Primitive Archer
Main Discussion Area => Bows => Topic started by: seantOH on January 05, 2009, 11:50:31 am
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I have started a new BBO bow based on Dean Torges video. The lower limb is 1.5" shorter than the upper limb and the overall length is 66" ntn. Everything was going along fine until I braced at about 3". I got it braced and then the string slipped/ twisted around the bow and the the bow was "unbraced" under tension. What can cause this to happen? How do I fix it?
Thanks in advance for any help!!
seantOH
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Starting off with that much reflex and being a R/D style bow the limbs are unstable and your string must be off to one side a bit. Try reducing the weight a bit more...and use a stringer to string it if you are not. Pat
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Pat B,
Thanks for the quick response. I will reduce the weight some more by tillering and using the long string. I have left the nocks plenty wide so that they can be adjusted. How do I determine if they need to be adjusted to get the string in the middle? I have been using a stringer but using the adjustable tiller string makes it a bit of a challenge keep the string in the middle. Thanks and take care!
sean
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With a R/D bow I made a little while back, I found that when stringing, I had to brace it pretty high or it was unstable like yours. Do more floor tillering before trying to string it again. I would so the same as Pat said, while keeping watch on any sign of twisting. If it wants to twist, remove a little more from the stiff side.
I like the name. ;D
Sean
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You will need to brace it a bit higher.. I looks like when you braced it your string streched or Make sure your knot is not sliping past its self..
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The way I tell if the string is tracking is when I first brace the bow, but low...4" or so. I've only made a few R/D bows and they are difficult for me to tiller. Getting a low brace will be difficult also with R/D. Pat
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I put this BBO bow down about 11 months ago because it twisted when I low braced it at 3". I have finally got around to trying to finish it. I can low brace at 4" now without it twisting. I am not sure what to do next with the tiller. The lower limb is 1.5" shorter than the upper limb and it is 66" ntn. Thanks for any advice you can give me!
seantOH
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If it twisted when you braced it, before you put it away, it is still twisted but just not showing it yet. Check the thickness of the limb from side to side along both entire limbs. Sounds like one side is slightly thicker than the other. Many times the twist will show up in the last 1/3 of the limb but not always.
Which limb is the lower limb?
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It looks to me like the right limb is the lower limb, if so the upper limb need to bend a bunch more in the middle.
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Thanks for the quick responses! The lower limb is on the right as you look at the picture. As I look at it, I think I need to remove wood between D and F on the left side. Do you agree? Thanks!
seantOH
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OKay, I have done some more work on the tiller of this bow since last night. Please take a look at the picture and give me some feed back. I am shooting for 55# at 24" draw and I am at 56# at 22". The tiller looks a pretty good to me but I am an amature. I still thing the left side (longer by 1.5") needs some work but I am not sure where to remove wood next.
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Everyone has said it all already, I'd just add you should modify your tiller rig so that the bow is supported at a single point, allowing it to pivot, it gives you a better picture of how it will flex in your hand.
Del
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Your right limb, from point"B" to point "D" looks a little stiff to me. Are you exercising it well between wood removals?
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With a R/D bow I made a little while back, I found that when stringing, I had to brace it pretty high or it was unstable like yours. Do more floor tillering before trying to string it again.
Sean
You will need to brace it a bit higher.. I looks like when you braced it your string streched or Make sure your knot is not sliping past its self..
I agree..... I never brace a bow low if it has much reflex. I like full brace or no brace at all on those types of bows.
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Thank you both for the response!
Del,
I can look at modifying my tree.
Patb,
Looking at it now, it does look like the right side, as I look at the picture, does not bend as smoothly as the left. Does the left side tiller look good to you?
sean
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PatB,
As far as working the bow after removing wood, I am floor tillering each side 30 times and then I put it on the tillering tree and pull it progressively to 22" 50 times. Should I work it more?
sean
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Justin,
Thanks! IT has not twisted since that original time and it seems to be stable now, the string seems track in the middle of the handle and limbs.
sean
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PatB,
As far as working the bow after removing wood, I am floor tillering each side 30 times and then I put it on the tillering tree and pull it progressively to 22" 50 times. Should I work it more?
sean
I don't think there is a magic number to pull, but 50 is probably plenty. I guess I don't understand the progressively to 22". I hope you aren't pulling beyond the target weight as this would do unrepairable damage to the wood. Anyway, the point to Pat's post and mine is just to make sure you are exercising the limbs. If you hit target weight by pulling to 15", pull no more than 15", but do it a bunch.
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Ok I have added tip overlays and I think I am done with the tiller on this bow. Please let me know what you think about the tiller. This is a BBO osage bow. It is 63.5 ntn and 66" overall. The left limb, as you look at the picture, is 1.5" longer than the right limb. I was trying to make the bow 50-55 lbs at 24". It is currently 58 lbs at 24". I am afraid to remove any more wood because I don't want to screw it up when I am so close. Be brutal :) and tell me if I should do anything esle to this bow. Thanks and take care!
sean
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Tiller looks right on to me.
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looks good I'd leave it. If you want the extra 3-8 lbs you can remove a little wood in long, even strokes equally down both limbs. I would just do like 2 or 3 per limb and then go back to the tree to exercise it. Even a little wood removal now will drastically effect the tiller and draw weight now. Have you sanded all your tool marks out yet or rounded all your edges off? If not you can go ahead and get that done that will sometimes cause a 2-3 lb weight decrease too. :) -josh
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seantOH:
your tiller grid behind your tillering stick is the best i've seen. i'mma copy that idea today! it's SO easy to see assymetry with your battleship style grid!
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i wouldn't remove any more wood until you have shot the bow 100-200 times. chances are the bow will loose 3-5#s after shooting it in.
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With a R/D bow I made a little while back, I found that when stringing, I had to brace it pretty high or it was unstable like yours. Do more floor tillering before trying to string it again.
Sean
You will need to brace it a bit higher.. I looks like when you braced it your string streched or Make sure your knot is not sliping past its self..
I agree..... I never brace a bow low if it has much reflex. I like full brace or no brace at all on those types of bows.
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i had two staves this year that were strongly reflexed and which did exactly what you show there. The way around it, is to shorten the string. I may have been to aggressive with it, because the one stave took a kink in the lower limb. But even so, i tillered it to bend properly and that is a wild-fast bow.