Aerodynamics

[Richie]

This is a question that I posed and nobody answered in the last thread about aerodynamics. Just thought I'd repeat it in case anybody wants to have another go:

 

Do you get less drag with a roof on? What about with half doors rather than full doors?

 

This is in my 1.4K series.

 

Go on dare ya to reply.........

[Matt Prior]

Alrighty then:

 

A roof will reduce the drag co-efficient by a bit, because it promotes laminar airflow to the rear of the car. A flat plate (like the winscreen) is as bad as you can get for aerodynamic efficiency.

 

However, the roof would be better still if was fitted flushly, not by press studs, and was rigid so it didn't flap about in the breeze.

 

Doors should be used with the hood to reduce drag, as the roof with no doors is like any other open car window.

 

Without the roof on, whole doors are likely to be better than half doors, which are better than nothing.

 

Unless, you remove the windscreen, then half doors are better than full doors (especially as you'd have nothing to attach the full doors to teeth.gif).

 

Better still though, remove the windscreen, rollbar and spare wheel, sit as low as possible in a half-doored car, remove the headlights and affix teardrop style enclosed fairings around the front and rear wheels (like on a light aircraft), reduce ground clearance to an absolute minimum, slap on a flat aluminium plate to the bottom of the car and fit a rigid tonneau.

 

Result: you'd have an ugly car with a still-appalling co-efficient of drag. smile.gif

 

[Richie]

Thanks for the useful advise Matt.

Unfortunately, the suggestions for the 'ugly' car I cannot adopt as this is for a non-roadgoing car, (races in 750MClub) so regulations prevent the no windscreen etc suggestions.

 

I will invest in a hood though, its a bloody nightmare racing in the pouring rain with no hood; you get soaking wet in your race suit which trebles in weight, and you can't see a bloody thing (not a good idea when doing racing speeds whilst virtually touching the car in fornt).

 

Therefore, does anybody have a hood for sale?

[Blatman]

Putting the hood up won't help with visibility at all............

Unless you use the heater and electric screen to keep all the condensation at bay. Just put the doors on and resign yourself to getting wet.

[Richie]

I also imagine that you would have to look at the gains in aerodynamics against the weight of the roof!

[EFA]

Throw the screen away and buy a R500/JPE one.

 

Weather gear is for wimps.....

 

 

AW

 

Arnie Webb

Organiser- L7C Le Mans Trip

[Slipper man]

....like me!