Author Topic: Tri-Lam Bow. Why?  (Read 40969 times)

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Offline DarkSoul

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Re: Tri-Lam Bow. Why?
« Reply #15 on: April 24, 2014, 05:12:45 am »
One reason is it's easy to add perry reflex (glued in reflex) with a trilam.
Exactly the opposite! Perry reflex uses a thick laminate, that is basically too thick to use for heavily curved recurves or severe reflex. It will lose some shape due to spring back, but it will again gain some shape as you remove belly wood during tillering. To quote Dan Perry: "By reflexing a thicker than finished dimension bow before applying the backing." Read more about Perry reflex HERE.

Toomany, your statement should be: "it's easy to add [more] reflex (glued in reflex) with a trilam."

Arachnid, many wood species will work as a core. Some folks use a pretty wood, just for looks. Then you could use purpleheart, bloodwood or bubinga. If you're looking to increase performance, then maple is probably best. But also walnut, cherry, vertical bamboo flooring, yew or juniper would work just fine.
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Offline zenart

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Re: Tri-Lam Bow. Why?
« Reply #16 on: April 24, 2014, 07:47:21 am »
The best tri-lam ELB I ever built has a maple back, thin ipe core, and Osage belly. It shoots like a demon at 52#, and took very little set with a slight elliptical tiller. Plus, it looks great with the contrasting dark core.

Adam- Would you mind giving more detailed spec's on this bow build ?  I'd like to give it a go.  If you have a mind, pics would be great too. Thnx- Ron
Huntington Beach, CA … there's no trees here but we do have lumber yards.

blackhawk

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Re: Tri-Lam Bow. Why?
« Reply #17 on: April 24, 2014, 07:54:05 am »
Why? I'll tell ya why....cus there SEXY!!!!  8) ....that's why  :laugh:

Offline adb

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Re: Tri-Lam Bow. Why?
« Reply #18 on: April 24, 2014, 10:04:43 am »
Any other options besides maple and walnut?
Something that may improve performance

I totally forgot to mention yew heartwood. It's a really great core. It's very light, strong in compression and glues very well. I've used it a few times, but not often because it's hard for me to get.

Offline arachnid

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Re: Tri-Lam Bow. Why?
« Reply #19 on: April 25, 2014, 01:17:38 am »
Does the core need to be straight grained like the other lams? If not, with how many runoffs can I come by?

Offline DarkSoul

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Re: Tri-Lam Bow. Why?
« Reply #20 on: April 25, 2014, 06:54:23 am »
Straight grain is obviously best, of course. But while the backing MUST be absolutely straight grained - no exception - the belly and core can have a few grain run offs. Stay away from knots and sudden wild grain patterns. I use laminations that do not meet the criteria for backings (or selfbows) as cores, since they are about the same thickness.
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Offline Marc St Louis

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Re: Tri-Lam Bow. Why?
« Reply #21 on: April 25, 2014, 06:50:16 pm »
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
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Offline adb

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Re: Tri-Lam Bow. Why?
« Reply #22 on: April 25, 2014, 07:51:07 pm »
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.
« Last Edit: April 25, 2014, 08:05:22 pm by adb »

Offline Marc St Louis

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Re: Tri-Lam Bow. Why?
« Reply #23 on: April 25, 2014, 08:07:19 pm »
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. Any wood in a bow is going to be doing something. I do agree that lighter woods are good for cores, but they still need to be strong in compression. Yew, osage, ipe, etc., all make great core wood. 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. With a compression strong belly, which ends up being thinner, a bow like this will take more set.

No more work?  Right.  Everybody knows that cutting 3 lams is the same amount of work as cutting 2 and then spreading glue on 4 surfaces as opposed to 2 is the same amount of work.  Whatever  ::)

If the core is that thin then it is not working in compression, it may be working in tension though.  If the bow has less set then it will shoot harder anyway.
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Offline toomanyknots

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Re: Tri-Lam Bow. Why?
« Reply #24 on: April 25, 2014, 08:34:05 pm »
It was padauk (which in my opinion is very brittle and just sucks all around as a bow wood). I do have to respectfully disagree that maple does not work as a core wood in an elb, I use it often and it is my favorite corewood, I use it on target weight and warbows alike. Looks pretty nice sandwiched between an ipe belly and a boo backing too. I use yellow heart for cores too, I like it a lot for cores. I find it is pretty weak in compression though and chrysals easy as a belly wood (or at least my stock is). First trilam I did with it as a belly I got some huge chrysals. I know of you guys Adam and Mark have used it though, plus I see some UK bowyers using it as a belly wood, so I don't know if mine just sucks, or I suck, or what?  :) Something is this situation sucks,  ;D. Didn't Jaro make a bow out of it too?
"The way of heaven is like the bending of a bow-
 the upper part is pressed down,
 the lower part is raised up,
 the part that has too much is reduced,
 the part that has too little is increased."

- Tao Te Ching, 77, A new translation by Victor H. Mair

Offline Marc St Louis

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Re: Tri-Lam Bow. Why?
« Reply #25 on: April 25, 2014, 10:18:58 pm »
The problem is with using a white-wood backing and a white-wood core.  If you use a Bamboo backing with that white-wood core then the results are quite different.

Now I know that the dense tropical woods can, can being the operative word here, work extremely well as backings, almost as well as Bamboo.  The only problem is they are generally to brittle and fail.  Putting a high density wood, such as Ipe, under the backing increases the overall tension strength of the backing while giving support to the Ipe, sort of like putting rawhide over a questionable bow's back. 

I have a bit of high density Bubinga which is a bit low in elasticity so it does chrysal when stressed too much, in compression.  It is a very straight grain board so as an experiment I decided to try it as a backing, in an RD design, with Yellowheart (Satinwood) as the belly wood.  The bow kept a great deal of the glued in reflex while tillering and the backing behaved much like a Bamboo backing would, up until it failed.  The bow was not under built but at around 24" it exploded ending up in several pieces scattered around my shop.  Probably if I had glued on a very thin Maple backing the bow would have survived

P.S.  The Yellowheart I have is quite nice and works well as a belly wood.
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Offline adb

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Re: Tri-Lam Bow. Why?
« Reply #26 on: April 25, 2014, 11:26:06 pm »
I was just wondering something Marc... have you ever built a classic tri-lam ELB? I've searched your website, and this forum, and I can't find one. Not one. Not reflexed, or anything else... just a straight up tri-lam ELB. Deep rounded belly, follows the 5/8 rule more or less, at least 72" long, slight elliptical tiller... you know.

I was also wondering something else... do you think it's possible for one person to be an expert on all aspects of bow building? Even if it's a design or type of bow they've never made?

I don't offer any advice about heat treating, horsebows, sinew backing, or a whole raft of other subjects because I've never done it. Is it appropriate to offer advice on something I have zero first hand experience with?

Offline PatM

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Re: Tri-Lam Bow. Why?
« Reply #27 on: April 25, 2014, 11:32:11 pm »
The term "classic tri-lam" combined with the 5/8 rule are ridiculous concepts.
 The longbow history is nothing to do with those things and I'm surprised it has ever come to that.

Offline adb

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Re: Tri-Lam Bow. Why?
« Reply #28 on: April 26, 2014, 12:13:35 am »
The 5/8 rule was implemented to prevent people from showing up to a BLBS shoot with a flat bow.

Offline PatM

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Re: Tri-Lam Bow. Why?
« Reply #29 on: April 26, 2014, 12:34:09 am »
 The real reason is that they don't want people showing that other designs work better and destroying the longbow myth.