JB QWik Weld

I was thinking of using this to tack fins onto the mmt for my 7.5" nike smoke. The set time is 4 minutes. Anyone have an opinion on it?

I don't see a problem, as long as you "dry fit" the fins first. Once you're satisfied they fit properly, go for it. Good choice for mmt due to heat resistance. Just remember, once they're set, it's FOREVER!

Whoa, just noticed it said "7.5-inch"

Since the root chord on your fins is probably pretty long, is there any reason you can't get your hands on regular JB weld? Kwik weld should be fine, but the regular gives you a longer working time, which I prefer.

As long as it's just a tack-good to go, but the regular is stronger. Scuff well.

I do have a the regular and the 4 minute set time is pretty short. I will use the regular.

JB Qwik is ordinary fast-curing epoxy, basically the same as any other 5-minute epoxy on the market. I am not a fan of using fast-curing epoxy for structural bonding of critical components like fins, but I'm sure that you'll hear a variety of opinions on that. You did say that you just wanted to use it for tacking them on, which implies that you are using something else for the permanent bond.