Gator417 wrote:Yes, Andrew, many misconceptions here.
Like I said, nobody using plywood structurally. These campers have steel underpinnings, just like TDs, and the floor rests on the steel.
Not sure where you get $250 for sheets of foam, but I'm happy to sell you as much as you want for half that, since I get it for $15 for 1/2" & $25 for 1".
The facts are plywood just won't hold up to the elements like synthetic materials, and its substantially heavier. You can make it lighter with cutouts, but it won't be nearly as strong and with all the increased surface area, will be much more prone to damage by moisture.
As I and others have said before, the strength come from the structure, the design, rather than the choice of materials.
Most people are using plywood either because everyone else is or because they just don't know of other options or they don't know how to use the other materials. Good enough answer for me.
Gator
Spirited conversation we have here
Lots of good information coming forth. Thank you for your questions.
1. Like I said, the structural use of plywood in a stick-and-tin camper seems a non-issue ... stick-and-tin campers get their wall strength, what little they have, from the framing and skinning. And I don't think you can successfully laminate fiberglass or other synthetics over plywood due to expansion rate differences. So, while you're right that plywood isn't used much in RV superstructures BESIDES the subfloor and interior paneling, that doesn't seem to be an argument against the quality of plywood itself ... I mean, when was the last time a mainstream RV was considered a bastion of quality?
2. $15 foam isn't what I'm talking about. That's probably rigid building foam, and it won't hold fasteners worth anything, and it's not UV-resistant, and it has yield strengths an order of magnitude less than wood. I'm talking about Coosa board and the like, polyurethane foams that are intended to be near direct substitutes for plywood.
3. Weight seems to be a big concern here ... but I'm not understanding why? We're not building rockets. We're building teardrops. It's not uncommon for 2/3 to 3/4 the weight of a camper to be in the chassis and features, not the shell. For most people, saving 100 pounds will have no measurable impact on towing capacity or fuel savings.
4. "As I and others have said before, the strength come from the structure, the design, rather than the choice of materials." - Well, um, yeah ... sorta ... but you can't use that as a blanket statement to justify all other, possibly weaker materials. Stress is stress, no matter what material bears it.
5. Again, I'm not saying you shouldn't go for glory!
Synthetics are awesome. Seriously. But preferring one doesn't mean the other is useless. Besides, synthetics have their own issues. Most semi-structural plastics, like HDPE, don't glue well. And most honeycomb panels don't hold screws or play well with bolts.
Lastly, let's remember that the teardrop revolution started as a grassroots movement, a rebellion against consumerism, a bunch of people from all backgrounds trying to find freedom on the road with their bare hands, and they used what was available to them. And their basic designs have worked well for, oh, about 80 years now. Lots of people on this forum are doing the best they can to build their first camper with a jigsaw and a bottle of wood glue, and I think that deserves respect from all of us. *end of sermon*