Todd, if it aint broke dont fix it!!!!

 

You are right about the boundry layer.  But you can make up for that with a little extra size or maybe moving closer to the prop (eg P-40).

 

Also, Doug dempsy has been telling me how Chuck Dunlap had a real problem with a duct that was away from the boundry layer, but fixed his issue when he make it bigger and more like the smile.

 

The smile votes seem to have it so far...

 

Dave Leonard

 

On 1/30/07, Todd Bartrim <bartrim@gmail.com> wrote:

I was thinking that the "oh cowl" would be better at excluding the boundary layer, which would be better for cooling. This is just based on comments I've read on the list during previous ducting discussions. Based on this info, I felt my oil cooler duct was less than optimal (even though temps are good), so I figured I could reduce the size of my inlet if I eliminated the boundary air layer. As your "smile" duct is similar (see attached pic) I figured this would be applicable. I hope I'm wrong and you prove it before I change my cowl.

Todd    (building Electric Bob's Audio Isolator Amplifier today)

On 1/30/07, Ernest Christley < echristley@nc.rr.com > wrote:

David Leonard wrote:

> I call them the "Oh Cowl" and the "Smiley Cowl..."his

Go with the smile, but put a raised ledge on the cowl side just behind
the spinner to accelerate the air and thin the boundary layer.  Reduces
the ingestion of turbulent air.  Check the CAFE Foundation's drag
reduction report.  They have a picture of what it looks like on a
production aircraft.  I have a link to it at home, but not here.

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----===<{{(oQo)}}>===----    Dyke Delta Builder      |
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