Tri-Lam question (all wood)

[Powder]

Hi guys,

I have been building a lot of tri-lam longbows lately. When I read up on them, the prevailing wisdom is to use a light weight, porous wood as the core.

However... I have used mostly the opposite of that. I like the color variation that the tropical woods give me. So my cores have been bloodwood, purpleheart, chakte viga, osage, ipe, and ziracote. I have also used chestnut, cherry, and black walnut... But mostly the hard, dense, tropical woods.

So what gives? I now know you "can" use dense woods. But I see no measurable difference between the performance of one with dense woods from one with lighter woods.

I have dug through the internet, old posts, books and so on... But I cannot lock down a definitive answer on this.

The only thing I have really seemed to discover is more lams seems to equal a smooth draw and a pleasant shooting bow.

Any of ya'll have some wisdom to share?

Jim

[simk]

Hi Powder
I made plenty trilams and my conclusion is, that the lighter in mass your midlam the better (faster/comfy) your bow comes out. I have long wondered abbout bowyers that put heavy woods in the center of their bows; meanwhile I'm pretty convinced that the cons (additional mass) are much more important than the pros (additional energy storage). I never used a real heavy wood like IPE as a midlam. But I can already feel a clear difference in performance and shooting comfort if I only use a semi-light wood for the core like black locust instead of my superlight sycamore or bird cherry. To my understanding, the midlam is only a spacer that does contribute very very little to energy storage. But maybe I'm totally wrong (-;
Simon

[mmattockx]

To my understanding, the midlam is only a spacer that does contribute very very little to energy storage.

This is correct. The inner 50% of the limb thickness only stores 25% of the energy, so it isn't working very hard and doesn't need to be as strong of a wood as the outer portions. There will be performance gains to be had by using a lighter wood for the core, but depending on the bow design they may be very hard to notice or measure.


OP, you may need to use a chronograph to be able to notice the difference. If your bows are not very high performance screamers shooting lighter arrows there may be no significant gain at all. If you're happy with how the bows are turning out and you like the accent you get from using tropical woods in the core, keep doing whatever makes you happy with them.


Mark

[Pat B]

Cherry would give you a color mid lam and is fairly light in weight. I've used ash and elm for mid lams but they are light colored like the hickory backing.

[Powder]

Thanks guys. I do have a chrono, but it died... So I am not being very scientific here. I have also used cherry as a core, osage for the belly, but the belly had a weird spot so I had to put a plug in it. (dutchman, I think it's called) It works... But I tend to not shoot that bow because of a lack of confidence in it.

Have you guys noticed an increase "smoothness" in bows with more lams? Or is that just in my own head?

Jim

[Roy from Pa]

I used red elm a lot for core lams in my tri lams, it's very springy wood.

[Powder]

I have a source of elm... (maybe) and I think I'll give that a try. I have used elm on the belly, but not as a core yet.