Over and Under or around the sides

[Ciro Pabón]

Caramba, slimjim, if I had kept the "Member of the week" thread alive, you certainly would had earned the distinction. Better yet, "Member of the year".

55% of drag is a lot, a lot, a lot. I guess slimjim should be made honorary member of the team. I would add a decal with his name, if the shape he suggest were adopted...

Thanks for the video, GPDR, nice.

Is the diameter of the wheels regulated? I would go for a car as long and as low as possible (taking in account the extra weight you get for departing from a "spherical chassis" which I think would be the lightest), those wheels are really high.

[Gecko]

Excellent work, slimjim! =D>

Out of curiosity, since fences are an easy modification to the current car, would it be possible to add those to your model at the first third of the length just to see if they have a desired effect?

[greenpower dude reloaded]

WOW slimjim that's incredible. I can't thank you enough!!

I haven't really said much about this before but on the website under sponsors we have a "knowledge sponsors" section http://horsfallracing.co.uk/Links.html which i try to include all the people that help out. Carlos is already on there and there is plenty of space for more Conceptual is heading the right way about it as is Slim Jim, checkered and a few others.

Let me know what format you can accept 3D drawings in, I've got a couple of nice ideas i'd like to see tried out. Ideally i think we should aim for a similar but much smaller to this



Our car is half the width and about 150-200mm lower. the drivers from that team reported not being able to see us sneaking up on them.

No minimum size on wheels but rolling resistance accounts for a lot and there aren't any decent tyres for wheels for any smaller than 16" we switched from 20" last year to 16" we could get a little closer though. we've got it down to 15watts per corner where as most other teams use tyres that are 28watts at the same speed

deffinately something we have to consider though ciro

[wesley123]

Maybe a flat shape would help?

it can certainly help to make the car as compact as possible, so really flat, it is used in the solar cars too, maybe you evne have to make boubles on it to fit the driver :p

i think that slimjim cna help you really good with cfd tests, so maybe, if he thinks its alright you cna send drawings to him and he can help you get the aerodynamics ok?

i think a factor of drag i that the car is really fat, the car i saw behind was much more slimmed down in the small film.

the car is possibly too wide and that creates the drag, also the sharp endges do actually the same, a real rounded car would help much more, so print that in your mind :p

[greenpower dude reloaded]

It's something we have considered wesley problem is it means the cars have a tendancy to roll over, with my little sister driving all of a sudden I become less interested in that route.

Here is my initial design, needn't really take too much to mould this shape..


Running out of time and with our opinions changing rapidly we decided to reuse las years chassis and came up with this...


ran even tighter on time and NEEDED to be at the first race the fundementals of the chassis stayed the same but the body shape had to change.

[CarsonAu]

Have you ever considered a three wheel design?

[greenpower dude reloaded]

Banned unfortunately, Have built 3 wheel cars for the shell eco marathon though, got 2904mpg out of them
http://horsfallracing.co.uk/Shell%20eco.html
Fully enclosed are also banned, had fully enclosed 3wheelers have been an option I could have made something VERY fast.

[greenpower dude reloaded]

Ok! so somewhat predicatbly I'm running out of time to get a new body finished/ started in time for the commence of the main season so, what should I do to modify this current body.



SlimJim posted some excellent pictures that displays where the high and low pressure areas lie on the body at speed. So i'd be really interested in your suggestions on how to manipulate the air. It's not something I like doing i'd much rather let it flow naturally than trick it.

Fences were mentioned before which should stop the air detaching from the side but is there anything that can be done to stop the really low pressure area at the front, bearing in mind i can't round anything off.

As a reminder of what it looks like in the wind tunnel here's the photo SlimJim Posted

[Carlos]

How about mounting a 'wing' to the rear to lengthen the rear body work profile to imitate a very long 'tail'? Maybe use fences the full length of the chassis. Looking at slimjim8201's modeling grahics, his idea of a front 'chin' spoiler (spliter?) also looks like a good idea.

[flynfrog]

How about mounting a 'wing' to the rear to lengthen the rear body work profile to imitate a very long 'tail'? Maybe use fences the full length of the chassis. Looking at slimjim8201's modeling grahics, his idea of a front 'chin' spoiler (spliter?) also looks like a good idea.

both of these will only add drag

you could fair in the drivers head

have you looked at the bottom of your car it may or may not be worth it to make this part of the car smooth not sure what you have down there.

also your seams in the body are adding a large amount of drag

[Ciro Pabón]

What about adding a bumper shaped like a wedge in the front? I mean, ahead of the low pressure zone. Would that increase drag too?

Intutively, it seems to me you do not need a wing profile (in a lateral view of the car), with a blunt front, but a missile profile, with a needle-like front. Something like this:



If this bumper is kind of an extension (you say you don't have the time to modify the body) you should try to build it from light materials. Perhaps a bare bones frame and plastic film cover. Slimmjim COULD check how much (if any) it reduces drag, and you could compare that number with the "drag" of the extra weight.

If it works, maybe you could make it narrower than the car, to see if you can diminish those high pressure (blue) zones on the front of the lateral panels, like this:



Now, watching the image, perhaps I drew it wrong: the shape (I imagine) could be tangent to the front of the chassis, and maybe (it it works in the CFD) it needs a couple of wires for better rigidity of structure, from the center of the top edge to the front corners (the frame elements would be lighter). It seems like a weekend project to me...



btw, nice paintjob, GPDR.

[flynfrog]

What about adding a bumper shaped like a wedge in the front? I mean, ahead of the low pressure zone. Would that increase drag too?

Intutively, it seems to me you do not need a wing profile (in a lateral view of the car), with a blunt front, but a missile profile, with a needle-like front. Something like this:

A missle is super sonic this car is not

a blunt front end is ideal in the case. I would go through a NACA book for an airfoil that fits your needs then work from there.


Try to find a book called "The Leading Edge" BY Goro Tomoli

I think I butchered his name.

It is about building ultra low drag solar cars and how we arrived at the various shapes.

[Ciro Pabón]

Thanks, flyn. Do you have any links for a little reading on the subject of blunt fronts for dummies?

[Steven]

Fences were mentioned before which should stop the air detaching from the side but is there anything that can be done to stop the really low pressure area at the front, bearing in mind i can't round anything off.

I still think the best thing to do would be to round off the left and right corner of the nose. While increasing the pressure at the sides it would also reduce the pressure a little bit at the nose cone.

Would it not be possible for you to construct this by filling the front corners up with construction foam from the inside? That would be of low weight and allows you to cut away the corners and then paint on the hardened foam.

ps: nice thread

[Belatti]

A missle is super sonic this car is not

After this forum contributions, I have my doubts