sooooo....any ideas?

[soy]

The trade bow I was working on and about to shoot in( just put tip overlays on)I had 30 shots on it before the overlays...initially I had thought I narrowed the tips too much or perhaps The nocks were too far toward the tips now I wonder if it was a starved glue joint....what have I done wrong?

 

 

 

 

[bjansen]

Tell us about the glue up process.  I am guessing something went wrong there.

[kennym]

I'm with Brad, that last few inches looks like a mighty clean separation.....

[soy]

Ground tapers brush dust off acetone clean glass butter up both sides with smooth on...Set in form with 70 psi approx.36 hrs in form @ 75°f.... there were only 2 deviations from the usual course one being I ground my own Lams , and#2 is I went with a .045 instead of .050 taper rate    should I back off to  65 psi  on the form? Oh I guess #3 would be I brushed the lams instead of cleaning them with acetone

[soy]

Also it broke at brace after the overlays with no new shots....I highly doubt that matters but I'll throw it out there anyway

[monterey]

Looks like a glue failure.  Did the acetone dry off completely before you glued up?

[soy]

Yep...but does it appear to be wood related or cause more from the glass???? I suppose that's what came first the chicken or the egg but I would really like to figure out how to avoid that from happening again

[rmorris]

Soy, is that bamboo or wood?

[soy]

A-boo alternating with walnut

[Bowjunkie]

You can inspect it much closer than we can. Did the glue joint actually come apart or did the wood itself tear apart?

That's really weird that it came apart just sitting there at brace with no further shooting. How much heat was the bow exposed to AFTER glue-up? How hot was it when it came apart? Inside? In the sun? What grit paper did you use to grind the lams?

[Pat B]

If the glass doesn't have wood bits still glued to it I would say it was a glue failure.

[bjansen]

I don't think the brush vs acetone would have impacted those woods.  

Could it have been just an unmixed portion of the glue (I am assuming you are using smooth on).  One thing I always do it after I have thoroughly mixed the two parts together, is then empty the mixture in a new glue cup and use a new mixing stick to mix another 30 seconds prior to the application. It would only take an inch or so of an unmixed part a or part b to begin a delamination.

[rmorris]

Originally posted by Pat B:
If the glass doesn't have wood bits still glued to it I would say it was a glue failure.

X2 , otherwise take a look at the walnut and see if there is any character in the wood there that may cause it to break( vertical grain or knots)

[bornofmud]

Wow, that's wild.  Definitely glue related.  What glue did you use?  You're certain the room was atleast 75 the whole time?  Didn't drop at night or anything?  Is the delamination on the aboo side or the walnut side?  The walnut could have drank up the glue and caused a starved joint, but the break almost looks too clean for that.  Super weird!

[soy]

The wood looks free of defects there is some glass on the wood and some wood on the glass....but a clean separation between the walnut and Boo

[Beanbag]

I've had walnut separate like that.40-50 shots, set the bow down and started to hear little pinging sounds. Put it on my scale to check poundage and boom. The wood actually let loose, glass had bits of wood still attached. Many types of walnut out there, what kind was it? There is some inferior stuff out there. I also think using a higher temp helps impregnate the wood better.

[Ice Mike]

I'm not a glass bow bow guy yet, so forgive my ignorance. ..but is it a mortal sin to glue the wood and boo sections together and then use the smooth on for just the glass lams? It seems to me that a good coat of titebond III on the wood to wood or wood to boo joints would penetrate and hold better than the epoxy.

[bjansen]

That is a good thought.  I know of at least one successful bowyer who uses urac on anthing wood to wood, and smooth on only for items touching glass.  

I personally think smooth on would be a better wood to wood choice for items that will be flexing and bending than TB1, TBII or TBIII though, but have no evidence to back that up.

[Bowjunkie]

Titebond is best used on mating surfaces that are smoother as it has practically no gap filling properties. Smooth On is best on more roughly 'ground' surfaces. Smooth On is MORE than adequate, and proper, for all surfaces that are ground. Use the glue that suits the surface preparation.

Adequate mixing is vital. Heat would help, but I've made a bunch of bows curing Smooth On at room temperature.

[Ice Mike]

I've been doing a little digging into this issue and I have one more question. This may be a stupid question and I certainly don't want to insult you, but...

You didn't wipe the wood with acetone did you?