Assembled the pieces I need for my next bow.

Having a go at a tri-lam.

1/8in hickory back
1/8in ipe lam
Zebrawood riser
1/8in ipe belly - lams running up the back of the riser.

I made a 3D model of what I'm thinking - helps me visualize.

Anyone have any serious doubts about the feasibility of this?

 

3/8ths isn't thick enough for much other than a low draw weight.
1/8th isn't thick enough for a belly lam on a design you have just come up with as it leaves very little room to do any tillering. Better to make the core thinner and the belly thicker.
I would also use a lighter core wood. Ipe will work for a core but it is really too heavy to give you max performance from a trilam. It is very hard to beat hard maple.
A pyramid taper will give you 'automatic' tiller.

X2 on Mike's reply.

Thanks.

As luck would have it, I have a 6ft x 3in x 3/8in piece of maple.

My most recent bow is maple backed ipe. 1.25in wide at the fades - 7/16 thick at the end of the fades down to 3/8 at the tips which are very slightly over 3/8 wide.

#47 @ 28in

That's why I was thinking 3/8 would be enough.

I did have doubts about the belly lam, which is why I asked the question.

Started work on this tonight.

Went with maple, based on recommendations.

Made the Ipe belly lam 3/16" thick.

At the moment it's 1.5 in wide - want it to be 1.25 at the fades when finished.

Thing is, it really doesn't want to bend very much. Going to be a struggle to get it to go up the back of the riser.

Don't know if I've got a particularly hard piece or what, given my last bow used a slice off the same plank came in at #47 with a maple back - lamination for the new one from the same piece of maple.

!/8 hickory back
1/8 maple core
3/16 (at the moment) ipe belly

All suggestions gratefully accepted.

Looking for suggestions from those with more experience than I have

Getting an Ipe lam to bend up the riser fade is the main trouble with that type of design. Might try to steam bend it.

Personally I would add a powerlam a couple inches longer than the riser, and then slightly thin the belly lam only in the area of the riser fade in order to allow it to bend.

Also I recommend tapering your core lam to prevent tillering through the belly lam.

To your question of feasibility, yeah it's feasible. The lam bending hurtle is definately the main challenge to this particular design. This is one of the main reasons many people just use a powerlam and a glued on riser. It works just as well, and it's a lot easier to glue up.

As an aside, if you're building with a thick riser like that you can cut in a pretty serious shelf without any trouble.

IPE is some really strong wood.

You need to work on your picture size
600 X 480 I think

What the heck are you using for a computer??

Even my laptop can cope with twice that size!

My desktop has 2 1080P monitors, but then, I do make my living doing computer graphics.

I tend to go high res, by default!

Cool concept. I like seeing more of these wood lam bows. Mike's advice is perfect.

LittleBen....

Still going to try the belly lam running up the riser, just because I have a stubborn streak. I'm going to taper it so that it is full thickness at the beginning of the riser and gets thinner as the curve gets tighter.

Will be taking some of your advice, except for the steam bending part. Did some research, it looks like steam bending ipe is a bit 'iffy'

Glued up the back, core and riser yesterday. Won't be able to get back at it until Thursday at the earliest.

As for the shelf, I won't go quite to centre. I find it's best not to take too huge strides making bows.

Here it is all finished.

Need to make a string.

Its pretty, like most said 3/8ths will not get much weight.  What kind of weigh scale are you using..?  Tiller looks good.

It's a fraction over 3/8

I have a luggage scale - I've tested it with known weights and it's pretty accurate.

Not committed to the idea yet, but contemplating boo backed ipe D/R for the next one. I have enough ipe for at least 2 more bows.

Pleased with the glue lines at the riser!

Dave,
 Very nice trilam. You really got me thinking about, or planning my next build. I wish I had the computer graphic skills that you show, I will try to draw my idea out using colored pencils. Well I do think that  making a drawing as part of the overall plan helps to get ideas out of a person's head and a step toward completion.
Thanks for sharing
 I built a red oak pyramid style board bow, 66" tip to tip, with a 45# @28 draw weight. And the limbs on that bow measure 7/16" just past the fades and very quickly 3/8" for the remainder of the limb. My limbs start out 2.25" wide at the fades, down to 1/2" at the tips. i thought that with your trilam the limbs would indeed be less than 3/8" thick. Am I missing something or is that just how it works out? How long is your bow?

Ok...I now see that your trilam bow starts out 1.25" at the fades where as mine start at 2.25". I imagine that that makes al the difference.

Been messing about with computers for a looong time.

My first go at computing involved punch cards back in 1969!

Bought my first computer in 1984.

I find modelling stuff in my 3D program (Blender - free and open source if anyone's looking at trying 3D works on Mac, Linux and Windows) - I work to real world size. The ability to look at things from all sides and angles means I can see some potential problems with no real cost.

I use it for a lot more than bows.