aluminum boat alloy?

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I've been asked to weld a sheet of aluminum to an older flat bottom aluminum boat to create a deck. I have no idea what alloy the boat itself is or the sheet of aluminum. The boat I'm guessing is 5052. I personally would have riveted this in and suggested it but the owner wants it welded. I plan on welding the perimeter of the sheet with smaller spaced out sections rather than one continuous weld. Not shown in the pictures, the sheet is supported with cross braces. Any recommendations on what filler to use and any other tips is greatly appreciated. Thanks guys. Attached Images
Reply:Oh yeah, TIG welding it btw
Reply:Given the amount of flex it will likely see I would vote for 4043 or 4943. I would be concerned that 5356 may crack more easily due to the flex of the boat.-DoogieMiller 350PMiller Trailblazer 325 EFI w/ Excel PowerLincoln LN25 suitcase welderXMT 304/22a feederMiller Syncrowave 350LXMiller EconotigHobart Handler 140(2) Uni-Hydro 42-14Hypertherm 65 plasmaWEBB Gap bed lathe
Reply:If the boat was originally riveted, rivet the plate. I knew the owners of a specialty welding shop that did aluminum all the time. Every once in a while they'd get a riveted fishing boat in to fix a leak by the strip that's riveted down the center. All they could was try to tighten the rivets or possibly install new rivets. The aluminum is heat treated and welding it will just crack again in the HAZ.
Reply:recommend you contact    http://www.fishonfabrications.com/index.html   proprietor at Fish On Fab, he does this work all day, pics at the site.My take is the plate will make the boat rigid if welded to the sides as the former inverted channel shape becomes a box beam. If the boat is 5052  (ask bass-man @ fishon he'd know) then I'd stay with 5356 filler but if the boat isn't a 5k series metal, then the 4943 seems like a better filler? If you can't confirm the mfg from nomenclature plate you could try a few test patches to see how it flows?Cheers,Kevin MorinKenai, AK
Reply:Originally Posted by Kevin Morinrecommend you contact    http://www.fishonfabrications.com/index.html   proprietor at Fish On Fab, he does this work all day, pics at the site.
Reply:Thanks guys for the help and especially bassboy1 for the great explanation. I talked owner out of welding the sheet in and doing more of a framework like you suggest and then lightly attaching it to the boat if any at all.  Btw, the name plate was completely faded but owner now says it is a 68' landau.