Sometimes it's because it's all you have to work with. I generally avoid tri-lams if I can, they are more work than they are worth
I've heard the argument of using a dense core wood being better before and I don't believe it. The only time you might get any work out of the core is if the belly lam is very thin. If the backing and core together amount to 50% of the thickness of your bow then the core is unlikely to do any work. The only forces a core wood in such a situation may experience are shear forces and any wood that glues well will tolerate those. I've used BC, Maple, Ash and they all worked quite well. I know that the horn bowyers like Maple as a core and there is a reason for this, it glues extremely well and strong enough to resist high shear forces
Rubbish. Gluing 3 lams in no more work than 2. If I'm cutting and sanding lams anyway, it's no more work, and gluing them takes the same amount of time.
Of course the core lam is going to be doing some work. Resistance to shear is still of benefit. I do agree that lighter woods are good for cores, but they still need to be strong in compression. Yew or cherry is probably the best I've used. However, I save the maple for the backing, as it's superior in tension.
As heat treating is your 'speciality' Marc, tri-lam ELBs are mine. I've stopped counting how many I've made, and in my experience, a tri-lam ELB with a harder, compression strong core wood is superior. As long as the core lam is thin, like <1/8". Bows made like this take less set and shoot faster in my experience. Believe me, I've experimented. I've found a whitewood backing, like maple or ash or hickory, with a core of maple, only makes a thicker backing. Adding a compression strong belly, which ends up being thinner, will make a bow which will take more set. Similar, I believe, as having a yew selfbow with too much sapwood.
I do agree with less is more. I can make more bows using a tri-lam style, because I need less of each type of wood.
Making a horn bellied, sinew backed horsebow is NOT the same as a tri-lam ELB. With a horsebow, I do agree that maple is great, but not for an ELB.
There was a post here not long ago... I think it was toomanyknots. He made a tri-lam, and used bloodwood (I think) as the core, and it chrysalled. It was clear and easy to see. I've never seen chrysalles or frets on the back of a bow. This is just more evidence to me, that the core is experiencing mostly compressive forces. The bow didn't fail in tension, but in compression, and in the core.
