Forensic experts - how did this break?

[Stinger]

A little background.  This is a bow that my father originally made about 35 years ago.  I took possession of the bow a few yearsa ago and last year reshaped the riser and took some weight off the limbs by removing material from both edges.  I did this methodically and used a tillering tree to ensure the limbs worked properly and were in synch.  I did not remove any glass from the face or belly of the limbs.  I then refinished the limbs and riser using Tru Oil.  The back of the limbs have snakeskins that I applied with super glue following instructions I learned here.  They held up well during the break as the glass on that side never split.  Since the refinish I have shot maybe 3000 arrows with the bow and never had a single problem.  I inspected the bow routinely and it never showed any signs of stress and never any limb twist.  On the day this happened.  I shot 6 arrows with it and then set it aside for 15 minutes while I shot another bow.  I then shot another 3-4 arrows with this bow.  On the next shot as I got about half to two-thirds of the way through the draw, the bow came apart.  You can see in the two pictures what it looks like with the bow still strung and the third after I released what little pressure remained on the limb by taking the string off.  

Obviously I'm sick about this.  My Dad just turned 88 recently and my goal was to take a deer with this bow this season, which starts here in just 2 weeks.  He still has the forms for the limbs and eventually I will probably make another set for the bow.

I have seen delaminations before but have not seen a break like this.  It looks like it broke cleanly right at the fade.  I'm looking for your opinions on what you think happened.  I'm thinking that perhaps I removed too much from the limbs, but I did shoot roughly 3000 arrows with it before the break.  Your thoughts?

 

 

 

[SportHunter]

Not sure of the reason for failure but since you still have the forms your father used why not order up some lams & get it shooting again?

[rmorris]

I am sorry about your loss and hope you get a new bow soon but,2nd picture down looks like the failure point is just above the riser on the backside of the bow. It looks like no wood came off and it is just glass there. That is a common failure point in a bow because unlike the rest of the limb that portion just above the riser is not able to bend creating huge amounts of shear force between layers. There may have been some glue problems there because it looks like the joint broke and not the material. what happened next is there was huge compression forces with not tension to counteract resulting in the rest of the failure. In many cases that worst looking part is not where the initial failure point occurred. I do not think there is any problem with your limb design.

[kennym]

In the 2nd pic, it looks like the wedge was a bit blunt like Ralph said, creates a lot of stress in one small area. Use a longer thinner wedge on the next one if you can, or possibly a power lam to spread the stress a bit.

How thick is the wedge at the butt, how long, and how long is the tapered part, just so I can visualize(sp) it?

Looking again at the top pic, the riser is thin at ends, maybe the wedge was to take pressure off it.

 Maybe not thin it at butt, but make longer and add a power lam to move stress out a little.

[jess stuart]

It does look like the wedge is a little thick.  Thirty five years is probably a pretty long life, don't think is has any real design problems or would have gone much sooner.  Sometimes bad things happen to good bows just like people.  It is amazing that they stay together with what we put them through.  Some good glues and materials available for sure. Sorry for your loss, but at least you have the forms and can build another.

[Tron]

Pretty common break point.  As said, the transition from the fades to the working limb looks a little sharp.  Possibly a suspect glue joint because if done properly, the wood should fail before the glue.  Even if it's a small, interior failure, once something has failed, the whole thing goes.  Seen the same thing several times, all on take down recurves.  More gradual transition is the key I think.  And mix up that epoxy well!!

[Robertfishes]

sorry your loss, that's a good looking bow your father made! When you make the new limbs the bow will have part of you and your father in it, thats strong mojo. I have only made 1 piece bows myself. I try to make long thin fades like Jim Brackenbury did on his bows and I started adding some power lams too, that makes the fade even longer.