Basically, can any one give me some info on why/why not to bother with this?
I am aware of the basics, but was wondering if it's worth sheeting the underside, and poss adding something diffuser-like at the back? The plan
was to do this and run with roughly 25-30mm of rake on the car. My chassis is book, but 4" wider throughout and 4" longer in the passenger
bit, if it makes any difference.
FWIW, i intend to try this. The only difference is panelling the engine bay (not always easy) and maybe adding a few aerodynamic touches front and
back. You car should always be nose down a bit anyway.
I have been thinking of this as well- but if the underside is covered then there has to be lots of venting on the sides or bonnet.
Dale
Panelling underneath is going to be fairly easy. I'm planning on putting the engine in so i don't have to cut rail C. This also puts it inside the chassis, and that's with the standard sump on it. I was also going to have vents in the bonnet due to using twin dell'ortos and having (prob) the exhaust come over the chassis. Since i'm going De-Dion, i was going to panel literally everything, from the nose to the tail. This will, however be a fair bit of hassle. So, what if any benefit is there to be gained?
I would have thought that with the ground clearance required on a road car ( to clear speed bumps etc. ), the only benefit of totally sheeting out the
bottom of the car would be a cleaner engine bay.
F1 cars that take advantage of groung effects have a ground clearance of next to sod all. I am willing to stand correction but I think they run at
about 20mm clearance. They are not limited to 70mph either.
Unless you are thinking of a seriously quick track car I wouldn't bother.
As I said though, I am willing to be corrected, if wrong.
If it's of interest, this car on eBay has side pods, presumably intended to provide some down force
eBay Link
The car used to live just a few doors along the road from me (though I never met its owner)
That looked quite nice.
With those side pods you could fit really sexy non SVA compliant mirrors.
paneling the bottom of the car is a good idea aerodynamically as it reduces drag. Air flows over the top and the sides of the car bue people forget
that there is air underneath as well.
as for ground effect. You only start to get this with ground clearances of, I don't know, 30mm or less. It also helps if you have side skirts
that are closer to the ground. The curve up at the back, the rear difuser, acts like an upside down wing. the air flow is lower underneath the car
greating down-force.
The angle and curve of the rear slope is critical it drag and downforce. A lot of testing, preferably in a wind tunel, to get it right.
If you panel under the engine bay, you will need to make some vents to let the air out that comes in to cool the radiator. Otherwise you might find
your bonnet lifts up at speed.
I don't pretend to be an expert but I thought that the car had to sit really low to the ground (6mm) reasonable downforce through side pods and venturi effect under the car. I suppose the diffuser would add a little.
Doubt they provide downforce, but will clean up the flow off the front wheel and over the rear arch, reducing drag a little. (edit: referring to those
westy sidepods). As confused said a road going seven has way too much ground clearance to get any significant ground effect. The tapered front is
also a problem as there isn't gonna be much air getting under the car. To get any significant ground effect you'd want to run a tiny ground
clearance and maybe even extend your flat floor straight out at the engine bay rather than tapering in and have side skirts to keep the air under the
car. I recall an old CCC article on some SBD (I think) westy that had an extended floor for ground effect. This was of course a super low and fast
racer. No point on a road car at all.
Still, a fully pannelled floor is certainly worth doing just to reduce turbulence and drag, and may help reduce high speed lift - just dont expect
loads of downforce.
A big problem is front end lift on a seven, casued mainly by the front arches(especially if you have horrible clam shells!) and blasting air through
the nose straight into the engine. In the new Caterham CSR, for example, they eliminate this with a vent in the top/rear of the front arch which lets
out all the high pressure air. You also want to run the front arch as close as possible to the wheel. And it also ducts all the air going through
the rad up out of the top of the nose.
I'm doing the nose and front arch ducting on mine and will panel what I can underneath within practicality. Still not expecting downforce
though.
Liam
[Edited on 2/3/06 by Liam]
KAK Liam, I've just got some clam shells for a retro look!
:
[Edited on 2/3/06 by Confused but excited.]
Cycle wings give a surprising amount of lift. It is caused by the top being curved. It is basically a wing. The curve causes the air over the wing
to go faster, reducing the pressure over the wing, sucking it up. I'd never thougt of puting vents in the wing. The low pressure would just
suck air through the holes rather than giving lift. Mind you, it would also suck rain water and mud through the holes. You could always fit a little
spoiler on the back of the wings
Um dunno what KAK means, but hope i didn't upset you! Clamshells aren't to my taste but plenty will disagree. Each to his own and all
that. But it's true that they act like a big set of wings so just make sure they're sturdily mounted. Wont be a danger or probably even a
noticable handling defect on a road going car, but you wouldn'r get a racer using them.
Liam
Does this all really matter? The whole point of a 7-style car is that it's an over-sized go-kart that goes like hell up to 100mph, and corners
like it's on rails.
Life's complicated enough, without making life harder for yourself! 
(but don't take my views too seriously - do whatever rings your chimes...)
David
quote:
Originally posted by David Jenkins
Does this all really matter? The whole point of a 7-style car is that it's an over-sized go-kart that goes like hell up to 100mph, and corners like it's on rails.
The car is mainly for road use. I kinda forgot about being so low to get any real effect. As said by Liam, the wings will somehow have vents in them
and the nose cone will also basically be a tunnel for the rad to sit in with the air going up and out the top. Still not quite sure how i'm going
to make all this yet! Thanks for all the help, and at the least i'll have a cleaner engine bay!
Off the top of my head I would think there would be a distinct aerodynamic advantage in panelling the underside of a book chassis from the rear
bulkhead to the back of the car. Not so god for IRS as you would have to allow access for the lower bones in droop.
Mick
Liam,
KAK=POO, more polite than; "Oh SH1TE!"
radiator could be arranged in a similar manner to ultimas, though the styling would be affected.
I've managed to get my little rad tilted forward in my chassis (ultima style) ready to be ducted out behind without any mods to the nose. Quite
a small rad though, but 2" thick and even made of copper so should be up to the job with the air flow it will get. Off a fiat 126 if I
recall...
Liam
Rescued attachment DSCF0027.JPG
From recent threads, I will do these :-
1) wheel-hugging front cycle wings from 45^ in front of wheel to 60^ behind wheel (possibly vented)
2) radiator ducted out through top of nose cone
3) flat panelling underneath nose to tail (may need cut-out for sump)
4) wheel-hugging rear cycle wings
5) brookland screens (passenger's removable)
6) toneau cover for passenger's side
7) enclosed boot
8) rear diffuser
9) compact headlamps
10) inboard coil-overs
11) aero tube wishbones
and sliding skirts for real ground effects
Sure some funny people on here
First they decide to build a 7 style car, which has the aerodynamic shape of a brick, and than they start talking about the aerodynamics of ground
effect.
I would not waste any money/time on this but invest it in the comfort (seats-upholstery etc....)
On the other hand.....it's your money/time so spend it the way your most happy about it
Cita
Why not build a different style car that is designed with aerodynamics in mind? Surely this will be easier
quote:
Originally posted by cita2
Sure some funny people on here
First they decide to build a 7 style car, which has the aerodynamic shape of a brick, and than they start talking about the aerodynamics of ground effect.
I would not waste any money/time on this but invest it in the comfort (seats-upholstery etc....)
On the other hand.....it's your money/time so spend it the way your most happy about it
Cita
Ahhhh...!!!!
But it's our quircky individuality that makes it fun
Mick
I am not happy with a brick. I want a brick with rounded edges, damnit!
quote:
Originally posted by kreb
I am not happy with a brick. I want a brick with rounded edges, damnit!