Quote:
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.
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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.