Quote:
Originally Posted by ebacherville
I think this would be the ideal shape for a full boat tail on the CRX.. just going by eye.. however has no mathematics behind it..
AM i crazy enough to make this thing??  |
aerodynamically your new image is way better and since "a picture is worth a thousand words" I'd like you to take a look at something.Go to GOOGLE Images and do a search for gentoo penguin.When the images come up,go to page three,and there you'll find the image of a single penguin swimming underwater.I printed this image and did some biometrics on it.The back 53% of the bird is "boat-tail".the aftbody of the bird is 2-body-lengths long.In the first half of the body,the angle never exceeds 10-degrees (as recommended by Kamm).In the last half of the boat-tail,the slope-angle of the penguin's body never exceeds 20-degrees ( as recommended by Mair ).All this makes for a long tail,and for fish,its no big deal.By the way,this penguin has a drag coefficient of 0.07,the lowest ever recorded for an emmersed structure of it's size and speed.On our cars,its a different ball game.What Kamm and Korff and Fachsenfeld,and the others have recommended,is to "truncate" ( chop-off ) the tail at any length that is convenient.Flow will be attached right up to the chop,and then the wake forms kind of a "phantom" boat-tail of turbulence which in theory,the surrounding air flows over like a solid body.It doesn't actually work as good as they say,but its a compromise for parking and turning and pedestrian safety,etc..Take a look and then think maybe about a shorter tail.Korff figures that if the chop occurs at about 50-% of frontal area,you're pretty much home free with respect to drag.