Primitive Archer
Main Discussion Area => Bows => Topic started by: Lee Lobbestael on December 09, 2012, 11:18:53 am
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Hey guys. two years ago I cut and split five or six black locust staves. I let them cure for a year and attempted a long flat bow with one. It chrysalled badly so I scrapped it. Someone on here suggested that it may not have been dry enough or I tillered to fast. Well I attempted another over the last several months. I spent a month on tillering and stood near my wood stove between sessions.
Well I thought the tiller came out as close to perfect as I could get it but looking at the belly under a bright light just now I noticed that both limbs have tiny tiny compression fractures all up and down the belly. They are so small you have to be a few inches away and under a bright light to see them. And they are almost uniformly spread out over both limbs. They are so fine that a picture wouldn't show them. I cannot even feel them
My question is, Is this bow doomed or is it worth finishing?
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Lee I would go ahead and finish the bow. If they are the sort of micro compression fractures and are evenly spread out then the tiller may be just fine and the bow could survive a long, long time I believe. I have one similar to what you described that I've shot now for
a couple years without and further change in amount of chrysals or any change in tiller or draw weight, I'm confident enough in it now to even take it out strung all day hunting. I've made a half dozen from bl and all have survived and only one came out with none
of these tiny fractures. If your close to finished with your bow you may as well complete it and see what happens, can't do much about the fractures now that their there. Keep us posted, I'd like to know how it works out for you.
Greg
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When chrysals are spread out over the length of the limbs that is an indication that the design is not adequate for the draw length or weight wanted. Perhaps you could indicate your draw length, Lee. Also tell us about the length and width of the stave and the weight wanted. You could finish it but eventually the bow will fold up at one of those weak spots. Been there. Jawge
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Thats the odd thing George I overbuilt it for that reason. It is sixty eight inches ntn inch and three quarter wide untill the last twelve inches and tapers to three eighths inch tips. Its about 55#@28"
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Lee, have you shot any arrows out of it yet? If so have more fractures revealed themselves? If not and your tillered out I would continue to shoot a couple hundred rounds and check along the way for changes.
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I have shot about a dozen arrows through it. I noticed the fractures after that but they could have been there before I shot I just never looked at it under the light until this morning
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Lee, seems like you did the right thing. How big is the non bending handle section?
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A 3/4" wide bow is very narrow and usually made with a D cross section. This places extreme compression stress on the narrow belly. BL is known for its tendency to crysal in compression. A flatbow design with nearly flat belly would put much less stress in the compression zone near the surface of the belly by spreading it out over a larger area.
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1 3/4", shaun
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Id like to see your tiller before making any comment as to why.....and how is the growth ring ratio in the stave? The best locust I've found is dark wood,and big ringed,and has a small early growth compared to the late wood....the locust with light colored wood with small rings and thick early growth to late growth seems much less dense and more prone to having issues....
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Hey guys sorry I didn't have internet access for awhile. Yeah I meant 1 3/4" wide Shaun. I don't have a camera to get pics of it right now and I don't know if it is lighter or darker than average because it is the first BL tree I have cut. I hope this bow holds up because it shoots great and has almost no set so far.
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Lots of fractures and not much set doesnt go hand in hand. Sumpin's fishy Lee. Maybe the wood is wet? It may have been cut years ago, but that doesnt mean its dry. Where was it kept prior to your build?
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Yeah maybe it will take more set. It hasn't as of yet tho. Upstairs in a closet for several months and then by my wood stove as I was building it. I assumed the woodstove would dry it quick
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I have made about 6 BL bows and none had these problems. I also heat treated the bellies on them very well, to the point of significant color change. I didn't do it quickly either, one bow took 2 hours to heat treat. I was shooting bows 50 lbs at 25 inches that were only 60 inches long and 1 1/4 inch wide with no problems. Try a good heat treat. Your tiller will change after it and it wont take much to fix it. Just brace the bow and scrape away until the tiller i even at brace and fine tune after that as normal.
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Black locust is a very stiff wood for it thickness.
It is very strong in tension but a little 'brash' in compression. Can't think of a better word...it's good in compression but almost too good in tension. A very good candidate for trapping and heat treating.
The fact that the chyrsals are small and evenly spread is a sign that the tiller is likely to be good and bending correctly - if it wasn't then then would be worse where it was bending too much. However the reason they are there is that you have asked the wood to bend too far for it's thickness. If the bow had been a little longer, or wider or lower draw weight then the limbs would have been a little thinner eg. able to safely bend further, and you may have got away without any.
Anyway yes I would finish it BUT only if the chrysals don't change after a few hundred shots. Maybe put some rawhide backing on and don't get too attatched to it.
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Ok thanks guys. I will finish it and then go back to ol faithful (hickory) got lots in my woods! btw anyone want two nice BL staves? Trade ya for an osage! :laugh:
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I've made a lot of locust bows. I like the wood. It seems to me that your bow just isn't wide enough for the weight, meaning, it would have been a little thinner if it were wider and still pulled the same weight.
My first locust was made from a tree about 3" in diameter under the bark. I decrowned the sapwood and left it on. Limbs were about 1-1/2 wide at the fades, straight taper to 3/8" tips, 66" ntn. The bow had nearly 5" of reflex when first finished. Kept about 3" after shooting.
That bow had a spider web of chrysals from end to end. I shot it for a year or so and it kept that reflex. Shot great. It would still be going If I had not accidentally overdrawn it.
I think you have a shooter and I would just make the next one a little wider for that weight.
Jim Davis
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Thanks Jim! I think a lot of people mis read my post. I said I made the limbs 1 3/4" wide. Thats wide enough isn't it?
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You said "almost uniformally" along the limbs...what do you mean almost? Is there a break in between some of them? And how long(measured) is the section of frets? 1 3/4" might not be wide enough if you tillered your bend into too short of a concentrated area or areas. Again,id need to see the unbraced,and full draw pics to say for sure what went wrong.
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Lee your on the right track with osage. Get some and be happy.
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Thanks Jim! I think a lot of people mis read my post. [some definitely did, I didn't.] I said I made the limbs 1 3/4" wide. Thats wide enough isn't it?
With locust, I try to make my pyramid limbs 2" or more wide at the fades. And, my bows turn out around 45#. But they have no chrysals, even after several years of use. I do think your belly wood was just under too much strain.
I say was because now that the surface has fretted, the strain is being carried below the surface, essentially behaving as if it were thinner.
I'm guessing that when you finished tillering, the bow was a little heavier than it is now. The good side is, the bow will sustain the weight it is now, and as i opined earlier, it will be a shooter.
Just go wider next time and try for the same weight, or a little less than this one is.
One other thing that doesn't get considered with ring porous woods is that a tapered belly requires more of the compression forces to be carried by spring wood where a growth ring feathers out. A pyramid bow is one thickness throughout and growth rings on the belly run from fade to tip, resulting in a uniform consistency everywhere on both belly and back.
That's why I make only pyramid bows.
Jim Davis
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That is a very good point about pyramid bows Jim. I have never tried one. Maybe that is what I will try next.
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woud it be worth trying to heat treat the belly really good and then dropping the poundage as well?
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Lee, I think the poundage has dropped by itself from what you had it tillered at. I think it's time to just shoot the bow and enjoy it.
Can't really see heat treating at this point. But, it's your bow. If you want to see what happens, go for it.
Jim
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I think I will just finish er up an shoot it.