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Re: 54" Laminated Youth R/D Longbow Build-a-long

PostPosted: Sat Feb 21, 2009 10:29 pm
by jwillis
Good stuff Jumper. This build along is pretty interesting. Jim

Re: 54" Laminated Youth R/D Longbow Build-a-long

PostPosted: Sun Feb 22, 2009 8:25 pm
by Kirkll
nice job guys....brings back memories of working with my Pa, and my grandpa at that age....A father son apprenticeship is rare anymore.... :D

got all choked up there.... :oops:

Re: 54" Laminated Youth R/D Longbow Build-a-long

PostPosted: Sun Feb 22, 2009 11:21 pm
by Jumper
It’s time for the dreaded timing and tillering!

String that baby up. I hold it under my foot and draw it back about 100 times. Really. Draw it back slowly at first, then however fast you want to. Every time I make a change to the limb during timing and tillering, I do the same thing and pull the bow back to full draw a bunch to help settle everything before measuring again. Place the bow on the tiller tree and take a look at where you are to begin with. Take your initial measurements and get started.

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Use the belt sander to take more off the upper or lower limb as necessary to get the limbs timed or bending uniformly. Sight down the bow from one end to the other while it’s strung to determine if the limb has a tendency to twist in one direction or the other. If it does, take more materiel off of the side that it’s twisting to. Take your time, this may take a few iterations to get it right. Less is more here, go slow. I am trapping the limbs in this picture. I already have the limbs bending pretty evenly so I put the trap in both the upper and lower limbs. I don’t have a given angle. I use good ol’ redneck guestimation here again. I probably have the limbs at close to a 45 degree angle when I’m making the passes on the belt sander to trap my limbs. I have learned that if you trap from the belly to the back of the limbs, you can gain a few FPS of performance. Mine are from the back to the belly on this bow as I usually do. I’ll have to try reversing it in the future. My limb backs are narrower than my limb bellies when I’m done trapping the limbs if that makes more sense.

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Once everything is flexing uniformly, check and set tiller (remove materiel evenly from both sides) 1/8” to ¼” for split fingers and dead even for three under.Come on guys, give your oppinion here so we get the best information out there. I put 1/8” positive tiller in my limbs (lower limb has a shorter measurement of 1/8” to ¼”). Measure the longest distance on the upper and lower limbs at a given location. I use mid handle in the arc where I can measure on one of the accent stripes or at the end of the fade outs, to make sure that I’m measuring the same place on both limbs. Sorry guys, I suck at describing this stuff.

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Back to the tiller tree to make sure that everything is still bending evenly. If you have flat spots (stronger area of the limb) carefully remove materiel with a rasp and block sanding. Never time or tiller with the bow strung. You can get hurt fast!

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Now that the limbs are finished, you can determine final draw weight. I check the weight throughout this process and take more materiel off the limbs if I’m still too heavy during timing and tillering. Actually, I confirming timing, draw weight, and tiller throughout this process over and over. Seems redundant and it is but it’s the way that I confirm everything is where it’s supposed to be.

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If you have done it correctly (I may not be doing this correctly! :oops: ) you will end up with a nice even profile that starts to bends at mid limb just out from the fade outs and stiffens back up just prior to the limb tips. Small light weight and stiff limb tips equal speed.

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It’s hard to see the limb profile in this picture. Maybe you should scroll back up to the full draw tiller tree picture a few above. But these limbs bend evenly, are trapped, have power wedges, positive tiller, and are timed evenly. Now that’s a mouth full! I haven't mentioned it before but the upper limb is built 3/4" longer than the lower also. On my adult bows they are 1" longer. :mrgreen:

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Re: 54" Laminated Youth R/D Longbow Build-a-long

PostPosted: Sun Feb 22, 2009 11:33 pm
by Jumper
A bunch of sanding follows. We also have to have time for the purpleheart to darken in the sun which we don't have a whole heck of a lot up here right now, and I have to head out of town again so I'll go ahead and post pictures of the unfinished product. :?

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Here you can see the trapp from the backs to the bellies. The upper limb from the tips down a few inches is sealed with super glue so that string wax does not cantact the wood.

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No bow can pass this stage of completion without thorough testing by our strengent quality control officer ;)

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Re: 54" Laminated Youth R/D Longbow Build-a-long

PostPosted: Sun Feb 22, 2009 11:38 pm
by Jumper
Hey guys, this is the point where I would really like for someone who is better with words to post better and more thorough timing and tillering steps. :idea:

Re: 54" Laminated Youth R/D Longbow Build-a-long

PostPosted: Mon Feb 23, 2009 7:00 am
by superkodiak38
Cant help with descriptions Scott but I will pat you both on the back for a job well done and the birth of an heirloom. I hope it brings you and him, and his kids for that matter lots of good times.

Re: 54" Laminated Youth R/D Longbow Build-a-long

PostPosted: Mon Feb 23, 2009 3:23 pm
by BK in TEXAS
Jumper wrote:Sight down the bow from one end to the other while it’s strung to determine if the limb has a tendency to twist in one direction or the other. If it does, take more materiel off of the side that it’s twisting to.


I thought (and it's dangerous when I think) that you took material off the opposite side it was twisting to, because it's stronger.

BK

Re: 54" Laminated Youth R/D Longbow Build-a-long

PostPosted: Mon Feb 23, 2009 9:57 pm
by jwillis
That bow has an awesome full-draw profile!

BK is right about removing material. The bow will always pull to the weak side, so you need to remove material from the strong side.
Jim

Re: 54" Laminated Youth R/D Longbow Build-a-long

PostPosted: Mon Feb 23, 2009 10:51 pm
by Jumper
Thanks guys, anyone care to weigh in on timing and tillering? :D

Re: 54" Laminated Youth R/D Longbow Build-a-long

PostPosted: Tue Feb 24, 2009 1:33 am
by Crooked Stic
One thing I do while tillering is shoot the bow a lot with the tips close to done. The string settles good and you can work from there. Never had much of an issue on longbow twist (as long as the string grooves were even) unless I had radical reflex in the limbs.