Once again the fora present a hundred different projects and even more ways to do it. The basic goals are to provide a flat floor you can screw into and to insulate for sound and heat gain/loss. The flat floor part requires you to fill in between all the ribs. Most if not all people use strips of 1/2″ genuine Home Depot or Lowes rigid insulation foam for that. Then the solutions vary wildly. Reflectix is a popular product as you will likely also use it somewhere else in the super structure. Most top layers are plywood with a variety of finished floors. Sound proofing requires mass. Dynamat is a good product and some use it in the floor, but it is expensive. The plywood provides some sound insulation as well. 3M has some new high tech stuff which apparently doesn’t mind compressing, but it’s also not cheap. The floor is one serious sound board. And, while new the body, wheels, tires and drivetrain are still nice and tight (and quiet) 50+ thousand miles later it will all get progressively louder. And I like quiet.
I did something different: The ubiquitous foam strips between the ribs, but then rubber stall mats from Tractor Supply, topped with 3/8″ plywood. The stall mats are 4’x6’x3/4″. Just under $40, you need three. It has mass, 3 pounds 11 ounces per square foot!….. 88 pounds per sheet, and as floppy as they are a little bit of a pain to man handle. The floor is roughly 66 square feet, so that comes to 240 pounds. This should quiet things down nicely and put some mass down low for handling. And, it will have a little give and provide a place for screws coming through the plywood to go. The only major drawback is that initially it smells, like burned rubber. I’m sure a few days of sitting in a hot van will cook most of that out. Rubber is about R-1.30 per inch, so 3/4″ is roughly R-0.975. The foam is about R-1.875…. Not sure if this is a scientifically sound assumption, but lets say 50% of the floor is covered with the foam so that’s R0.9 for the whole floor. The plywood is R-0.31 so the total floor in theory comes in at R-2.185 Not great but for load bearing material (1 inch) not too bad. Also, there is still a finished floor to go on top of that, or at least a rug/carpeting. And, I bet it will be quiet. (Testing to be done when completed, see the “Sound” article on this page: https://flyingdutchman.blog/design/ ).
So, here’s the installation. I started by fitting a whole foam floor. The stuff is easy to cut and the extra after cutting out the ribs will be used somewhere. If you piece the third and most rearward section, two 4’x8’sheets will do the whole floor. I wanted to overlap the seams, so as the rubber is 4′ wide and harder to cut I started with a 3′ foam piece.
Then I used the foam as a template to mark and cut the rubber. This way I only had to heave the mats in there once for fitting. (And a few more times after that for other steps of the process) Did I mention they are heavy? A new utility blade will get through the rubber in a few passes.
After the rubber was cut I removed everything and used the foam templates to cut the plywood, again starting with a three foot wide piece to offset the seam versus the one in the rubber.
Then it was time to get it in there. I proceeded to take a small paint roller and some oil based paint (I tried Latex but it dried too fast, even in 40º weather), don’t worry about the mess…… it’s soon out of sight, and then I rolled all the “ribs” in the floor, nice and thick, then I placed the foam pieces in place and pressed.
Back out and on the bench there was enough imprint to cut out the ribs with a utility knife.
I then placed it on top the corresponding piece of plywood and hit the openings with some spray paint.
I now had a marking on top of the floor where the ribs below it were, ie where the metal is closer to the surface. Now it was a matter of putting it all in: Foam, then rubber then plywood.
And here is the finished result. I put some screws in there (plywood into the rubber, to keep the seams flat. There is enough holding power in the screws to accomplish that. They’ll be covered up later.
Altogether I’m going to say it took about 6-8 hours for the whole thing. It has a very nice feel to it. A little give, yet not squishy. With some carpet or vinyl on it it will feel like a million bucks. Meanwhile I’ve taken it for a 350 mile drive and although the iPhone db meter doesn’t show it (probably the phone and not the actual level) it is noticeably more quiet and nothing squeaks or rattles! Can’t even hear the tank sloshing anymore!
On edit: Forgot to mention, I haven’t smelt the floor, at all. Not even after it sits in the sun. Apparently the few exposed edges are not enough to spread it and the surface is covered…. go figure.
Well, no carpet, no vinyl. I remembered I had a pile of unfinished 3-1/4″ x 3/4″ oak flooring in my “inventory”…. Not quite enough so I went and got a few more bundles. Couldn’t find any 3-1/4″ so got some 3″ and 2-1/4″ and laid a random width floor. I love this stuff. Did the front 2/3 and the back 1/3. The seam will be covered by a bulkhead of some sort. I glued it on to the plywood. In theory the whole thing can come out in two pieces if that is ever needed. Yes, it added another 3/4” to what has become a “substantial floor”. Standing height is getting a little tight for me, but it’s still good for my wife. Again, we’re not going to be spending weeks in this. If that were the case I would have gotten the high roof.
The transition from wood to cockpit is an oak piece that pulls right out to give access to the wiring under the carpet. You can just see it in front of the floor.
When it was done I gave it a sanding and oiled the whole thing with boiled linseed oil….. I LOVE that stuff. The finish is pretty, it smells good, it is extremely water resistant, and it wears really well. If it ever gets a little tired you just wipe on another coat and you’re good to go. I have used it in several applications over the years and like it more every time I use it.
Did some fancy work around the entry…….
Last part was the treatment of the back edge. Since this is the “cargo area” I wanted something that would stand up to the abuse of loading/unloading generator etc. etc. I like working with steel. So, got 4 pieces of 1/8″ x 3″ flat stock and got the plasma cutter and the welder out:
The finished result: This should hold up pretty well!
Well, that’s the floor. Meanwhile the fan is in, the layout is coming together and it’s time to do some insulating and finishing of the ceiling!