Why'd this board break?

[Jake Spoon]

Hello everybody!

I am a longtime lurker here, who is trying to return to archery after not working on a bow since I was in junior high school (some 9-10 years ago). 

Over the last two months or so I made two red oak board bows of medium draw weight that are serviceable and shoot ok. More recently, I wanted to try making a hickory board bow. I was taking a picture of this one to evaluate the tiller when it exploded quite suddenly.

The picture is not the best, but it is the only one I have. I am hoping to use this as a learning experience before I start again on a new bow. For all I know my tiller was awful--like I said, I'm just getting back into bow making. Thanks for any feedback/criticism.

68" long
1 1/2" wide tapering to 3/4" tips from mid limb.
Hickory backed with that ugly stuff from Poor Folk Bows which shall not be named 

Jake

[Kidder]

Welcome! Your tiller looks pretty good - maybe a little whip tillered but I don’t see any real hinges or anything. I’d like to see a close up of the break - bows can break for any number of infinite reasons, some directly caused by the builder, others inherent in the wood itself.

[Pat B]

I too would like to see pics of the break and where the break is on the bow.

[bjrogg]

I too would like to see pics of the break and where the break is on the bow.

Me to. Tiller isn’t perfect, but it’s really not that bad.

Bjrogg

[Jake Spoon]

Here are some pictures of the broken limb. It broke on the bottom limb at full draw, all at once. There were no ticks or anything that I heard beforehand.

[bjrogg]

Which side is the back?

[Jake Spoon]

The back is the side against the picnic table in both pictures.

[bjrogg]

Looks like it failed in tension. I have never tried hickory but from what I hear it is really good in tension.

You mentioned some type of backing? It wasn’t spliced there or something?

I don’t see anything in the tiler that would have indicated that.

Bjrogg

[Jake Spoon]

It was backed with three layers of fiberglass tape + Titebond. They were continuous sections.

[superdav95]

Yes interesting.  Did you manage to avoid grain run off and we’re you able to get to a single growth ring on you back prior to the tape?   

[bassman211]

You have grain run off above the break.

[Pat B]

Looks like the side grain, from back to belly was too steep. Breaks like this break along the grain.

[Kidder]

I suspect it’s a combination of things. As Pat mentioned the grain appears steep on the side in that area. However, I suspect that your backing (that we shall not name) contributed to the failure. We believe your bow broke under tension. Which means your backing most likely failed first, causing a massive tension failure that carried through. Short of a Time Machine and setting up a slow motion camera we will never know for sure, but that’s my theory. Yet another reason to avoid that stuff like the plague. On to the next…

[Jake Spoon]

Thank you to everyone for the feedback! I really do appreciate it. It sounds like I need to use better backing material and to be more careful with grain runoff on the sides.

I will start another one this week with both of those things in mind, hopefully with better results!

I had never had a bow explode while I was drawing it, and that was unpleasant enough to be good motivation to do better on the next one : )

Thanks again!

[willie]

Looks like the side grain, from back to belly was too steep. Breaks like this break along the grain.

this.   with a board bow the ring lines need to look look they do on the picnic table board below the bow in the last pic.
and also straight without swirls down the face of the board.  Its hard to find a good board for bows at most retail yards these days. cutting a stave from a tree may be easier.
Backing cant really make up for poor grain, and when using a board one might want to go a little wider or longer than if using a stave.