In my understanding, Airflow dislikes corners so nothing beats a round inlet.   Aircraft design is all about compromises so other factors may require a different shape.  

Tracy

Sent from my iPad

On Oct 10, 2012, at 6:10 PM, Stephen Izett <steveizett@me.com> wrote:

Thanks Tracy.

So given the right inner and outer radius', do you believe creating a circular inlet over the current trapezoid shape?

My concern with the current shape is that the largest area of the inlet is towards the hub.

Steve Izett

On 10/10/2012, at 9:54 PM, Tracy wrote:

Hi Steve,   out here in Colorado again with limited access to internet.   Somewhere in the archives is the report I did on the inlets.  They were based on a NACA study which mainly defined the optimum inner and outer radius for the inlets.   I found it made a very big difference in capturing off axis airflow (climb attitude and prop wash) .  The difference between the raw tube inlet (like a huge pitot tube) and the radiused  inlets was very noticeable, especially in climb.   They were at least a factor of 2 better at capturing the prop wash in static conditions as measured by pressure at the face of the heat exchangers.

Tracy

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On Oct 9, 2012, at 11:45 PM, Stephen Izett <steveizett@me.com> wrote:

Thanks Steve

I wonder if Tracy is lurking and can comment on the value of reworking the cowl inlets?

Cheers

Steve Izett

On 10/10/2012, at 1:32 PM, Steven W. Boese wrote:

Steve,

 

I am not the right person to try to answer your question.  Having retained the stock Van's cooling inlets for the coolant exchangers with essentially no diffusers, the result appears to be marginal cooling and high drag.  So I am asking myself the exact same question.

 

Steve Boese

RV6A, 1986 13B NA, RD1A, EC2

 

 

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From: Rotary motors in aircraft [flyrotary@lancaironline.net] on behalf of Stephen Izett [steveizett@me.com]
Sent: Tuesday, October 09, 2012 6:39 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: cooling airflow concepts

Thanks again Steve

My current snout looks similar to the attached image.

I'm considering going to the trouble of reworking the cowl into two circular duct openings, keeping them as far from the centre of the prop as possible.

Current opening is approx 7'' x 3'' - 21sqin.

Tracy I believe uses (Water Side) 5 1/4" so - 21sqin.

Multiply Tracy's by 2/3 (loose a rotor) + a bit for the extra side exhaust energy (Renesis) going into the coolant - say 15sqin's or 4 1/2 inch diameter.

The other attached photos are modified Glasair snouts

What do you think I should consider given the amount of work involved and the possible improvement factored in?

Cheers

Steve Izett