MIMF

There are so many times where I read about sticking cleats on with one's fingers, holding them for a few seconds and calling it good. So then, realistically, how long does a structural glue joint need to be clamped? Until the glue gells? Until it starts to harden? Until it's under 90 degrees? Until ALL the water has evaporated?
My empirical data implies that clamping is necessary only until the glue squeeze out gets a bit past gummy. Please slap me down if necessary.
But I don't know the TRUTH.
Does anybody know the TRUTH?

Where is the joint and what do you plan to do with it? I don't clamp center seams for mandolin tops and backs at all (rubbed joint) so I don't have to take any clamps off.
Joints that -fit well- need no clamps, like a rubbed center seam, a cleat or a tentelone. If clamping is needed to hold something in place, like a sprung joint where the jelled glue is probably not strong enough to maintain the joint, it should be clamped until the glue dries. Some say a couple of hours, some say over night. If I have a joint that needs to be clamped, I usually wait over night to remove the clamps, or at least many hours. Better safe than sorry.

When I started using hot hide glue Carleen Hutchins told me to leave it clamped for two hours, and I did that for years.

Several years ago I was demonstrating HHG for a friend on mine, and showed him a rubbed joint, using a couple of sticks of cut off bracing stock. I rubbed them together, set them down for about fifteen minutes, then clamped one in a vice and whacked the other with a hammer. I got 100% wood shear.

So, for sure, somewhere in between those two times will work in one case or another I'd say that the larger the area, and the more critical the joint, the longer I'd leave it clamped. These days I've started leaving top bracing in the go-bar deck for 45-60 minutes, and then being careful to not stress it for at least six hours. It seems to be working.

Alan Carruth / Lutrhier

I leave my fan braces in my classical guitars, which are sprung in, and under tension, clamped over night. The flat and un-stressed I only clamp for a couple of hours.

And, that is the truth.

60-60 for me. It has to be clamped within 60 seconds, then left clamped for 60 minutes.

I only have one go-bar deck, and I'm often pressed for time, so I've unclamped after about 30 minutes to glue something else (yes I know, just make another go-bar deck...). No disasters yet, though.

Depends on the component. Some things, finger held for 30-60 seconds and call it done if it sticks. No clamps at all. Other components where there is more pressure (bends with stress involved) backs braces and the like, I leave for at least an hour and often much longer because I do it at night and then remove the clamps the next morning.