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From: "Ed Anderson" <eanderson@carolina.rr.com>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
References: <list-1155455@logan.com>
Subject: Re: [FlyRotary] Re: Remove Turbo
Date: Thu, 15 Jun 2006 12:02:34 -0400
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Steve's comments are on the money, Thomas.  Yes, you can certainly design a 
cooling duct system optimized for cooling in a climb.  However, as Steve 
indicated you will then pay with additional drag/weight,etc for each of 
those many hours at cruise airspeeds.  Many (most?) of us try to design for 
optimum cooling at cruise (minimum drag) and accept the fact that for a few 
minutes during/after takeoff we may incur a cooling deficient.  My limits 
are 200F oil and 220 Coolant, so long as my full power climbout does not 
cause either of those limits to be exceeded, I feel comfortable.

 Now, once I have reach 120 MPH IAS I start to get into the sufficient 
cooling capacity region and all temps start back down.  At cruise my cooling 
temps are normally around 160-170F for both oil and cooling - which could 
indicate that I still have a bit too much cooling capacity (and therefore 
cooling drag). Ideally at cruise, I would like to see oil and coolant at 
180-185F.   However,  since I don't wish to exceed my establish limits in 
climbout, I accept that I probably have more cooling drag at cruise than I 
need to have.

If I were flying a Bush plane in and out of hills and valleys carrying heavy 
loads and at relative slow speeds, then I would opt to optimize the cooling 
system for takeoff and climbout.  If I were flying a canard type I would opt 
to optimize the cooling system for cruise.  With an Rv I'm someplace in the 
middle {:>).

Like most of areas when discussing aircraft, cooling is another one of those 
"compromise things"

Ed

Ed Anderson
Rv-6A N494BW Rotary Powered
Matthews, NC
eanderson@carolina.rr.com
----- Original Message ----- 
From: "Steve Brooks" <prvt_pilot@yahoo.com>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Sent: Thursday, June 15, 2006 9:51 AM
Subject: [FlyRotary] Re: Remove Turbo


> Thomas,
> You could design a cooling system for extended climb, but you would be 
> adding
> significant drag to the aircraft.  There is only so much you can do with 
> cowl
> flaps.
>
> I believe that most builders (and also most certified aircraft) design 
> cooling
> for cruise, and tolerate temperatures climbing somewhat in climb.  There 
> do
> have to be tolerable limits, however.
>
> I'm afraid that if I built my cooling system to maintain temps on an 
> extended
> climb, at full power, on a 95 degree day, I would have much cruise speed 
> when
> I leveled off.
>
> I've seen several discussion on this group, where people leveled off for a
> while, or reduce power and go to a cruise climb, in order to let thing 
> cool
> back down.
>
> On my aircraft, the oil temperatures are fine, but coolant is marginal on 
> hot
> days.  On a 95 degree day, I could only get to about 2000 feet AGL before 
> my
> coolant temperature was at redline.  Leveling off and reducing power, 
> cools
> it down, and then I can increase power and continue climbing at a cruise
> speed.
>
> I have some more gains that I can make on mine cooling system by making
> improvements in air flow.  Currently I have some dead space below the
> radiators which I'm sure allows some air to roll back out.  I also have a
> couple of spots that are allowing air to leak through, which I need to fix 
> as
> well.
>
> Steve
>
> On Wednesday 14 June 2006 09:30 pm, Thomas y Reina Jakits wrote:
>> ""
>>
>> > While it doesn't make sense to try to have sufficient cooling for 
>> > climb,
>> > I think that I can still make some air flow improvements and get a 
>> > little
>> > better cooling.
>> >
>> > Steve ""
>>
>> Steve, what makes you think/believe that!?
>> I always assumed that one would design/plan for the worst case scenario:
>> Slow/steep/pro-longed max power climb....
>>
>> You always can close the flaps/louvers (streamline/reduce drag) when you
>> change into a less severe regime.
>> But what good is a 250hp engine if you can't use it for more than 2 
>> min....
>> I would at least want a 5 min limit for T/O-power. As Rotaries go, they
>> will hold up fine with max power for cruise/racing/etc. fine too - but if
>> you can't cool it.....
>>
>> What if you are in line on really hot day? You might not even get 2 min 
>> of
>> max power.
>> I would rather err on the wild side of cooling - you always can cut down
>> and close off, once you know your ride...
>>
>> TJ
>>
>>
>> --
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>
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