motorhome aerodyamics

[skyking]

It is also easy and very nice to replace the roof air with a faired skylight. I really appreciated all the skylights I have had in my trailers. The small bump in frontal area is a small price when you fair it properly.

[aerohead]

Originally Posted by chefdave

Hi
could you draw a rough sketch of door fairings you where talking about. roof next spring will have air con unit and front sky light removed. mirrors have been thought about. thinking of mount ing on bottom of overcab unit and some sort of drag reduction fitted. this hopefully will remove the scaffolding holding mirrors at present. Mirrors will go to 10x6 instead of 4 units of 6x6.
Thanks
dave

Here is an image of what NASA did to a Ford Econoline van.The large radius nose sections of the van would be placed in front of the squared-off leading edges of the RV.
They could be 1/4-section members,hinged at the outer edge,and swung into place and latched after the doors were closed,or attached to,and move with the doors (which would be safer if you had to egress in an emergency),with the upper section of Plex or Lexan so you could see through it,just as NASA has done.
Here's the photo

[chefdave]

hi
had put aerodynamic tool on photo of my motorhome. ummmmm not fesiable to do boat tail but can alter back to make it aero dynamic make upright courners curved add a small roof extension to carry air flow away from rear wall. hope to design some sort of diffuser on bottom rear to aid air flow and cover grey water tank found some lawn edging on ebay made out of recycled plastic an is 1mm thick by 165mm. got some bracing sorted out. going to add skirts and front airdam of this lawn edging. suggestions on how to cover rear wheel arches to allow for change of tyre and if nessasscery rear brakes. underbelly on engine looking to fit sump guard and follow on from there.

[renault_megane_dci]

Nice project !

So which is the most streamlined approach for the does to cabin section ?
A nice fat radius or a tapered angle ?

If it happens to be the angle, you can even use standard doors on a dummy frame for a little more room and a nicer look and fully functionning doors.

[aerohead]

Originally Posted by renault_megane_dci

Nice project !

So which is the most streamlined approach for the does to cabin section ?
A nice fat radius or a tapered angle ?

If it happens to be the angle, you can even use standard doors on a dummy frame for a little more room and a nicer look and fully functionning doors.

The air prefers the acceleration/pressure profile of the radii compared to a simple angle.If you're forced into using an angle due to some project constraint,it will be better than a hard 90-degree corner.
If you purchase a couple ice cream cones and take them up to the laboratory elevation of the Eiffel Tower and drop them onto the American tourists below,ice cream first,then cone first,you'll find that the ice cream first type will fall at twice the velocity as the pointed ended one.
The blunt,convex-hemispherical nose is the benchmark for lowest drag in sub-transonic flow.

[renault_megane_dci]

Sure, that was my first thought but then I wondered because it is a transition area so the flow is along the (half)door then turns around then back to the initial direction.

The door at an angle with appropriate radius everywhere possible sounded like a smoother transition in the full system that is the motorhome.
But I assume I was wrong ...

[aerohead]

Originally Posted by renault_megane_dci

Sure, that was my first thought but then I wondered because it is a transition area so the flow is along the (half)door then turns around then back to the initial direction.

The door at an angle with appropriate radius everywhere possible sounded like a smoother transition in the full system that is the motorhome.
But I assume I was wrong ...

There's no 'wrong' about it.
The original cab-top air deflectors for tractor-semi-trailers did the angled panel and to good effect.
You could probably put the RV in a wind tunnel and actually 'open' the doors with the windows rolled up,at varying angles until you found the degree of 'opening' which produced the lowest drag.Then fashion 'spoilers' which mimic'd the open door.

[chefdave]

Hi
have fitted some rear wheel covers and altered the front of my dolphin. i had a full width bull bar on front. made a cover out of 3mm ply that covers radiator grill. this was fasten to front of bull bar. so nowair that would normally go through grill is now forced over the bonnet. as the bull bar keeps the plywood away at top by 1" and 5" at bottom. also air can get in around the sides for cooling. hope this makes sense. if not i will take photos and post.

[renault_megane_dci]

Let's hope you don't run in cooling issues.

Do you plan on using the dolphin anytime soon ?
I am curious of of the evaluation of aero mods on such a big vehicle

[chefdave]

Hi
use my dolphin as a daily runner. cooling at moment is not an issue but will moniter it. as air temp is just above freezing don't expect any probs until spring. initial feeling is good. can feel overdrive coming in at 45mph. when gliding up to a junction i can lift off accelerator a lot earlier. have log fuel condumption on every tank since i bought it. gone from 13mpg to best 16mpg. am trying to reach 20mpg. any higher is going to be very difficult. toyota camery with same engine finds it hard to reach 30mpg.