Primitive Archer
Main Discussion Area => Bows => Topic started by: dylanholderman on February 11, 2017, 11:26:54 pm
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Ok so my first foray into a lam bow didn't go well. Bad gaps in the fades probably from not enough pressure.
But sense that's the case I figured I'd bend it and see what happens.
Any thoughts or advice before I do?
(http://i1074.photobucket.com/albums/w411/dylanholderman/Mobile%20Uploads/2017-02/F3D3D3E3-1FEB-4228-994D-C0C2CED61996.jpg) (http://s1074.photobucket.com/user/dylanholderman/media/Mobile%20Uploads/2017-02/F3D3D3E3-1FEB-4228-994D-C0C2CED61996.jpg.html)
(http://i1074.photobucket.com/albums/w411/dylanholderman/Mobile%20Uploads/2017-02/01D57D36-9649-4030-AFE0-9B1D2B41FCF7.jpg) (http://s1074.photobucket.com/user/dylanholderman/media/Mobile%20Uploads/2017-02/01D57D36-9649-4030-AFE0-9B1D2B41FCF7.jpg.html)
(http://i1074.photobucket.com/albums/w411/dylanholderman/Mobile%20Uploads/2017-02/43288912-05A3-43A7-8745-CCA589A4C254.jpg) (http://s1074.photobucket.com/user/dylanholderman/media/Mobile%20Uploads/2017-02/43288912-05A3-43A7-8745-CCA589A4C254.jpg.html)
(http://i1074.photobucket.com/albums/w411/dylanholderman/Mobile%20Uploads/2017-02/4C6A4BBF-043C-47E4-875F-FDF7304C6FFE.jpg) (http://s1074.photobucket.com/user/dylanholderman/media/Mobile%20Uploads/2017-02/4C6A4BBF-043C-47E4-875F-FDF7304C6FFE.jpg.html)
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Yep...Armguard and Safety Glasses!
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What glue did you use?
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When you make a powerlam you need to feather the ends very carefully to nothing. The very end should be see through and it will go 'wavy'. I inch from the tip should be no more than 1/16th thick. You had too steep a transition. If you had clamped hard enough to close the gap then you likely would have ended up with a weakness there anyway through excessive pressure.
why not bend it to destruction! You will learn something!
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Haste is the big enemy with preparation and glue up. There is a lot to be said for doing a dry run first, assembling with no glue, it will show up problem areas. Regarding pressure, I use rubber strapping, at least two layers. IMO, if you can see any wood between your clamps or strapping, you don't have enough.
Don't worry, we all screw up, I've had to rasp off a bamboo backing before now and re-do it. :-[ >:( :laugh:
Del
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I have had similar glue joints on BB osage bows, I filled the void with superglue (no clamps) and forgot about it, no failures to date.
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I've done the same as Eric.
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Go without on the next one. You don't need a power lam. It's extra work, complication, and risk.
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Thanks for the advice guys
I'll fill the gaps with CA glue and see what happens when I go to bend it.
The glue this time was TBII.
I think the next bow I try to glue up will just be a straight longbow maybe will a little reflex
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Powerlams are a really useful technique. In my eyes it is better to keep at it until you get it right rather than do it once then move onto something else. Another 15 minutes sanding and prep and this would have been fine.
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I've done the same as Eric, but in my case I was totally sorry later.......
Now, this worked for me a couple of times, but I'm NOT saying I recommend it, exactly.
If you just put more glue in and clamp down harder, the dried glue inside maintains the gaps and stops you. But, the glue is strong, it just doesn't fill the gaps well.
So, once I really wanted to save a hickory backed black locust recurve I made. The hickory had cupped when wet, and my clamps didn't span the whole backing width, creating gaps a lot like this. The limbs were fine once I trapped them, but the fades were iffy, and some backing on the handle was lifted in bad spots.
So took a propane torch and an old butter knife and an old utility knife blade held in some vise grips, heated them red hot and burned and melted away any glue in the gaps, but not doing anything. Then I tried to guess the general shape of the little flat cavities I had made. I clamped the area so it couldn't spread.
Then, I took some hickory veneer I had, snipped it into bits and slivers, dipped them each in TB III as I went, and tapped them in, like little shims using a tiny stick for a mallet. I filled the hole with glue ahead of time, too. The shims drove almost all of the glue, and I basically smashed as much wood as I could pack in there, gently.
It worked, the bow is still shooting (gave it to a work buddy). You could barely tell once sanded.
I don't think it would work in every case.
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Gaps are no good >:(.
Take it down and re-do it properly it's simple as that.
OK you may get away with the occasional filling the gap with CA fix... if you really have to for some reason, like you need a bow at short notice.
I think the main thrust of this forum is to promote good skill and craftsmanship.
Yes there is room for rough and ready experimentation at times, but as I see it we are about good sound quality of work and sharing our skills and experience.
After all we have bow of the month, not botch of the month! >:D
Del
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I am with Del. Perfect is good enough. Anything less is not satifactory when you are gluing surfaces that will take strain.
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I am with Del. Perfect is good enough. Anything less is not satifactory when you are gluing surfaces that will take strain.
Yes we aren't making a piece of furniture! Laminated bow gluelines have to take quite a bit of 'workin'!
Perfect is good enough :) Now there is a saying worth putting on the wall of my workshop :)
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We say "Perfect is good enough." in Radiation Therapy, when aligning and positioning patients for treatment.
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just for fun:
https://en.wikipedia.org/wiki/Perfect_is_the_enemy_of_good
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Pat, somehow both statements are true. Some things I think have to be perfect, but especially with primitive equipment, too good starts to look like factory made, and also offends the senses. Is there such a thing as perfect imperfection?
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Pat, somehow both statements are true. Some things I think have to be perfect, but especially with primitive equipment, too good starts to look like factory made, and also offends the senses. Is there such a thing as perfect imperfection?
Right on Jeff. I guess those promoting perfection are not thinking of perfection of precision, but perfection of physical integrity.
I think it's worth noting that most of the glue gaps are at the edges of the limb and are the result, as noted above, of the thin wood cupping from being wet with glue on only one face.
The thing is, less than half the back is needed at all to carry the tension load, because most wood is much stronger in tension than in compression. (Hickory is about 3.7 times as strong in tension.) I made a little ash "parlor bow" of ash. It's 3/4" wide at the fades and 3/8" wide at the tips. It is about 3/16" thick (pyramid) and 36" long. It has a hickory backing strip about .050" thick and 3/8 wide. It bends to full draw and launches an arrow nicely. Unstrung, it has no string follow, in fact the tips are about a half inch ahead of the handle.
I have a hickory backed Osage bow with a few voids an the edges but nobody told the bow. It's holding up fine.
Jim