Just to help me learn something, here's the situation. Friend calls up says he has an aluminum boat (you know, 10-13 foot boat for fishing, rivet construction) that has a crack in the bow...the skin, not the keel or anything thick like that. Right where it takes a pounding from the water as the boat moves forward. My girlfriends dad is a professional welder, but I know he doesn't deal much with aluminum. Has a MIG welder, so I know he can do the job, (he knows what he needs) but I'm curious if welding the skin of the boat in that area will just "work harden" or otherwise weaken the pop-can thick skin, and cause it to fail around the weld after a few good hits from waves? I know aluminum can be heat treated, so I would suspect that welding isn't going to be without risk. I've got an aluminum boat as well, but as far as I can tell it was made in the 50's, and is pretty thick construction. Of course the rivets on the keel leak, but since it is so thick there, I plan to have her dad weld that up for me. I guess I could re-rivet, (still not as good as welding IMO) but man that's a lot of rivets to remove and reinstall. Again for the people that weld aluminum, are both of those ideas impossible or impractical due to the material being dealt with?