Max, I’ve been building backed and bellied tri lams for about 10 years. I learned how right here on TG. There was a lot of trial and error and I’m still learning. There’s no hard and fast recipe as each piece of wood and bamboo is different.
Basically, I taper the bamboo back and belly lams from 1/8” to 1/16”. The wood for the core lam has about the same taper rate, but the thickness will vary depending on the draw weight you want.
This is the one I built for last year’s swap.
I built a total of 4 bows last year. Two failed for different reasons, one came in light, but a nice bow, and this one was a bit heavy, but it looks really nice and shoots well.
That’s why I ground so many core lams. If I have a failure, I’ll just move on to the next.
Dave.