Postmortem Analysis (where'd I go wrong?)

[Innocente]

here's my latest: 72", white oak, superstraight grained, put on some walnut tip overlays, glued on a hickory handle (10"), the arrow shelf is 1/4".  55# at 30", backed it with linen and TBII,  had just completed tillering today, and was on my 3rd 320grit sand. (wet, dry, then sand, etc...) i put a couple quivers through it, and heard a TICK while drawing it.  examined it, and sure enough, a crack was visible on the lower limb.  i put on glasses, drew it again, and sighed as it detonated on me. (BOOM clatter clatter clatter). 
i do NOT have a shot of it pre-break on the tillering tree, unfortunately, and i didn't think to photograph that crack before i completed it's grim work. 

anyways, look at the pics, tell me where this one went wrong.  the dark lines that seem to be runoffs are NOT grain, by the way, the grain is gloriously straight, the lines are rays, i think.

one final thought: my cross section is a flat back, rounded edges on the back side, and a gentle dome on the belly side.  i use this cross section for all the bows i make, is that my issue?

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[sulphur]

its hard to tell, but it looks like the grain runs out where it broke.   white oak is pretty tough stuff, but thats my guess.

[Parnell]

I've been fiddling around with white oak boards.  I guess they're kiln dried.  I think they stink.  I've taken my time with a couple and on one I had the back of the raise a splinter in the middle of the bow.  I think the wood was too dry.  Maybe this is what happened with yours?  Dunno.

I give white oak boards a general thumbs down.  I'm sure there are examples of it working out, but in my opinion, hickory is a better choice, by far.  Seasoned staves are probably a whole nother matter.

[jthompson1995]

The next to the last photo tells the story, there was a runoff in the grain where it broke, the arrows made by the rays actually point to it. It looks like it was a fully quartersawn board so it would have been tough to tell from the grain on the side of the bow, but the grain made a little bump toward the belly of the bow and I guess it wasn't strong enough to handle it and the belly crushed.

Ususally a flat belly is better with whitewoods to spread out the force, a crowned belly will concentrate the compression force at the crown and can cause fibers there to give, then it's just a chain reaction for the rest of the limb at that weak point. Would this have saved this bow? I don't know for sure and I doubt it with the runoff but just some info for your next bow.

Hope this helps.

[half eye]

Innocent,
       Have to agree with JT '95 on the grain anomaly...pic # 137 you can see a woop-de-doo (towads the belly side) but it looks to this old man that there was another minor problem as well. If you look at pic # 143 you can see where the belly comes out of the grip fade it is flat across the width,,,,and just above the break the belly is way more round (convex cross section) and the break looks like it may have occured at that point.
      Like JT said, the rounded belly concentrates force to the middle of the limbs' width, so it might have been because you transitioned from flat to oval in that short distance. If you have a vise, you could clamp the handle in it and CAREFULLY pull the good limb back and see if it wants to show signs of trouble in the same area....if it does it might be the design....if it does not then it would seem that the trouble was with the grain anomaly. ( if you do the "bench bend" be carefull and remember your only pulling half the bows original draw weight)
      I'd be real curious to know how that experiment works out...if you do it.....remember I have broke WAY MORE bows than you
half eye

[George Tsoukalas]

On 1/4 sawn boards the edge grain has to be completely straight. No run offs. What kind of bard was this? Jawge

[Innocente]

it was a quarter sawn piece, and while i really didn't see a runoff in my grain, i am forced to agree that that break does show grain clearly running off the edge.  dangit.
this is my first attempt with white oak, (i've broken a record number of red oak projects, but i read about white oak's sturdiness and thought i'd try it). i don't know if it was too dry, but i am sure it wasn't too wet.  (i tested the wood inside the break right after it happened). 
appreciate the hickory recommendation, i have a soaking wet hickory board i have all roughed out drying in my house right now, i'm totally going to test the famed sturdiness of hickory.
thanks for the recommendation halfeye and JThompson, i think i read up on ELB's and subconsciously soaked up a D profile, then it mysteriously showed up in my work. i've been suspecting my cross section was the source of my misery.  i'll make my next a flat profile with rounded edges. 

[George Tsoukalas]

Don't think that hickory boards are bullet proof. LOL. I had one break at a little tiny pin knot. Considering the # of red oak board bows I've made I've never had one break if I've picked out the board. I had 1/4 sawn one break for the reason I outlined above. Jawge

[Gordon]

When a bow makes noises STOP! And don't draw it again until you understand the problem and have fixed it.

[woodstick]

dern. bad luck.

[Innocente]

good question.  when i examine the linen closely, it's a grid, strands going north/south, strands going east/west.  i don't know that it matters, but i always line up the strands perfectly with the long axis of my board.  course, you've seen how many i've broken, so mabey lining them up is a fatal flaw.  i'm thinking of trying a wood backing next.

and on that note:  this bow was once part of a 1x6 plank of white oak, i got another quarter sawn plank identical to the one that failed me here.  i think i'm DEFINITELY going to put a hickory backing strip on that thing. 

[ken75]

i could be totally off on this but i think i see pockets inside the break from deterioration, wether bacterial or low moisture im not sure . could just be my eyes though

[akila]

It looks like the grain  in that area is not straight.....its going to the left, where the bow has broken...and   form the picture it looks like the wood was to drie....low moistre...

[Innocente]

i can tell when the plank is too wet, but too dry...i'm less sure of.  i'll take that twin board i got for my 2nd white oak attempt and stash it in the bathroom for a few weeks, mabey up that moisture content. thanks for the suggestion, didn't even think of that.

[Grunt]

Sometimes the folks at the dry kiln put different thickness of boards in and dry them together. The 8,12, quarter will be dry and the 4 quarter will be too dry. It is mostly ok for cabinets but not for bowmaking. Quarter sawn will lie to you. Quarter sawn can be in plane radially but out of plane axis wise. You got to look at the sides as well as the face.