Primitive Archer
Main Discussion Area => Bows => Topic started by: DC on March 27, 2019, 08:21:59 pm
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Does it cause any harm to performance if a Molle's levers bend maybe 1/2". Enough so that you can see they are bending and get them as light as possible. I'm thinking enough to pull this straightish.
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I don't know,,,but the chrono,..will tell u...right....it might be a wash,,..maybe an advantage with light arrows?
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I think your fine as long as you don't change the string angle the shorter the bow the more pronounced the effect would be , the last one I did I got the tips to thin and they just started to bend but where able to heat treat rigid again .
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All a matter of degree... they are bound to flex a little.
If they didn't flex at all they would be too heavy...
Del
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I guest it's a tradeoff between lighter and a little flex and heavier and a little stiff. If it really matters in speed? I don't know. Would be nice to test with a chrono but you already slimmed the tips down right? Personally I would slim them down as much as possible until you just start to see a little bend at fulldraw.
The trick I use when I build a molly is let the levers a little longer during the build and trim an inch off when I am finished. This just stiffens the levers enough so the tiny amount of bend I see at fulldraw straightens out and I am sure I did not overbuild them
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as del pointed out, there will always be some deflection. how much is a function of the load (basically directly proportional to the load)
of course, an equal mass of lever materiel can be arranged to bend more or less by varying thickness and width or crossection,
Are you thinking of how much one should want them to bend for light arrow performance? or how to keep them essentially unbending, but as light weight as possible?
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I did glue a splinter on the back to measure the bend. I glued it on unbraced and was surprised that the levers bent about 1/4" just bracing the bow. They bent another 1/4" by full draw, still not enough to straighten them. I just didn't know if there was something about the stiffness(other than lightness) of the lever that contributed to the speed. They are both recurved so I don't think string angle enters into it. Maybe something to do with short working limb? I'll probably start slimming them out. I would like to narrow them but I got so lucky with the string alignment I hate to risk that. I guess if it started to go bad I could glue veneer on both sides to rescue it. Does anyone know if, when a limb is going to twist off sideways, does it go a bit at a time or does it just break off sideways?
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DC,, I think this is usaully when I request you start another bow,, ;D
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I had to do some plumbing today. Me and plumbing don't get along, usually. Today it went well unless the upstairs is flooding as we speak ;D ;D So I'm heading out to the shop.
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So you have a working recurve...lol but this is what I have found threw my exsperments & chrony tests with ridgid tip bows , once the tips are lightened with out bending as far as speed goes there is no gain beyound that , think about the little mass diference between flexing and not & but even small changes in string angle make a bigger difference in fps I have gotten more fps out of narrowing the working limbs especially in the upper 3rd then ultra light tips , gaining performance is so much more then just light tips at least thats what I have found with chrono testing as I remove material I sent Brad some tests I was doing a while back and it was amazing whatching the speed gains even thought the draw weight was dropping , I also did some tests with un thinned leavers and shot threw the chrono as I thinned & its much less then I imagined Im not saying light tips are un important Im just saying if your after performance there is a lot to look at , I think when Im making a bow for performance the number one thing for me is string angle at FD & total mass none of this is my ideas just applying what I have learned from guys here that have made some fast bows !
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it was amazing whatching the speed gains even thought the draw weight was dropping ,
Were you dropping the arrow weight to match the draw weight loss?
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Just had a wacky idea :)
Half way up the back of the lever, glue a vertical post say 1.5" high. Tie a string to the root of the lever where it joins the limb, run it over the top of the post and down to the nock where it can be tied off. This triangular bracing should stiffen it up with very little weight penalty :) it can always be tied in before the post is fully pushed home to get some good tension on it.
I'd patent this, but it's doubtless been done before, and I've just put it into the public domain. (If anyone gets rich off this idea they are welcome) ;)
Del
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The thought crossed my mind when I glued the splint on to test for bending. ;D I dismissed it as silly ;D ;D ;D
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Tim Baker proposed that idea in TTBB. You could just drill some holes and lace some FF through them and back around the nock.
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Tim Baker proposed that idea in TTBB. You could just drill some holes and lace some FF through them and back around the nock.
>:( ::) ;)
Del
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Would any of these ideas add or at least maintain the torsional stiffness.
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Would any of these ideas add or at least maintain the torsional stiffness.
I don't think so.
Not sure why you have the flipped tip on a molle' ... not sure if it achieves much... mind it makes it easy to add the string stiffening idea.
To improve torsional stiffness add ribs to make the lever a T section (or an inverted T) or V/inverted V
Del
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Not sure why you have the flipped tip on a molle' ... not sure if it achieves much...
Del
I've had such good luck with the RD's that I've made that I decided to try combining the two. I've measured the "dynamic" limb length on various limbs and found that a straight bow shortens quite a bit as it bends. RD not so much and recurved RD's even less. Whether this means anything, I'm not sure but I'm going to run with it for a bit.
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anyone else have good ideas on how to thin levers, limbs or near the handle so it *almost* bends?
how do you know that the next shave you're going to remove will be too much?
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As Del said: "inverted V" must be best for torsion stiffness. hollow it to save mass.
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Good alignment makes torsional rigidity less important. The Asiatic composite bowyers had it figured out though. Thin bone plates and a teardrop cross section is lighter than needing width for a groove.
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Good alignment makes torsional rigidity less important.
This is so true. With the Molle I just finished I got really lucky and hit the alignment right on with just one little tweak. Now it draws like a straight bow even with 3" of reflex. I'm going to pay extra attention to having everything straight and true on the next one. Getting it right the first time sure beats 15 heating sessions.
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There is an existing very old composite bow with super long siyahs unsupported by side plates. The tips are even said to be willow. It is twisted to a corkscrew now but it likely was fine during its active life.
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I tried to bend some Sitka Spruce and it was having none of it. It just crushed the inside of the curve so I'll keep it for arrows most likely. I'm thinking of Hazel but I'm bending my last small piece of straight Yew.
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May be worth cutting the spruce into thin strips, laying them on a form and laminating them.
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Good thought, I'd forgotten about that choice, I've never done it. I thought I would make up one of each and weight them.
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I would just "plywood" it and cut the shape you want.
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How many plies 3-5?
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Your backing is presumably going to support it so I would go with 3-4. I would run them vertical and at 45 degrees.
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Thanks Pat. I'm not so sure about it. I'm sure it would be strong enough I'm just afraid it would look like, well, plywood. Especially if you tapered it. I guess if you tapered through a layer you could veneer it.
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It would not look like plywood. By that way i make stems for my woodstripe canoes. If You cut stripes in order from the same board, it will look like a grain.
http://s1105.photobucket.com/user/maitus/media/kanuu%20nr2/P7250001_zpsvzvmtt0e.jpg.html
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Nice boat Maitus. That look like strip construction. What is "plywooded about it"?
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He is refering to the stem only, laminated strips.
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DOH!
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He is refering to the stem only, laminated strips.
Right :)!
And thank You DC :)!
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very nice detail on that strip plank, what species are you planking with?
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very nice detail on that strip plank, what species are you planking with?
Can not answer here as its not a bow, but canoe and its not my topic either :D... sorry! PM sent...:).
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very nice detail on that strip plank, what species are you planking with?
Can not answer here as its not a bow, but canoe and its not my topic either :D... sorry! PM sent...:).
Its the bow of a canoe, still counts. Awesome to see another wooden boat enthusiasts on here however.
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Thank You sleek :D.. ! It actually is a bow :D :D...