Weights and aerodynamics - where do I post and query?

There are some threads on air tabs.

Good question. I don't know of any sites for aerodynamics on Class C or other RV's.

As mentioned by pianotuna, a site for air tabs would be a good place to start.

Let us know if you find any sites, I'm sure most of us would be interested.

Only way to tell what your RV weighs is get it weighed at a scale.
Lots of info here on Air Tabs and other improvements on RV.NET.
Here is one thread in Truck Camper forum. It shows making a air foil to stop wind noise between and cab over and truck cab. I used Air Tabs to stop noise from wind in the cab over/cab area and cab side windows. Helped a lot. I have Air Tabs around rear of my MH. Helps with handling. But cannot tell if it helped fuel mileage.

Tech Issues or General RVing Issues?

In the 10 plus years I have been reading RV and Tow Vehicle related forums the folks who post the results of changes they have made to improve MPG, the improvement has been small. 1-5 increase in MPG after spending up to $2500 in aero or engine or trans or a combo of improvements doesn't impress me.

The one thing RV'ers have done that improves gas mileage and is free is to slow down. Instead of doing 70MPH do 55 or 60MPH. It's much safer as well.

Aerodynamic drag becomes more important as speed increases. Rolling resistance probably stays the same, running tires with max air pressure loosens fillings in your teeth.

Maybe post in the Tech Issues
There a few threads on aero using Air Foils as stated above and there are

Air tabs
Also a few threads on the subject.

HERE

And HERE

They may have some answers for you.

I liken my class C to a flying brick. There is NOTHING aerodynamic about it. I do manage to squeeze 10 mpg US but that is by driving at 48 mph.

The air tabs made no measurable difference to mileage, except in a tail wind where I got about 2 mpg better. They did reduce wind noise dramatically.

Definitely check out the forum at ecomodder.com.