Equal thickness on laminations?

[warden415]

I wanted to hear opinions on various thicknesses of laminations in a glass bow. If I am using 3 lams, One parralel and 2 tapers, do all 3 have to be the same thickness. For instance, if I was shooting for a total thickness of .210    Does it matter if I use .70 in all 3 pieces  or would the bow perform the same with say two tapers of .65 and a parralel of .80?
Is there any advantadge in keeping them all the same vs. altering them to end up with the same overall thickness?
Also I am attempting to make my own lams. I am grinding 2 36" and gluing them together, Should the taper begin at the very end of the lam and continue to taper evenly  to the tip or should the lam be left untapered for the first 8" or so ( the part covering the riser where they will be glued together) and then begin the taper at 8" and taper all the way to the tips?  Thanks Steve

[ChuckC]

Steve, when you use tapers, remember, the thickness changes as you go away from the butt of the taper.  Usually in terms of .001", .002", or .003" (thousands of an inch thickness / per inch of run).  It probably doesn't matter at all what any of them are at the butt or "riser" end of them, but as you move towards the tip of the limb, it matters a lot.  Example.  If you start with a taper of .065 (check your numbers) and you taper at .002", than after 36 inches of run you will have tapered away .072 inches. Your taper (the piece os wood) would not go all the way to 36"!.  

I am guessing that it would be better the other way around, one taper and two parralels.  Make the parralels constant, always say .050, then the only thing that changes is your taper.  You can change either (or both) the starting thickness or the degree of taper.

By the way, although I believe almost all "store bought" tapers go from one end to the other, I have also been thinking about what you brought up, leave that portion of the thick end of the tapers as parralels and start the taper at or near the end of the riser.  This MIGHT make it a tad easier to fit the riser to the correct shape.
Who knows....

Either way, the total thickness of the lams and the taper profile will affect how your bow shoots.  Note.  You actually don't even NEED a taper in there, as you can adjust this from the sides as well, but I think it is generally accepted that a taper allows a changing or gradient limb profile, both in terms of weight and flexibility.

PS...If you grind your own, be sure to do some excellent QC on the side to side and longitudinal thickness.  Make sure that if it is .150" on one side it is near that on the other, and also along the length of it if it is a parralel.

Good luck
ChuckC

[warden415]

ttt