Primitive Archer
Main Discussion Area => Bows => Topic started by: Kidder on December 28, 2020, 07:12:27 pm
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Working on a BL recurve. Got it moving nice at floor tillering. The stave has some pretty substantial reflex and it’s not terribly even either. Now for my question: when tillering an uneven reflexes stave, at what point do you want the tips to line up? Do you only work towards even tips at full draw, brace, pulling flat??? Thanks in advance.
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I wouldn't attempt to tiller a stave with that much reflex difference. You are going to over strain the limb with the most reflex. I make them as close as possible first before tillering. If you have a caul and a heat gun you can adjust the tiller, take out any limb twist and temper the belly at the same time.
With a wood bow the only true proper tiller is at full draw.
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Thanks Pat. Would you reduce the more reflexes limb, increase the less reflexed limb, or try to meet them in the middle?
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I'd reduce the reflex on the left limb, simply because that's a lot of reflex and will make the bow a real bear to deal with.
That said, I'm not opposed to making bows with different shaped limbs, i.e. one with more reflex or deflex than the other. Such limbs should be balanced relative to the shooter's holds, which generally means they'll travel equal distances to get to full draw, but not 'line up'. In other words, if one limb starts off behind the other unbraced, it should be behind the other at full draw too... if they're balanced and working in harmony, as all should be.
You would only over strain the limb with more reflex if you tried to make it come back the same distance behind the handle as the one with less reflex. That is, trying to make it resemble a bow with identical limbs, which it is not. The limb with more reflex would have to be considerably weaker to achieve that look, thus creating imbalance between the limbs.
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ok Ill put my 2 cents, good advice from above,,
put it on long string at about brace, and leave it a few hours,, then look at it,,
string the bow and see how it looks... leave it braced a few hours,,
then it may change some from the way it looks now, then if you feel you need to heat it more to match ,, do so,,
I guess what I am trying to say,, is, the way the bow looks now, may not be the way it will settle in with a little bit of pressure and no need to adjust it,,if its not a true representation of the profile,,
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More than about 3 or 4 inches of reflex can be a problem for not only bracing the bow for the first time but can also over strain the stave causing more set.
I also agree with Brad. Working the limbs may help to settle the them in and bring them closer together. That's why I like to exercise a stave with 20 to 30 pulls after each wood removal, only pulling to the length it has been tillered to. Once I hit first low brace and both limbs are bending evenly without any visible hinges I will leave the bow at brace for an hour or so and as the tillering increases I leave it braced longer until when done I will leave it braced for up to 6 hours.
For me, having both limbs even to start with will help to make a successful bow. Both Brad and I have been making wood bows for many years. All we can do is give you advise to help you over the humps we struggled with back then.
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All very good advice - thanks! Dances with Squirrels - that answer makes sense (limbs move evenly and finish at different positions but maintain equal travel)...just not at all what I would have expected though.
I think I’ll get them moving real nice and then heat treat them, reducing reflex a little in the upper limb and try to balance them. It’s funny that limb had nowhere near that amount of reflex until I started straightening things a bit and then it took off. All a learning curve...
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Sounds like the wood still wasn't dry enough and it drew into reflex as it dries.
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Sounds like the wood still wasn't dry enough and it drew into reflex as it dries.
That’s possible but I doubt it. That stave was cut in May and stored in my garage rafters all summer in a very dry climate and has been reduced down to dimensions and in the house for at least the last 60 days. If anything it took on too much moisture from repeated steam bending. Either way I think we’ve nailed the solution going forward. Thanks for your help!
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Staves that move do so because of the stresses in the tree as it grew. When you remove the stave from the tree and then as we further reduce things those forces are strong enought to move what is left. It would be possible for a stave to dry into reflex if you only dried the back :)
Dances is right, if you tillered that stave as he said above you would be ok and in no danger of overstarining one limb. However it would make things a lot easier for you if you reduced the refelx in the left limb. :) Too much reflex is not good (until you know how to deal with it, even then failure rates go up!), 2 inches would be a great starting point with your bow.
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So this bow was coming along beautifully until I strung it for the second time and it exploded into the back of my leg without warning. Tension failure. This was what I was hoping to avoid by backing it with rawhide but maybe it wouldn’t have mattered. I was almost there - just had to even the tiller and then heat correct the string alignment and I would have backed it. Oh well. Left a good bruise but just glad it wasn’t the top limb. Either way, learned a ton - mostly about the challenges of questionable wood. So on to a different tree with different challenges.
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If I am working on a questionable piece of wood I always make a Minnie bow from a sliver of wood and do a bend test to see how the back will hold up, you can usually tell if you are going to get a tension failure by the way it breaks . Sorry for the break. :(
Pappy
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Second time it was strung? There is a big difference in BL stave and trees to be sure. Some are really good other are junk. Looks like there was not enough width in the limb where and before the catostrophic area. Hard to say from the pic.
Shawn~
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It’s possible it was your method of bracing to.
Reflexed bows can be tricky to brace. What method do you use? If you use step through it is really important to have handle on your leg, not limb. You always have to evenly spread out the stresses. Even just while stringing it. It took me a while to get the hang of it, but I use the push pull method now. A stringer is probably better yet, but I never used one.
Bjrogg
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Glad you're alright. I think we sometimes underestimate the danger of wooden shrapnel, though of course some bows just crack, not explode.
I hope the next one works better.
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Glad to hear you just have a bruise, could have been much worse! I use a stringer or a stringing board - and try to keep all my body parts out of the line of fire if something gives. I likely would not hear any warning ticks
Hawkdancer
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I don't know how many Bl bows you have made, but if their is one wood that will test your tillering skills. Bl is it. Heat treat the belly,and trap the back with a good piece of wood, and you can get their. I failed with the first 4 Bl staves I got from one bad tree. The backs either broke, or the belly had frets. I made the 2nd four bows from good Bl. I trapped the back, and heat treated the belly. Then tillered with a Gizmo. I still have 3 of those 4 bows. 2 are sinew backed, and very good shootersand one good self bow. I gave the other one to my son.
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Thanks for the encouragement and words of wisdom. It was 1.75 inches wide to mid limb so I think it was designed correctly. I just think the rings were too thin and the ratio favored early wood too much. I had already heat treated it - amazing how it basically turned it into a leaf spring. The first string was on the step through method. I immediately unstrung it because of how unbalanced the limbs were - the lower limb which broke was much stiffer. I took wood off and restrung it with the step through method. I had my leg probably on the fade when it exploded. I think I should just get a stringer and not worry about it. I was examining it last night and was still impressed with how nice of a profile and how good of a job bending recurves and evening reflex I had done. So not all is lost!