Class a motorhomes aerodynamics

[aerohead]

The 5-Cyl, BMW, Diesel-powered VIXEN, morphing-roof RV is perhaps the gold standard for mpg.
It's around here somewhere. If I could find it, I wouldn't be able to link it. Sorry.

[freebeard]

It doesn't have to be hard.

Vixen
RV

The Vixen was a recreational vehicle designed by Bill Collins and built from 1986 until 1989. A total of 587 Vixen motorhomes of three different types were built: the Vixen 21 TD, Vixen 21 SE, and Vixen 21 XC. Often noted as the "Driver's RV", it has an exceptionally low center of gravity and wide stance for an RV.Wikipedia

[aerohead]

It's not 'hard', it's 'impossible.'
Something's happened in the last week here at EcoModder.com.
I can't even share my own work.

[freebeard]

I see others have the same problem. The 'conspiracy theorists' are suggesting a total Global shutdown for the Midterms.

How many devices, OSs or browsers have you tried? I'm fortunate, but alternatives available to me would be Vivalds, Midori or GNOME

[sregord]

Originally Posted by aerohead

Yeah, 14.5-mpg got everyone's attention!.

Yes it did,
apples & apples... Orbywan started at 13.1mpg... & upped it to 14.5/15.97... there's the 10% or 22%. if I could get (starting with 8mpg) 9.75mpg...or more?... this is encouraging

[aerohead]

Looks like I don't even have permission from the administrator to say thanks to a member.

[freebeard]

The Following User Says Thank You to sregord For This Useful Post:
aerohead (Today)

I don't think the mods are in total control.

[sregord]

I'll keep posting...see if what I find is helpful.
It may be redundant ...but where I have found the EcoModder Forum Link(s) I'll include them.

I did a quick read thru the Orbywan's RV mods(Boattail & belly pan), very nice builds, a true craftsman.
https://ecomodder.com/forum/showthre...d-e-18151.html


...surprised that the underside smoothing didn't have more impact.
https://ecomodder.com/forum/showthre...n-s-18427.html

Being familiar with racecar aerodynamic history, and changes from the early 60s(if it LOOKS aerodynamic) to Jim Hall's Chaparrals of the late 60s...and then the crazy downforce numbers of the late 80s(Nissan blowing tires & Spice collapsing suspension components) Mulsanne's Corner: Road Atlanta 1992, Rough and Tumble, attributed mostly to the underbelly's relationship with a diffuser. Today's endurance motorsports, is designed for "enough" downforce, and more efficiency(limited fuel capacity) than ever. https://www.racecar-engineering.com/...ta-ts050-2019/

How to connect any of this to a rounded corner big box/brick is a challenge.
We are working with something that is not <3" off the ground, or moving at over 75mph. ...but efficiency is what the goal is, not making the vehicle aerodynamically heavier.

Regarding the BellyPan: "pulling" air thru the underside with a <15*(degree) angled diffuser at the rear, with strakes ...extended into the(now revised bottom) boattail?. The other issue IS the "in the way" straight axle & rearend. Mulsanne's Corner: 1991-1993 Toyota Eagle MkIII
Don't you wish you could afford carbon fiber?

Regarding the Boattail addition, nice, clean, updated... obviously functional. Again Orbywan, a real craftsman.
It would be interesting if a measurement of the constructed angle from the sides & top is available. For reference... the NASA data:
https://www.nasa.gov/centers/dryden/...ain_H-2283.pdf
...doesn't reference a "best" boattail angle from the side or top. I did a little more checking and found:
https://doi.org/10.1155/2020/7580174
and
https://www.vortaflow.com/consulting...0reduction.pdf
The angle needs to be around 16* before separation of airflow. Funny there's that 15-16* again. I saw Aerohead had mentioned this number. 20-22* is too much but maybe less important at <75mph? Question: Does a curved side/top "inflated" boattail basically compound that 15* to a point? Has the group found more info about this?

[freebeard]

Thanks for providing links to what you find helpful.

Has the group found more info about this?

I can't find the thread, but I've fallen into disagreement over 'angle' vs 'tangent'.

The Ahmed body has a break angle and a flat afterbody. The Template is a compound-curved half-body of revolution.

[sregord]

Originally Posted by freebeard

disagreement over 'angle' vs 'tangent'.

Ah...sorry ...been a long time since trigonometry.

Originally Posted by freebeard

The Template is a compound-curved half-body of revolution.

https://www.goldennumber.net/wp-cont...hi-squared.gif