Message

=20 Sent: Wednesday, April 06, 2005 9:43 PM Subject: [FlyRotary] Re: rule of thumb and RV-3 sizes- was Cooling = Inlet Areas/Bernie's RV9 snip I mentioned that on the other list, but I was dismissed as " you = can't compare aircooled engines with a rotary".=20 I don't think there is a great difference on the amout of cooling = necessary, as the efficiency of both engines are fairly close. So some = heat goes out the exhaust and the rest has to be cooled. For sure you = need different ducting, but the amount of heat energy should be about = the same and you want to get rid of it with the least drag, either way. snip[ ------=_NextPart_000_005F_01C53B6A.3B12D7F0 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Message

This does "sound right" but the few studies I've seen showing = the=20 exit air temp on air cooled engines was very close to what water cooled = engines=20 have been.

My delta T air temps on my 3.75" rads is 70 - 80 degrees F at=20 cruise, much higher than most people assume. This is THE = reason I=20 advocate thick rads, at least on 200 mph class aircraft.

Tracy

The amount of heat rejected is very similiar, however the delta-T = available to drive the heat into the air is less for the Rotary than = for the=20 air cooled engine because of the temperature limitations of the water = cooling=20 circuit. Therefore we cannot heat the air as hot, and therefore need = more air=20 than for a direct air-cooled engine.

Bill Schertz
KIS Cruiser # 4045

----- Original Message -----
From:=20 rijakits

To: Rotary motors in = aircraft=20

Sent: Wednesday, April 06, = 2005 9:43=20 PM

Subject: [FlyRotary] Re: rule = of thumb=20 and RV-3 sizes- was Cooling Inlet Areas/Bernie's RV9

snip

I mentioned = that on the=20 other list, but I was dismissed as " you can't compare aircooled = engines=20 with a rotary".

I don't think = there is a=20 great difference on the amout of cooling necessary, as the = efficiency of=20 both engines are fairly close. So some heat goes out the exhaust = and the=20 rest has to be cooled. For sure you need different ducting, = but the=20 amount of heat energy should be about the same and you want to get = rid of=20 it with the least drag, either way.

snip[

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