EPOXY: HOW LONG CLAMP?

[davebrown]

I layed up a scarf this morning at 6 with slow epoxy--west systems.

In my garage today, it got up to at least 80, perhaps more.

From the identical pot, I also spread a dollop or three on a knee that was sitting in the sun on another boat.

The knee is totally hard to the touch--no fingernail mark will disturb it.

I need my clamps to lay-up another plank. I do not have to move the glued plank--but I must remove the clamps if I am to continue tonight.
Is 12 hours enough time, in 80 or better heat, with slow hardener to remove the clamps (again, I don't ahve to move the planks until tomorrow)?

[Bruce Hooke]

Yes! If the epoxy in the pot is hard then I think you can quite safely remove the clamps.

[JimConlin]

A dense mass of epoxy will cure more quickly than will a thin film. So, if the epoxy you're worried about is the thin film in a glue joint, look at the film on the side of your mixing pot as a guide.

[JimD]

12 hours on a warm day ought to be fine especially since this is a scarph presumably just laying flat. Thickened epoxy requires very little clamping, usually just enough to keep the different pieces of wood from moving around. I'll sometimes just use bricks or cans of paint or whatever heavy objects are available to hold the wood down for a scarph. As others say, pot life is always shorter than epoxy spread out thinnly.

[Bob Smalser]

Careful now....clamp time and working the piece are two different critters...epoxy doesn't reach full strength for a few days, so be careful what you do with it.

I've broken more than one joint at the 6 to 8 hour point because I ran out of other stuff to do. Plan your work so you've other tasks to perform in the meantime.

[ 06-02-2005, 01:45 PM: Message edited by: Bob Smalser ]

[Seth Wood]

If you happen to mixing in a plastic container, you can wait a day or so for the epoxy to mostly cure, then bend the container and pop out your little plug of leftover goop. Then, as the days go by, bend or snap that little flat disc, or pieces of it. Bendy? Not cured. Snaps? Cured. Even when it's warm, I've found it takes a few days to fully cure. No sense rushing things and risking the joint.

[davebrown]

thanks for replies--i took off the clamps and then immediately sat about 20 lbs. of weight on a 2x4 over the scarf--we'll find out tonight.

[ssor]

Actinic light, that is sunlight full of U.V. will cure exposed resin in short order where resin shielded from the sunlight will cure at more normal rates. Make haste slowly.

[Bruce Hooke]

You should be fine. There is a huge difference between simply removing clamps and otherwise leaving things alone, and removing the clamps and beginning to move the object around, bending it and twisting it and stressing the joint.

As an aside, the worst case scenerio is something like a laminated curve because as soon as the clamps come of the joint is under stress as the pieces try to straighten out...

[Bob Cleek]

I hope you are aware that epoxy adhesive doesn't require strong clamping. Only clamp enough to hold the pieces in place while it cures. Tight clamping will only drive the adhesive out of the joint. This is the opposite of using other adhesives.