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Main Boards => The Bowyer's Bench => Topic started by: Justin Falon on August 23, 2008, 07:19:00 PM
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What is the secret to getting good glue lines when using C clamps to glue bows up? I have had good success with wood bows this way but can not get the same outcome with laminated bows. Pressure strips? Thanks.
justin
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I would suspect it would be with a fairly stiff pressure strip. I use rubber and have had some super glue lines.
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Okay, where to get the rubber? My last glue up turned out the right weight but had 2 air pockets...Only doing Hill style bows so it's pretty straight forward.
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I use 1/4 inch aluminum strips, backed with cork. Cork on the form as well. My glue lines generally seem real even. Because glue seeps out, however, you do have to go back and retighten a couple times... but the clamps shouldn't be cranked.
Mike
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Justin,
I've never used c clamps,but I did use the rubber band system once,some broke,went to air and never looked back!
Did you use heat with the all wood bows? Maybe the glue thins with heat ??
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Lots of clamps, fairly heavy pressure strip that matches the bow well and rubber to even things out. Always worked well for me.
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I don't do many laminated bows and only one with glass. I had terrible luck with screw clamps because they would loosen when I cooked the glue. I guess the wood shrinks. Then I went to spring clamps with better success but still not very good glue lines. On my last glue up, hickory backed black walnut, I got very good, thin glue lines using bicycle inner tubes to wrap the glue up.
When using "C" clamps and spring clamps I always used a sheet metal pressure backing plus with "C" clamps a wood pad under each clamp. Pat
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I may be working in the dark ages here, but strips cut from bicycle inner tubes work really well for me. I space 1/2" dowels along the form to wrap the rubber around. I can put a lot of pressure with these rubber strips. I usually get two from each innertube, and get them free from the bike shop. I haven't had one pop yet and have heated as high as 184 degrees. I use a 1/16" aluminum pressure strip the same width as the bow (1 1/2"). I have a 1 1/4" piece of pvc lattice glued to the top of the aluminum, and 1/8" rubber on the underside. The thinner aluminum allows me to tweak it at the fades to get a really good fit before clamping. I use this system on straight longbows, and have just finished a form for a mild R/D with the same clamping system. I will let you know how it works out with the R/D.
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I use to use C clamps as well but quickly went to an air hose. C clampps loosen especially in an oven because the glue thins and squeeses out of the laminations prior to the glue curing, you have no option but to check and retighten the C clamps as the bow is cooking as they will loosen, you really need some kind of a good spring clamp which will take up as the glue squeeses out. I use a good steel flat bar and rubber pressure strip...Glenn...
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toss the c clamps and use 1/4" - 3/8" rubberbands or long strips of innertube. you will get much more even pressure with innertube strips.
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So...now that I have 3 dozen c clamps...time to buy an air hose or rubber bands. Go figure.
Thanks guys!!
jf
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jf, If you build self bows, you never have too many "C" clamps. They, along with a heat gun, are good for inducing reflex, bending recurves and straightening staves. Pat
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Just check your C clamps during the drying stages and you wont have a proble at all. You're right Pat you cant have too many C clamps...Glenn...
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use "west system" epoxy and you won't need a hot box. it cures without heat, should help solve your problem. smooth-on will also cure without heat but it does take a couple of days. I personally use the rubber band system. I put a medium nail in the side of my form every inch for the length of the form on both sides to hold the rubber bands
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Can we maybe see some pictures of yalls forms & setup?
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http://www.kennyscustomarchery.com/Bow_forms.html
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Yes I would like to see your rubber band setups. I know mine is rough but would like to see what yall got.
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Here is my straight form with dummy riser and pressure strips laying on top.
(http://i121.photobucket.com/albums/o203/Apex-Predator/First%20Glass%20Bow/Straightform.jpg)
Here is a glue up with the straight form. Hint- Use more clamps on the critical areas like fade outs. I had some thick glue lines on this one, which was my first.
(http://i121.photobucket.com/albums/o203/Apex-Predator/First%20Glass%20Bow/Clamped.jpg)
First R/D form. Just after removing the clamping strips.
(http://i121.photobucket.com/albums/o203/Apex-Predator/Apex%20bows/Unclamped.jpg)
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Notice the pressure strips laying in front of the form on the second shot! Remember to use them! Also notice the hole drilled and c-clamp on the R/D form. This is very useful in holding the riser in place. If you don't use this it's very hard to clamp the limbs without the riser sliding.
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I use spring clamps on my wood laminate bows and get some nice glue lines. Constant pressure even if glue thins. I use air hose on my glass lam bows.
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I have used rubber bands cut from truck innertubes. and they work everywhere around the shop too and are free from tire places and good big sissors. put lots on the mold and then heat it up some will give up but with lots it still works just fine and the pressure is still there in the oven if something shrinks
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I've only glued up bamboo backed bows. Never done glass, but I use c-clamps. I bought some rubber from McMaster Carr (they're on the web)and cut strips from it. You can probably buy a roll of it in the size you want also. They're good folks to deal with. Anyway, I lay the rubber against the bow surface, then top the rubber with a wooden pressure strip, about 3/16" thick, ripped from a clean 2X4. The wood sucks up the dents from the clamps and spreads pressure to the rubber. The rubber spreads the pressure out evenly. Tighten the clamps with your thumb and two fingers, and you shouldn't overtighten. When it feels like it wants to stop, then stop! Don't crank down. I clamp approximately every 2". Throw away the wooden strip or cut it up for some other use when done.
That said, if I were to crank out a bunch of glass bows, I'd use an air hose.