Any tricks to get Aluminum transom to tighten up post Tig?

[fastang50]

Dad and I have been replacing the plywood transom in our '98 Lund this winter. I had assumed the source of the leak and thus rot to be the poorly sealed engine mount bolts the dealer installed and they were surely a factor but we also found nearly two dozen corrosion holes thru the aluminum. Looking online it seems this isn't uncommon. We took the boat to our local welding shop and he ground out and Tig'd in all the holes. I didn't think this thru or I would have realized the effect the heat would have, it's effectively made the aluminum "bigger" across the transom. Any tricks to shrink this back down? Thinking back to HS welding class, no ideas I'm coming up with will be very healthy for the boat. Right now we're planning to pull down the waviness from the center first, then evenly each side. Thanks.

The pic won't help you much, but it's something to look at.

 

[jhande]

Could use a shrinking hammer used in body work.

 

[jbcurt00]

Dont forget, welding tends to work harden aluminum ao dont make a bad situation worse over working what you have now.

 

[Scott Danforth]

hammer and dolly.

welding should shrink the panel. generally 3%, however up to 6% of the weld length.

when we have weld distortion at work, we simply weld both sides.

another thing you can do, heat the area up with a heat gun to about 350F and then rapidly cool with a few cans of freon.

welding an aluminum panel and not getting it to pucker is a black-art.

 

[fastang50]

This is the sort of thing I wondered about:
..heat the area up with a heat gun to about 350F and then rapidly cool...
But was concerned about this thing:
..work harden aluminum..
So you guys have it covered!
Would I start this process in the middle and do a bit at a time working outward on alternate sides? I can't think I'd get enough heat into the whole panel at once.

 

[dingbat]

You could anneal and hammer it out to a point.

But was concerned about this thing:
..work harden aluminum..
So you guys have it covered!
Would I start this process in the middle and do a bit at a time working outward on alternate sides? I can't think I'd get enough heat into the whole panel at once.

To prevent cracking, you first need to anneal the area first.

If your working with a 5XXX series (marine) aluminum as I suspect, your looking at 650 F to anneal.

See methodology below

Repairing Aluminum: Straightening Tempered Aluminum Sheets

TM Technologies: Tools, Sheet Metal Shaping Machines, Gas Welding Supplies, Articles & lWorkshops for Better Metalworking

www.tinmantech.com

 

[Scott Danforth]

most likely 5052 for the material

 

[fastang50]

You guys are well over my head. I'm going to pretend I didn't see it at this point and go center first, outsides evenly. Appreciate the input.

 

[jhande]

Don't know if aluminum reacts differently than steel sheet metal. But doing auto body work usually always started from the outside of the warp or dent and worked in to the center.

 

[Scott Danforth]

aluminum acts significantly different. however you still work from the outside in.