Primitive Archer
Main Discussion Area => Bows => Topic started by: DC on November 04, 2015, 01:13:29 pm
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I'm working on an OS R/D and the limb is twisting and the string comes off at full draw. I need some advice on where to remove wood. I've been through all the posts about limb twisting but just have no confidence in my understanding them. And I think the recurve throws another curve(heh heh) into it. In the picture the limb twists so that the top moves to the left and the string falls off on the left. The string alignment is actually good at brace, I just couldn't hold the camera steady. Do I remove wood from the left side of the belly or the right?
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The right.
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The left as I look at it. The limbs lean to the weak side, they appear to lean to the right from my chair.
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Dammm. I studied this for hours and I was sure it was going to be the left. The right side is the thinner side already. Do you know where I might find a good explanation? I have to understand this. I've got this thread http://www.primitivearcher.com/smf/index.php/topic,27206.msg364231.html#msg364231 in my bookmarks but to me just about everyone that comments says something different.
Oh crap PD posted while I was typing, now I even more confused. I'm going to hold off scraping for a bit.
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Left side.
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Left side
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how do the limbs look in relation to each other when the bow is un-braced?
will the bow balance 'flat' on the recurved radii?
i mention this because i've had to heat correct at Bear FG recurve because this was happening. obviously the limbs where the correct thickness, however, there was a slight twist on the upper limb that was causing this to happen. the bow also looked fine when braced, partly due to the tension on the string holding it in place. once the bow was drawn enough, it was allowing the string to pop outward (to the left) from the string groove.
we heat treated with a damp microwaved towel until the un-braced bow balanced perfectly flat on the radii.
hadn't had a problem since.
you may want check for any twist on that limb before removing material.
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It looks fine unbraced and braced. I can see the limb twist as I draw it. It's just out a touch, the string doesn't come off every time. I haven't shot it yet, it might come off more often then.
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Be sure your string grooves are straight across from each other on both tips. Depth needs to be the same as well.
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I always have a hard time understanding this as well,, I think I get it here,, take off the left, and the tip will lean that way ,,,, keeping the string from coming off the left,,,,????
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You said it looks fine braced and unbraced. Isn't the bow braced in this photo?
I personally haven't had the best luck with the whole remove wood to make it bend one way method.
On 99% of my recurves I use heat to get the curves lined up perfect.
I secure the bow really well sideways,and hang a weight or just use clamps on the very end up the recurve.
I try to do this heat correction a couple inches before the curve starts
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Since I didn't have a lot of wood to spare I tried about 10 scrapes on the left side. Didn't seem to help. I've chickened out and I've heated the tip and moved it over. If that doesn't help I'll try removing wood again. I actually did this before I read Ryan's post. With the bow being R/D it's really hard to see both tips at the same time so I don't know. We'll see in a couple of days. Busy tomorrow. Thanks for all the input, I appreciate everyone's responses.
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yes I usually just heat it to line it up,, I am not good at the wood removal either,,
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I'm going by his description of what happens on the draw, not how things appear in the picture. But if things are heading in a particular direction then removing wood on that side will just encourage that.
I prefer to just manually torque things while the bow is being drawn on the tree. Carefully.
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so if you wanted the tip to go to the right as you draw the bow,, taking wood off the right side would work,, would you take wood off of the tip and curved area,, or below that on the limb,,???
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Just the working portion B-rad.
Many things can make a static do the twist. When the bow lays flat unbraced and the thickness is right on, then the bow wasn't laid out right and you're fighting inner twist, for lack of a better term. String grooves make a big difference. You can deepen the groove on the side opposite the lean and it will pull the tip over more than you might think. If it lays twisted unbraced, well that's an obvious fix. Just have to evaluate and think about the forces at play to make what you see happen.
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I agree with pearly on the belly grooves. All my recurves get them, and they can for sure help in small adjustments. I try to get my recurves perfect at full brace height, I've had recurves that look a little off when unbraced but are fine when braced and drawn
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I read that in TBBsomething, the recurve chapter. A little off at brace is OK as long as full draw is good. I'd like to add the DC version, It doesn't matter what it looks like as long as the string stays on ;) ;) ;)
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You can also do a tear drop cross section so that a larger loop straddles the recurve and then rests on a string bridge. A string bridge can be better arranged to catch an errant string and guide it back to center.
(http://i399.photobucket.com/albums/pp78/pat_05/IMG_1868_zpsa5e87503.jpg)
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well, lot of good advice above!
I personally wouldn't take such much wood off on one side so the difference width is seeable. Next time you should heat correct the string alignment before doing only subtle scrapings on one or the other side of the limb. By the way side corrections with scraping on one limb side is a good thing on D-bows, but on recurves it is much more complicated. It belongs a lot where you scrape (mid limb or outer limb, or hardest thing at the lever).
Back to your problem/bow:
Clamp your bow in the vice at handle. Crap the lever and pull it in right position while watching what the limb does. There should be a portion where it wants to break out, scrape here! Hope that makes sense, always hard for me German to explain in English.
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Well I've been heating and bending this thing every day and I just can't get it just right. I got it close once. I was looking at my older R/D today and noticed that the limbs on it are quite a bit wider. On this one the limbs are 3/4" wide and 3/8" thick right where the recurve stars and they are 1 1/4" at the fades. Is it possible that they are too narrow and that's making it throw the string? It has about 4" of reflex and deflex. The tips are even with the handle. Just noticed that.