I'm wondering if any of the big manufacturers are using fiberglass reinforced plywood for siding instead of the aluminum.

FRP seems more user friendly. Doesn't dent or scratch as easy, smoother sides, no rivets, temperature neutral...

Any comments on the two materials?

Renegade does. I have an FRP trailer and aluminum skinned motorhome - they both have advantages and disadvantages, not sure yet which I prefer.

Would anyone know the weight of both sidings when they are similar in strength...?

......not comparable since aluminum needs a superstructure and FRP's it is built in.....with alum you can use any interior wall-I have 3/8" plywood and 2 " Polyisocynate foam board....FRP are a 2 skin bonded laminate with a structure built in.and some insulation....I did see one with a honeycomb in between the laminate skins.....very expensive and used on ambulances...Horten I believe?.....geofkaye

The FRP has been used for many years in the trucking industry. A 48 or 53ft trailer made of the FRP and one made from the Aluminum sheet and post will weigh about the same. The FRP is said to be stronger and has the advantage of being smooth. However if the FRP ever gets water in between the bonded fiberglass and into the plywood you are in for real trouble. We have had several trailers develope a leak at the top seam and by the time we caught it the damage was already done. Repairs can be expensive and difficult to blend in. With the sheet and post aluminum you can always replace panels.
Wick
2006 30ft Show Hauler "Almost Done"

Here's one for all the insulation geniuses out there: About what is the R-value of the above-mentioned FRP as used in truck boxes and RV's? I'm sure other inquiring minds are dying to know, but were too chicken to ask....
Gary

....aluminum=R.nothing worth mentioning///air film inside and out is about a R.007///2 " of polyisocynate board is a R.15.///3/8 plywood is about .37.....Total is about an R-16 which ain't too shabby in terms of RV industry standards......I have no idea what FRP R-value is but I doubt it is more than a R-3 without adding and interior space and plolyisocynate insulation.....geofkaye

Whats FRP?

can be two things:
Fiberglass Reenforced Plastic (the ugly wall covering in commercial building restrooms ) or
Fiberglass Reenforced Plywood https://www.truckhome.com/infopop/emo.../icon_wink.gif

.....FRP has many different grades also...one needs to look at the grade issue also before makeing a decision....FRP is known to bubble on the sides....'specially the cheaper end of the box truck body builder like.....[oops shouldn' t say anythig negative about any builder-I'm being PC-puke].....But I've repaired 3 bubbles now and it is a matter of cheap materials and nothing else.....FRP can also be two layers of fiberglass plstc glued to a wood frame with styrofoam in the spaces as a filler material-advertized as "insulation"....also called stress panel in the housing industry...they are a trainwreck looking for a place to happen.....one small puncture and water......geofkaye