The 2-Part Aero-Body Concept

[kach22i]

Originally Posted by drmiller100

mclaren mk6, circa 1969, complete with 3 seats.

Your car would be more aerodynamic if you ran it backwards.

I looked up that particular Mclaren and it's a 2-seater, sorry.

My concept car's canopy fits the template, how would turning it backwards be an improvement?

The nose also fits the first part of the template, how would that work better backwards?

http://s184.photobucket.com/albums/x...ransportation/


What I am doing is taking different parts of the car, which do different things and applying the aero-templates.

By maintaining a 2-part concept or strategy, each part can do it's job more effectively over that of globing it all together into one giant compromise. At least that's the theory I'm operating on right now.

[aerohead]

Originally Posted by kach22i

I looked up that particular Mclaren and it's a 2-seater, sorry.

My concept car's canopy fits the template, how would turning it backwards be an improvement?

The nose also fits the first part of the template, how would that work better backwards?

Industrial Design - Transportation pictures by kach22i - Photobucket


What I am doing is taking different parts of the car, which do different things and applying the aero-templates.

By maintaining a 2-part concept or strategy, each part can do it's job more effectively over that of globing it all together into one giant compromise. At least that's the theory I'm operating on right now.

The thing about the 'template' is that it has to be taken as a whole.You can't divorce parts from it.
*Developed from a body of revolution,it has leading edge radii everywhere
*It has body side camber
*Its roof is fully integrated into the body.there is no distinguishing where one begins,and the other leaves off.
*The windshield in fully integrated into the body.
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*on your model,you have no vertical leading edge radii.
*all the air is vectored over the vehicle,which will cause attached vortices at your front edges where the air is much slower.
*you have a minimum pressure just ahead of your fender crown,then again just ahead of max cross-section of the roof.
*the roof opening cannot support flow,so closing it is good.
*on the top sides the flow is flowing horizontal and the roof is inducing a downwash.There is no radii where the air would flow into the void below the wing so you're going to see a vena contracta there,with some of the flow choked off and extreme turbulence,which will kill the wing efficacy.
*low base pressure of the wake may communicate forward into the void which may induce spanwise flow on the top sides of body which in turn may induce attached longitudinal vortices as the side flow attempts to flow upwards over the top an into the void.
* since there is no plan-taper and side top is parallel to ground,the air will detach facing directly aft with a distinct burst,forming a rather large wake of low base pressure,as there are few surfaces for pressure regain.
*the open wheels aren't completely flush,so there'll be interference drag there.
*with no diffuser,you lose some opportunity there as well.
*Jaray's most effective combination form was with the very narrow car.I think it measured at around Cd 0.20.And it had very generous radii throughout.
*with you width and hard edges you could be pushing Cd 0.5+ territory.Without a tunnel it's hard to know.
The car would be a blast to drive but I don't know that you'd be rewarded at the pump.

[ERTW]

George is using valid logic. He can apply the template wherever he can, knowing that it will help, but obviously not give him full benefit. I've shown that a brick with rounded edges is ~70% worse than an ellipse, and sharp edges are worse still.

fyi, a circle has the smallest perimeter for its area - hence the lowest skin friction geometrically possible. An ellipse is the next best cross section wrt aero.

All of the details that Phil mentions are important. He's shown many times how aerodynamic basic shapes go to pot when they make a full sized prototype.

I was literally thinking of CFDing a very similar shape last week. Your car is a spitting image of the 1980's group C cars...like the Porsche 962, minus the German flag

Are drag, lift, and f/r distribution (pitching moments) a big concern for you?

[kach22i]

Aerohead, it took me a while to do this, it was the only way my brain could process all the information. You need a large computer screen or a viewing program which allows you to zoom in and out a lot.

Proper viewing could be done with the larger original file, which I can e-mail to anyone willing to send a PM with an e-mail address (or just e-mail me). Unfortunately Photobucket shrinks down the files for easier posting and this limits forum reading and detail.

Mark-Up Reply
Industrial Design - Transportation pictures by kach22i - Photobucket


Pre-Mark-Up Copy:


ERTW, thanks for posting that car, a real inspiration. I need to replace the long tail Porsche 956 on my "Inspiration Board" with the Porsche 962.

A short tail 962 with rear wheel skirts, very interesting.
http://classic-auto.fr/porsche-962-a-vendre-1890

Originally Posted by ERTW

Are drag, lift, and f/r distribution (pitching moments) a big concern for you?

Yes, look at the links in my signature, I very much favor the safety of down-force over anything else. My aero-mods have left me with zero gains because what ever I gain, I also take away for added safety.

[kach22i]

I took one of the more lingering concerns and turned it into a simple mark-up.

Industrial Design - Transportation pictures by kach22i - Photobucket

[drmiller100]

1969 McLaren M6B GT Images, Information and History | Conceptcarz.com

when it was a kid hauler, it had 3 seats.

[ERTW]

from the rear view, if you can imagine the template being taller in the middle, and lower at the edges - like an ellipse. you have the exact opposite here. you have high pressure in the middle, and low pressure above the fenders. air will be streamlined around the greenhouse. as aerohead said, you'll have vortices off the front fenders, and twin counter-rotating vortices coming off the rear fenders. having a flat trailing edge will kill two vortices.

imo, safety is not an issue here. a racecars' biggest problem is that wings that generate enough downforce at low speeds generate TOO much at high speeds. downforce is not linear with speed...so the car handles differently at different speeds! imo that's more dangerous than a little lift. your rear diffuser goes a long way to kill lift. a front splitter and perhaps a small rear spoiler should be more than enough.

how fast WILL you take this car? downforce at 150 mph is purely academic if you only take it up to 75. the biggest reason oem's look for zero lift at highway speeds is to reduce vortex drag, and boost fuel economy. it is NOT a stability issue at typical speeds. i'm saying that you can style it any way you want without causing problems.

[aerohead]

Originally Posted by kach22i

Aerohead, it took me a while to do this, it was the only way my brain could process all the information. You need a large computer screen or a viewing program which allows you to zoom in and out a lot.

Proper viewing could be done with the larger original file, which I can e-mail to anyone willing to send a PM with an e-mail address (or just e-mail me). Unfortunately Photobucket shrinks down the files for easier posting and this limits forum reading and detail.

Mark-Up Reply
Industrial Design - Transportation pictures by kach22i - Photobucket


Pre-Mark-Up Copy:


ERTW, thanks for posting that car, a real inspiration. I need to replace the long tail Porsche 956 on my "Inspiration Board" with the Porsche 962.

A short tail 962 with rear wheel skirts, very interesting.
Rare : Une Porsche 962 à vendre ! - Classic Auto | Actualité Classic Auto


Yes, look at the links in my signature, I very much favor the safety of down-force over anything else. My aero-mods have left me with zero gains because what ever I gain, I also take away for added safety.

I was looking at the short-tail 956.Porsche was reporting Cd 0.42 for that car.I think that a little bit of side camber and radius in the front and down the top edges would show a measurable drag reduction.I think they also show a smidegeon of plan taper at the rear.
I know you've got a ton of work wrapped up in the model,and she'll be a hoot to 'drive',and just a little 'finessing' would show at top speed and at the pump.
I'm not real cerebral and it can take for ever for some things to creep into my psyche.And I'm certainly not slamming your work.
Without the extra views of the 'Template' I kinda went off half-cocked,opening the door to some confusion,so I hope you and any others will accept my apology if I've created extra work and headaches.If we all lived on the same street we could just visit each others shops 'n 'see' what one another was 'talkin' about.

[kach22i]

Originally Posted by aerohead

Without the extra views of the 'Template' I kinda went off half-cocked,opening the door to some confusion,so I hope you and any others will accept my apology if I've created extra work and headaches....

No problem, just trying to learn. I took what you said to heart, but did write off about 90% (no offense).

What did stick is the issues with the rear deck.

There are issues there, even more so when I tried working on several alternates per the commentary. I'll post some of that work when I get a chance. Real life keeps interrupting, have to work to pay the bills, and I have to remember this is just for fun.

I must have Porsche on the brain...........see some similarities?

Industrial Design - Transportation pictures by kach22i - Photobucket

[Grant-53]

The flat sides and sharp edges do need to be rounded. This is hard to do on a model made of Coroplast. I suggest cardboard from cereal boxes. Try some paper model techniques.