Trad Gang
Main Boards => The Bowyer's Bench => Topic started by: D.A. Davis on May 02, 2015, 02:06:00 PM
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Looking for some input here guys. I've finally got my health problems under control, and got back out in the shop. I've been building a 64" Hybrid longbow, and everything has been going great until today. I had it on wall checking the poundage and tiller when I heard a couple ticks, and it let loose. It doesn't look like the adhesive let loose. All the glue lines were pulled apart by pulling the wood apart. I was using an Actionwood riser with 2 -parallels, 1 - taper, 2 - lams in the Green Mountain Camo, and 2 - clear glass. Can anybody give me any input on what happened? Here's some pics.
(http://i11.photobucket.com/albums/a178/bayman1975/IMG_0302_zpsrwqdmc6l.jpg) (http://s11.photobucket.com/user/bayman1975/media/IMG_0302_zpsrwqdmc6l.jpg.html)
(http://i11.photobucket.com/albums/a178/bayman1975/IMG_0301_zpssqmlvt8c.jpg) (http://s11.photobucket.com/user/bayman1975/media/IMG_0301_zpssqmlvt8c.jpg.html)
(http://i11.photobucket.com/albums/a178/bayman1975/IMG_0300_zps39xf2ac5.jpg) (http://s11.photobucket.com/user/bayman1975/media/IMG_0300_zps39xf2ac5.jpg.html)
(http://i11.photobucket.com/albums/a178/bayman1975/IMG_0299_zpsy31vp4jf.jpg) (http://s11.photobucket.com/user/bayman1975/media/IMG_0299_zpsy31vp4jf.jpg.html)
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DA , from here it looks like the fades needed to be thinner. Can't tell for sure, but I make mine .065" thick at 1 inch from tip of riser and about .140" at 2", then a nice sweep on up.
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What Kenny said was my first thought, then I noticed that it looks like you didn't roll the edges of the glass enough as well.
Combine those two things together and disaster is headed your way.
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I was afraid that might be it, Kenny. Well, I've got the materials for one more bow, so I guess I'll start over. Here's a pic of how I have things on the wall. This picture was taken yesterday when I exercised the limbs, and identified the lower limb.
(http://i11.photobucket.com/albums/a178/bayman1975/IMG_0285_zpsdearx4rl.jpg) (http://s11.photobucket.com/user/bayman1975/media/IMG_0285_zpsdearx4rl.jpg.html)
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Looks like a flawed design to me from the draw picture. All the stress or bend is at the fades. Outer 3/4 of limb has very little flex.
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Like Al says, the fades are working real hard in that drawn pic. More taper per inch would help there. What taper are you running?
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Al, this was done before I began shaping the riser, and limbs. The limbs had been been narrowed to approximately 3/8" at the tips running in from the fades. I had more flex in the limbs on the outer 3/4 when the bow let loose. I'm sure that what you're saying is a valid point that I need to address. I appreciate your input. I'll go back and try it again.
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Kenny, the taper was .002. I'll just try it again, and pay more attention to the fades and limb taper.
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Looking at your pictures on small screen cell phone. I am no expert but It looks like your putting a lot of stress on the fade area..You could add a power lam that extends 3 inch's past each fade along with a longer thinner riser fade. Not really a powerlam but I use a 040 parallel and make it 6" longer than my riser, then taper the last inch of each end.. What is your total taper?
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Wow..I'm a slow Typer..and I had a phone call before I hit send..
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Wow..I'm a slow Typer..
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Robertfishes, my total taper was .088; .352 at the tip of the fade and .264 at the string grooves.
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Im sure the next one will go better. I now see your taper is 002/inch. Kenny has done alot of proto typing.. He is "the man"
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Can someone point me the right direction to view some posts on power lams? I might have to give it a try with the next one.
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Here ya go buddy!
http://tradgang.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=125;t=011391#000000
http://tradgang.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=125;t=007528#000000
http://tradgang.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=125;t=002968#000000
http://tradgang.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=125;t=008109#000000
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You dont need a power lam. Create a more gradual fadeout with the riser and put more taper in your limbs and you'll be ok. Oh, and I shape the bow and riser almost completely before I draw it.
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Thanks, Bowjunkie. That's what I need to do.
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I agree with Bowjunkie, you dont need a powerlam if you make long thin fades..
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All good advice here.
Another tip - change your riser design to have some deflex in it as well since this is a deflex/reflex bow.
There's simply way too much bend right at then ends of the fades.
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So, you guys are saying that I need to lengthen the thin part of my fades. Looking at the picture below, I need to extend the end of my fade about 2", or so, and maintain a gradual increase, not to exceed .060, or so, for that 2". Then, ramping up to the riser handle as gradual as possible.
(http://i11.photobucket.com/albums/a178/bayman1975/IMG_0251_zpsnmh2gwtc.jpg) (http://s11.photobucket.com/user/bayman1975/media/IMG_0251_zpsnmh2gwtc.jpg.html)
And, adding more deflex to the riser design would require building a new bow form, correct? Here's a picture of my current bow form setup.
(http://i11.photobucket.com/albums/a178/bayman1975/IMG_0231_zpse52detbr.jpg) (http://s11.photobucket.com/user/bayman1975/media/IMG_0231_zpse52detbr.jpg.html)
Thanks for the help guys.
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Is that the Bingham hybrid?
A longer riser with thinner fades would work as would just thinning the fades you have there. They have to bend a little so you don't have a hinge and a breaking point.
the fades for me need to be 1/16" at 1 " from end of riser and a fuzz over 1/8" at 2" from end. Anymore I mark 1 and 2 inches from ends on both sides of riser and measure with the dial calipers. .065" at 1" and .140" at 2" from the ends.
Sent you an email too..
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Yes, Kenny. I purchased the pattern for the form from Binghams. The riser block I use is 18".
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Oh, and the bow pattern came from Binghams, as well.
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They almost always use .002" PI in their limbs , I'm more of a .003" PI guy... :)
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So Kenny, if I wanted to add deflex to my riser/fades, I could take my existing form, and remove material from the area where the riser is pressed into the form. This, of course, would have to be done carefully, and evenly, across the span of the riser/fades and flow it out toward the limbs some. I would also have to add material to the top half of the form to ensure even pressure across the span of the bow.
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Yep , just maintain the space for air hose and riser...
Did the email work I sent? That may help...
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Originally posted by kennym:
They almost always use .002" PI in their limbs , I'm more of a .003" PI guy... :)
^^^^this in addition to finer /less abrupt fade should resolve the issue
---the .003 taper will make it bend further out on the limb [spreading the loads]--think of an abrupt fade as a fulcrum that pryed your glass off tour riser
---you'll get it this time!!good luck!
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Yeah, I would be tempted if I were you to build a black glass one without changing the form and like Mike says thin the fades and go with .003 total taper. Changing taper will lighten the bow a little going from .002 to .003 but I don't know how much...
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Yes, I got the email, Kenny. I had to move it out of my junk folder. But, it's good now.
That's some good information, Kenny. Thanks. That'll help me a lot.
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D.A., If you want to try a .003 taper with a power lam built into your stack "superlam". I can grind you one out if you want some maple. That would help the bend move out a little past the fades. In my opinion.
I am in Paragould. Send me a pm if you want to give it a try.
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Thanks David. I sent you a PM.