Primitive Archer
Main Discussion Area => Bows => Topic started by: DC on April 27, 2015, 01:16:23 pm
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This was my favorite bow up until a couple of days ago. I made a new string and it was too short. The brace height went up to 8+" from the normal 6" and for some dumb reason I pulled on it. Momentary brain dead I guess. Anyway, I want to make another much like it so I thought maybe you guys could look and see if you can see areas that need improvement. It's an Ocean Spray R/D 62" NTN following the curves. 39# at 28". 1 1/2" wide at the fades tapering evenly to 1" about 7" from the tip and then down to 1/2" tips. It broke 11" from the center on the bottom limb. It looks like there is two very very small pins there but I think by that point it had to find a weak spot somewhere. I tried to take some pictures of the break but it doesn't show very well. It's an "H" shaped break right on the crown,1/2" wide and 6" long. I would think it is a very typical tension break. Here's the pictures I have. I can chop it into chunks if it will help.It broke where the red arrow is.
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And full draw showing where it broke
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It actually looks flat where the red arrow is. How does the back look otherwise?
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I'm not sure what you're looking for but the bottom limb is very clean, nothing over a 32nd of an inch. There is a typical OS lump halfway between the break and the handle. Can I try to take a pic of something for you?
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That looks like it was a sweet bow man. Oh well I'm sure your next will be even better! :D
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I thought same as pat
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Your brace height increase isn't the culprit, if that helps you rest at all.
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Heck of a coincidence then.
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A high brace height can change your tiller shape at brace, if the area that broke was starting to bend more at brace it would continue as you drew it. I still wouldn't say the high brace was the culprit but it likley exagerated a slight weak spot you allready had. +
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Wood is wood it does what it wants. You could have a thousand shots thru a bow and one day you go out and shoot it first thing and it breaks. Breaks happen. Move on to the next project.
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Looks like there is a knot just above the break.
Did you leave the knot slightly wider and did you tiller that part slightly stiffer?
Jawge
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Here's a pic between the break and the handle. You can see the OS lump. There is probably a knot inside that. It's a bit wider and about 1/8" thicker. It's 4 1/2" from the break. The break is marked in Sharpie.
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Saw the lump in half and see what's in there.
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There was nothing but wood in there. I think there was a knot in the other half of the stave and this was just a swelling coming around. OS over reacts to knots and injuries and makes these ugly lumps. It makes it nice for us because there is lots of strength around them.
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I'm with Jawge. It looks like a very small knot right about the break. My guess is the lump between the handle and the break caused a stiff spot that put more stress on the limb where the little knot is and finally caused the break. Just a guess though, as I am still a beginner and have only made 8 or 9 Osage pyramids to date.
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There is a tiny knot right at the break and I suppose that is why it broke there. It's awfull small but I guess it doesn't take much.
Anyway before I start the next one, can anyone see any design changes that I could make that might make the next one better. Not just from a breakage point of view. Is 62" for a 28" draw asking for trouble? Could I make the recurves straighten out a little more to add a little working length to the limbs? With OS I'm kind of limited as far as limb width goes. Anything you think would improve the bow.
Thanks
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When you have a hump DON'T leave it stiff. If you do you are dumping extra stress at another spot. Knots etc (IMO) should be made to bend just like the rest of the limb.
Maybe go to 64 inch in length. Look for the widest stave you can find. Make your recurve shorter/sharper so you have more working limb.