Converting from traditional aluminum siding to smooth skins?

....have a look at Foamular C-300, at 30psi compression strength (shiplap), 96 inch lengths...Owens Corning.

I figured rigid foam (blue board) would be best and more then likely is what I'll go with and "expandyfoam" the joints and voids.

I've worked with the foil faced polyiso in solar heater builds for heat resistance.. I can get it locally so may go that route too.

I've got time to figure that out cause it'll be a bit before I can get it framed and skinned. Long weekend coming up.. hopefully I'll get something done.

Gaco Western (Firestone Building Products), here-->

...that sounds like a very interesting and robust roof build-up! I'll probably use Gaco to 2nd skin my TPO roof down the road (perhaps in 7 years....BEFORE a roof leak happens). Have you considered just using 3 sheets (do the cut-outs) of marine ply (12-foot sheets for sidewalls all the way out to tip of cabover, and scarf lower & scarf a couple of smaller ply sheets to form the rear wall) and doing the same build-up as the roof (as a smooth camper "skin") ?

...also, check the under-wings and camper tub and tub under-floor for rot, too. I had to re-build mine a few years ago...also, it appears (in your photo) that the cabover underbelly could be delaminating (??)

Ditto on not using fiberglass. Not only low R, but with vibration and moisture it tends to drop down-leaving voids.
The best would be polyurethane and sprayed. Lot of high-end houses are build this way with excelent results, but that is expensive.
Still buying polyurethane pads and finishing with "Great stuff" will do good job.

I would dissuade against fiberglass batt insulation and use rigid instead.

Stay away from the commonly referred block foam (styrofoam) which is the cheap expanded polystyrene (EPS) and use the blue or pink extruded polystyrene foam (XPS) instead. It has a better R-value and is reasonbly priced. If you want a better R then go with the polyiso (polyisocyanurate.) It is more costly but provides the best R-value for limited space.

Got the roof plan sorted I think...

Talked to a buddy of mine who has been a general contractor for the last 40 years and basically has a private lumberyard (has been buying bulk material for years by the trailer load for dirt cheap because it was odds and ends..)

Anyways... he owes me a favor or 2.. so he stopped by and helped me layout the roof design and offered up the majority of the materials that I don't already have. Here's the plan...

The main bows will be cut from 1x6s... set 16oc. They will be ~2" higher in the center then on the outer edges and they will be notched to saddle the walls instead of just riding on them flat. The bows will be tied together via 1x2s on edge every 10-12". Roof will then be skinned with 1/4" marine ply, glued and screwed, with the seams and edges glassed/sanded... then a few coats of epoxy topped with Gacoroof silicone roll on.

Reason for going with ply is availability in my area. If I find something different before I get the skin material.. I may go that route instead.

Anyways... once the roof it built, it will be fully insulated either using foam or fiberglass... what ever I can get my hands on that has a decent R value and is reasonably priced.

Doing it this way, all I'll have in it cost wise is the skin material and coatings.

Sound like a reasonable plan?

If it was me, I would remove the roof, rebuild the walls using foam block insulation, rebuild the roof, then reinstall the existing metal. It goes on real easy and is very durable. Especially with it looking so good.

Check the floor while you are at it as it may pay to do a complete rebuild using what you have as the pattern.

One thing to try and avoid is aluminum contact with the wood. And make sure you don't use treated wood because though it seems like a good idea, the chemicals love to corrode the aluminum.

I very well may just keep the current siding... I just like the looks of the smooth siding so figured I'd ask.

If I did it, I would probably go with 1/4" ply with the seams glassed/doweled and several coats of a high grade epoxy.. then paint. Would still be expensive.. but cheaper then buying panels I'd say.

This all depends on how easy the aluminum comes off.

If you can salvage some of the aluminum siding by cleaning away the corrosion on the underside, it can be treated with a paint primer containing zinc chromate that is made for aluminum. Also there is a product called alodine that is used in the aircraft mfg industry that is used on bare aluminum to prevent corrosion. That is what I did when replacing some bottom floor wood with treated marine plywood at the contact points. I had the local napa order the zinc base primer for me. I believe the alodine can be purchased on line. Maybe someone with more experience working with aluminum can chime in.

I would think that throwing away the existing siding and purchasing all new would blow your whole plan of having this camper road ready for $2000 out of the water. The siding is pretty expensive.

I don't see why it wouldn't work. The filon stuff is much more dimensionally stable than aluminum.