Basically, these guys that had an RV-6A with a Suburu engine just kept
adding small radiators until they had enough. OK, that's a terrible way to
do it. But they did mention some good tidbits like the fact that thicker
cores are bad. It's better to have a longer, wider rad than one that is
thicker (i.e., having more cores). But space requirements may force you
into more cores to make it fit. You can also glean some info by looking at
the total area and volume numbers they came up with. Compare that to the
size of their engine to the one you want to use and you might start getting
in the ballpark. I also plan to look at automotive installations and the
total area and volume used for engines my size. Of course, the way you flow
the air through the rad will have a big effect on how big the radiator needs
to be. The greater the pressure differential you can manage between the
inlet and outlet, the smaller the rad will need to be. Hey, we're
definitely experimenters here when using non-standard engines. We'll all
probably have to just try different sizes, airflow designs, etc. just like
they did unless we just get lucky the first time. Of course, you can spend
the rest of your life trying to optimize the system for lowest drag achieved
with sufficient cooling in all phases of flight, or you can stop when the
system provides sufficient cooling and not try to tweak out another knot or
two. I had a Murphy Renegade Spirit with a Rotax 912 that was definitely
running too hot. So one day I totally removed all the carefully made
baffling around the engine, leaving the entire engine compartment wide open
under the round bump cowl leaving a big open hole in the cowl behind the
prop. Temps came way down and I never had another problem, even though I
was flying all over the Australian outback with outside air temps well over
100 degrees F. Don't ever do this with a Lycoming, but it worked for the 912
Renegade. I may have lost a knot or two but with the Renegade you'd never
notice anyway.
Mike
-----Original Message-----
From: mike.davis@dcsol.com [mailto:mike.davis@dcsol.com]On Behalf Of
rickhm@comcast.net
Sent: Tuesday, December 14, 2004 10:09 AM
To: rebel-builders@dcsol.com
Subject: Re: SR Chevy Cowl/Cooling design and cabin heat
A question that I have long pondered is how do you determine the size
(widthxheight) of your radiator. There are so many variables here that are
hard to predict. Thickness of the radiator, density of cooling fins within
the radiator, airflow, etc. I finally concluded you just give it a try and
see what you get. A more analytical approach I would prefer. Any thoughts?
-------------- Original message --------------
thinkActually I'm not sure what the RV6 did but I have uploaded two of my old
pix. The backs (inside?) of the side ramps continues forward inside the
cowl about 6 or 8" so hopefully the exit air picks up speed as it nears
the exit. The rads in the nosebowl thing on the RV6 has packaging
advantages but it doesn't seem to work for everyone and it is a far from
optimum solution. There is not enough room (length) for reliable
pressure recovery in the intake duct and the intake is closer than
usually desireable to the prop among other things.
The opening just below my spinner is ducted to the heater core and there
is a 5" muffin fan to assist while on the ground to make sure the
windshield stays clear. It was the highest power 5" muffin that I could
put my hands on and I think it draws about 0.8 amp.
Yes I'd have also put the rad below the oil pan if I could have fit it
in but now that it is done I do like not having the rad in the way when
working on the engine. I had to exit the exhaust out the far side of the
cowl to keep it away from the cooling air intake.
Ken
Mike Kimball wrote:
Heater core in the cabin just like a car was my first thought. All those
other thoughts came later. After all your comments and more thought I
cabin.the ideal system would be to have the heater core and the fan in the
smell(At first I was trying to avoid coolant in the cabin since I can still
wouldleaked coolant in my Mustang's carpet when it's warm outside.) Then I
therejust need two holes in the firewall for the coolant hoses. But looking at
the available space on the cold side of the firewall I don't know if
heateris enough room. I am excited about the comment on using a computer fan. I
had been envisioning much larger fans as found on cars. I could probably
even rig a rheostat to vary the fan speed. I will also check out the
withcore sources mentioned by a couple of contributors. I would like to run
dedicated ducting to the back seat area but right now I'm putting that in
the "too hard and I want to get flying" box. So I am going to progress
firewall,the idea of mounting the fan and heater core in the middle of the
sideinside, with an air box with five outlets. One pointing right down the
middle to hopefully send warm air towards the back, two outlets to the
bridgefor the front passengers, and two outlets for the windshield defrost. If
humidity from using inside air is a problem I'll have to cross that
oilwhen I come to it. By circulating air from inside the cabin that should
pretty much eliminate the possibility of CO.
As for the radiator - I think I'll progress with mounting it below the
havingpan somewhere. I think the comment about ducting air to it and then
havea separate system for general air circulation around the engine is good.
About the "tapered flush side cowl exits (acceleration ramps)", do you
any pictures Ken? It's probably similar to the ones used on the RV-6A in
the article you pointed out for me to read. Thanks.
Mike
-----------------------------------------------------------------
List archives located at: https://www.dcsol.com/login?mode=HTML
username "rebel" password "builder"
Subscription services located at:
https://www.dcsol.com/public/code/html-subscribe.htm
List administrator: mike.davis@dcsol.com
-----------------------------------------------------------------
-----------------------------------------------------------------
List archives located at: https://www.dcsol.com/login?mode=HTML
username "rebel" password "builder"
Subscription services located at:
https://www.dcsol.com/public/code/html-subscribe.htm
List administrator: mike.davis@dcsol.com
-----------------------------------------------------------------
-----------------------------------------------------------------
List archives located at: https://mail.dcsol.com/login
username "rebel" password "builder"
Unsubscribe: rebel-builders-unsubscribe@dcsol.com
List administrator: mike.davis@dcsol.com
-----------------------------------------------------------------
