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Eartheart 08-24-2013 10:30 AM

Extending Frame Depth
Hi all,

I am tinkering with a 62 GT and insulating below the sub-floor and modifying the fresh tank location to below the floor. (was hidden behind gaucho in this model)

My GT came with the belly rotted out, mostly missing, so I didn't have the convenience of a template going back. The best capacity fresh tank I could find is 8" depth. I also custom installed a spare tire carrier into the front below the hitch / tanks. (I didn't like the bumper mounted carrier)

What I'm proposing is to add perforated channel metal (similar to the existing frame in 18ga galvanized with a durable coating) to the existing frame and outriggers. This will extend the "utility space" of the belly and allow me to hang a seamless (read aerodynamic) belly pan to the bottom of the GT. It would need to notch up around the axle, but overall it would run flush to the depth of the axle (no loss to my maximum clearance).

This approach seems better than to add just one bulge to accomodate the new tank. This would not be aerodynamic and would hurt the aesthetic appeal. Also the bulge in the spare tire will be concealed in profile.

After reviewing all the threads on insulating vs not insulating, I have chosen rigid polyisocyansurate (ISO) insulation adhered below the sub-floor and adding louvered vents in the belly pan to provide adequate airflow to dry it out if condensation forms. (don't ask me about dew point i'm not an engineer) Something to do with humidity and divergent temperatures interior / exterior.

My interior flooring will have a 6mil vapor barrier to prevent spilled water (gonna happen) from migrating down to the insulation or sub-floor. Was thinking floating cork which can expand and contract. (per classic rides episode, youtube it)

You can tell, I'm not nostalgic about keeping things original. This is my custom job and I'll do as I please here. I'm looking for flaws in my strategy. Anyone shout them out, I'm listening. Thanks.

putback 08-24-2013 05:47 PM

Why not? But I'll toss out some maybe glitches. Even on a 19 ft you will loose some clearance maneuvering into steep incline campsites, tail drag. But with a 45degree down angle axle and a high profile mount you lift up 3 or 4 inches, could be a wash. Most RV water pumps don't do well on "lift", you're gonna have the pump a floor level and the tank 6/8"s below. A two stage or piston pump should do it. Vintage trailer supply has special 4" tanks to fit in Airstream frames. A potential bonus. '62s can have the toilet on the curb side w/above floor black tank, drain outside the frame rail, mine does. Todays dumping stations are often set up for street side draining. Real P>I>T>A**. No real way to cross the drain over, or discharge out rear center with a 4' frame. With your idea it can be done. The additional frame depth will also make gray water tanks easier and cheaper.

Eartheart 08-24-2013 06:03 PM

Good points putback.

I already fit the new dexter axle at 32 degrees. I can still taper the belly skins at the front / rear to help with the steep incline drag issue.

I am adding BAL stabilizers expecting to need to unhitch at some camp sites and they also hang as low as the new fresh tank. I can recess these and give it a clean look .I want to keep the original stream line look without too much distortion. Not sure how 4" of depth will really change things.

Thanks for the heads up on street side discharge. I am new to trailers, really just wanted a project. With my layout, I can't use the raised toilet original components. My layout fortunately is already set up for street side.

I'll find out how my pump performs soon enough.


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