View Single Post
Old 01-23-2013, 06:57 PM   #401 (permalink)
aerohead
Master EcoModder
 
aerohead's Avatar
 
Join Date: Jan 2008
Location: Sanger,Texas,U.S.A.
Posts: 12,671
Thanks: 20,336
Thanked 6,289 Times in 3,893 Posts
0039

Quote:
Originally Posted by Tesla View Post
Ok, I think I'm just about done with this story.
Through a roundabout way I started looking at different t/c ratios to get the tail ratio of 1.78 and came up with this one:

Aspect ratio 2.5411:1
t/c is 0.393935
Tail ratio is 1.7800

I have tweaked the equation just a fraction to finish curve at 0, I have not done the overlay to the template (still need to work out how), but I think the numbers indicate it is damn close and probably closer than achieved in normal construction errors in scaling.
With an equation greater accuracy is possible by being able to extract data for any point on the curve.

It is just a fraction steeper at the start, then tapers out and curve accelerates again after the 80% mark, though this is pretty much irrelevant in the real world as even the keenest modders will finish their tails around this point.

The analysis of the angles may to some degree be irrelevant as I do not know exactly how the template angles were arrived at.

Below is the 0039 section, again scaled as best as I could on screen





Just edited a couple of little details, minor bugs in spread sheet and adjustment to curve.
It looks pretty good!
The faster initial may trigger separation,but the geometry is so good a little downstream that reattachment is a given.
In Hucho's book,he presents a drag table which contains the 2.5:1 L/D streamline body of revolution that was the inspiration for the 'Template.'
If you can gain access to his book,you might be able to cleanup this 'tiny' image and scale it up.
I did what I could with copy machine photo-enlargements,but it renders a fairly 'dirty ' image.
Thanks for all the gee-whiz image and math noodling.
I've been working on three other 'Templates,' to present which will give some options and different perspectives.No telling when I'll get those finished for posting.
Thanks again for all the work! I think she'd look pretty good in a tunnel!

__________________
Photobucket album: http://s1271.photobucket.com/albums/jj622/aerohead2/
  Reply With Quote