----- Original Message -----
From: "Ernest Christley" <echristley@nc.rr.com>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Sent: Thursday, August 07, 2003 10:42 PM
Subject: [FlyRotary] Re: Cooling / Pressure recovery


> Tracy Crook wrote:
>
> >     Here's the thing that makes it confusing.  If you look only at
> >     cooling results,  Paul was right.  I could have gotten equal or
> >     better cooling improvement by using a cowl flap.  BUT,  this
> >     improvement comes at the expense of added drag, especially at cruise
> >     & top speed (racing).  By improving the pressure recovery instead, I
> >     got the improved cooling with almost no increase in cooling drag.
> >     This is the ultimate goal in aircraft cooling design.
> >
> >     Tracy Crook
> >
>
> How can you tell, Tracy?  That is to say, is opening up the intake
> producing more drag than a cowl flap would?  How do you measure the
> effects of both so that your not just guessing?
>
> ----Because I can----
> http://www.ernest.isa-geek.org/
> ------------------------

A good question but..........
I do have to say that if we don't use the existing (well proven) knowledge
base and stop to prove every point as we go, we will never make any
progress.  Cowl flaps obviously increase the frontal area and the airflow is
fully turbulent behind them so the Cd (coefficient of drag) is very high.  I
accept this as well proven fact.  I believe Bill Eslick specified the speed
penalty as 12 mph (or was it knots?) when he opens his cowl flap.

There is some drag induced by the increased airflow through my rad from the
reshaped inlet but far less than that of a cowl flap. Note that there is no
increase in frontal area.  The increase in drag was not measurable during
the top speed run I did after the inlet mod (i.e. there was no drop in top
speed) but the improved cooling certainly was.

Tracy Crook