design of longbow

[ghost rob]

In the past I've made some longbows (great northern critter gitter style) that were 62" long with an 18" riser and two lams of .050" glass and four lams of wood that tapered .0015" each for a total taper of .006". The lams all measured .085" at the butt end. My question is this; I always ended up around 50#@26" which was what I wanted, I want to make a 60" bow on the same form and reach the same weight, so do I shorten the riser and use thinner glass or what? I'm thinking of going with a 17" riser and .040" glass and seeing what I end up with. What do all of you think? Thanks, Rob.

[Apex Predator]

I think if you went with just the .040 glass instead of .050 you will wind up where you want to be.  Either that or use the same glass and reduce the riser to 16".  I think you would like the performance of the thinner glass though.

[TradBowyer]

if you reduce your glass thickness, you'll need to increase your wood thickness a tad. Going to a thinner glass throws your wood/glass ratio off and you'll come out way lighter if you don't increase your wood thickness a tad. i did this on one of my recurves that has about 1# of weight change for every 0.001" lam thickness. I went with 050 glass instead of 040 (for a heavy bow)and had to change my lam thickness by 20-30% from what I had figured I think to hit weight. Best thing to do is try something and see what the outcome is. Whats the worse thing that could happen? You might have to build another bow...so what the downside LOL.

[Apex Predator]

He's planning on cutting it down two inches though.  I figure it will be close to a wash.

[TradBowyer]

good point Apex.

[wingnut]

2" cut off on that bow will probably be about 8# or so.  Drop each of the lams .002 at the but and give it a go.  Do not change the glass thickness or the riser size.

That should give a bow about 8# lighter so you can cut it down to your 50@26.

[ghost rob]

Thanks guys . Wingnut you are exactlly right about two inches cut off equals 8#s. I got that difference when I made a 64" bow. So if I use the same riser length and cut off two inches, at the same 50# draw I should pick up some speed due to a shorter working limb, right? Will I lose any smoothness or gain any handshock? I really don't notice much shock right now. I guess I just need to glue one up and see as suggested. Thanks, Rob

[ghost rob]

Anyone?