Quote:
Originally Posted by basjoos
The Cd would go up because you'd have quadrupled the size of the recirculation eddy trailing the car.
When I first built my prototype boattail, it was cut off at the point where the back edge of my hatch glazing is now, then later I added a tail cone to complete the boattail (see pics in my Photobucket site). I got a noticeable increase in coasting performance when I went from the partial to the full boattail. There's a reason you don't see subsonic aircraft flying around with kammbacked boattails, its called increased drag.
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basjoos,
I've been going over the old German stuff and it's in agreement with everything you say.And I was surprised that there is a certain degree of ledgerdermain with respect to the claims by the "experts" with respect to cropped posteriors on cars.---------------- With Jaray's and Lay's research,along with Dornier,Messerschmitt,etc.,full drag reduction does not occur until the full boattail is achieved.---------- Even when Korff eludes to Dornier's aircraft fuselage being truncated for the rear gunner's turret,we're only talking about 2 % of the tail length being compromised before extreme drag increase occurs!-------------------- Sure,there are practical limits to the length of a car,and Kamm openly admits that his 50-% tail- "Kammback" was to address "length" issues not"drag" ,but in purely aerodynamic terms,whether practical or not,its incorrect and untrue to say that a 50 % crop is as low drag as a full tail.The science simply does not support the claim!------------------------ Not to go off-topic,but if people expect to ever achieve high levels of fuel economy,they are seriously going to have to re-consider how they think about what cars should look like.---------------------- Thanks for all you do,and for remaining a constant source of inspiration for an old tin-knocker like me and so many others.It makes it easier for me when I know there are a few out there that "get it" and are willing to apply themselves,sometimes amidst an environment of zero encouragement and support.My hats off to you!