BEST + CORRECT Aerodynamic Streamlining Template

[aerohead]

I think that this is the Lange car which inspired the early Porsche sports cars,like the 60K10 which Ferdinand drove between Stuttgart and Berlin before the war.

To the Cd 0.14-16 featureless,smooth model,we'd have to add in all the features drag,interference drag,drag due to lift,cooling system drag,etc..
Also,if you look at the Lange car in plan view,it has extreme plan taper,nearly from the front of the car.Never done in the production cars.


The Volkhart Sagitta V2 is very similar to the Lange body.Cd 0.21.

[Magajgfha]

Volkhart Sagitta is Cd 0.21:
http://ecomodder.com/forum/showthrea...tta-25351.html

[aerohead]

Originally Posted by Magajgfha

Volkhart Sagitta is Cd 0.21:
http://ecomodder.com/forum/showthrea...tta-25351.html

Thanks! I went back and edited the Cd.

[freebeard]

I'm devastated.

[aerohead]

Originally Posted by freebeard

I'm devastated.

*If we pulled the mirrors off we'd be looking at around Cd 0.198
*If we lost all the features drag,we might see Cd 0.18
*By lofting the greenhouse up to Kamm/Fachsenfeld standards we'd be below Cd 0.17.
*A 'retro' version of the V2 with some finessing would embarrass all current production cars,and many low drag concepts.

[freebeard]

Thanks. I was for adding those and pushing further down into the teens.

I guess better than anyone else isn't that bad.

[aerohead]

Originally Posted by freebeard

Thanks. I was for adding those and pushing further down into the teens.

I guess better than anyone else isn't that bad.

yeah,she could really shine.all the right elements are there.her frontal area is a coup all by itself.

[aerohead]

Originally Posted by Frank Lee

There are some horrendous looking, lumpy vehicles (aerocivic, illuminati seven) that claim ridiculously low Cd so perhaps strict adherence to a profile is not as critical as one might think.

I can't speak for Lay,Kamm,Fachsenfeld, Hucho,or others,but the implications of their reporting is,that if you want to approach the drag of the basic body ( around Cd 0.08),that we'd have to be very careful.
If you keep with an 'ideal' contour,then you can just decide on a practical length,then chop the body off there and live with the difference.It's a sure thing.
If we're looking for Cd 0.16-0.15 we have many choices.To go below this threshold requires extra vigilance.

[aerohead]

If you look at the bottom of the smoke trace,it kinda defines where the roofline ought to be.

Here,we can see how VW/Porsche/Audi/Bentley/Bugatti/etc.. is correcting for the pseudo-fastback roofline over the decades

[aerohead]

Originally Posted by aardvarcus

Doing some overlays in the past, I noted that several low drag Toyota cars fit AST-2 pretty well. Honestly the difference between the two templates mentioned is so slight, I am not sure how you would pull off building one versus the other without specialized equipment.

As others have mentioned the AST-2 side overlay template is just a starting point in one dimension, however it is a really good starting point for those of us who wouldn’t have a clue were to start without it.

The hard part is actually going out and building something. It really doesn’t take that much creativity to start with a 2D view/print and figure out a decent (but non ideal) 3D shape that will work for your vehicle and your intended purpose. Personally, I am shooting for a shape that is “not as terrible as it used to be” which is within the realm of my abilities (I hope) and tools (as I am presently wind tunnel deficient). Actually implementing that by building something is where the work is.

There is a top overlay and rear view of the AST-2 vehicle that have also been posted, which with a bit of imagination describe the AST-2 “vehicle” in full 3D. It is probably "too ideal" for direct implementation on typical boxy vehicles.

Boxy is okay.Jaray went from a half-semi-circular airship-inspired half-body front,to a more rectangular cabin section,then back to a half-semi-circular tail section.
The important thing according to Hucho is that we not introduce any velocity or pressure spikes or kinks along the air's pathway.Which is a different way to specify high solidity/sectional density/area-rule/Coke-bottling.
The cross-sectional area cannot vary any more than what Rolf Buchheim and his team came up with with their 1981 VW Flow body

This shape is right on the ragged edge of flow separation.If the body contracts any quicker,the attending pressure rise will kill the boundary layer adhesion and trigger separation.It is absolutely the limit.The template is just a smidgeon more conservative.
In the absence of a full-scale wind tunnel,any body,which doesn't vary more in cross-section than this body will have attached flow,regardless of it's cross-sectional shape.It's virtually guaranteed.
Here you can see the more 'rectangular' Schl'o'r pillbug and how it's body cross-section varies

For length,just chop the body to a length you can live with


Just remember,the lowest drag is achieved when the car length is 5X the height.This isn't negotiable.