Trad Gang
Main Boards => The Bowyer's Bench => Topic started by: Cherry Tree on December 13, 2021, 08:35:17 AM
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How much space do you leave for your hose in a fiberglass recurve glue up? I recently had a delamination started at the tip so I pulled it apart with no pressure and the entire limb came apart (glass to wood) it appears to be super dry no visible glue really. New design and ive never had this happen before I did get laminations from a new source but everyone speaks highly of him here and I asked what the moisture content was. I glue both sides of every lamination so its always wet to wet. Just wondering what my problem might be if my hose had to much pressure or moisture I always assume is the problem. Or my heat box got to hot and made the glue to thin and squeezed out? Any thoughts appreciated
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My hose is right around an inch space, 60# pressure. I always check my hose the day before for leaks before glue ups. JF
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I do #60 of pressure and run 7/8s to 5/8s in the center of the riser and tapered back out to 7/8s.
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That sounds good. Must have a moisture problem
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There is a chance that one of the lams could be contaminated... Some say that wood oxidizes over time and should be freshly sanded before glue up...
What kind of wood was that lam?? How did you prep the wood and glass ??
I personally like to use just over 35# psi... In any epoxy instructions I ever read it always says to not clamp too tight... It needs space to work properly and is not like wood glue... Flem vacuums his bows and gets by with 12 to 14 psi...
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Only prep i do is wipe it with a dry rag and let all laminations sit in hot box for 15mins before gluing. Hard maple was the wood.
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I wipe my glass with acetone... Which I think is a must...
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First off, thank you for not giving the suppliers name when the cause of failure is unknown.
I sand all glue surfaces right before glue up. Then blow them off with the air compressor. I would recommend against wiping with a dry rag. Epoxy works by filling voids. Wiping with a rag will imbed any dust into the voids needed for adhesion.
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Glass doesn't adhere as well as wood, Chad Holm made me aware of this when he said he peeled the glass off a D/R longbow and put new glass on it. I checked this on a failed test bow and it peels pretty easy. No fix on that that I know of, but it isn't common for one to fail like that.
I run 70 lbs in my hoses ,so don't think thats it.
Was it clear glass so you could see any glue dry spots?
I make space on D/R bows 1 1/8 to 1 1/4 inches, the hose needs to be elliptical , not round or dogbone shaped. Recurve would be a little less for thinner limbs.
Pressure strip used?
Not sure if the heat would thin the glue out , but doubt it.
Wish I could give you a definite answer, but it's hard to tell .
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Pressure strip was used. Black glass was used. It just seems super dry you can tell the wood took some of the glue but still is very dry looking. Does everyone use acetone for glass?
What is everyone's method of regulating tempature?
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No acetone, maybe sometimes denatured. Bingham Temp limit switch on 4 - 150w bulbs. Off 180° on at 145-50°
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Okay thats what I use. Seems like there should be a better option.
And I will add the bow failed before I even sprayed it I was doing final sanding and making sure I like the grip and limb alignment and it popped free. Like I said never had this happen and I do make bows regularly and have for years..
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I stopped wiping wood with solvent, fresh sanded surface and blow with DRY compressed air.I do wipe the glass with Al or acetone.
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I use 60-70 PSI in the hose, always run a sheet of 80 grit once down the wood and air blow, and wipe the glass with alcohol. Never had a delamination…yet. Only thing I can think of is that the lamination was contaminated - oil or wax, or something that impaired the glue from bonding, and most of it squeezed out.
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Noah, do you really live in Nelson??
That is the one of the nicest, most beautiful places I have ever been!
I'm so envious, I don't think I am going to be able to sleep tonight
:notworthy: :notworthy: :notworthy:
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Even better, I’m about half an hour up the road, on the shore of beautiful Kootenay Lake! Truly one of the best places in a province that has more than its share of stunning scenery. As long as you like mountains, that is. I’m very lucky to live here, and appreciate it every day!
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That being said however, Montana certainly ranks right up there as well!
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I appreciate everyone's input. I always avoided blowing my lams off with a compressor due to the potential moisture from it. While on the subject what does everyone think moisture content should be of all wood parts?
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You blow off your wood. Put on a moisture filter on your air blower. They are about 2 1/2 diameter plastic. They work great. JF
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Here is one similar to what I use. JF
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The space on new forms should be 5/8" it gets a little bigger the more you use the forms as the bolt holes get stretched and the hose gets broke in if the gap is too big the hose will try to roll . Places like fade outs, limb tips, and the handle sections you can apply small pieces of wood above the hose to make a tighter fit .
All surfaces should be cleaned with acetone, wood and fiberglass, the difference between using it and not using it is the difference between a clean glue up and a dirty glue up if you use a clean white cotton cloth you will see whats on the cloth even after just grinding out the lams. Actone does not hurt the wood it does not bring up the oils it washes them off . Woods like coco bolo and bocote you have to wash alot and the more you go over it the lighter color the glue surface gets as the oils come off . I use 70#s of air pressure .
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Appreciate all the thoughts shared!