Yesterday since my truck bed was finished and ready to be tested on a minivacation I decided it might be wise to lay on it here in the driveway longer than the one or two minutes that I had laid on it while putting it together, and its a good thing I did.
After stretching out on my new truck bed for 10 or 15 minutes it became apparent that things weren't working as well as I'd first believed. Within a few minutes my butt, dainty though it is, was sinking down and starting to touch the plywood. And not only that, the rest of me was sinking down along with it, not enough to touch the plywood but enough that I felt enveloped in foam which became warm enough that it was uncomfortable.
Crawling up out of this foam hole I had created, I retreated to the Arctic Fox to sit in my easy chair and debrief myself on what had just occurred. Measurements showed that I had 6 inches of foam laying on the plywood, and you think that would've supported a battleship let alone my minuscule butt, and yet I was still bottoming out, no pun intended, no matter how much foam I added to the bed.
In order to keep the cost of this project as affordable as possible I was using foam that I could scrounge or had laying around, and all of these layers of foam that I was using were what is normally called mattress covers, foam that you buy from Walmart and put over the top of a mattress that's too hard, so all of the foam I was using was very very soft, apparently too soft to use as a mattress.
Now I'm aware that some foam is firmer than others, after all I had just gone to a upholstery store in Tucson Arizona last winter and bought some pieces of upholstery foam to make the seat for my little Beta motorcycle, but I thought the lack of firmness of my foam could be overcome by adding more foam, I guess that would eventually work but I probably wouldn't be able to get out of the hole that I had sunk into overnight.
Coming to the realization that as usual this project was going to cost more than I anticipated, I took the advice of Hachita, one of my commenters, and looked into some folding mattresses. These would've worked just fine, but since the folding capability wasn't important to me I found that I could buy upholstery foam from Amazon relatively cheap so I ordered a 72 x 25 x 3 piece and it's supposed to be delivered tomorrow. It's hard to believe you can now get Amazon deliveries on Sunday. What a country!
I ordered a 3 inch thick piece of foam because I had a small scrap of 2 inch thick upholstery foam left over from the motorcycle seat project, and it had more support than all 6 inches of the mattress covers, so I figure if the upholstery foam is too hard I've got plenty of soft foam to put on top of it.
I'm still trying to get used to driving around without a passenger seat. And I believe anyone looking in the truck and seeing the bed is probably going to assume that I'm a homeless bum living in my truck, not realizing that I have a very nice home and the truck is just my vacation home.