need to tig hole in alum. boat without burning the foam

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Ok, finally getting my circuit board repaired on my machine.  I'll finally try and fix that hole in pop's boat.  It's an aluminum Basstracker.  Problem is, there is floatation foam in the bottom of it.  I don't want to set it on fire.  I have to weld from the bottom.  Can't get to it from the top.  any advice?Tack It!!
Reply:Patch..Sealer..Rivets!!...zap!I am not completely insane..Some parts are missing Professional Driver on a closed course....Do not attempt.Just because I'm a  dumbass don't mean that you can be too.So DON'T try any of this **** l do at home.
Reply:Be careful and make sure it's not cast Al
Reply:I'm with ZAP, rivet a patch over it.  i can ell you that Flotation foam will BURN severely when it gets hot, and almost impossible to put out.I'm a Lover, Fighter, Wild horse Rider, and a pretty good welding man......
Reply:You could always clear the foam from the area to be welded.  Afterwards, you can use some of that "Great Stuff" expanding foam.  I'm not sure how good it is for floatation, but it's likely good enough for a small area that you'd need to clear for the weld.  I'd feel more secure with a welded hole and a little missing foam than I would drilling more holes and using sealer on a patch.  Just be careful, because if that foam starts burning, it may put out deadly gas, and be near impossible to put out.  I don't think I'd want to weld it in my garage unless I had the area near the weld cleared back of foam really well.
Reply:Fiberglass the hole and the surrounding area.
Reply:I would go with a patch, sealed and riveted. Tens of thousands of boats are entirely built this way and they hold up really well.-Ryan McEachern
Reply:can you slide a piece of thin plywood in-between the foam an metal ,that will protect the foam or a piece of thin steel .. i do it all the time. just need a buffer twix the 2 hope that helps ya  it won't take much to protect the foam
Reply:Lots of planes are glued and riveted. Take care of the tacking surface like you would with preparing the weld area.I gues you could use some polyurethane based glue with a proper primer. In Europe we have SIKA products. Also used for glueing windscreens into cars, my nylon clutch cover on an aluminium ring, tiling on walls etc. Almost impossible to remove (attaches very good to skin also - wear gloves ).
Reply:Originally Posted by EngloidYou could always clear the foam from the area to be welded.  Afterwards, you can use some of that "Great Stuff" expanding foam.  I'm not sure how good it is for floatation, but it's likely good enough for a small area that you'd need to clear for the weld.  I'd feel more secure with a welded hole and a little missing foam than I would drilling more holes and using sealer on a patch.  Just be careful, because if that foam starts burning, it may put out deadly gas, and be near impossible to put out.  I don't think I'd want to weld it in my garage unless I had the area near the weld cleared back of foam really well.
Reply:Rojo, I'n gonna have to disagree with you on the fact that flotation foam will not readily burn.  The reason I know is because I did some customizing on two aluminum boats a couple years ago, and I had to remove a rather large block of foam to do it.  Well a few days later one of my workers was cutting with a torch near the blocks of foam and they went up in flames like crazy.  Some may not be flamible, but some can be pretty rough.I'm a Lover, Fighter, Wild horse Rider, and a pretty good welding man......
Reply:That's not so good to hear Hammack!!! It is supposed to be flame retardant urethane foam in boat hulls, due to the inherent flammability of gasoline stored in the hulls.And then, after so much work...... you have it in your hand, and you look over to your side...... and the runner has run off. Leaving you holding the prize, wondering when the runner will return.
Reply:That was always my understanding as well.  I would not have believed it myself had I know witnessed it.  Now I'm not saying ALL of the foam used is that way, but some appearantly is.I'm a Lover, Fighter, Wild horse Rider, and a pretty good welding man......
Reply:Originally Posted by Hammack_WeldingThat was always my understanding as well.  I would not have believed it myself had I know witnessed it.  Now I'm not saying ALL of the foam used is that way, but some appearantly is.
Reply:Well, I've thought about riveting a patch, but the hole is right on the keel, which is a piece of angle aluminum that's already riveted to the hull.  And we beach the boat a good bit, which is probably why the hole is there.  But patching it in that spot is more difficult than on a flat part of the boat.Tack It!!
Reply:I am curious how large the hole is...  got any photos?Build a Barstool Racer at BarFlyRacers.com!
Reply:Originally Posted by bigcountry1009Well, I've thought about riveting a patch, but the hole is right on the keel, which is a piece of angle aluminum that's already riveted to the hull.  And we beach the boat a good bit, which is probably why the hole is there.  But patching it in that spot is more difficult than on a flat part of the boat.
Reply:Originally Posted by ElGuapoLots of planes are glued and riveted.
Reply:Originally Posted by EngloidThey float well too.
Reply:Got something to do with fatigue.  Also in steel design a weld is the start of a crack. Depending on the weld form the allowable stress can differ. Ally shouldn't be any different.
Reply:I would just use some Marine Tex and call it a day, no need to go 20,000 leagues under the sea for an easy fix.Disclaimer; "I am just an a$$hole welder, don't take it personally ."