----- Original Message -----
From: "Ed Anderson" <eanderson@carolina.rr.com>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Sent: Wednesday, October 19, 2005 1:20 PM
Subject: [FlyRotary] Re: NACA scoops


> Hey, I'm not against NACA - if they work and you like them and they fit
you
> need, then go for it.
> The report did not say they would not work, just that they would not work
as
> well as other types (streamline duct for instance) if you need pressure
> recovery (decrease airflow velocity and increase pressure recovery from
> dynamic energy).
>
> However, I don't think using a streamline duct after a Naca duct is going
to
> avoid the "bullet", the problem is any thing that causes a pressure
recovery
> is going to cause "back pressure" to the air flow.  From what I think I
> understood the Naca duct is great where you keep the air velocity up (like
> it being sucked into a jet engine) but don't have a lot of pressure
> recovery. But whatever you have (radiator, streamline duct) that causes
back
> pressure tends to adversely effect the performance of a Naca duct because
it
> slows down the airflow.  At least that is what I think I understood.
>
> Since I have my ducts right up front and am not faced with some of the
> challenges of the pusher type installation - I can say I don't have a dog
in
> this fight {:>)
>
> Ed A
>

That would go right in line with the Lycosaurus engines: Air-cooled there is
way less pressure buildup before the engine, the volume is higher though,
but that doesn't really matter as long as the air goes through easy and
takes the heat.
However once you use a radiator the pressure drop across it will ask for
some serious pressure recovery before the radiator...

Thomas J.