16 replies to this topic

[robroy]

Hello everyone.
I'm thinking about a future project which is to be a frugal but fun single seater car for road and track use. It will have fairly narrow tyres, weigh between 400 - 500 kg (spaceframe), have a 1.0 to 2.0 litre 3 cyl turbo or 4 cyl engine and between 150- 200 hp (sorry phantom2 - an LS2 V8 won't fit).
I'm looking for an 'efficient' aero design with as low drag as possible but also a little downforce at high speed (say 100 kg at 120mph). However, ride height must be at least 140mm with no skirts (due to speed humps and kerbs etc), so will be out of ground effect 'range'. With all the recent activity over l/d I'm hoping some more learned people may be able to point me in the right direction, and let me know if I'm barking up the wrong tree.
A quick drawing to give a rough idea (suspension, not shown, will be pushrod /wishbones)



This first idea is to start with a simple fully enclosed body and no wings, but with two tunnels down the middle. I'm thinking this should reduce the front drag(?) and the rear drag(?) and possibly give downforce opportunities, but I'm still pretty vague on tunnels. Will the tall ride height with that extra layer of air underneath reduce any downforce to non existant levels? Also, will the extra surface area reduce any drag improvement to nil? Would high speed stability be increased or not change? Would I be better off just sticking to an 'unmodified' enclosed body?
Or would I better off trying to improve on the open wheel design with much less weight and wheel covers to reduce drag and a couple of wings to provide downforce:



Any suggestions on which might be best or variations would be welcome.

[imaginesix]

Not one of the 'learned people' but the first design doesn't have anything to generate downforce. The venturi tunnel appears to be closed so any low pressure it causes under the body shell will be nullified by the same low pressure acting on the top surface of the floor of the car.

[robroy]

Yep. I've confused myself somewhere along the line. Don't want to be speeding air up and making an area of low pressure just above that top section of floor do I. Quite the opposite. Rethink required!

[Paolo]

Also, "cutting holes" in body will not decrease drag. As you feared, increased friction drag from area will (more than) offset any pressure drag reduction.

[scarbs]

If you want a frugal car in terms of build cost then ditch the enclosed body idea. If you want some downforce then go for simple wings which can be bought from motorsport suppliers, they can even tailor them your downforce target.

I’d say stick with open wheel design and stick on some wings

[robroy]

Thanks for the advice chaps. Think I might keep it light and simple and go for an open wheel design.....

[cheapracer]

Originally posted by scarbs
If you want a frugal car in terms of build cost then ditch the enclosed body idea. If you want some downforce then go for simple wings which can be bought from motorsport suppliers, they can even tailor them your downforce target.

I’d say stick with open wheel design and stick on some wings

Disagree, enclosed basic coke bottle easy to do and you can hide everything underneath.

For example, with open wheeler everyone will expect you to have pushrod suspension.

Go to sports car network and look around the older cars in the chassis section http://sports.racer.net/

[NRoshier]

Go and purchase Katz's book racecar aerodynamics...it is very good and will help. You will also see the l/d difference between enclosed body and single seater,

[robroy]

Great website!
Lots to look at, and more relevant to me than the excellent Mulsanne corner.
I was going to get Katz Aerodynamics last year but the shop only had McBeath aerodynamics, which turned out to be a bit disappointing. Just ordered Katz via Amazon.

[NRoshier]

Katz is a lot better and deals with whole car aero.

[Powersteer]

Just out of curiousity, with the amount of bodywork planned, is this something is able to drive to track days and probably a short dart to the nearest store?

[robroy]

Yep! Maybe the odd longer journey if I can find enough space for a small bag. Think I might stick to open wheel design for simplicity as it'll be my first time making all the bodywork.
Katz book is very good by the way.

[cheapracer]

Originally posted by robroy
Yep! Maybe the odd longer journey if I can find enough space for a small bag. Think I might stick to open wheel design for simplicity as it'll be my first time making all the bodywork.
Katz book is very good by the way.

..and build it from square tubing, makes everything a lot easier and mounting bodywork a breeze.

[NRoshier]

glad you though Katz was worth the read.

[Ray Bell]

If you go 'openwheel' with neat cycle guards, then you can support the front end of the front ones with wings across from the nose. You could probably do something similar at the rear, but maybe at the top.

As for luggage space, if you look around you'll find room. The real problem is going to be stashing the spare wheel.

[robroy]

Two lines of thought on front cycle guards:
-Fully enclosed, with an open rear edge and attached to the hub. Extra weight on suspension, less room for front wing and more potential to look odd (or odder), but lower drag.
-Or, as you suggested, guards similar to the drawing attached to bodywork via wings.

I like the idea of connecting rear wings via the rear and top of the guards, but this may be too close to the driveshafts and suspension to produce that smidgen of downforce I'm after. May depend on how and where I mount the radiator (currently undecided, but probably two low down, mid-mounted radiators in sidepods).
I'm still skimming the web for ideas, but there's obviously not much on open wheel race cars with cycle guards (fantastic Caparo excluded).

Spare wheel isn't required for the SVA test in England, a tube of tyre weld will do for legallity.

[jeremy durward]

this one is from the us i think