Primitive Archer
Main Discussion Area => Bows => Topic started by: Don Case on June 24, 2014, 01:07:16 pm
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I'm going to make a caul today. I'm going to be using it mostly to correct deflex and lumpy bumps before tillering. Should it be circular or a little elliptical with more curve toward the end? I am thinking about 3" reflex, is that about right? I will probably be making more as my experience builds but I'm looking for ideas for the first one.
Thanks
Don
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Don, 3" to 4"of reflex is perfect IMO. A shallow, circular or elliptical form will work. I like a back on a form for straightening and removing twists. For reflexed or recurved tips I use separate forms just for that. Look at Pappy's form on the "Life is Good" thread. You will get a good idea from that.
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Gary Davis gave me a pattern you can copy while I was at the Twin oaks a couple of years ago, I love it. I could print that up some time later today if you like. I could proably explain it easier than draw it.
If your cawl is 66" long at each end of the cawl mark 1/4 marks until they are 4" high ( 16 marks) Start your first mark even with the back of the bow.
Now measure out 5" each side of center. You will have 28" of limb to mark. Divide the 28/16=1.75. Ok starting at 5" from center make horizantal lines every 1 3/4" until the end.
Once you have the lines and dots on your cawl you will start laying out the shape. Hold your yardstick at the bottom of the first line and aim it at your lowest dot. Only draw your line to the next 1 3/4 line even though your ruler is lined up to the end. Next line put your ruler where the first line intersected the second line and line that up to the next 1/4" dot. Only draw this line to the next 1 3/4 mark. Keep doing this till the end, the radius gradually gets tighter as you near the end of the tips. Maybe Pappy can review this but I am pretty sure this is it.
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Thanks guys, I think that's all I need. Well that and a 2x6 :D
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Ive come to like maybe 1/2" of reflex from center out 18-20", then really drop it off mid limb, say 2-3". I noticed my bows took the set they did at the width taper.
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Don, I was just going by memory so you might wait till someone reviews it. I refine mine a bit on the belt sander after I get the intitial shape done with the lines.
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Steve is close
I lay out for the Handle I want then dived it out
I also use 1/8 instead of 1/4 inch marks for a smother transition less sanding
Go from last intersection to next
You will end up with a progressive radius that works very well even if it is hard to describe!
Guy
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Use an aluminum yard stick and avoid all those marks and sanding/rasping. It forms and bends, you just trace it out on the wood. Zero clean up off the saw. Keep it simple!
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I found the Gary Davis more simple and more symmetrical than any other method I've used in the past. I used to do the bent yardstick trick but for me Gary's way was better.
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I'll make a bunch of marks and then join them with the yardstick/batten. That'll make everyone happy and I'll get a smooth arc with no rasping. When I'm using this thing and the stave has a big knot on the back I imagine I would have to space the whole stave out. How far apart should the spacers be? I hope you followed that.
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Band saws tend to follow smooth arcs anyway. Pretty hard to male a sharp turn with one.
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The sanding is the east part for me
the hard part is remembering where I put the template so I don't have to lay it out again
since I make the caul out of hard Maple they last way longer than my memory!
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The sanding is the east part for me
the hard part is remembering where I put the template so I don't have to lay it out again
since I make the caul out of hard Maple they last way longer than my memory!
I made mine out of doug fir boards, next time I will use a plywood I think.
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Hard Maple taks the heat better than anything else that I have tried !
anything else is a waist of time in my opinion
plywood may be a bit toxic when it smokes
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I will price it out I think maple is about 10.00 bd ft down here.
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I will price it out I think maple is about 10.00 bd ft down here.
I hope not that would be like robbery
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Don, I was just going by memory so you might wait till someone reviews it. I refine mine a bit on the belt sander after I get the initial shape done with the lines.
Your memory worked. I've got a bow clamped in it now ;D ;D
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Glad to hear that Don,nothing like a good cal. We have several with all different shapes,more reflex/less reflex/RD/flipping tips or recurve you can make them and experiment a lot of different ways, but for just initial straighting and reflex [what Steve said] Gary's seem to work the best,not to much and not to little. As far as clean up,no matter what I cut them with I always have to do a little sanding or rasping to smooth it out. :)
Pappy
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Badger, can you post some pictures of Gary's caul design?
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Badger, can you post some pictures of Gary's caul design?
Pappy's "life is good" thread is full of pics of them!
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I got the design from Twin Oaks, as Bukeye said, go to the life is good thread, you will see plenty of pics.
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Got it, thank you
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Here is the caul i made after Pearl drums posted his a while back. the pictures show what he means about using a yardstick to form the smooth bend.
Hey pearly i didn't notice your last post on this old thread about "Golder Lopher!", like my grandpa used to say, "I resemble that remark". It was my junior year as a Gopher when the gophers had the worst collapse/choke job ever against Michigan, and thats saying something, 'cause the Gophers have had a lot of collapses!
http://www.primitivearcher.com/smf/index.php/topic,37851.msg501777.html#msg501777
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Thanks for the pics. Im not good at explaining things, pic are so much better at that than I.
Im a Lions fan Gopher, I know all about collapses and failures!
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Thanks for the link Gopher! I like the backboard. Would 1/2" or 3/4" plywood be stiff enough for that? It would make it lighter. Not that a little exercise would kill me. There is sure a lot of molds and jigs in the hobby, almost as bad as my model sailboats.
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I made the caul badger described last night. Once I figured it out it came together pretty quick and easy.
Does the back board ever deflect heat and scorch the back?
When you are heating your limbs, do you put a weight on your tips or just push with your hand?
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It will scorch the back if your not careful. I rub oil on the back to keep that from happening. I prefer to make all my bends at once, that's why I backed mine.
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Like Pearl said you have to be careful or will scorch the back, just heat slow and keep the heat gun a few inches away and keep it moving and you shouldn't have much trouble,small learning curve but you will figure pretty quick how to keep that from happening. I also get the wood hot enough you can touch it but you know you don't want to hold it,not to scientific but that is the only way I know how to explane it. I use c clams to pull everything in like I want it. :)
Pappy
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Looks great. Thank you for posting your pictures gopher.