two lams vs. three

[willie]

Just curious as to what are the advantages obtained by incorporating a third wood in a laminate bow? it's a bit more work to use three lams, but it must be done for a good reason I would hope. Seems like most of the bow energy work is done in the back and belly, so if those lams stay the same, what does adding/changing the center lam do?

[jaxenro]

Ignoring the performance aspects it does look sharp to have a dark strip between two lighter ones, like a racing stripe, the contrast and looks are one of my main reasons for making them

That said not everything is always done for the logical reason we seek it could simply be aesthetics, marketing, or even status

I'm not saying "hickory-elm-yew" offers a performance increase over "hickory-yew", it may not and I will leave it to more educated posters to address that, but it could be as simple as the tri-lam was more difficult and expensive to make therefore if you shot one you were obviously more wealthy. Displaying wealth visibly was important in some time periods for showing ones status as long as performance didn't suffer

[Pat B]

Probably the only advantage I see for a tri-lam is being that the lams are thinner you can manipulate the shape into a reflex or R/D easier. They are more work and you have to do some figuring about the thickness of each lam to get the right recipe for the bow weight you want.
 With a backed bow(2 piece) you attach the backing to the belly and remove wood from the belly by tillering without trying to figure the thickness of the belly.
 I've made both and prefer to make just backed bow and not a tri-lam bow.

[Dances with squirrels]

Like Pat said, it allows profiles to be glued in that couldn't be with just two pieces. It actually makes a rather big difference in that regard and worth the few additional minutes it takes to grind another lam. More lams seem to hold their glued in shape better too in more highly stressed designs. I've used them to make some pretty intense d/r and d/recurve bows.

The center lam can be a lighter weight material, or 'lesser bow wood' and still make a top quality bow, since it mostly just takes up space and doesn't have to be exceptional in compression or tension resistance properties, which may aid in performance.

A third lam also makes any minor or moderate imperfections in any of them less sinister, especially if in the center.

Yeah, they can look cool, but I often cut the center and belly lam from the same piece of wood, or dye the bow, and so the finished product makes it almost impossible to see that it actually is a trilam... still worth doing

 

[jaxenro]

I was thinking more historically than current with modern tools and glues it is a different dynamic

[PatM]

Apart form the already mentioned points it also allows you to get more out of your belly wood sources. Many of the best  or most exotic tropical woods are incredibly expensive and don't require much to make a belly. You can double the amount of bows you get by substituting a cheaper core wood that will be just as functional.

[willie]

I was thinking more historically than current ...............

Yes, of course. Many good responses in this thread, from a different perspective.

BTW,  There is an interesting related thread

http://www.primitivearcher.com/smf/index.php/topic,60690.0.html

[Marc St Louis]

Ignoring the performance aspects it does look sharp to have a dark strip between two lighter ones, like a racing stripe, the contrast and looks are one of my main reasons for making them

That said not everything is always done for the logical reason we seek it could simply be aesthetics, marketing, or even status

I'm not saying "hickory-elm-yew" offers a performance increase over "hickory-yew", it may not and I will leave it to more educated posters to address that, but it could be as simple as the tri-lam was more difficult and expensive to make therefore if you shot one you were obviously more wealthy. Displaying wealth visibly was important in some time periods for showing ones status as long as performance didn't suffer

Haven't made a lot of 3 lam bows but I haven't seen any performance advantages to them, in the ones I made or claims from others

[jaxenro]

I wasn't claiming there were any more wondering if they were basically a marketing ploy when they first started coming out

[bubby]

I think patm nailed it, some of those exotics are very pricey and it helps extend the wood you have to more bows

[Badger]

  I usually do two lams but there are several advantages to three. It is easier to get a curvy profile with thinner lams. You can use less expensive wood in the cores as well as lighter cores. The one big thing I like is that when the bottom lam is run under the handle I believe it makes the handle less likely to pop off or crack at the glue joint. I don't see any difference in performance beyond being able to get a better profile.

[jaxenro]

When were what we consider tri-lams first developed? Why? Were they used in 1840 to 1940 time of Ford, Pope and Hill?

[jaxenro]

I was wrong reread Ford again backed bows and trilams were cheaper

I think it was a way to stretch wood as was mentioned he has some interesting comments along those lines plus he recommends yew backed yew if you can't afford a good self bow