REFLECTOR: NACA scoops

Dave Bertram v350tx at comcast.net
Wed Oct 19 19:20:45 CDT 2005


I am running a 383ci v-8 making up to 425hp.  I cool it with a belly scoop
the inlet of which is 45sq.in..  My radiator is approximately 21x16x3.5 in..
 My max temp (water)  on take-off and climb is about 220 on a 95 degree day.
 After power reduction at cruise it drops to around 180 degrees.  
Dave Bertram
V350TX 
 
-------Original Message-------
 
From: Velocity Aircraft Owners and Builders list
Date: 10/19/05 10:43:36
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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