Bow autopsy

[arachnid]

Hi guys.
Had this bow finished 3 weeks ago. Gave it to a friend to check it out.
After about a 100 arrows (maybe more, I`m not sure) the bow broke.
I thinks it`s a de-lam between the belly glass and the core maple (too much glue sqeeze out?) , but I`d like some
opinions from the pros. So any info would be welcome so I can learn and avoide these mistakes from now on.

[mwosborn]

Do you happen to have a picture of the riser area before it blew?  Or take one of the other fade area assuming it is similar.

[Pat B]

Looks like a glue failure at the fade. That is where most of the stress in a bow occur because of the leverage of the limbs. Any imperfection would be amplified.

[EvilDogBeast]

Looking at the second picture, it appears you have two dry spots (they look white-ish compared to the rest of the maple around it) and a large section of the belly ramp seems to not have adhered for whatever reason. I'd say starvation and surface prep are the culprits, but take that with a grain of salt as I'm making those guesses based on aircraft composite work.

[Bodork]

Ouch! Looks like he rolled it it up in the back window of his 55 Chevy station wagon. Maybe there was oil or dust on the ramp. It doesn't look like the epoxy adhered to the black glass there. Hope he wasn't hurt

[JDBerry]

My bet would be it came apart in the riser, the rest is just travel.   ..OE

[Pat B]

That sounds very plausible, JD, now that you mentioned it. You, as a long time bow builder would have the experience to know.

[JamesV]

I agree with JD, the lams on the back of the bow turned loose from the riser first and caused the belly glass to come loose. I have had several of these failures and it was always caused by a glue starved joint from too much pressure.

James

[JDBerry]

JamesV,  Maybe I am misreading what you are saying. I feel where the riser is in two parts ( Zebra WAS glued to a Maple high lite) is were it all started.  It is a easy mistake to make when glueing up, just a little to much pressure.  ..OE

[Bvas]

Which came first the chicken or the egg?
Which came first the delamination or the riser failure?

The lack of fiberglass splinters on the wooden lam suggests poor adhesion. This could either be bad surface prep or starved joint. If there is evidence of glue, but no remnants of fiberglass on wood or wood remnants on fiberglass, than I’d say bad prep work.

Other thing is your fades still look a little thick. Tips should be paper thin. Then 1/16” at 1” and 1/8” at 2”. Hold the riser up to a bright light. You should be able to see light shining thru the first 1/8-1/4”.

[kenneth butler]

The separations of glass and wood and wood from wood, indicates failed glue joints. Whether it was starvation or bad glue I can't tell. Sure sorry for your loss.>>>----> Ken

[Shredd]

  It Buckled... 

Everyone has made valid points but the bottom line is unless you have a slow motion video of the break you will never truly know exactly what happened...  We can only guesstimate what happened and there could be more than one contributing factor that could have led to the break...  This Bow is History!!

   Bottom line is to practice good building habits and use good material...

  Use a good adhesive...   Use plenty of adhesive...   Use good core woods...   
     Use the right thickness of glass...   Make long lean fades...   Have a good design...
        Wipe down glass lams with solvent...   Keep contaminants off materials to be glued...
           Stay under 40 psi on the hose...  ( my own personal rule )
              Keep beer in Fridge...  ( especially when gluing the bow )       

     These are some of the basic rules... I am sure you could add 10 to 20 other good bow building habits to this list... If you follow these basic rules it will greatly reduce the chance of this happening again...

   Would anyone like to add to the list???

[jess stuart]

Mix the glue really well.

[Shredd]

 Good One Jess....