a book on tri-lams

[Bowjunkie]

Yeah Roy, maybe you should.

[Roy from Pa]

Roy has enough to do already.

[BMorv]

knuklhed, I started out using spring clamps and they work okay with just one lam, like if you are gluing on a backing.  When I started making tri-lams I switched to c-clamps, as I didn't feel like the spring clamps provided enough force with the r/d shape and the 3 lams.  I use the 2" C-clamps and they work fine.  You ALMOST can't over tighten the 2" clamps as the tighten pin is so small (obviously don't crank down as hard as you can)

[stretch2]

tons of great information thanks

[knuklhed]

It's been forever since I asked for help starting, but I finally got ready, and glued something up. It is 1/8" hickory back, 3/32" elm core, and 3/16" maple belly, around 69" ntn, 1 1/2" wide through the riser to about 6" past the fades, tapering to 1/2" at the ends. The riser is maple layered with bubinga, about 12" long and about 2 1/4" deep right now before contouring. After grabbing some mason's line to use as tillering string to start, it looks stiff in the middle of the limb, yes? I think that might be because I expected this one to be a spectacular failure , and didn't taper the lams. The fades look kind of steep to me, too. I think there is room to make it work if I play with the limb shape more, and reduce the thickness of the riser. What do the more experienced eyes of Trad Gang see? Any suggestions?  Thank you for any input!

[BMorv]

Your fades have me nervous.  Can you explain how you glued it up?  Looks like the handle was flat and a lot of bend is happening right after the small fades end.
A bend through the handle glue up allows an almost seamless transition. 
 

[knuklhed]

The handle was cut on a very shallow arc to follow the deflex in the lams. I think, after seeing it in assembly, I messed up by not making the riser at least a couple of inches longer each side. Now I'm stuck with what I have, and need to figure a way to save it. I don't mind making it a fairly light bow, that was kind of the plan to begin with for my first one. Any suggestions? I don't know if it is doable, but my first thought is to put another partial lam or some kind of reinforcement strip on top of the backing, to stiffen the center. But when I cut a shelf, that may not help. Maybe make the mid to outer limbs quite a bit thinner to balance the loading?

[BMorv]

So there's no thickness taper on the bow?  If so, that is a big part of your problem.  Tapering the lams allows the limbs to bend in an even arch.  No taper and the middle and outers will be stiff putting a lot of stress on the inner limbs, and in your case right where your fades end.  I put between .004" and .006" taper per inch total.  So the thickness at the end of a bow will be about 1/8" thinner than near the fades.
I would try and put the taper in since you are willing to experiment with this one.  It won't be easy to maintain even taper now that the bow is glued, but you should learn a lot from the process.  And I would try and make your fades longer.  If you riser is 12" you should have room to make your fades 2.5" or more and gradually transition from limb to handle. 
These are 2 that I'm working on for friends.  These have power lams which allows me to have smaller and more steep fades.  It's especially important to have nice smooth fades with no power lam. 

[Tim Y]

Hi all,
   I have been following this thread with interest. I find it packed with solid information that clearly outlines the tri-lam build process. Thanks for posting.
   Timing is everything as I, like knuklhed, am building a trip-lam too. So I have a picture and a few questions...
 BMov, how thick, at the center is your power lam? I ground mine 5/32" and 16" long, I tapered paper thin at the ends, 1/16" at 1" and 1/8" at 2" continued that taper for about 5" on each end. I intend the riser to be 12" long.
  My goal is 40 to 45# draw, stack is;
 Ipe 3/16" w/.001" taper.
 Red Elm 1/8 w/.002" taper.
Power lam. 16" long 5/32" tapered.
Bamboo 1/8" tapered to 3/32".
  I feel ready to go with this, but what do you all think...your thoughts, concerns.
Thank You,  Tim Y

 

[DavidWood]

People often make reflex/deflection longbows this way. Has anyone had luck making recurve bows this way? Any pictures?