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Offline ccase39

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Question about a tri lam
« on: October 17, 2015, 05:30:16 pm »
I tried a R/D trilam and it broke basically because I got in a hurry and out thought myself lol. I was using Osage and Hickory with bamboo back. I thing the problem was that the osage and hickory were too thick. If I had tapered any more I would have had to shave passed the osage belly wood into the hickory near the tips. If I did this the osage would have been running about 3/4 the length of the limbs until I hit the hickory. I figured it would split at the glue seam so instead of tapering it any deaper I decided to make the bow thinner by removing from the sides. It snapped because the limbs were not wide enough and too thin. Could I have just kept scraping the belly wood into passed the osage into the hickory?
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Offline Pat B

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Re: Question about a tri lam
« Reply #1 on: October 17, 2015, 06:06:06 pm »
Case, can we see pics of your first try tri lam?  How thick were the lams?   Any time you use more than a backing you have to know how much thickness for each lam so it comes out even at the finished draw weight you want. 
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Offline ccase39

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Re: Question about a tri lam
« Reply #2 on: October 17, 2015, 08:54:04 pm »
Hickory and Osage were 5/16 boo backing 1/8. I would post picS but I cut it up for scrap.

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Offline Dances with squirrels

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Re: Question about a tri lam
« Reply #3 on: October 17, 2015, 09:42:30 pm »
I like to taper the Bamboo from 1/8 at the handle to 1/16 at the tips.

I also like to taper the center lam at least 1/16, but less than 1/8, from dips to tips. Usually, in osage, it's about .200" at the thickest. This pretapering of the core lam generally eliminates the need to thin the belly so much during tillering that you work down into the glue line.

The belly lam is usually osage on mine, it's ground parallel, and it is about .200" as well.

These dimensions would work for a d/r boo/osage/osage trilam 60" long, and 55-60 # @ 28"... give or take.

Of course these thicknesses are adjusted according to draw weight, overall length, riser length, and other factors.
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Offline ccase39

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Re: Question about a tri lam
« Reply #4 on: October 17, 2015, 11:58:56 pm »
Yea, I knew I should have tapered the middle lam going into it. I have only had a table top belt sander for a few days now and wasnt confident enough in my skills to get it tapered from mid handle to tips.I will give it another shot with red oak or something. I wasted some perfectly good osage and hickory lol. Lesson learned though. I was able to salvage the handle so I will use it next time.
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Offline Springbuck

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Re: Question about a tri lam
« Reply #5 on: October 18, 2015, 03:16:40 pm »
The final thickness is almost always, especially on a RD trial or similar with Perry reflex, much, much thinner than people think.  A total thickness of 1/2 " is ridiculously this for most draw weights.

If you don't taper the middle lam, then it must be very thin, for the reasons you discovered.

I usually do simple Perry reflex, with power lam and possibly wedges at the tips, and use a 1/8" backing with a 3/8" thick belly, for most woods, and play with the width where needed.
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