First Broken Bow

[Otzi]

Started this American elm bow last spring and got it to the shape shown by June. Since then it has been sitting in my house drying. Over the past three days I have been checking the tiller and probably pulled on it 30 times or so. Right where it broke the wood compresses itself as it grew around a knot (I also steam straightened this area in August). I left a portion of an additional ring at this spot for extra strength but kept the width tapered the same as the other end. Since this is the first bow I have attempted to make I wondering if anyone has input on why it broke, how it broke, and what I can do to prevent this in the future. I have more staves from the same tree and woukd like to make additional bows... but wiuld alao like them to survive tillering. Any input would be greatly appreciated.

Thank you

[George Tsoukalas]

One should leave the knotted area wider than the rest of the limb.

Also, I would not use  power tools while learning. They take off too much wood too fast.

Check my site.

http://georgeandjoni.home.comcast.net/~georgeandjoni/index.html

Jawge

[Otzi]

No power tools used only splitting wedges, a draw knife, and hand plane.

[Badger]

  Hard to say for sure but I suspect you may have had a hinge there. Is that red elm. How wide was the bow? How much weight were you drawing on it?

[bow101]

Am I missing something.?  Whats up with that straight slice, never seen that before.

[Otzi]

American elm 1 5/8" in the middle for 8" and tapering to 1/2" tips on either side. I'm guessing over 100lbs it's wasnt close enough to measure yet.

No idea on the straight break, as shown in the picture there are no signs of a cut on the back where it broke. It almost appears to me that the break started between the belly and the back. Is that possible? My theory on the straight break on the back is that the wood was too dry, hence the brittle break, but then again I really don't know much about bows in the first place.

[Otzi]

Pics

[mikekeswick]

First off the golden rule in bow making is NEVER pull harder than your intended finsihed draw weight 
It looks to me like a simple tension break, probably a combination of factors tipped it over the edge. Weight you were pulling, tiller, potentially a hinge there, width of the stave.
If you are going to try again with this wood if would be a good idea to make the limbs wider at the fades (still ending up at 1/2 nocks). This will give more working wood on the belly and back to lower the strains. Maybe start at 1 7/8ths or so for a 50# bow. You can always narrow the limbs during tillering if necessary.
Good luck!

[SLIMBOB]

I would add that leaving an extra ring on a spot for strength is rarely a good prescription for any number of reasons.  Go wider for added strength at a trouble spot, not thicker.  An extra ring (on the back) can lift off and then you got real problems.  Thicker wood cannot bend as far as thinner wood without taking set or breaking.  How far were you bending it when it broke?

[Pat B]

Tell us about the source of the wood and the seasoning.  IMO it is rare for a bow to break across the back, especially as cleanly as that did. Too dry could do it I guess but I suspect rot. Even the growth ring separation is suspicious. Red elm has interlocking grain and I would imagine any break in red elm would be splintery and not straight across the grain.

[ohma2]

Like pat said elm looks like a say a ripped apart rope , the grain is so interlocked .that wood does have a doty look about it.the white woods have to be protected from rot and decay after cutting.i would do a bend test on a piece before using any more to make a bow.

[TimBo]

That looks just like a bunch of elm I have seasoning in my garage.  It is not similar to any other elm I have tried, and I believe it is the Siberian variety due to the small leaf size.  I was hoping it was red/slippery elm, but apparently that type has much larger leaves.  American elm would have a lot more sapwood.  I have been reluctant to make a bow out of it, since the simple bend tests I did on small pieces broke just like your bow - a very clean, straight break of the sapwood.   My plan is to take off most or all of the sapwood, and probably back at least the first bow. 

[PatM]

When you steamed the area  you cooked it and likely gave it a perfect compression fracture on the back as you attempted to straighten it. When bent the right way the compression fracture opened up.  That's my take.

[Otzi]

@Mike
     Oops! I'm sure I was pulling >100#s
@Slimbob
     Around 20"
@PatB
     Chopped down the tree June 2013, sealed the ends w/ Elmer's, removed the bark, and split into staves. It was shaped to nearly it's current shape by the end if June. During this time it was stored in a garage with very minimal ventilation and very high humidity. It was then moved into the house in July.
@ohma2
     I'm guessing your referring to the last picture with the white dots. The white is the reflection of my high intensity fishtank light, there is no discoloration of the wood. I will definitely try a bend test.
@PatM
     Can you elaborate on how I may have caused a compression fracture? Possibly understeamed and over stressed?

Thanks for all the input

[autologus]

Oops! I'm sure I was pulling >100#s + Around 20" = tension failure most assuredly.  I am guessing it just could not handle that amount of tension and let go.

Grady