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I would not argue with your assessment, Paul.

I mainly put it up so you folks could see the source that many "experts" use to tell you "Dummies" why what you have working - can't possibly work {:>). I was offering a hypothesis as to why in some cases the results "in-the-field" might be different from what NACA found in the wind tunnels. I had not heard about the NACA supposedly not being good for carburetors. My impression was that so long as there was not back pressure (such as a cooler block will produce) anything that created a lower than ambient pressure region behind the NACA duct (such as engine intake or duct into a cabin) would cause it to work OK. I know that the NACA duct that feeds cooling air into my cabin always has a tremendous rush of air coming through it. Have to keep it closed off most of the time at altitude or freeze my butt.

Ed Anderson
RV-6A N494BW Rotary Powered
Matthews, NC

----- Original Message -----

From: sqpilot@earthlink

To: Rotary motors in aircraft

Sent: Friday, July 16, 2004 6:45 PM

Subject: [FlyRotary] Re: New Scoop

Hi, Ed.....I am of the opinion that the NACA report you provided is old and out of date. Note that they also state that the NACA duct does not provide desireable recovery characteristics for carburetors on reciprocating engines. Tell that to the many LongEZ builders (myself included) that found it to be very efficient in supplying air to our carburetors in all attitudes, from cruise attitude to steep climbouts. They came up with a very nice, low drag inlet, but I don't think they spent as much time studying their creation or finding out it's true potential. Just my experience, based upon a very succesful NACA duct feeding my MS carb on my Lycoming (ugh, sorry about that) powered LongEZ. Paul Conner

----- Original Message -----

From: Ed Anderson

To: Rotary motors in aircraft

Sent: Thursday, July 15, 2004 6:52 PM

Subject: [FlyRotary] Re: New Scoop

Looking at John's cooling set up, it appears that the cooler core exits are in an excellent position to benefit from any lower pressure region that may exist at the rear of the canard fuselage.

Its been my contention that this is one of the reasons that at least some canard installations appear to defy  both the conventional "wisdom" and the NACA admonishment that NACA ducts are not well suited for radiator cooling (or other uses that produce a back pressure). That is - as in John's case - the successful arrangement appears to minimized the back pressure across the core and perhaps benefits from a localized area of lower than ambient pressure.

Attached is an extract from a NACA report which makes it clear, that at least in their opinion at the time, the NACA ducts were not suited for radiators. But, as John and other's have shown, they can work very effectively. So something they are doing must be different. The only thing I can come up with is that the canard arrangement provides the opportunity to benefit from what must be a lower pressure area behind the fuselage as it moves through the air.

However, in my own personal experience in using a Naca duct in the front of my cowling (in one of my five attempts to solve my oil cooler problem) the results were consistent with the NACA assessment. It was not successful for me.

One of the differences is my oil cooler was approx 10" from the firewall and did not have exit to a negative pressure area. In fact, the pressure inside the cowl was probably slightly positive. I don't know that would have made a difference but seeing the success of John and others with it, I am led to believe that having the back of your cooler cores in a lower pressure area will enhance the probability of success in using a NACA duct.

My 0.02 worth.

Ed

Ed Anderson
RV-6A N494BW Rotary Powered
Matthews, NC

----- Original Message -----

From: John Slade

To: Rotary motors in aircraft

Sent: Thursday, July 15, 2004 6:48 PM

Subject: [FlyRotary] Re: New Scoop

>I believe that his cowling must extend down approximately 4-5 inches to achieve that.

Nope. The cowl is level with the fuselage floor, then curves upwards.

It's tight, but it can be done.

John Slade (Got my EM2 .... manual)

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