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Hi Bob,
I fly a Rv-6A with a 13B. I started out using 24 square
inch opening for each of the radiator cores AND 24 square inch opening for the
oil cooler for a total of 3x24 = 72 sq inches.
I have since reduced the radiator openings to 18 sq inches
each - leaving the oil cooler at 24 sq inches for a total of 60 sq inches, but I
spent a lot of research and experimenting with the ducts to get
the best pressure recovery I could.
I estimate (based on fuel burn) that I am producing between
170-180HP. Naturally the more HP you make the more cooling you need.
So what may work fine for a 160 HP engine may be marginal (or worst) for a
180-200 HP installation.
50 sq inches will probably cool at cruise with no
problem - however, it could be marginal or worst on a hot day with a
max power climbout. A lot depends on how well the ducting and exit of the
air is done. Ducting and associated detail is one reason why
seemingly identical installations may vary greatly in cooling
ability.
Its all about trade offs, given sufficient surface area and
airflow - IT WILL COOL. However, you may encounter lots of cooling drag if
you have not make an attempt to optimize your compromise.
Its possible that using one 50 sq inch duct (such as the James
cowl) may be adequate (I believe Tracy Crook is intending to use such with a 20
B - so if it will cool a 20 B then there is little doubt it will cool a
13B). I am eagerly awaiting the results of using such approaches
.
Ed
----- Original Message -----
Sent: Monday, January 30, 2006 9:22
AM
Subject: [FlyRotary] Re: Cooling air
inlets
Bob; The 40 sq. will not cool the engine. Ed and others are
using a 2 1/2 inch x 10 inch hole under the spinner for the oil cooler, as
more than half of the engine cooling is through oil, as I understand it.
I'm working on the oil cooler opening as well as the round holes to cool the
coolant. My exit is currently 61.8 sq. inches, so it appears that I need
to add some type of cowl flaps to exit more air.
JohnD from the farm
----- Original Message -----
Sent: Sunday, January 29, 2006 9:19
PM
Subject: [FlyRotary] Re: Cooling air
inlets
That's good to know that you think around 40 square inches of air inlet
will cool your motor. I'm planning to run an underbelly air scoop to the
radiator that will have 51 sq. in. inlet. I had no idea if that would be
enough. but from what you guys are saying, in should be sufficient for my
20B.
Bob Mears
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