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-   -   motorhome aerodyamics (

chefdave 11-02-2013 02:51 PM

motorhome aerodyamics
own an american imported motorhome built on a hilux chassis. this was built 24 years ago and when aerodyamics where just starting on main stream cars. i understand my motorhome is an aerodyamic brick. so looking for reasonably easy and cost effective improvments. will take a photo tomorrow and using supplied tool in this forum. looking tofit an airdam at front and down the sides. motorhome body sticks out bothsides from cab approx 1 foot. airdam would run from front down sides to front of rear wheel arch. also smooth wheel trims on rear wheels only. front wheel design makes it impossiable to fit wheel trims. will try to post photos to show what i am trying to explain. or google dolphin motorhome 1989 model.

aerohead 11-02-2013 04:34 PM

I grabbed a image:
a second image
The big offenders are all the leading edges of the motorhome.
*The nose above the cab should be more like an AIRSTREAM trailer or motorhome.Very bulbous,which really helps in crosswinds and guarantees full flow attachment onto bottom,sides and top.Consider having an awning company construct a rolled aluminum superstructure and fabric cover which would mimic (without compound curves) what AIRSTREAM does.
*You would need full-height,12-inch radius fairings attached to the doors themselves which,when closed, smoothed the airflow onto the sides,killing the separation which is there right now.
*Everything on the roof should be streamlined as Orbywan has done with his Ford-based motorhome.
*I streamlined the front of my next door neighbor's Toyota,just like yours,with sheet aluminum grille-block,airdam,with rolled-radiused outers.Since you will at times need all of your radiator,consider blocking only the grille opening which is not directly ahead of the radiators tube and fins.Extend the dam down even with the lowest suspension members.
*Run your side skirts at the same elevation as the bottom of the new airdam.
*The rear wheels could also be enclosed within skirts.
*Consider some length of boat tail after the front is cleaned up,to reduce the enormous turbulent wake which is eating your lunch at the filling station.This wake represents 72% of your aerodynamic drag.

NachtRitter 11-02-2013 04:48 PM

And posted:

Check out a few relevant links here:

chefdave 11-02-2013 06:20 PM

thanks on pointers
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.

redyaris 11-02-2013 09:18 PM

It has been my observation that the underside of pickup trucks are as un-aerodynamic as you can get. Simple flat panels covering much of the underside has quit an affect on fuel economy. On my 2012 Sprinter van my fuel economy went from 11L/100km to 8.6L/100km with a not yet finished belly pan.

user removed 11-02-2013 10:14 PM

My oldest brother had one of thos (1983) but parked it under a Magnolia tree which rotted the camper portion out and we ripped it off. Welded the back of a regular pickup cab on what was left of the cab and put a trailer like this on the back (minus the frame and axles). We swapped the tailgate and the corresponding panel in the front of the trailer to get the fenders to sit over the rear wheels on the Toyota truck chassis.

Later he put a real one ton Toyota rear axle on it and got rid of the dual wheels. It really is a neat looking truck, now 30 years old. Got the engine out of my youngest brothers truck and a 5 speed tranny when the donor truck got flooded in Isabel, 9 years ago.

TNJ Murray: Military vehicles and parts surplus - Trailers - 1987 AMA CO MDL M101A3 2 WHEEL 3/4 TON CARGO TRAILER SER# 5000270249


chefdave 11-03-2013 07:47 AM

hi red yaris
Hi red yaris
what did you use for the underbelly to streamline it. also how did you fix it to the chassis

320touring 11-03-2013 08:12 AM

John O' Groats eh?

I may need to take a drive:-P

redyaris 11-03-2013 08:38 AM


Originally Posted by chefdave (Post 398036)
Hi red yaris
what did you use for the underbelly to streamline it. also how did you fix it to the chassis

I used 1.5mm [0.06"] thick aluminium for the belly pan, which I afixed to the main frame rails with self drilling screw covered with silicon sealent to prevent rust. What you need to do is take a look around under the vehicle and see where it would be conveniant to attach. I would take some pictures of what I have done, but there is over 20cm of snow on the ground.
On one section at the front I instaled a peace of pressure treated wood onto which I could scew the aluminium panels.
I had a sheet metal shop make some angle peaces for the section behind the rear wheels.
What it all comes down to is each vehicle is different and needs its own solution...

skyking 11-03-2013 11:09 AM

the front vent cover only serves to allow the vent to be open in all conditions. If you simply remove that cover and build a very simple fairing behind it, no need to delete.
Same with the roof air. if it is not needed/not functional, it is easy to replace with another low fan cover. A small fairing behind each of those will re-attach flow nicely.
The roof air is typically installed through a standardized 14" by 14" hole.
I picked up a replacement fantastic fan for my bathroom for $126 at PPL motorhomes.
The better unit is about 160, with a thermostatically controlled fan.
I have one of those at the back of our trailer and it is very nice to turn on the fan, set the thermostat and go out for the day.
As the temperatures go up, it only runs as needed to keep things reasonable.

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