Broke a bow and not sure why. PICS.

[Jesse]

This is a hickory board bow I was making with a friend from work. It is backed with an 1/8" hickory backing. 66 ntn it was pulling 45 #  at about 20" and the tiller was right on I thought it would be my best tiller job. Then I went to string it again after a few scrapes and we were talking about how bad it would suck if it snapped and BANG! I was left in disbelief with two jagged pieces of wood in my hands. I glued it with tb 3 . on one side of the break you can see the backing separated about 1/8" wide and 6" long during the break. I was wondering if it might have been the week link that caused it. I Want to learn something from this besides that sometimes bows explode violently and unexpectedly

[Ryano]

Hard to say. Looks to me like to much run out on your backing strip.

[Pat B]

Looks like the back failed...but why?    Pat

[Jesse]

Well after sitting on the couch in sorrow  >:(looking at it closely I have discovered what I believe to be the reason. I dont think it was run up on the backing. the strip had nice straight long grain on all sides. I think part of the glue joint was dry. I found another section that is a clean line and if the glue job was good it would have more wood chunks on it. I dont think this bow would have failed without a backing. I think part of the backing failed and ripped the rest with it. Its the first time I tried tite bond3 on a backed bow. Normally I use rescorsinol. I Know a lot of you use tb3 with good success. Whats the trick? I sanded with 80 grit then cleaned with acetone then put a lot of glue and clamped with rubber wrap clamp like always. Only thing I did different than with rescorsinol is I didnt grove the surfaces. I want to use tb3 because its easier and not as toxic.
                                                                                                                                    Jesse

[Jesse]

Another thing I was thinking is that I might have twisted it a little while stringing it and that caused the separation at the backing? I had it pulled back much further on the tree with no problem. Man it was looking perfect he was all excited to make  his own bow and was already thinking of what color to stain it. We spent 7 hours on that thing today and kaboooom. Im glad it failed without hurting anyone though.
                                                                                                     Jesse

[Pat B]

Jesse, You can learn a lot from that "failure". Hang on to it and study it periodically, it will teach you things.
Hickory is strong, tough wood. I have used hickory backings with terrible violations in the grain but never lost a bow to back failure with hickory...I did have one hickory backing crack across the back but it turned out the whole log we cut into backing strips and belly slats was infested with fungi. This 12" log had been in a garage for 2 years. if fungi gets into hickory it doesn't take long to go bad. If any white wood isn't handled properly after harvest, it will rot.    Pat

[PK]

I had a hickory that looked just like that break and it had some kind of fungus When It broke I saw dust, I checked for PPbeatles ,no sign of those.
Now I look For Hickory that does not have that oak looking grain to it.

[Jesse]

Ya Im learning from this even if I dont know 100% why it broke.
 The wood in the center of the break does look a little suspect to me. I got it from home D. Who knows where its been.
 I was going to make it from stave but when I started pealing back the bark all my hickory staves were full of wood bores so I had to go and buy boards.
Jesse
 

[Rich Saffold]

Jesse, you do this enough, and you get to see perfect bows explode even thought its very rare..

[wvfknapper]

In the next to the last picture (the darker one) it looks to me like the wood is bad, looks dry and rotted,, is it just the pic?

wvflintknapper

[Jesse]

Thanks for responding. in the second to last pic that is what I meant when I said it looked funny. It is solid though. I cant stick a thumb nail into it  but it looks like rotten wood. usually when wood looks like that you can pick it apart with your finger nail. I also noticed when tillering this area did not want to bend. I had to work on it a lot before  it would do anything. like I would take 20 scrapes put it on the tree and it would still be the same . 20 more and still nothing. finally it was bending perfect shortly after that it was all over.

[Pat B]

The log I talked about above seemed solid enough and was still very hard but the tensile strength had been robbed.      When you find stiff spots like the one you are talking about that don't register wood removal its good reasons why you should exercise the limbs after each wood removal. This bow probably would have broke anyway if it is fungi but it may have happened sooner, before you put too much in to.
   I have bought red oak boards from Lowe's, etc but I study them carefully. Wood that is suitable for building and hobby projects may not be good for bows if they weren't handled properly. I bought some hickory from a specialty lumber Co a few years back. They let me pick through their piles if I put every thing back as I found it. I got a very nice hickory board that was 10' long and was 8/4x 6" and it cost $30. I cut it into  6' and  4' pieces and cut a lot of backing strips and a few staves from the 6' piece and still have the 4' piece that I will cut to backing strips.
  My point is, if you have a specialty lumber Co in your area see if they will let you pick through their stacks for desirable bow wood. These specialty lumber places seem to be more particular about where they get their wood and how they handle it.     Pat

[Jesse]

Thanks Pat I will check a specialty lumber yard. I know there is one in town I dont know why I didnt just go there to start with. As far as exercising the limbs that is great advice. I usually pull 20 to 30 times between scraping but this one was stubborn. Like I said before it didnt break on the tiller  tree it broke when I was putting the string back on. I will use a stringer next time you can bet on that

[Pat B]

You may have put a bit much pressure in just the wrong spot when you were stringing it...or like Rich said, even good bows break on occasion just cause they are wood. It part of the mystery.    Pat