Glue for Z splicing

[bowhunter15]

What do you guys use for Z splicing two half lams together? I tried JB Wood Weld but it doesn't flex well and cracks when I try to bend the lam into deflex. Do you mix up a micro batch of Unibond?

[Roy from Pa]

Smooth On Epoxy.

[Pat B]

I think I used super glue when I built a glass bow many years ago.

[Mark Smeltzer]

I use super glue or the 5 ton epoxy. Both work but the epoxy seems to hold up better.

[bowhunter15]

Haven't tried the smooth on or 5 ton epoxy yet, but I did try some super and surprisingly it held up the best so far. I also tried titebond 3 after a 24 hour cure and it broke wit has very little bend. The superglue allowed me to bend the bow into the form after a 5 minute cure. Then it too broke after sitting a couple minutes under tension, but I can let it cure longer too.

[Roy from Pa]

Are you using a 4" Z splice? How thick are the lams and how much are you bending them? Do you place a heavy clamp on the Z splice when you bend it in your form, before bending down the limbs? Pictures?

[Bowjunkie]

Bowhunter15, it would help to know if you're talking about gluing two thin laminations together for use in a laminated glass/wood bow... or a couple of thicker lams for use in a tri-lam, or what exactly you're up to.

[bowhunter15]

My image hosting site is currently down so I can't post any pics. But basically my core lam (about .120" thick) is in two 36" lengths. I held them together and then beveled the ends to the same angle against a disc sander. Then I flipped one of the pieces around so the bevels could rest together. Basically the same process as is shown in the very bottom of this link. He uses 2 ton epoxy. My form currently has quite a bit of R/D, and it is a short bow, about 56". I'm gluing up the back and core first, then adding the riser and belly as a second step.  

 http://poorfolkbows.com/glass3.htm

One thing I could try also that would probably work is to decrease the angle of the bevel, so there's more total surface area for the glue to be present.

[Roy from Pa]

That's not a very strong splice done like that. You have enough length for a 2" Z splice?

On my tri lam builds, I just butt the core lam riser ends together without glue. Then I lay my belly lam, core lam, and boo down and string it straight. Then clamp it down and drill 2 holes in the handle area and 2 holes on each side of the tips. Then after the glue is applied, I place tooth picks into those holes to keep it aligned while clamping up. Those core lams never move.

[bowhunter15]

I'll try it tonight like you've described. I think the only difference between what I'm trying to do and yours is that your handle is on the outside of the three lams, and mine will be sandwiched between the core and belly. Roy, what keeps your handle from popping off? I've read that you either need to sandwich it between lams, use a power lam, or have the belly fade out in thickness as it transitions to the handle, but it appears you've had success without doing any of that.

[Roy from Pa]

My flares are 1 1/4 wide, I maintain that same 1 1/4 width out into the limbs another 6 inches, then taper from that point to 1/2 at the tips. That makes the 6 inches out past the flares a little stronger. Also when I do my facets, I leave that area a little more square.

[Bowjunkie]

Bowhunter, don't believe everything you hear. I don't sandwich it, no power lam, no pedestal, no handles popping off. I even tiller them so they bend right up into the handle piece some. I'm talking upwards of 70 lb bows too. Good gluing surface prep and practices are what makes the difference... the same goes for gluing lams together on the butt ends.

With .120" thick lams that you expect to stay together while bending over considerable deflex, I would taper them like you did, so that you had at least a 3/4 - 1" gluing surface, then I'd groove it with a toothing plane blade, glue it with Smooth On and cure it near a shop lamp for heat.

[LittleBen]

Originally posted by Roy from Pa:
Smooth On Epoxy.

Smooth on is almost always a good answer to "what glue"