Explosive failure!

[Julian]

Hey, so my Molle just whacked me a good one. I kinda expected it though, this little area in the bottom limb kept throwing up splinters. I think there were lots of grain violations off the sides in that area.

So, looking at these pictures, can you guys identify anything I can learn from? Apart from board selection, which I'll be more careful with next time.




Thanks for all the help in my previous threads, too.

[Julian]

Maybe I'll make a paddle bow next time. The molle design might just be too much stress for my temperemental spotted gum.

[mikekeswick]

It wasn't the design of your bow. All bows should be strained the same, regardless of design, draw weight etc because the wood doesn't know what bow it is in and feels only strain. Once that strain goes over acceptable levels bad things happen! It has its limits and bow making is about being able to read when it tells us it is close to those limits.
Board bows are a different animal to a split stave with undamaged back fibers and the rest of the fibers paralleling the limb. Boards almost always have damaged cut through fibers. If your board was lifting splinters it is no surprise it failed there. In fact if the grain was violated there it did really well to make it this far!
Board selection is vitally important. Pick only the very best. Learn to leave boards that are even a little 'iffy'. When there is no other option than to use a dodgy grained board then a good thick and strong backing is called for. Rawhide is great and readily available. Sinew of course and hardwood with interlocking grain.

[Julian]

Cheers, that makes sense to me.

[Stick Bender]

Oh man that sucks been there bud ,more times then I want to admit but it can happen board or stave most of my failures had a reason that I could figure out mainly a tiller issue,poor wood quality  and making self bows to short for my draw ,it seems to be part of the learning curve , but I guarantee your success rate will go up the more you make , but using raw hide is really a win win it adds very little mass & adds some insurance , I agree it's not the design ! You can increase your working limb by decreasing your leaver length or shortening your handle/fades or making the limbs wider for the same given length , what was your limbs working length fade to fade ?

[simson]

Never had spotted gum in my fingers. But looking at the break I would say no good bow wood, very short fibers!
Use a sapling next time. And go harvesting staves!

[Pat B]

I do see an atlatl in one of those pieces.

[bushboy]

Yes,staves are the way to go ever broke one ever,except osage!have broken prob 50 board bows though.most fruit trees will yield good staves!

[Julian]

I do see an atlatl in one of those pieces.

interesting idea

[Morgan]

Julian, where are you from? What types of timber grows locally? If there is a sawmill or pulp mill close by, you can sometimes purchase raw timber from them, you would have to pay close attention to the outside of said timber as they can be treated pretty rough. If there is hickory, pecan, or white oak available to you in board form those would treat you well if you did your part. I’m with some others though, it’s hard to beat a natural stave bow. Follow the grain in layout of a stave you harvested yourself, with a clean undamaged back, and your chances of success is much much greater than with 90% of boards you will encounter.

[joachimM]

Too bad... That's a pity, but also a lesson learned.
Once you see a splinter lifting, or even just hear a sound you don't trust when drawing the bow, stop and back it.

My favourite protective bow backing is sisal with hide glue (or kitchen gelatin). It's more elastic than any other plant fiber backing, super cheap, easy to work and easy to find. And it will add a fair bit of poundage to your bow. And you can all do it in your kitchen with a minimum amount of mess and smell (important when doing this in an apartment!).
Here's a how to: http://www.primitivearcher.com/smf/index.php/topic,56612.msg

Keep going at it
Joachim

[Julian]

what was your limbs working length fade to fade ?

Working limbs were about 18" on the bottom and 19" on the top. My fades were very gradual though, so they took up quite a bit of the length.

[Julian]

Julian, where are you from? What types of timber grows locally? If there is a sawmill or pulp mill close by, you can sometimes purchase raw timber from them, you would have to pay close attention to the outside of said timber as they can be treated pretty rough. If there is hickory, pecan, or white oak available to you in board form those would treat you well if you did your part. I’m with some others though, it’s hard to beat a natural stave bow. Follow the grain in layout of a stave you harvested yourself, with a clean undamaged back, and your chances of success is much much greater than with 90% of boards you will encounter.

I live in inner Melbourne, Australia. No good local bow woods here. And I don't have any permission to cut woods anywhere nearby. I could purchase staves but it's quite expensive and I don't have the funds at the moment. This board only cost me ~$10 so its no great loss apart from time. I did harvest some saplings though, but I think they're damaged from lying on the ground too long before I got to them.

[Julian]

Too bad... That's a pity, but also a lesson learned.
Once you see a splinter lifting, or even just hear a sound you don't trust when drawing the bow, stop and back it.

Keep going at it
Joachim

The bow was already backed with linen. The Linen stopped several splinters from travelling further than 1cm, I filled them with runny CA and wrapped tightly. But I think it wasn't the splinters, the grain just failed in that area.

[Morgan]

Julian, go to Lucas mill homepage. There is an option to find sawmill contractors close to you. It may take some calling, but I guarantee you can find a swingmill operator that can help you out. Swimgmills like very large diameter trees and most of the operators won’t fool with any branches under 6” in dia so they just chop them up. When I owned and ran a Lucas mill I made acquaintance with a man from your neck of the woods named Allen but I cannot think of his last name. I know he would help you if he’s still in the game. He helped me troubleshoot some problems on my mill and we had many conversations about local woods over there and a lot of them sounded ideal for bow making. Heavy, dense, tough, rot proof woods that laugh at a saw blade. I will look through my emails and see if I can find contact info for him if you would like...