Aero RV (custom boat tail for '95 Ford E-350 Class C motorhome)

[wyatt]

The long nose on the bullet trains is there to help reduce the shock load when they enter a tunnel.
Trains are very long when compared to road-going vehicle. Even double semis don't hold a candle to them. When you get a form that's that long, things get a bit disrupted just do to the skin drag along the sides. The boundary layer towards the end is so thick that a boat tail does little to nothing to help.
Hope that helps.

[ennored]

That does help. Tunnels, eh? Wow! And long hurts with respect to the back, one might have thought the air would be flowing nice WAY back there.

[wyatt]

That's the way I understand it. We had a thread a while back about Railroad Train Aerodynamics, and that's what I remember. I don't have time to go re-read it at the moment. Enjoy!

[Nerys]

holy crap. going to read this thread later but just reading post #1 even a 1mg gain at 14mpg is HUGE on something like an RV. pure awesome man! design it right and you can put a bike rack in their etc.. and have protected storage for bicycles etc.. have a hitch rack with an addition welded onto it protrude inside so the aero shell itself does not become load bearing.

VERY COOL can't wait till later this weekend to read this thread!

[Shepherd777]

Originally Posted by wyatt

I remember reading that as long as the extension is not increasing cargo volume, that on semis and the like, a 4' extension is allowed for aerodynamic pruposes. I have seen a number of extensions on semis that are more than 18" in length, and reports say that the 4' versions are good for about 7% FE increase.

Originally Posted by orbywan

I wasn't sure about the length, but I'm glad they allow 4 feet, that's more like it.

Hi orbywan and wyatt -

I don't mean to split straws, but in actuality, the FMCSA (Federal Motor Carrier Safety Administration) allows us big rig guys up to a 60" boat-tail.

Not sure how much that 12" will help, but my the nice folks that make that Trailer Tail, ATDynamics, are building a custom unit for my new trailer. So I guess we will find out after we model it and build and test it.

[aerohead]

Originally Posted by wyatt

That's the way I understand it. We had a thread a while back about Railroad Train Aerodynamics, and that's what I remember. I don't have time to go re-read it at the moment. Enjoy!

That's how I understand it.The nose/tail helps mitigate pressure spikes which could occur upon entering or leaving a tunnel.When running in reverse direction,the nose/tail does likewise.
The tunnels themselves are crossed-drilled,like a muzzle-brake, with air shafts at strategic locations to further aid pressure bleeding.
Good news for eardrums!

[aerohead]

Originally Posted by Shepherd777

Hi orbywan and wyatt -

I don't mean to split straws, but in actuality, the FMCSA (Federal Motor Carrier Safety Administration) allows us big rig guys up to a 60" boat-tail.

Not sure how much that 12" will help, but my the nice folks that make that Trailer Tail, ATDynamics, are building a custom unit for my new trailer. So I guess we will find out after we model it and build and test it.

Bob,I believe that a 'rigid' tail,as used by the Waggoner's Trucking Company would be limited to 48-inches,whereas a 'collapsible' tail as with Trailer Tail,and inflatables would qualify for 5'.
Look forward to the new rig.Thanks for all you do!

[CrazyLee]

Orbywan, great job. I really like your rig and your mods. Anything you can do to save gas, even though it's now below $2.00 a gallon is still a great idea.

I have put a Front air dam and wheel skirts on mt 26 ft Fleetwood Flair. Now your design of a "caboose" looks like it would save gas. Maybe paint flames on it! Actually if the paint scheme is continued on the back that would be awesome.

Are you going to put the back up camera on the back? It looks like you need that.

Here is my link to my build.
1993 Fleetwood Flair

Side skirts would be easy if I could find cheap flexible plastic panels to screw on.

I am trying to get a consistent 15 mpg, but I usually drive a little too fast, 60 mph, to get much more than 10.5 mpg. Better "tail feathers" to my rig may be the key.

Cheers, Lee

[orbywan]

Originally Posted by CrazyLee

Orbywan, great job. I really like your rig and your mods. Anything you can do to save gas, even though it's now below $2.00 a gallon is still a great idea.

I have put a Front air dam and wheel skirts on mt 26 ft Fleetwood Flair. Now your design of a "caboose" looks like it would save gas. Maybe paint flames on it! Actually if the paint scheme is continued on the back that would be awesome.

Are you going to put the back up camera on the back? It looks like you need that.

Here is my link to my build.
1993 Fleetwood Flair

Side skirts would be easy if I could find cheap flexible plastic panels to screw on.

I am trying to get a consistent 15 mpg, but I usually drive a little too fast, 60 mph, to get much more than 10.5 mpg. Better "tail feathers" to my rig may be the key.

Cheers, Lee

Hi Lee, my RV is a test vehicle for my camera business. It has two of our Total Vision pan and tilt cameras on the back (two for comparing camera performance side by side) two side cameras, two roofcams on the top for checking A/C housing clearances going forwards and back wards, two dually cams, one looking at each dually set to check for rocks stuck in between the duallies when I'm off road with it (which is a lot), plus they let me check the status of the belly pans when they are installed, and last but not least a hitchcam inside the boat tail looking at the 36" extended hitch, which sometimes is handling a 3500+ pound boat and trailer.

All of that video is managed by one of our 8-camera digital switchers, as well as the quad input 9" monitor on the dash console. Sweet setup. It's funny, I just looked at a 2000 flair thinking about a newer rig, but I like this turbo diesel a lot. The power on hills and when towing is addictive.

Haven't had time to do any more aero modding for quite a while. I took most of the belly pans off to work on the drive train and the added drag has deleted most of the gains brought about with the boat tail. Never enough hours in a day.

I need to re-install the belly pans, add a front spoiler and I'd really like to do some work around the duallies, there is a lot of drag there.

[ennored]

OK. We have two wannabe Aero RV'rs in Michigan. If you were just a little closer...