Which RV have the best aerodynamics? A, B or C?

Some of the best IMO are the new Forest River Windjammers. We've had ours for about a year and a half and love it. The V-Hull design really works and we're sold on it. No bugs on the front either. Wasn't sold on the unconventional looks at first but love it now. Ours has a large walk-in closet in the v-hull that the wife really likes. They make them in all sizes. Tows like a dream.

FR WINDJAMMER

Keeping it simple, three primary vehicle parameters impact fuel consumption. Aerodynamics, rolling resistance and weight. Aerodynamics is a combination of shape factor, frontal area and speed. Rolling resistance is tire friction due to tire construction, air pressure and vehicle weight. Weight affects tire loss slightly and is primarily important in speed and elevation changes. For three similarly sized trailers the rolling resistance and weight will only be a very minor factor. The big factor is aerodynamics where the resistance goes up in proportion to the square of the speed.
Note: the frontal area is the "projected frontal area", basically a cross-section area. The added area caused by a v-nose is accounted for by the "drag coefficient". A flat plate has a flow coefficient of 1.28 and a streamlined body, similar to an airfoil shape, has a flow coefficient of .04.

I agree. At speed. Acceleration MPG is all about weight, not frontal area.
After 50 it's mostly about frontal area and aero dynamics; not weight.

And don't forget that putting a long tapered point increases frontal area and creates
MORE resistance.

Big Katuna wrote:

So a 4000 pound car with 250 HP gets 30 MPG compared to a 30K pound motorhome with 250 hp that gets 8 MPG because of frontal area?

This year both Freightliner and Peterbilt streamlined one of their production models and trailer. Both were able to achieve 10 mpg. The Freightliner was 76,000 GCW and the Peterbilt was 65,000 GCW. The industry standard for a regular combo is 5-6 mpg. Aerodynamics plays a huge role once up to speed.

Most of the aerodynamics of TT would come from rounding the front corners, like an Airstream. The sloped nose probably makes very little difference, but it looks good. Canadiankid is right a rounded back, again like an airstream, would make the biggest difference. A pointy tail would be ideal but unusable. The most aerodynamic shape is a raindrop but it's not very practical, except for a rain drop. Find a floor plan you like and forget about the shape.

So a 4000 pound car with 250 HP gets 30 MPG compared to a 30K pound motorhome with 250 hp that gets 8 MPG because of frontal area?

Once you get that heavy load up and moving, yes it's mainly the frontal area.

I keep detailed notes on fuel economy.
Here is one of my notes:
Hauled 4 tons of fertilizer (+ 2500lb spreader) = 10,500 lbs.
Drove 55mph got 12.8 mpg.
Returned empty 2500 lb spreader at 55mph. Got 14.5mpg
This was with my '13 Ford Powerstroke.

I do the same thing when hauling cattle. If I take 5000 lbs of livestock to the sale barn and then return empty, the mpg difference is about the same as above.

Big Katuna wrote:

Mike Up wrote:
Jayco changed their profile on the Jay Flights

My 2008


My 2012

I want the Shasta!!

Sorry went to Kids4Kars a few years ago.

My dad lost interest in camping and put that interest in his many show cars. He spends most of his time at the car shows now. Hopefully someone who likes vintage RVs, and doesn't mind restoring them a bit, got this camper.

My brother, sister, and myself used that camper when we were kids many decades ago, and it was perfect for us. It had a double bed sofa in the rear with a double bed accordion bunk above, along with the dinette bed my parents slept on.

Had a wet bath which made you sit on the toilet to shower. :) Had a single door refrigerator and a 4 burner stove/oven. Air pressure powered running water (no water pump) and gas lights through out (no 12 volt lights or battery) with some 120VAC lights.

NO AIR CONDITIONING! Probably the reason they lost interest in it although it had plenty of air circulation with the many windows and fans it had. Had more windows than most newer and larger campers. Also had a water heater and furnace.

NO A/C, No microwave, No TV, but had everything a family of 5 needed to camp.

Here's another pic:


If you notice from the recent pic, it even has an upper bunk bed window at the top, just like the Jay Flight 19BH and 26BH.

Mike Up wrote:
Jayco changed their profile on the Jay Flights

My 2008


My 2012

I want the Shasta!!

johndeerefarmer wrote:

Big Katuna wrote:
Doesn't matter much; its about frontal area and they are all rolling bill boards. Weight is more crucial and HP. More HP used equals more $$$.

Important question is
"Can you afford an RV?'

Fuel consumption is not the most expensive part of RVing.

Weight has very litte to do with it. It's mainly in the frontal area. I can pull an empty fertilizer spreader or a full one (with 4.25 tons in it) and the mpg difference between the two is less than 1mpg difference.

You can find "v" shaped trailers here, I am just not convinced that they help that much.

http://www.forestriverinc.com/TravelTrailers/VcrossClassic/default.aspx

So a 4000 pound car with 250 HP gets 30 MPG compared to a 30K pound motorhome with 250 hp that gets 8 MPG because of frontal area?

Here is some interesting data from NASA http://www.nasa.gov/centers/dryden/pdf/88628main_H-2283.pdf

It is somewhat technical - but interesting just the same.

Basically, with a big brick, curving the edges and tapering the rear has the most impact without a radical shape change.

I'd think that C would be the most efficient - but the difference would be so very minor it wouldn't matter in the real world.

A smooth top and a Kamm back or boat-tail would have the most impact.