Limb broke, new one seem to hinge- opinions needed PLZ

[arachnid]

Hi guys.

Lats week, the top limb of my takedown broke (my first glass lam bow). I didn`t tighten the nut all the way and I think that caused the limb to rise in the pad, causing it to break.
Here are some pics of the brake (soory about the blur):
       

       

       

       

According to the last picture, it seems like the lower part of the limb (just under the bolt) took too much stress and caused the limb to fail. BUT, it broke right at the end of the wedge. I had  pretty good glue line. So, what do you think? Is my theory currect? (It`s importent for my so I`ll know to avoid it next time).

So, I spent the weekend making a new limd. After a few adjustments it now has a positive tiller of 1/2". Thing is, the limb seem to hinge right after the wedge when braced, like so:
           

But, when drawn it looks pretty good:

           
   
What do you guys say- should I be worried by it?

Thanks
Dor

[kennym]

Can't see last 2 pics, but here some thoughts:

What kind of glue?

Wedge tapered out fairly thin(can't tell)?

What kind of glass?

what kind of lams?

If the new one is hingey at end of wedge, you may need more taper or a power lam as the bow is putting extra pressure there.

[Wagstaff]

Just a guess, but could have been wedge failure.

The wedge needs to be full thickness (Approx .250), and flat past the end of the riser, before you begin the taper to fadeout.

[arachnid]

I'll try to get the pics fixed.

Kenny:
I used smooth on
Glass is Bearpaw powerglass 0.8mm thick
2 maple lams, 1 parallel and 1 with 0.003" taper.

Wagstaff:
I didn't make a flat on the wedge. It just tapers through all it's length.

[arachnid]

I thought of a possible fix for the bow.
My wedge is 8" long. I can add a 10" underlay over the belly glass with a flat section and the taper and blen into the belly of the limb(kind of an outer power lam). Figure it might stiffen the fades a bit.
Your thoughts?

If that won't work, is there anything else I can do to prevent faliure?

[kennym]

The wedge looks to be not stressed too much, (bending the wedge).  Not in your form when you add the wedge in stack , is it?

I don't get why the full draw doesn't show more hinge.....

I use the same straight tapered wedge with 0 probs.


How about a pic of wedge area with bow unstrung?
But, I use the superlam with the builtin power lam with it, so your idea of an external power lam might work too.

[kennym]

How about a pic of limb from side with bow unstrung?

[arachnid]

I don't use a fire hose form. I just use clamps. Can it be that I put too much clamping pressure at the end of the wedge upon glue-up?

And Kenny, do you have any idea about the failed limb? Why did it happen?

[Dale in Pa]

Are you sure that your form doesn't have a ripple in it at that questionable spot? In other words, the hinge is actually glued in.

Sight down the edge of the limb with the bow unstrung to check.

[arachnid]

     

The form is fine. I think I put too much clamping pressure on that spot. On the other hand, if I don`t clamp it tight it`ll give me a glue joint.
So, is it fixable?

[Dale in Pa]

Yes, easily fixable. Use Bondo, auto body filler and smooth out the form.

[arachnid]

Originally posted by Dale in Pa:
Yes, easily fixable. Use Bondo, auto body filler and smooth out the form.

The form is not the problem. It's fine.
I meant are the limbs fixable?

[Wolftrail]

I think i would still add another lam, like a shorter power lam in the mix to ease the stress in the fade area. Thats how I built mine but then again they are wood limbs.

[arachnid]

Originally posted by Wolftrail:
I think i would still add another lam, like a shorter power lam in the mix to ease the stress in the fade area. Thats how I built mine but then again they are wood limbs.

That's what I thought of doing. Good to know someone has good experience with this method. Since my wedges are 8" long I thought of making the external power lam 10" long. Is it enough? Should I go for 11" or 12"?

[kennym]

Can you measure thickness at the end of wedge compared to out past the end of the drawn oval, looks thinner at wedge end than on out from here. May be the pic tho.

[Crooked Stic]

Maybe a wood failure or glue problem.

[arachnid]

Originally posted by kennym:
Can you measure thickness at the end of wedge compared to out past the end of the drawn oval, looks thinner at wedge end than on out from here. May be the pic tho.

Sorry Kenny but I didn't get it    
Explain please...

[kennym]

Sorry, limb thickness at tip of wedge and out say an inch and two inches. Pic makes limb look thinner at tip of wedge. If so that would explain the hinge.

[Al Dean]

Sure looks like a form [problem to me.

Originally posted by kennym:
Sorry, limb thickness at tip of wedge and out say an inch and two inches. Pic makes limb look thinner at tip of wedge. If so that would explain the hinge.

Limb does look thinner there...  Could be your lams are off or things could have start compressing there...  What draw weight is the bow???  Unless I am wrong .8 mm is about .030" and .030" is light for anything over 40#...

  I am thinking 3 things...

1.  Glue failure...  Too much squeeze out...
2.  Too thin of glass for poundage causing it to compress and buckle there...
3. Lams could be off and too thin in that one spot, by the looks of the pic... But if so I would think you would see a hinge in the draw pics...

   Or a combination of the two or three...

  Would like to see those close-up pics...  Try moving your camera away about 3-4 feet and zooming in...  That works for my camera...