of the twist with a c-clamp and a 5kg
dumbbell using a heat gun...worked like a charm.
Now, is it BAD for the wood to be reheated multiple
times? I can probably do the lateral correction and
reflex in one shot the second time around, but all
three? I think I'd have to be some kinda wood
whisperer or something.
Thanks in advance,
Japbow.
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I have reheated staves three or four times with no bad results as far as weakening the wood, but when you correct one thing at a time, it seams that what you fixed last time will tend to go back to it's original problem when you heat that area again, unless it is clamped to a good form. I have found with a severely prop twisted stave that I can work on that first (in the vice with a pipe wrench and heat gun is my favorite) and then later clamp it to a form for the finished heating and straightening, like what was described above. All at once is easier. I believe time spent building reflexing, recurving forms is time well spent.
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Japbow I have no way to measure damage done by heating a bow or an area several times. On that note, I don't worry much about it either. I heat it up until the blank looks the way I want it to. However many sessions it takes, which usually one if done right on my oart.
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Bear in mind its easier to make a lateral shift in a thinner handle than it is to make a lateral shift in a wide mid-limb.
This one has lots of twists, bumps and off-set limbs. I found it easier to use a g-clamp and a weight. Box if spanners just off-shot attached to the clamp with a rolling hitch so it can be adjusted as it warms up. This one took several attempts to straighten as it was just too much to clamp it flat.
(http://i121.photobucket.com/albums/o218/dwardo/Bow%20making/20140609_211721_zpsbt25gbpv.jpg)
(http://i121.photobucket.com/albums/o218/dwardo/Bow%20making/20140610_114238_zpsizno7bcf.jpg)
Then a spreader clamp forcing the lateral away from the wall.
(http://i121.photobucket.com/albums/o218/dwardo/Bow%20making/20140610_133938_zpsr6zx4mex.jpg)
Its much easier to find flat wood :laugh:
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I may take one shot at such a stave on my caul but never get it corrected to suit me but will lessen what I need to correct to be finished. After the first caul session I attack the problems one at a time.
As for heat damaging wood, don't think it will unless you burn the wood. One of my best bows has at least a dozen heating sessions in it to "tame the beast" so to speak.
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Generally I'll get the twists out and straighten a stave first (sometimes this takes a few sessions) then in another session I'll add reflex to the limbs then in another session I'll add recurves and reflexed tips.
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Something I'll add here. Most of the time I will get the tips aligned by bending the handle a little. That move I will make by itself. The reason to make any other bends all at once, or I should say the reason I make them all at once is to eliminate losing the bend you did earlier when you reheat an area.