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Date: Fri, 10 Mar 2006 11:29:29 -0500
From: Ernest Christley <echristley@nc.rr.com>
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To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Subject: Re: [FlyRotary] Re: NACA's, Cooling and Sport Aviation Mag..
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Al Gietzen wrote:

> I agree that the 'automatic' assumption that a NACA will not work for 
> a rad/oil cooler is not always valid. Equally incorrect is the 
> 'automatic' assumption that the NACA scoop is lower drag. Drag is a 
> measure of the directed energy of the air in vs the directed energy 
> out. It’s about the design of the scoops, the core and the ducting – 
> both in and out.
>
> All we know for sure is that a ram scoop has a better chance of 
> successfully providing the cooling you need because you have a larger 
> pressure head to work with.
>
We work so well together, Al. I agree with you 100%. Design the most 
efficient exhaust and internal ducts possible. That will set the tail 
pressure. Go all the way to the P-51 style scoop, including the 
seperation from the fuselage to avoid the boundary layer, in order to 
maximize head pressure. Start sinking the inlet if the pressure isn't 
needed.

Kelly, I've worked out a few other particulars of my cooling design.

The oil cooler will fit better than radiators in the right strake. I 
have a dual oil filter fixture mounted on the firewall, and I can feed 
the oil straight through to the cooler mounted in a duct. The stock oil 
cooler has both the inlet and outlet on the same end, so this works 
nicely to keep the lines short. I'll just need a few short jumpers and a 
straight run from the firewall to the front of the engine (airplane 
orientation). A flap arrangment on the exit will seal the top of the 
fuselage on the ground and provide for drag reduction in the air.

I'll suck the boundary layer (what there will be of it) from the 'scoop' 
just in front of the entrance, and use it to supply cool cabin air. 
Another pick-up after the cooler will supply heated cabin air. I'll 
bring the two together into a mixer before dumping it in the cabin. I'll 
build a perferated tube into the upper fuselage skin around the cabin to 
direct air up onto the underside of the canopy for defrosting. Another 
tube will run through the lower front of the passenger's seat to direct 
air to the passenger's feet. I'll provide a shortened exit duct just 
behind the fuel tank on the turtle back to help drop the cabin pressure 
(otherwise the boundary layer pickup wouldn't work).

The left strake will hold one radiator, with another one mounted in the 
nose in front of the exhaust. Two firewall mounted T's will split the 
water. Individual electric water pumps after the split. Still need to 
work out a suitable check-valve arangement. The strake mounted one will 
also have a flap arrangement. The nose mounted radiator's air will exit 
across the exhaust, and help to pull some of that heat from under the cowl.

I hope to skin the belly of this beast tomorrow.

-- 
         ,|"|"|,               Ernest Christley     |
----===<{{(oQo)}}>===----     Dyke Delta Builder    |
        o|  d  |o          www.ernest.isa-geek.org  |