Aluminum floor thickness

My father-in-law had an old 1970s pop-up camper sitting on his farm for years. When I saw it and realized it was made of all aluminum, I knew I'd struck a goldmine for my tinboat project. I took a trailer to the farm, cut the camper up and brought it home. Now I have a lot of material to get me going.

I have read several threads about people using .125 and/or .063 for their floors, and I feel like .125 would be the better route to go, unfortunately the majority of the aluminum is .063. So I figure I can simply double up the sheets to make it thicker where I need it. I assume I can just rivet the sheets together and then install in the floor of the boat, put some carpet or hydro turf down and be done with it. Anyone see any issues with doing this?

Sounds like a good idea. Only problem I can think of is water/moisture getting between the layers and causing corrosion. Maybe you could run a thin bead of 5200 or something at the edges to seal it up.

That's why I post on here, I hadn't considered the water getting trapped between the layers. THanks for the idea!

MrSimon said:

Sounds like a good idea. Only problem I can think of is water/moisture getting between the layers and causing corrosion.

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I would say this would be a big concern. A bead of 5200 will prevent a lot of water from entering, but I really can't see completely eliminating the water from entering entirely.

If most of your material for your flooring is only .063. why not just add additional framing and only use one layer. Intead of going through the time and hassle of trying to glue two layers together, and still possibly having water intrusion issues. If nothing else use some of your extra .063 as bulkheads for additional support.

I used .63 alumimum tread plate 4x8 foot sheet for the flooring in my jet jon boat with grate results,no regreats at all.I buy a 1 1/2 inch foam sheet from Menards and put the foam between the ribs for suport.I keep my jet boat light so she runs good on the river.i never load these tin boats down with to much weight like some do here. #-o

hotshotinn said:

I used .63 alumimum tread plate 4x8 foot sheet for the flooring in my jet jon boat with grate results,no regreats at all.I buy a 1 1/2 inch foam sheet from Menards and put the foam between the ribs for suport.I keep my jet boat light so she runs good on the river.i never load these tin boats down with to much weight like some do here. #-o

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Same here, I used .063 for my 14 foot dura craft, and for my 16 foot dura craft jetboat, both floors were built identically, I used 1 & 1/2" foam board in between all the ribs in the floor, and in the gunwale panels.

Doubling up two thin sheets DOES NOT provide the same rigidity as using one thick sheet. Also, you can caulk those seams all you want, but water is also going to infiltrate around each rivet, and you're going to get crevice corrosion.

If it were me, I'd go with .063" and use foam board....this is a reliable method that many of us have used.

And just so you know how strong a floor like this actually is.....with my 14 foot Dura Craft, a friend and I were commercially harvesting shellfish from that boat, one day, we had it loaded with 22 bushels of oysters @ 60 lbs per bushel, plus the weight of two people. No buckling of the floor, but we only had about an inch of the boat out of the water....LMAO, if we had hit one little ripple, much less a boat wake, we would have been in trouble.

Is your boat a flat bottom, or v-hull. The slanted floors on a v-hull make it harder (but not impossible) to put foam in to properly support a floor.

If you end up doing just one sheet, you can lay out some 2x4s on the driveway in a grid pattern and set the aluminum on top. Walk around and bounce up and down. Adjust the 2x4 grid until you figure out what spacing works best, then build your bracing accordingly.

Also, if you go with .063" you'll find it much easier to form to shape if your boat is a semi-V hull.....unlike the .125" thickness, which isn't going to have much flex.

Another trick is to start riveting in the center, and work your way to the gunwales, one rib at a time. This will assure that the sheet is drawn up properly to the ribs, particularly in the center where there is a V.

Thanks for all the great insight and responses.

I agree with most of your replies. Sounds like it may be more trouble than it's worth to layer the aluminum. I will add more bracing and stack foam underneath to support the thinner sheets. Would 12" framing be enough to support the .063?

Also, I have read a lot of threads concerning the type of foam used in the boat. Closed-cell seems the best, but I don't see many posts about how this stuff holds up? Any issues with mildew, breaking down, or weight from water absorption?

12" framing should be more than adequate. The rib structure alone is enough bracing, if you use foam board that is thick enough that it properly supports the sheet of aluminum.

As far as the foam, as long as it's closed-cell foam, whether it's blue foam board, pink foam board, or plain white styrofoam board, it will be fine. Any water will drain through the gutter system of the boat, passing underneath the foam board. The gutters will also allow air to flow through, drying out the moisture.

When manufacturers pour foam into a boat, often times, these gutters become clogged, and this is what leads to the foam being water-logged, or crevice corrosion. This is why foam board is a better option than pouring foam, at least when it comes to thicknesses under 2", such as under floors or decks.