Quote:
Originally Posted by razordave
You are correct. I did not know about the air flowing forward. That could explain that previous tank being horrid.
If I reinstall the visor, I will tape the leading edge. The mounting hardware caused this gap. Attached is what I thought could be a slick easily removed mounting solution.
Free beard, I couldn't remember where I had seen a similar setup but had actually reviewed basjoos thread last night when I decided to begin planning a boat tail or at least a truncated one.
Did I read somewhere that 40% will give you 80% of the benefits?
Lastly, I got a lead on an estate with old airplanes. I may blow a circuit with a body swap on the old tdi..
Edit: it has been done with a pickup chassis and a delivery truck chassis and I'm sure a few more.
https://youtu.be/DHyZPVOT1xI
After having seen some people chop up a beetle to build small campers... |
Presently in England, Jeff Powell and his merry associates are reinvestigating the drag reduction mechanism of streamlined boat tails at Loughborough University.
What they're experiencing is that, the drag reduction tracks directly, as a function of the change in wake area. It's virtually linear.
If you know the actual wake area of the new Beetle, at Cd 0.39, and you want Cd 0.195, then, the wake area of your tail needs to have 50% of the original.
Carl Breer did this in 1934, on the Chrysler Airflow, with a Desoto Airflow test mule of Cd 0.51, which had a aft-body very similar to the original VW Beetle.
By transforming the ducktail into a truncated kammtail, of no added length to the car, the Cd fell to Cd 0.268.
Then adding about 36-inches of stinger onto the kammtail, drag fell to Cd 0.244, essentially rendering the Cd of the 2012 Tesla Model S, in 1934.
So it's not the 'length' of the tail that you're interested in, it's it's wake area.
Technically, if you were completely nuts, and optimized every area of the Beetle, and then threw a full tail on it, you'd be 'wake-free', and drag would be reduced to only surface friction. Pressure drag would be completely eliminated. What Wolf-Henrich Hucho says is what 'aerodynamics' is all about.
And the contour of the tail needs to be in the 'Goldilocks Zone' right at the front door of separation. Any 'shorter' and it's a pressure fail. Any longer and it's a skin friction fail. You want the contour to minimize both pressure drag and surface friction drag.
Hucho gave us enough crumbs to find our way back to that shape.