Back to the drawing board; practice trade bow failed

[Matt S.]

I've been working on a practice bow for the PA trade. This was a red oak 1x2x6 board bow, steam bent into a double curve design. I've learned some really valuable lessons on bending wood, but am still disappointed that this bow has failed.
I just got it to the short string and it was pulling between 40-45# @ 21 inches when I heard that dreaded CRACK! I'll include some photos, maybe all you bow experts can shed some light on where I went wrong?

Here's the bow roughed out. One of the tips isn't recurved as much as the other, and the other has a slight twist to it, but I did not think it would affect the outcome:


Here's the bow braced on the short string. The red circle shows where the crack developed. Unfortunately I didn't manage to get any photos of it bending, but it did seem to bend a bit near the handle, but I didn't think it was bending TOO much there...


And here's a close up of the point of failure:


Any advice would be MUCH appreciated as I really want to do a design similar to this for the bow trade and I figure I still have time!
Thanks, Matt

p.s. this was my first bow with some "major" heat bending (setback handle, recurves, deflex), so this has been a lot of new territory for me.

[Elktracker]

sorry about that, Was the board givin a good amount of time to rehidrate? You have plenty of time untill the ship date

[toomanyknots]

I continue to be impressed with the bending of red oak boards, nice job bending the tips. Really sucks in didn't make it. Sorry.

[half eye]

Matt,
     With that tension fracture, you may wish to either widen your limbs (thinner back to belly) or "trap" the Belly side into a low crown cross section. That is only if you are sure you didn't have a hinge going on at the break site, if not I think ya just need to tweek your design layout.....just a little bit.
rich

[DarkSoul]

That's a really weird crack - I'm sorry to see this. Straight across the grain, while the grain appears straight in this section and the corners rounded off. I'm thinking it may have been a defect that was already present in the wood from the beginning. Possibly a break from when the tree was felled? A felling shake it's called according to my dictionary. When a (big) tree falls down, it hits the ground or an object hard enough to partially break.

You might be able to salvage the bow by glueing on a lamination of wood to the back of the bow. I personally think a patch or rawhide backing won´t be sufficient in this case, but a wooden backing may just work. The back certainly seems flat enough to create a good glue line.

[George Tsoukalas]

First, the wood looks awfully thick to be bending and tillering. Second, if you look closely there is a run out in that area albeit a small one. If I had to guess as to why that broke it was just too thick to string up and tiller. Jawge

[Matt S.]

Thanks for all the advice guys, that's exactly what I was looking for!

sorry about that, Was the board givin a good amount of time to rehidrate? You have plenty of time untill the ship date

It sat for about a month after all the bends were made while I worked on some other bows. Is that enough time? I did coat it with shellac before steaming in hopes of preventing too much moisture loss.

That's a really weird crack - I'm sorry to see this. Straight across the grain, while the grain appears straight in this section and the corners rounded off. I'm thinking it may have been a defect that was already present in the wood from the beginning. Possibly a break from when the tree was felled? A felling shake it's called according to my dictionary. When a (big) tree falls down, it hits the ground or an object hard enough to partially break.

You might be able to salvage the bow by glueing on a lamination of wood to the back of the bow. I personally think a patch or rawhide backing won´t be sufficient in this case, but a wooden backing may just work. The back certainly seems flat enough to create a good glue line.

Now that's an interesting thought. I've never had a bow break in tension like this, to me it seems there is something else at work here. Like you mentioned, it could be an unseen defect in the wood, but I'm also wondering if maybe I caused some damage within the limb while steam bending it.

First, the wood looks awfully thick to be bending and tillering. Second, if you look closely there is a run out in that area albeit a small one. If I had to guess as to why that broke it was just too thick to string up and tiller. Jawge

It may just be the way the photos came out, but the limbs are no thicker than any of my other bows, and like all my other bows it went from floor tiller to long string to short string. But, I wonder if it was too thick when I steam bent the limbs. I did all the bending when the board was at its full thickness (3/4") and had just rounded the corners.

I think my next attempt I will get the limbs to floor tiller stage before steaming. Does that sound like a good idea?

[toomanyknots]

You know, I really think that that bow could be savable with a strong backing. If applied when in a bit of reflex to close the crack, maybe a bit of glue worked in the crack while in deflex before hand, if it was mine I would definitely try it. Unless the crack goes way down to the belly.

[Matt S.]

You know, I really think that that bow could be savable with a strong backing. If applied when in a bit of reflex to close the crack, maybe a bit of glue worked in the crack while in deflex before hand, if it was mine I would definitely try it. Unless the crack goes way down to the belly.

I just got home from work and managed to get some TBIII into the crack. What kind of backing would you suggest? I have three readily available options:
1) some flax string/twine. I could either apply this in string form or "de-string" it and apply it that way
2) red oak ripped on the table saw
3) Lowes has some 6' bamboo in the garden section, but they are all pretty skinny. Could I use this by cutting strips or by flattening the bamboo? (sorry, never used the stuff before)

I'll probably also retiller this bow for a lower draw weight, like 35-40#, or would you think the backing would make it safe enough to shoot for the original 50# goal?

[mullet]

Just my opinion, but I think that crack is too deep to salvage. If you back it the backing will probably over power it again in the damaged area.

[Elktracker]

Save the good limb, you never know if it may happen on another bow and you can splice the two good limbs

[Matt S.]

Save the good limb, you never know if it may when it will happen on another bow and you can splice the two good limbs

Fixed your quote so it would apply to me

[toomanyknots]

If you would use the linen string, take it apart to where it is just the fibers and apply it like sinew, that might work if the fibers are pure flax. I think you could save it with some linen fabric even if you reflex the bow a good bit when applying the backing. So when you take it out of reflex after the backing has dried it will stretch the backing really tight and should keep the crack from opening up again, as reflexing should also close the crack when you reflex it. But as stated the crack might be too deep as well. Either way good luck and sorry about the tension failure. As dearly important as it is to learn from mistakes, sometimes it's just not your fault.   

[hillbilly61]

Just my opinion, but I think that crack is too deep to salvage. If you back it the backing will probably over power it again in the damaged area.

I agree. I don't think I would feel good about sening it to someone as a trade JMO

[Pappy]

I have to agree,where the crack is located is a bad spot, You might save half but I would probably cook brats with it and start another. Looks to deep to me. To bad, but it happens.
   Pappy