Primitive Archer
Main Discussion Area => Bows => Topic started by: Julian on November 04, 2017, 02:56:06 am
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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.
(https://i.imgur.com/114zeIN.jpg)
(https://i.imgur.com/wEuZqL1.jpg)
Thanks for all the help in my previous threads, too.
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Maybe I'll make a paddle bow next time. The molle design might just be too much stress for my temperemental spotted gum.
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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.
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Cheers, that makes sense to me.
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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 ?
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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!
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I do see an atlatl in one of those pieces.
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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!
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I do see an atlatl in one of those pieces.
interesting idea
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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.
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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
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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.
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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.
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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.
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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...
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Julian, I sent you a PM.
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All bows should be strained the same, regardless of design
technically this is correct, but there are times that you might not want to build a bow the same level of strain. for instance if your bowwood is from boards where you have no control over the harvest and care of the stave, then you might choose to overbuild a bow some so you do not have so many failures. ultimately there is something to be said for working with staves that you harvest yourself. you can pick a healthy tree and take care of and season to your own specs.
nice looking work you have shown recently, looking forward to seeing more.
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The bow was already backed with linen.
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Seems that for these spotted gum boards you need a backing that can take most of the tension.
The sisal hide glue combo works fine for me.
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Seems that for these spotted gum boards you need a backing that can take most of the tension.
The sisal hide glue combo works fine for me.
I'll try it, next time. Is Sisal the same as flax fibre?
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Nope, flax is the raw material linen is made from (from the flax plant Linum usitatissimum).
Sisal is from a species of agave (Agave sisalana, surprise surprise).
They have rather different properties. As far as my research data and experience go, flax is extremely strong, and stacks enormously beyond 1% stretch.
If your flax backing is too thick, it will force the underlying wood entirely into compression. When you then draw the bow, the tiniest flaw in the belly (a hint of a hinge) may cause such a crushing of the wood that a true hinge quickly forms and is immediately exacerbated in a chain reaction leading to a tension failure of the flax. I've experimented with flax backings and had explosive bow breaks because of that.
Sisal is much cruder (thicker fibers), but stretches more easily and doesn't stack like flax. It can stretch at least 2% and has a much lower modulus of elasticity than flax (it is more elastic, requiring less force to stretch), more like strong wood species. Basically, it behaves like a stretchy bamboo backing, but one which you can tiller also on its back: when you applied too much of it, you can sand it down (moderately!). When you put too little on it, you can always add a bit.
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You have developed the skills to make a decent bow, all you need is some better wood. You'll be surprised at how much easier it is to get a durable, high performance bow with appropriate timber.
This is one of the reasons I don't like eucalypts for bows. Yes a bow can be made out of the stuff, but its usually luck as much as skill or design, as the timber can be so fickle in what it will give you.
Better board selection, backing, a much wider working limb than the timber density suggests, will increase your chances of success though. Limbs 2" and even up to 3" wide are not uncommon on successful eucalypt bows, usually pyramid or paddle bows with molle' tips.
Keep at it dude, you are doing really good with the materials you are using, but they are hamstringing your results for a durable bow. Its just not an issue when you use a decent timber.
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I have made a bunch of bows from Aussie timbers. Spotted gum has been one of the better ones, however I have had failures. Still got a couple nice shooters though.......
Have a google for a place in Melbourne that sells American Hardwoods (wink wink).... You might find a place in Burwood where you could get some Red Oak, Rock Maple, White Oak, Black Walnut, Cherry etc.......
Rounding the edges of your back will go a long way in preventing splinters and breakages also. Eliminate ALL sharp edges. About the radius of a pencil is fine.
I am backing all of my bows now. Black Walnut veneer on a trapped white-wood bow looks great, and is stretchy enough to not break, but is probably more cosmetic than anything. Still, put 200 arrows through a Queensland Silver Ash bow a couple weeks back. No breaky.
Flax fiber is good also, but be careful to not overpower and crush your bellies. Once again, trapping is the key, I believe.
Got some sinew on the way; really looking forward to backing a bow with sinew. Feels kinda like a bowyers milestone.
Have not been able to find a source for rawhide in country unfortunately........
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Hi Korey, Tandy leather sells strips of rawhide 1&3/4" wide x 42". They are a bit thick and very expensive but they would work for a backing. Birdsall leather also sometimes has kangaroo, deer and goat rawhide which is a bit thinner, and more suitable( not on their website so you might have to email/phone). Both these stores are in Sydney, but do mail/web orders.
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I was watching a show about animal motion. They said that kangaroo sinew is extra stretchy. I'm not sure if that would be good or bad. Sure works for the 'roo.
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Hi Korey, Tandy leather sells strips of rawhide 1&3/4" wide x 42". They are a bit thick and very expensive but they would work for a backing. Birdsall leather also sometimes has kangaroo, deer and goat rawhide which is a bit thinner, and more suitable( not on their website so you might have to email/phone). Both these stores are in Sydney, but do mail/web orders.
Hamish, many thanks! I am not even sure my advice to Julian will pay off, but is worth a shot. Gonna check out Birdsall for some roo. Cheers
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Nothing wrong with any of your advice Korey. I would definitely check out that American Hardwoods joint if I lived near Melbourne, they have hickory boards...awesome!