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Main Boards => The Bowyer's Bench => Topic started by: Jrunner on May 01, 2015, 02:56:00 PM
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I have just started tillering my first trilam. Any help is appreciated. I see my saddle is a little crooked to the left.
There is knot on the right side before the outer third. I am pulling to approx 45lb, shooting for a 50 lb bow. Thanks
(http://i1383.photobucket.com/albums/ah301/joeytrun/Mobile%20Uploads/image_zpsf9pfxkhp.jpg) (http://s1383.photobucket.com/user/joeytrun/media/Mobile%20Uploads/image_zpsf9pfxkhp.jpg.html)
(http://i1383.photobucket.com/albums/ah301/joeytrun/Mobile%20Uploads/image_zpsceyrmozx.jpg) (http://s1383.photobucket.com/user/joeytrun/media/Mobile%20Uploads/image_zpsceyrmozx.jpg.html)
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Looks pretty good. Could you give me some specs, I'm just finishing one up now. Is it pulling 45# in the pic..? I cannot see the knot so can't comment on that. Your tip ends look like they are working which is a good thing maybe flat mid limb.
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Looking good so far if you ask me.
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Looks good to me so far to. It looks like you have the tips moving far enough to put on a short string to a low brace. That may change the way it looks.
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Low brace will bring the outers round a shade.
Ipe belly??? If so be very careful of that knot.
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Looking good, get it to a low brace of about 3" now. Those long tillering strings don't work the outer third of the limbs much at all. Once the tips are coming down to about 9", take it to a 6" brace height.
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Thanks for the help guys. I copied the specs from one of Roy's builds. 1/8-1/16 hickory back, 3/16-1/8 cherry core, and 3/8-1/4 ipe belly. It is 1 3/8 wide 6" past the fades to 1/2" tips. After I short string should I start working the midlbs more? I am at the point where I am not sure where to scrape.
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Pull it and take pictures, then study them, that's always helpful.
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Ok guys, I made a bow stringer and got a short string on it. Instantly I noticed what you all warn about using the long string. The right limb as shown in the pic was stiff. I scraped the stiff area and worked it about five times and it is still stiff. I will run out of ipe soon. The difference it the short string is unbelievable.
(http://i1383.photobucket.com/albums/ah301/joeytrun/Mobile%20Uploads/image_zpstm5diugr.jpg) (http://s1383.photobucket.com/user/joeytrun/media/Mobile%20Uploads/image_zpstm5diugr.jpg.html)
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Don't string a bow when it's that uneven and definitely don't leave it strung to take pics!
Chances are you will have a little unnecessary set in the left limb if.
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Your bow's main issue has practically nothing to do with long string tillering. At least that isnt the root cause.
It was handicapped before glue up. It simply has too much thickness taper in the limbs. You glued it up with a total of 1/4" of taper. That is a LOT. I would have NOT tapered the belly piece at all, which would have meant half as much, or 1/8" total taper, which would have been plenty... and made those limbs look and act a LOT different than what you're seeing there.
Your extreme amount of taper is evident in the profile differences between the first two pictures. Yes, a long tillering string will tend to flex less of the outer limb, so they appear weaker when the bow is braced with a proper length string, but if the long string was the culprit, in the second picture, with the bow being pulled WITH the long string, the outer limbs should appear strong, but they don't. They already look like they're bending too much... your recurves are already opened up a lot... too much for all the more it's being drawn... and when braced with a shorter string, you lost even more of them. This is because there's too much taper in the limbs allowing the outer limbs to flex too much.
Solution? Tough one. I would either saw off the belly lam and replace it with a parallel piece about 1/4" thick, OR, remove enough wood from the belly piece to MAKE it like a parallel piece. Of course you can't get under the riser with the second option, so that wood would stay there and act like a power lam... though definitely not needed in THIS bow.
I would love to see you saw the belly and handle off, clean it up, and glue on a parallel piece. It would be a completely different bow... and awesome with that unstrung profile you got going on there.
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How long is your bow?
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Bowjunkie, I see what you are talking about and think it is due to my tillering. The ipe belly lam was too stiff to bend so I started scraping outside of the faces down towards the tips. I took the wood off to get it to bend. Should I have just started past the fades until I could brace it and then work towards the tips? I guess I'm not understanding how adding more wood to the belly would help when I scraped it mostly off trying to get it to move. I did taper the lams on a belt sander and noticed the stiff limb seems to have a thicker core lam midlimb than the other. This to me would explain the how I have less ipe but still stiff. It was 64" before glue up. Thanks again guys, I really appreciate the feed back.
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I have since started making my belly and core lams thinner. So I'll accept the blame for your bow being too stiff.. :) I now make my belly lam 1/4" thick with no taper and I make the core lam 1/4" thick, tapered to 1/8th at the tips. I start the core lam taper where the end of the riser will be.
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Hmmm, I remember telling you to do exactly that many bows ago.... knucklehead.
xoxo
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Jrunner, I understand what you're saying, but I'll stand by the statement I made about 1/4" of overall taper at glue up being toooooo much.
How long is your bow tip to tip?
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It was 64" lams before gluing in recurve.
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If you tapered those 64" pieces for a combined total of 1/4", that's a .0078/1" taper rate.
For reference, I usually try to ballpark it between .003/1" and .004/1". Though nothing is written in stone regarding this, and we can certainly each effect limb action in our bows however we want, the difference in these numbers may give you some idea of why you had a hard time and the shape of your bow isn't what you expected.
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So moving on, I followed bow junkies advice and sawed the belly off. I had about six more inches of belly to scrape and this happens.
(http://i1383.photobucket.com/albums/ah301/joeytrun/Mobile%20Uploads/image_zps9vsyk7wd.jpg) (http://s1383.photobucket.com/user/joeytrun/media/Mobile%20Uploads/image_zps9vsyk7wd.jpg.html)
My core cracked but not the backing. Is this the end or can I glue it back and sandwich with the new 1/4 ipe board?
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I don't understand. How did it break? Weren't you going to glue a belly lam on it? Why would you bend it before that was done?
That sucker is TOAST!
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I had it on my draw bench with the end hanging over and it snapped. It was near the recurve and felt like it was under tension. I was using a bowyers edge so not pushing very hard.
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I just looked closer and you can see it cracked on a ring.
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Dont feel bad runner most of us do it, I just broke one about 3 days ago. Bad design and had to much meat on the bones, bow was to thick and I did not want to taper it down as it was twisting somewhat.
So the next day I bought some wood and started 2 new bows, twins so to speak. When I first started out I broke 6 bows in a row...... :knothead: just could not grasp the tiller concept and my brute strength..