Message-ID: <4000718D.4070307@netdoor.com>
Date: Sat, 10 Jan 2004 15:41:33 -0600
From: Charlie & Tupper England <cengland@netdoor.com>
Reply-To: cengland@netdoor.com
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To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Subject: Re: [FlyRotary] Radiator ducting
References: <list-2926621@logan.com>
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Finn Lassen wrote:

> Hi Ed,
>
> As usual I didn't pay attention when I should have.
> I'm now replacing the right radiator for the 2nd time (this time with 
> a new one) and am starting to look at proper ducting.
>
> Bernie Kerr suggested pointing the inlet in the direction of the 
> slipstream from the prop to increase ram effect.
> Looking the the inlets on some turboprop installations it seems the 
> clearance between rear side of prop and tip of inlet lip is quite 
> small. My RV-3 cowling tapers back from the center to maybe 5" at the 
> outside of the cowling.
> Would there be any negative effect on prop efficiency if one were to 
> extend the outside of the cowling out close (1" or less) to the 
> trailing edge of the prop?
>
> Which brings me to the next question: With proper ducting, what is 
> your currently recommended mininum inlet area? I'm considering a 
> circular inlet as in Dave Anders RV-4 (see the Mustang II in Feb 2004 
> Kit Planes").
> The advantage of moving the inlet forward would be a longer duct, 
> closer to the optimal 7 degree maximum.
> Would having the inlet real close to the prop also increase pressure 
> in the duct?
>
> Others are welcome to chime in here too :)
>
> Finn 


Hi Finn,

Here ya go:

http://www.speedmods.com/pa24cowl.htm

and

http://www.speedmods.com/syncro-prop.htm

I tend to believe that anything LoPresti does is worth a close look. 
Also, Kent Paser ( 240mph in 160hp M-II, book: Speed With Economy) uses 
the extended inlets close to the prop trick.

re: Kevin's post about reverse flow in Van's stock rectangular inlets.  
I can vaguely remember reading that it's a common problem when the inner 
edge of the inlet is close to the spinner & that moving the inlets out 
toward the sides helps.

Charlie