Primitive Archer
Main Discussion Area => Bows => Topic started by: sleek on September 06, 2017, 11:09:15 am
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So i have bent in flat recurves.... aka... siyahs. They are 6.5 inches long and at brace they dont ley flat with the string but stick up 2 inches. I havent installed briges yet.the plan is to make a bridge and brush nock all in one. But every time it wants to twist one way or the other. Maybe I overcompensate when I correct it, idk, but this is driving me mad.
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How wide are your limbs? Wider limbs = more lateral stability
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Inch and a hald at the fades tapering to 3/8 nocks.its osage btw....
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How wide are the limbs at the base of recurves? I imagine that is where they are getting torqued
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7/8"
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I've only done a few recurve/siyah bows and they can be a PITA. I made a jig that holds the bow solid(basically a vise) and clamped a piece of wood by the tip. I marked where the tip is now on the piece of wood and a mark where I thought it should be. Then heated it at the base of the curve and twisted it to the "should be" mark. I was moving it 1/4" at a time with 5" of reflex. Don't count on sighting down an unbraced bow to decide if it's right. I based my guesses on which way the string moved when it lifted off the bridge. Just keep at it until it works or you give up ;D
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Best advice ever.
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<snip>Just keep at it until it works or you give up ;D
I think this needs to be on a refrigerator magnet somewhere!
OneBow
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Sleek, first measure how far the tip should travel.
Then clamp bow in the vise, add a weight and measure with a yard stick to the ground.
Heat and watch the recurve /siyah travelling, until you rech what you want.
Now way to do that adjustments just by eyeballing!
Somewhere here:http://primitive-bows.com/osage-static-build/
you can see the setup
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Thanks for all the help guys. I got it but certainly went about it the hard way.
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So i am at full draw now and have made an fd chart. Im 2 pounds shy of my 45 pound goal, I will heat the limbs a touch as they are untreated to get those pounds back. Here is the chart.
10. 7
12. 12
14. 15
16. 18
18. 22
20. 26
22. 30
24. 35
26. 38
28. 43
The bow when strung is 49.5 ntn. But with its curves, measured along the back, is 57. ( correction, 54 inches along the back )The goal of this was long bow performance with short bow advantages... also with the limb mass closer to center it should allow a faster return of the tips on release. I hope this is a fast bow....
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With having string bridges I am scared the string wont hit them on release and snap my tips. I got the tips aligned but still, its worrysome.
I think i just realised why they dont use slip nots on these bows..... LMAO
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How far behind the back of the bow are the tips when unbraced? how much set did it take?
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Took one inch of set. After unbrace the tips are one inch above the back.
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Took one inch of set. After unbrace the tips are one inch above the back.
I thought they were 2" above the back when braced😕
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2" Above the string when braced.
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If someone can walk me through the new way to oost pics I will try to post some to clear things up?
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If someone can walk me through the new way to oost pics I will try to post some to clear things up?
I need to know this too.
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I roughly calculate 38.9 ft pounds of stored energy in a 43 pound bow. Is that good?
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if you're taking pics and posting them off your phone you can download a free app called Photo & picture resizer. you take your picture and then open the app. at the top of the screen will be a button with four arrows going in from the corners. From there you can resize them and check the size. very easy to do once you figure it out. When you post click on attachments and choose from your photosizer gallery. I can take a picture and post it on primitive archer and less than a couple of minutes. I've been using it for a while and none of my pictures have disappeared off this website
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What size do they need to be?
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Here it as at full draw on my "tree" I am bowing to the tiller gods praying.
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Hopefully this is bigger at 40%....
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Braced
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Full draw.... I have since taken the left limb tip and straightened it out flat to match the one on the right. That changed the tiller slightly but i think for the better.
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Unbraced fresh off the caul and limbs cut and spliced into a strong reflex at the handle.
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On this design, I believe I can get some fast bows and honestly I am pushing for 200fps from them with 10 gpp arrow. Next one I build will have more limb reflex distributed through the limb, maybe 2 inches. The idea being at brace the reflex is still visible rather than pulled flat as this bow is. I am not certain if I will do siyahs or not. They are a pain to make.
Hopes with this bow are high however. Hope to have it shooting tonight.
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Full draw with siyahs complete
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Impressive looking bow. Sure interested to see what kind of performance you get out of it.
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Sleek, what is the final draw weight on this bow? How much set did it take? With designs like this you have to measure the weight losses due to compression, the limbs are thin and the tension will hide most of the set. Your braced tension after a couple of full draw pulls will tell most of the story. I too am curious as to what you get out of it.
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Nice!
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Sleek, what is the final draw weight on this bow? How much set did it take? With designs like this you have to measure the weight losses due to compression, the limbs are thin and the tension will hide most of the set. Your braced tension after a couple of full draw pulls will tell most of the story. I too am curious as to what you get out of it.
I never went back and heat treated the limbs after reducing the angle of the siyah so it is 43#. Steve, I have no way of measuring lost string tension, but i bet if I made a split string and mounted a bow scale between the string I can.... as for lost weight due to set I am afraid I dont know. It took one inch of set Is all I can say.
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Sleek, try that design using the no set tillering method. Let the condition of the limbs dictate what your draw weight will be. Thin limbs like the one you have will mask set because the tension will pull it back into shape. Let the bow rest for a couple of hours. Then measure the draw weight at about 12" very carefully. Write it down. Now go to full draw and make several pulls at full draw and then go back and measure it at 12" again and see if it is the same. There should be no difference. If there is a difference your design is overstressed. Good learning lesson on bows like this they will teach you a lot about design and material limits.
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I am going to link these two threads togeather as they are the same bow
http://www.primitivearcher.com/smf/index.php/topic,61463.0.html