Reading the grain in a break

[nyarrow]

I was just finishing up a bow I had a solid 20hrs into and had what I thought a perfect tiller when at about the 27" mark @57lbs the dreaded tick, ticked and was soon followed by a pop. Surprisingly I didn't get angry I took it off the tree and wanted to know why it happened. I spoke to a bowyer friend that mentioned the grain will often tell the story. I haven't been able to see anything obvious so thought I would ask for some insight into solving the mystery.

Bow specs: Hickory backed ipe,  1 1/4 from handle to 12" from tips, then a straight taper to 3/8" at knocks. Belly taper started at 5/8" at fades to 7/16" at tips. Bow length was 64 overall and 62 knock to knock. Handle was very stiff, I had built it up with a power lam, full 3/4 ipe thickness and two additional 1/4" handle lams.

[blackhawk]

Did the hickory backing lift a splinter? And pictures will help dissect your issue greatly.

[Pappy]

Hard to say without a picture of the break. Sorry on the break,I always hate that but it happens. It does help if one can figure out the cause,if it was something you did or the material.  Then you can learn from it. 
  Pappy

[JW_Halverson]

Sorry about the busted bow.  If you can learn anything from the autopsy ( auto=self, psy=see.  Literally, to see for yourself), then the bow didn't die in vain. 

Each failure teaches you more than the ones that work fine.  Just don't follow that line of logic to the extreme and purposely make every bow to blow up.  Although I don't see anything wrong with experimenting with pushing the limits and risking failures. 

[nyarrow]

The circled area is where the crack was initially. It was only the hickory backing and the ipe was still intact. In an effort to further investigate I broke it over my knee in hopes of finding an answer within the wood. My best guess is I didn't round the corners enough. I burnished the heck out of it 3 -4 times over. My other idea is the backing was too thin (3/32") Any suggestions?

[mullet]

 I've had hickory do the same thing with Osage. I'm repairing one right now. I super glued the hickory splinter back down and then reduced the thickness of the hickory backing by scraping and sanding. Then I'm going to back it with rawhide. I hate to waste a piece of Osage or Ipe.

[Hrothgar]

I think you are indirectly hitting the nail on the head. The hickory may not have been  thick enough, but based on the dimensions you give--parallel taper from fades to 12 " before the tips and the thickness taper--5/8" to 7/16" it seems pretty thick yet at the tips. Was the break at mid-limb or further from the handle? If so, I think this may be why.
Eric

[nyarrow]

The crack was at mid limb. Over the course of tillering I had to reduce the backing at one point it just seemed to be over powering the ipe belly. I noticed as I was chipping away at the belly that I didn't have a lot of wood left to play with, thus decided to reduce the backing a bit.

[ken75]

Dustin , i believe you were a little thin on the back , you have the best of both worlds with ipe and hickory . two tough woods that if balanced according to their strengths should produce an awesome bow. just as too thick of hickory can damage belly cores too thin backing can be done in by dense cores like ipe and osage. if you find yourself in the same situation again and you want to stop reducing the belly core and your backing strip is down to 1/8th already try some side tillering. it shouldnt take much to get you there , and width tillering reduces weight slower than thickness tillering

[Pat B]

When you reduced the hickory in one spot is that where it broke?    If you find the belly is getting too thin it is time to reduce the width of the limb, sort of tillering from the sides.  My first hickory backed ipe came out with the belly thinner than the backing. Under normal conditiond a hickory backing should not overpower an ipe belly. A hickory backing of 1/8" to 3/16" or even less is good, from my experience, for osage or ipe bellies.

[fishfinder401]

A hickory backing of 1/8" to 3/16" or even less is good, from my experience, for osage or ipe bellies.

i know this is a whole other class of bow than what  nyarrow made, but how thick should it be on a warbow of 130-170?
thanks
noel

[nyarrow]

Pat & Ken,

  Sorry I wasn't clear there. I reduced the entire backing to one uniform measurement and then burnished to a clear/smooth finish. I was worried the ipe was going to be thinner than the hickory and that's really why I started reducing the backing in the first place. Although I never read or heard it anywhere I assumed there was a ratio of belly wood to backing wood that was acceptable and having a thinner belly than backing didn't seem to make sense to me. I now realize that what I should have done is tiller from the sides. Thanks for the advice to the rookie. In my mind the dimensions were set and so side tillering never occurred to me. I suppose its all part of the learning curve. I just hope I can get another knocked out before the season arrives!