Trilam questions

[jandersson]

Good evening!
I want to make a trilam. 66-68"ttt, 50-55#@ 28". Some R/D glued into it with hickory backing, cherry core and erc belly. Some swear by maple core which I'd be fine with too also I can not get hold of Osage so I went for ERC which some suggested. I've been reading about trilams and its talk about tapering the core but it never says from where to taper,  from the handle to the tip? From the center of the bow to the tip? And which side do you taper, the back of the core or the belly of the core? There seems to be a lot of trial and error with these bows but if someone could give me an idea of where to start with thickness, width and handle length I'd be very appreciative!! An example of what I was hoping to build is GB's very pretty bow.
Thanks!

[GB]

That bow looks familiar    I can't give you a definitive answer for measurements using ERC for the belly.  But I've had the same thought about trying it in that R/D profile.  Think I'd start wider, maybe 1 3/4" at the fades, instead of the 1 3/8" I do with osage.  You can always narrow it later.  I taper the back of the core lam, but I don't know if it makes a difference.  I start the taper a couple of inches past the fades and carry it out to the tips.  I've used cherry, red elm, walnut, and maple for core wood and they all seem to perform about the same.  My handles are 10 to 11 inches.  Hope that's some help and good luck with your bow!

I made a red elm backed ERC bow that I glued 3" of Perry reflex into.  For as light as it is, ERC seems pretty strong in compression.  Hope it works well in the R/D profile.

[jandersson]

That is great help, Thanks! I was gonna do the backing 1/8, core 5/16 and belly 5/16 or maybe 3/8's. Does it look like a good start? And it seems like the people making these bows don't like to tiller them. Is that because the bows are more sensitive to having belly wood removed than self bows or the bowyers don't like to tiller? I was going to leave a little extra wood on the belly and that way have a bigger chance of getting the weight I wanted.

[DavidV]

I haven't made a trilam but I made a F****glass recurve and in those the taper depends on the front profile you use. If it's a wide pyramid bow I think you could keep the core parallel.

[GB]

Just my opinion, but I'd make the core 1/4" tapered to 1/8" at the tips and make the belly 3/8".  Unfortunately, you do have to tiller it just like any wooden bow.  Guys who have made a few of them with the same wood combinations probably can figure the lam thicknesses and taper rate so there is very little tillering to do.  But it still takes some tillering. 

[jandersson]

DavidV: I guess that makes sense to think about it just like a regular stave/board bow, maybe I was making it more complicated in my head then it really is.

GB: I think I like that as a start to have a little more belly wood to play with. Tillering is half the fun, it's like watching the puppy become a dog! I'll glue up some less spendy woods for starters to mess around with.

Thanks guys!