REFLECTOR: NACA scoops

[Greg Poole]

Very interesting Al,

 

 ..did you say you can create rain?  (.if so the paradise down here needs
you!) .Hope Kurt still has his pants on after seeing those calcs!  

 

Kurt; what radiator area do the auto racers using your engine combo/HP need
- that would likely give an indication relative to what you have would it
not?

 

Greg in Sydney.

 

-----Original Message-----
From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
Behalf Of Al Gietzen
Sent: Thursday, 20 October 2005 1:43 AM
To: 'Velocity Aircraft Owners and Builders list'
Subject: RE: REFLECTOR: NACA scoops

 

I don't want to rain on anybodies parade; but those considering liquid
cooled engines need to keep in mind that you are working with a limited
delta T for the air going through radiators.  About a 60F rise in the air
temp through the rad on a 90 F day is all you can expect, if everything is
right.  Considering that the specific heat of air is about 0.02 Btu/cu.ft F;
you're going to need about 2200 cfm for every 100 hp of engine output.  At a
climb speed of about 120 kts, that's about 28 sq. in. of inlet area for a
100% effective scoop for every 100 hp.  If you're lucky you'll get 75-80%
effectiveness with a NACA scoop.

 

If I calculate correctly 2 X 11 X 2 X .8 = 35.2 effective sq. in. with two
of these NACA scoops.  This will work fine for 200 hp extended climb on a 50
F day.  On a 90 F day expect this to cool about a steady 125 hp.

 

FWIW,

 

Al

 

-----Original Message-----
From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
Behalf Of NMFlyer1 at aol.com
Sent: Wednesday, October 19, 2005 5:07 AM
To: reflector at tvbf.org
Subject: Re: REFLECTOR: NACA scoops

 

Greg is right, 

 

 I talked to Scott S. about my desire to cool my 340HP V-6 in my 173 FGE
(standard size fuselage) with NACA scoops. He sent me the templates for the
XL due to the increased cooling needs. They are 11" x 2" at the aft
openning. I built them from the templates and found it quite easy. 

 

Although it might be more convienient to buy the premolded scoops, I don't
think it is necessary. I would call the Factory and ask about the drop-down
dimension you need (it is a ratio thing). By the time you ordered the
pre-molded ones and got them delivered, you could have finished building
yours "the old fashion way". 

 

Kurt. 

 

137 FGE 4.3L Alum. V-6 Chevy. 

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