motorhome aerodyamics

[chefdave]

Hi
another update smoothing out as much under belly as i can. reasults in improved mpg had to quantify but going down hill requires much less throttle almost at point where i csn free wheel. doing a coublr of tweeks underneath and deeping front air by 1" to match lowest point of drag under neath.
Have removed rooftop air con unit luggage rack and rear ladder.
Question would side window delfectors help push air around front camper body from driving cab.
Next job is to sort rear drag which i hope will net a couple of mpg and take exhaust diameter up to 2 1/4" as recommended by members of yotatech forum (am i allowed to mention other forums)

[freebeard]

I don't see that I've posted this in this thread. The idea is that all you need is a 3-4" radius on the front edges to make a sizable difference in the drag of that part. Half-round overlays are used so you don't have to address the internal structure.



Swing the driver's door open half-way and you'll see how big you can make it.

[chefdave]

Hi freebeard
will only be able to do overcab part. front doors when closed are tight aganist camper shell. thinking of using plastic pipe for the overcab. can bond to camper shell using butul tape.

[chefdave]

Hi freebeard again
can these half rounds be used on rear to help reduce drag. Do you need to use 4" or can i go up to 6"
Thanks
dave

[renault_megane_dci]

You certainly don't want the rear to be round.

You want the rear to be straight cut after a tappered portion (check the rear of a Mercedes Sprinter / VW Crafter).

As for diameters of the half rounds in front, you want them as big as possible.

Actually, half round starting at the door skin is best but not suitable at window level.

[freebeard]

Kep in mind this is just me spouting off. That said...

The half-round is a hack to save having to modify the structure of the conversion shell; maybe a 1/4 round that travels with the door? Is that the wind deflector you mentioned?

In back follow Mair:


The curve needs to be gentler because you trying to coax the air back together, not split it apart.

[chefdave]

Hi renault megane dci
do i need to make the rear vertial from top to bottom or from bottom to where the rear body sticks out the furtherest. having trouble posting photo.

[chefdave]

Hi renault megane dci
as i cannot post photo foto bucket keeps crashing. google 1989 toyota dolphin motorhome hopefully this will give you some images to show rear of my motorhome to explain what i mean.

[freebeard]

Buy a junk truck cab, cut the complete door jambs out as wedge-shaped pieces and trim them so they bolt on to your existing cab when you slip them inside the doors. Also shorten the two top legs on the rear view mirrors.

[chefdave]

Hi freebeard
doorskins sound good was going to add a frame to existimg doors and create a wedge shape with fibre glass skin. mirror mounts are going to be changed so that mirrors are hung from bottom of over cab using a 6"-8" pole and 10" x6" mirror instead of two 6" x 6" mirrors. new mirrors hoping to fit a half round to help guide air around them rather than slam into a flat plate.