Aerodynamics of caravan rear end.

Hetho · Senior Member

Aerodynamics of caravan rear end.

Whenarewethere · Guru

If it works and does not add too much weight, unless you can use it as an additional water tank, brilliant!

There is enough information on truck aerodynamics which I'm sure could be adapted to caravans, but care needs to be taken not to make the problem worse, or a secondary problem.

Cleaning will save weight and reduce running costs. An old 747 is about a tonne heavier due to ground in dirt.

mullpadd · Veteran Member

I am having trouble understanding how the pipe at the top of the van changes the airflow sufficiently to minimise drag. Can you add any more info or point me to somewhere that will help.

I like the idea of doing something about the drag.

Hetho · Senior Member

Hello Mullpadd.

If you do an internet search for Vortex/aerodynamics/drag/ on cars trucks and or caravan; or something similar, you will find some answer.

I cant remember where I went now, but the aim was to reduce the vacuum generated by having a square back.

Regards.

Hetho

-- Edited by Hetho on Monday 3rd of December 2018 01:49:34 PM

Aus-Kiwi · Guru

Its alittle about boundary layer . Being round . The air follows around the pipe . It doesnt spit the air causing vacuum . Notice an airplane wing is round at the front , thin to the rear ? They want the air to stay on wing, less turbulence too .

kgarnett · Senior Member

Surely the same aerodynamic principles would apply to the two vertical edges as well so that shaping these edges may also reduce drag.
Or would it be counterproductive ??

PeterD · Guru

Aus-Kiwi wrote:
Notice an airplane wing is round at the front , thin to the rear ? They want the air to stay on wing, less turbulence too .

An aircraft wing is built that way as that is the best shape to give the maximum lift force to the wing.

After WW2 sports cars were designed with bulbous front ends and tapered rear sections. This was supposed to produce the least drag. Subsequent wind tunnel testing showed that the designers could produce less drag if they changed their ideas. Wind tunnel testing showed that a nose with a fine entry gave the best drag coefficient. The next generation of sports cars then came with wedge shaped fronts and blunt rear ends. It appears that blunt rear ends are not as detrimental as they were previously thought to be.

ps - "airplane" we are not Yanks. It is an aeroplane in Oz

-- Edited by PeterD on Wednesday 5th of December 2018 10:37:34 AM

Aus-Kiwi · Guru

Yep thanks for proof ready my posts . Earplane air wait Flow here is similar to head porting . Look at 4 valve engines . Where two inlet ports merge . Its round . If you sharpen this area to a point ? You loose power .( We did a CNC program on Lexus race engine . Was I interesting in the bigger is not better) . It splits incoming air causing turbulence. Seems strange but the rounded tube will help air flow down the back as the rounded area keep the air or boundary to its surface . Notice any oil leaks are seen on rear way before seeing the real leak ? Leaking oil filter etc . Shows how much negative pressure is behind as ahh ! speed increases . Good ole house brick airo !!

Ron-D · Guru

I really cant see any advantage on sticking a pipe on the back of my van ,it tows well ,most vans would not benefit from adding a pipe on the back as they tow very well anyway...but I can understand where your coming from....

Aus-Kiwi · Guru

Its the vacuum behind this wall being towed . Not so much the towing itself . More economy and keeping back a little cleaner . Like in 80s when station wagons had wind deflectors off sides or roof to push air behind to prevent suction , vacuum causing dust, exhaust to enter or stick to rear .

Hetho · Senior Member

Thank you for the replys, and knowledge.

Im aware its Not Pretty but it was a quick fix for the trip.

Home mid January. It will be interesting to see the fuel economy across the Nullarbo in January.

A good tail wind would be nice but I know it will be from the West In January.

Regards.

Hetho.

aussie_paul · Guru

Aussie Paul. smile

PeterD · Guru

Paul, there was someone trying to flog those to caravanners sometime back. I don't know what happened to them. Maybe someone could shed some light on those.