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Old 08-07-2010, 12:10 PM   #64 (permalink)
3-Wheeler
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Quote:
Originally Posted by aerohead View Post
Jim,I did a graphical analysis of the airfoil curvature and it is defined by 4-separate and distinct radii,sweeping through 4-different degrees of rotation about each axis.Here's what I came up with :
(1) R= 3.35-H @ 12.5-degrees rotation
(2) R= 5.294-H @ 12-degrees rotation
(3) R= 6.588-H @ 7-degrees rotation
(4) R= 7.96-H @ 9-degrees rotation

This was actually for Mair's 22-degree boat tail but the 'Template' is close to the same solution.just smoother.
As with the template,H is measured from the road to the top of the max roofline camber point.
Hope this helps,Phil
Hi Phil,

I'm trying to understand your geometric description above, and spent about an hour using the CAD to analyze your numerics. Here's what I came up with so far, but I am making some assumptions:

1) Not knowing the exact shape of ideal airfoils, one assumption I am making that that all extended radii used to duplicate the airfoil shape are referenced to the maximum camber of the wing, or the thickest point of the airfoil.

2) This means that all radii center point originate from a tangental line draw through the maximum cordal thickness.

3) Being that I am not designing my own wing shapes, the assumptions above may not be true.

The first graphic shows four large circles draw over the AeroHead Streamlining Template.



The second graphic shows that the transition from the 3.35-H radius to the 5.294-H radius is incredibly short, and shown in location by the short black line. Your pictorial that you are working from must be much more detailed than the one I have to work with, because I could not make out that much detail.

The 5.294-H radius curve fits the pictorial quite well, and for quite some distance.



This graphic shows that the transition to the third larger radius occurs close to the 60% position on the streamlining template.

Notice that the point of intersection between the two lines, there is a small
"dip". This transition should be smoother to match the pictorial.



And here is the intersect point for the third and fourth radii. Again there is a dip at the point of intersection.

One way I can think of to avoid these dips is to create a airfoil shape where the wing curving surface is created with a constantly enlarging radius, or at least broken into smaller sections so that these dips would not be an issue.



Based on the above, it still appears that my constant radius Master Template made for the Insight would provide a good match to the AeroHeads Streamlining Template out to about the 60% point.

Because the car is currently jacked up I can't measure the height of the roof line exactly, but estimating with a tape measure, I got about 50 inches.

The 60% point on the Streamlining template is therefore about 103 inches back from this point, and this ends up about 42 or so inches behind the hatchback spoiler trailing edge.

Assuming the Master Template has the proper curvature in it, the tail extension should work fine by creating the remainder of the extension distance utilizing the same curvature it has up to the two-foot point, and extending out another 1-1/2 or so.

Jim.
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Last edited by 3-Wheeler; 08-07-2010 at 12:32 PM..
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