R/D bow failure - your opinions wanted!

[Souocara]

Just finished a glass reflex/deflex bow (using KennyM's templates - thanks!) I thought it turned out great and have been shooting it for the last few weeks pretty consistently.  Below is a picture of the finished bow - sorry, no full draw pic.  I made it a two piece takedown with a fiberglass sleeve.  Riser is rosewood with a 1/4" phenolic insert in an "I-beam" type configuration.

Anyway, I probably have around 500 shots through it and tonight, without warning, it failed spectacularly while at full draw. 

From what I can see, it looks like it failed on the back right where I reduced the grip to make room for the fiberglass wrap for the takedown sleeve.  I didn't think this would be an issue as there are tons of recurve bows where the glass backing is cut through in the riser for the grip. 

Any thoughts on this?  I am wondering if this is a glue failure that just manifest itself where I cut through the back.  The riser should not have been flexing there at all, so I'm still not sure why it would have failed in that spot. 

Any help would be appreciated.  I'm about to start another bow of similar design and I would like to avoid making the same mistakes twice...

[jess stuart]

Man that is to bad, it is a great looking bow.  I haven't got around to the sleeve yet but, when I do I will add a overlay on the back of the riser and not cut through the glass.  Sometimes things just seem to fail for no good reason don't let it get you down.

[typical2]

I had a blow up just like that with a Hill style takedown.  I now use an overlay and have  the back glass extend under the sleeve.  I have never had one fail done this way.

[Souocara]

Probably a good policy.  I guess I just wonder how people get away with cutting through the glass on the backs of recurves.  Is it just a difference in design that distributes the forces differently? 

[Bowjunkie]

The first thing I noticed when I opened this thread was how short the riser was and how steep the fades are. You said 'it shouldn't be moving', but it seems like maybe it was... something apparently was. And perhaps yours differs from the recurves you mentioned in that their risers are longer, deeper, wider, or fades shaped different, etc. Running the glass all the way to the end would be a good start, but I'd study it all. Often, it's a combination of things.

[kennym]

I think Bowjunkie hit on part of the problem, you need the end of riser to flex and do part of the work in the fade area. I can't see for sure but they do look steep. 

As far as recurves having the glass cut on back, look at 3 pc  takedowns . When I built the bow in my site , like yours, I cut the back glass to make the grip feel like I wanted, and my thought was if a TD can take it, I'll try it. I probably don't have 500 shots thru it but it is OK so far.

BTW, that was a beautiful job on that one!! I need to try a 2 pc....

[monterey]

If there was anything wrong with the glue joint it might just gradually break down from vibration.

I think the fades look a bit steep too but internet pictures can be hard to decipher.  General rule of thumb is to not exceed 1/16" (.062) at one inch from the end of the fades.  I have been seeing that rule for many years going back to my first bow and Bingham's instructions.

I have come to treat that .062 as an absolute max.  The last riser I did was .042 so if this clutz can get there anybody can!

[monterey]

Just a quick add.  I have never used a power lam but it might be useful in protecting a riser that short.

[Souocara]

Thanks everyone for the replies!  Now that it has been mentioned, I did lengthen the belly side of the riser slightly from my last bow of this kind so I wouldn't have to put much of an overlay on the fade of the lower limb.  I didn't lengthen the riser overall, so the radius on the fades got tighter.  I did try to follow the 1/16" at 1" from the fades rule, but the combination must have done me in. 

Live and learn! You guys are awesome!

[kennym]

x2 on the power lam Mike mentioned!

[Tim Finley]

If you wouldn't have cut through the glass on the back of the bow it would have been supported by the sleeve . Its probably what broke your bow,I would say by looking at it that it is not the fade outs but the pressure on the handle gave lift to the lams  .  All handles flex even metal td handles some flex so little you cant feel it  .

[Crooked Stic]

You got to put enough overlays on the front of the bow so when you releave the material for the wrap you dont go thru the fiberglass. Got to radius those corners to.