center lamination question

[willie]

Hi-
 I have built a few board bows and a few from staves, but never had a need to build a heavy poundage bow until now. My son wants an 80#, but I do not have anything to make it from unless I rip and glue lamination's. Might as well try to build a warbow while I am at it.. I have a basic understanding about the tension qualities needed for the back and the compression qualities needed for the belly, but...

why do so many make it a trilam, and what wood qualities are desirable for the center lam ?

thanks

[mikekeswick]

If you add a core then you can save a little bellywood. It also helps to make it a bit more pretty! If you like that sort of thing!
I used to use ipe and hickory with a maple core quite a lot. The maple is a good bit less dense than both of the others so you are saving a little physical weight. Theoretically this will give you a small increase in performance. The other thing that adding a core means is that your belly lam is thinner and can therefore be bent into a more pronounced shape - but that's not so relevant with a longbow. You can also use the gluelines to store a little energy (perry reflex). Finally you can do multiple glue ups (increasing reflex each time) to try and increase the gluelines ability to store some energy.
Long and short of it is it probably won't make a big difference so make it look pretty!