My aero (hopefully) fiberglass foam truck camper

[freebeard]

I would like to build a very sleek, lightweight B Class Toyota motorhome on an existing toy RV platfom.

Sounds like a plan. Here's a trailer based on the Airstream Basecamp, but it's got some interesting interior details: https://youtu.be/irAcBNe69zo

The wet bath will be heavier than the dinette/bed. When the vehicle is in motion, there's some advantage to having the CG between the axles. Look at the berths in the bow of a sailboat.

[pete c]

I would be using a composting toilet and putting the grey tank forward, just aft of the rear axle would take care of weight distribution problems.

Batteries, potable water would be under the dinette. I will come up with drawings soon.

[turbothrush]

Originally Posted by pete c

Love this thing. Have a few questions.

How many layers of glass do you use?

Could you give a rough price per square ft of construction? This is foam, cloth, resin, paint.

I own a Toyota Sunrader, which is a C class fiberglass clamshell construction RV.

Absolutely love it, but would love it more if I could bump the good (for an RV) mileage up from 17ish to something the other side of 20.

As the kids are grown, we don't need the extra bed provided by the aerodynamic train wreck of the cabover.

I would like to build a very sleek, lightweight B Class Toyota motorhome on an existing toy RV platfom.

There are literally thousands of old stick and staple Toyhouses out there that have suffered the fate of most, which is they are structurally shot due to water intrusion. Many of them have perfect frames and low mile 22RE drivetrains.

These things can be picked up for a pitance. I looked at one a few years back. 40K miles. It had an Onan 2800 generator that was optional on these and can bring 800 bucks in good shape. I could have bought the whole thing for 800 bucks! Maybe less, but I didn't have a shop to work on it.

I would have the dinette/bed forward, galley midship and a V shapped wet bath in the boattail rear.

I really thing such a rig could make 20 mpg with the 22RE, maybe 22-23 with a manual trans.

Give it a tdi re-power and we're talking Vixen RV mileage! Without all the Vixen headache that come when you use Renault in any part of your drivetrain.

i used 2 layers of 7 oz fiberglass cloth on each side and 3 layers on the front then skimmed the complete outside with micro ballons mixed with about 25% cabisol.it has good impact resistance.most materials from U.S. Composites. Primer and paint from System 3.

Compound curves in foam are not that hard. Get the foam as close to the final shape you want before glassing. The new sandpapers can cut epoxy based fillers no problem

Not sure of the shell cost .. ill dig out the receipts for you in a few days

i like your project idea very much.Hope you go for it. My goal is 20 mpg also but its not possible with the current setup so i picked up a Isuzu 4BD1T diesel for the Toyota tundra and i am going to make an adapter to mate it to a T56 Maginum 6 speed

[skyking]

you should make a simple plywood throatplate splitter for the table saw.

Picture of that?
Thanks again for documenting the kerf method.

[turbothrush]

Originally Posted by skyking

Picture of that?
Thanks again for documenting the kerf method.

Hey Skyking. I made one like this for 2” foam and of course a shorter one for the 1”. I had to play with the thickness of the hardwood splitter a bit to get it just right then waxed it to reduce the drag.

[skyking]

thanks man!
I was visualizing something like that, but wanted to be sure. I see the double kerf method there for the tighter/deeper bends, one deep cut and another just a smidge to the side shallower, to allow for a nice bend. You glassed it both inside and out 2x 7 oz cloth, which epoxy, and was that just owens corning from the big orange box store?
I was thinking of using highload 60 or even 100 for the floor and roof of mine.

[slowmover]

What would be the annual reduction in fuel price per mile based on your present use to engender a savings you deem worthwhile ?

At today’s fuel price of $2.15/gl it’s $145 @ 5k annual miles to make the jump from 17 to 22. That 3-cents per mile. But the savings isn’t free.

At 15k annual miles it’s still a “savings” of under $500. Again, not free.

With modifications, how long do you plan to keep it in service, and what are the projected miles? $1,500 in materials, tools & supplies means no savings until past 45k miles and three years.

That 20% increase might not pan out as a savings.

For RV’ng, the rule of thumb is that fuel is one-half or less the daily cost of travel (when the RV is wholly-owned AND not in need of serious repairs).

Engine compression, and a rig with ZERO steering, handling or brake defects (extremely unlikely given age) are the first steps in best mpg with an ancient vehicle.

What is the front/rear weight bias? Port to starboard? Cold cranking compression, per cylinder.

Aero won’t matter much until the hard work is done. Icing on the cake, is what it represents.

Finally, is this your only vehicle? As an aero TT coupled to the family car can shoot FAR past 22-mpg (with more interior space than that baby Moho). No high mph motorhome will ever have “good” mpg when it is a second vehicle (as you already possess a vehicle drivetrain).

Renovations, much less restorations, tend to take years. Modifying existing is worse yet.

Were it me and I were “stuck” believing:

1). Motorhomes a good choice
2). A decrepit version my only choice

I’d start from the ground up. Body & subframe bushings. Correction of frame twist. New steering gear. Correct weight imbalances. Etc.

This is assuming engine compression still within 10% of new.

Planned Use is how to make an RV more economical. The “test” is how many days at one location (no hookups) without the need to start the engine to leave on a re-supply mission.

From there are further details: time of day; best location to make acquisitions; best routing, etc. This REALLY IS what works.

A great big lumbering rig with 2X your per-mile fuel consumption CAN be the more economical choice as it has far greater storage capacities.

So, be certain in your allocation of time & money. Other rigs MIGHT better fit the travel you envision for your budget.

My 63’ combined rig (one ton pickup and 35’ travel trailer) which weighs 17,000-lbs loaded for camping gets the same mpg as you under best conditions. (Total acquisition cost just under $30k one dozen years ago).

Of we two, which will have to pack up and leave the campground first? I’d bet it’s twice as often with that Moho. So, in a sense, you’re at 9-mpg in comparison.

As I only own one drivetrain, how much greater are my actual annual savings versus yours?

All this was a way of saying, before you start cutting, make sure that the rig AND your actual use justify that which won’t start paying for itself until 2025 (Two years to build; three years of savings assuming 45,000-miles of travel).

The Year of Our Lord 2026 is the target.

.

[turbothrush]

Originally Posted by skyking

thanks man!
I was visualizing something like that, but wanted to be sure. I see the double kerf method there for the tighter/deeper bends, one deep cut and another just a smidge to the side shallower, to allow for a nice bend. You glassed it both inside and out 2x 7 oz cloth, which epoxy, and was that just owens corning from the big orange box store?
I was thinking of using highload 60 or even 100 for the floor and roof of mine.

I used US composites 635 thin 3:1 I didnÂ’t get much blushing. Home Depot in my area only sells formular 150 and sometimes 200. Most of my shell is 300 . Roof and floor was 300 and seems fine. I would have used 600 but itÂ’s not used locally and no one wanted to order such a small amount.

Kerf depth seems to depend on the density of the foam. Formular 600 may be different

I was happy with the System 3 primer but if I were doing this again I would at think about think about switching over to automotive topcoat after the primer. If anyone has thoughts/ experience on this please post.

[skyking]

Thanks again. I think shooting automotive would be easier ,once you have it primed.
I had not looked closely at the foamular products.
That C-300 you used may only have half the compressive strength at 30 psi, but it has equal the flexural strength at 75 psi.
It looks like a better choice. Flexural strength is more about the rigidity and I would not be surprised if it had comparable shear strength.
That's the one weak point of the common EPS and XPS foams, internal shear.
To get excellent shear performance you have to go to very costly marine materials.
I'll have to check on local availability of the C-300.