.125" aluminum flooring and support question?

I picked up a 4" X 10" of .125" aluminum from Bugpac this weekend and now have enough sheet aluminum to start looking at re-installing flooring in the center of my boat. The original flooring was 3/4" plywood, so I'm not sure how much different the support for .125" aluminum needs to be.

What is the center to center measurement for durable support of .125" aluminum sheet for walking on? I'm a big guy and I want to make sure this floor will not start sagging/denting after a year or two of use.

Thank you for the help,

From your resto thread it looks like your main deck framing is spaced on 12" centers and that should be plenty.

jigngrub said:

From your resto thread it looks like your main deck framing is spaced on 12" centers and that should be plenty.

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I was looking at your marine vinyl installation and was noticing how similar it was to the installation on your boat. They look like they kept most of their engineering processes and materials, but improved they way they did things from your boat to the one I have.

.125 is pretty thick stuff. 12" on center is plenty. You could even get away with 14 or 16.

Based on your two replies and unless no one says a big guy needs more reinforcement, here's my thoughts and a plan:

I think I'm going to pick up some additional closed cell foam from Lowe's or Home Depot (Prefer the blue color) and stuff the foam between the risers to "fill the gaps" between the original foam and the new aluminum deck. That should give just enough additional support and add some additional flotation to the boat as well.

Beyond that, I'll probably cut some drain slots in the original foam to allow any water to drain down to the bilge.

So for my console/center deck area, for example, I would:

1. Clean area between risers out good of dirt/debris.
2. Drill holes in risers to allow for drainage, making them big enough to pass leaves.
3. Cut some slots in each foam area to allow water drainage down to the center of the boat.
4. Cut and install additional flotation between the risers using closed cell foam from Home Depot/Lowes.
5. Clean up from fabrication work.
6. Cut and pre-fit/dry-fit center deck, mod as necessary to cover entire center deck. Splice strip to 4 foot section to make a complete deck. Drill for 1/4" rivet holes.
7. Remove new deck aluminum and cover with marine vinyl using contact cement. Over lap approximately two inches over edges. Punch rivet holes with scratch awl.
8. Reinstall deck using 1/4" aluminum closed end blind rivets, 1/2" long with steel mandrels.

No steel mandrels!! All aluminum high strength rivet.

Bugpac said:

No steel mandrels!! All aluminum high strength rivet.

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Why not the steel mandrel? Aren't you pulling the mandrel out when you set the rivet and doesn't the steel give you a better pull/seal?

Not the rivets i used, The mandrel just breaks off flush.


No way for the Mandrel to come all the way through, If your using something different than I maybe. If i was to push the mandrel back thru, then the rivet could loosen back up over time.

Based on Bugpac's inspection, looks like I'm going to be saving a good bit of money not having to buy much support bracketing.

If it was me, I would either use the big head rivets used for doors, fenders, etc on dirt cars such as these:
https://www.smileysracing.com/shopping/productDetails.aspx?i=12726&c=0

or exploding aluminum rivets like this if you want smaller heads:
https://www.speedwaymotors.com/Small-Head-3-16-Inch-Exploding-Rivets,42819.html - you would normally use these for smaller spaces where it's impossible to use a washer on the back of a panel for the rivet to suck up against. I'd just use the big head rivets from Smiley's. I've put hundreds in over the years and they work great on aluminum body panels.