Learning from failure

[kleinpm]

So it is not that often that broken bows are examined and posted. When I break one I usually have a hard time determining if the failure started on the belly or back. So I figured I would post a broken bow right before it was about to explode in the hopes that someone can learn from it.

A little back story. I have been trying to find the limits of chokecherry. I blew a self bow but I knew that one was gonna go and and kept pushing it. This was a 46 inch chokecherry that was a near identical copy of the bow on page 140 of the encyclopedia of Native American Bow, Arrows and Quivers vol. 2. I tillered to 20 inches before sinewing. Everything was going good and I had it to 24 inches and 52 pounds. I was shooting it in and thought everything was good with probably about 50 arrows through it, which was after a thorough workout on the tillering tree. It had taken about 1.5 inches of resting set. I was confident enough that it was going to hold together that I was about to start cleaning it up and making it pretty. I felt the handle give a little and stopped what I was doing. I think another full draw and the failure would have been complete.

I guess this is what a compression failure looks like. 

[bow101]

It looks like maybe you violated a ring, thats my useless 2 cents, as I know others will go along with assumption.
I have never used choke cherry, but have some for other projects.   Its a real downer when bows break,  for me its a matter of going slower and paying extreme attention to the Tillering process.  I can honestly say that allmost 100% of my failures are due to bad tillering, plain and simple.
 A 46 inch chokecherry bow is quite short is it not.?  I have seen many shorty Osage bows though.

[kleinpm]

Those pictures show the belly. The back was actually pretty pristine, plus a single thin layer of sinew.

You may well be right about the tiller. 46 inch's for chokecherry is short, and it's not the best wood to begin with so minor errors get magnified.

Patrick

[Mark Smeltzer]

I guess compression failures can come in several ways but that one doesn't look  like any compression failure I've experienced. Normally most of mine look like fractures in the limb that run side to side. I've just not ever had one come apart on the belly.

Mark

[half eye]

Kleinpm,
     You may not have done anything wrong at all. Cant speak for the book you refer to but can tell you that from my research, sinew-lined bows occur in 2 forms. 1: On the western slope (Sierras) the bows were often of softwood and were the lined "broad type" and 2: the interior basin side the bows were the hardwood-narrow types (like yours). The Shoshonean type (narrow) were sinew lined but also more commonly wrapped at a few inches around with shredded sinew as well. This type bows was also found used by the Athapascans in Canada, and the Apache, Navajo and Pueblo tribes further south. All of these narrow ovate section bows were, more often than not, both lined and wrapped. The Natives who spoke with the National Museum contributors said the wraps were specifically for both holding the sinew to the back of the narrow bow, but further to prevent "splitting"
hope that helps you some...
rich
PS: I can post a picture of a Navajo bow that has the identical section as yours but has 3 broad sinew wraps on @ limb as well. If you want it.

[DarkSoul]

I personally find that bow very rough looking. It has square edges, untidy tips, criss-cross sinew with loose ends, and scatter marks on the belly. I'm not sure if that contributed to the break, but that bow looked like a bow in the making, not nearly ready to be drawn more than a few inches. "The sooner it looks like a bow, the sooner it acts like a bow" is a famous phrase. This bow did not yet look like a bow much.
That being said, that is very weird break. Not a typical compression chrysal at all. Does the bow show signs of any other compression failures? Any more chrysals? I think this almost looks like as if the curing sinew pulled the bow into reflex, where the belly just gave way because it couldn't handle the tension. I can see a small knot about an inch to the right of that break. Since the bow is made from a very small diameter sapling with the pith of the tree still in the bow limb, such a small knot would span the entire width of the bow's belly. It's not uncommon to see a compression fracture around such knots that span a large area on the belly of a bow. But this break appears to be an inch away from the knot. Or is there also a knot at the break?

[kleinpm]

Half Eye,

The bow in the book was attributed to the Blackfeet. That is a kind offer to post the picture but I have several examples to go off that show the same sinew wrapping.

Dark Soul,

Thanks for the critiques. I don't hold the same regard for aesthetics in a bow that you do, I guess. This bow started off as a test to see if I could successfully get a 46 inch chokecherry and sinew bow to draw 24 inches. Towards the end I figured I might have a winner but it turned out I didn't. I could care less about looks over functionality until until I know for sure the bow is a keeper. Rough knocks, frayed sinew along the edges from post sinew tillering don't make any difference in how a bow functions. Your right that the sinew back itself did have some sinew going this way and that, but have you seen the sinew on Native American bows. Most of the bows from the plains and rocky mountain tribes that I have seen in museums, exhibit what we would consider these days to be a terrible sinew application. Not all of them certainly, but a lot of them.


Patrick

[bushboy]

Round corners go a long way in preventing a splinter to lift and not for pretty reasons. !

[Mark Smeltzer]

I agree with both above comments, it is possible for the sharp edges to contribute to failures, even on the belly. I wont draw the bow back until it looks like a bow and the back of the bow is 100% complete. That bow failure looks like what I would expect to see on the back of the bow, not the belly.

Half Eye,

 This bow started off as a test to see if I could successfully get a 46 inch chokecherry and sinew bow to draw 24 inches. Towards the end I figured I might have a winner but it turned out I didn't. I could care less about looks over functionality until until I know for sure the bow is a keeper. Rough knocks, frayed sinew along the edges from post sinew tillering don't make any difference in how a bow functions.


Patrick

I disagree on this point. You may have had a keeper but the unfinished belly could have contributed to the failure of the bow.
Just my 2 cents.

Mark