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Date: Mon, 4 Apr 2005 20:01:14 -0500
Subject: Re: [FlyRotary] Re: Cooling Inlet Areas/Bernie's RV9
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From: Jerry Hey <jerryhey@earthlink.net>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
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On Monday, April 4, 2005, at 07:23 PM, Ernest Christley wrote:

> Al Gietzen wrote:
>
>> Doug;
>>
>> I agree with your =91rule-of-thumb=92 numbers. My analysis came up =
with=20
>> coolant inlet area in sq. in. of 1/3 the HP (.33) for climb out on a=20=

>> 90F day. It assumes a 120kt climb speed for my Velocity. I used 45%=20=

>> of that additional for the oil cooler. Assumes scoop efficiencies of=20=

>> 85% or better.
>>
>> Al
>>
>
> snip
>
>> Second, even if cooling can get out, if it can't get in, it can't be=20=

>> there to cool the heat exchangers. Rule of thumb: 0.3 sq. in. of=20
>> cowling inlet air opening per HP. 200 HP x .3 =3D 60 sq. in. Note: =
This=20
>> assumes a reasonably shaped inlet cowl which has been discussed=20
>> online often. IMHO: Berni's plane inlet shape and inlet cowl is fine,=20=

>> but I question his inlet opening _area_.
>>
> snip
>
>> Don't mean to start another stream of threads on an old subject, but=20=

>> we sweated over this one for 3 months and 3 systems and one might=20
>> save a lot of time by comparing ones system to these simple "works=20
>> great" rules of thumb which are the result of LOTS of technical and=20=

>> experimental work.
>>
>> Doug Dempsey
>>
>> N6415Q and RV7 in process
>>
>> Colorado, USA
>>
>
> Don't won't do demean or dismiss your experimental work in any way,=20
> but Ed is running with half the inlet area, and unless something has=20=

> changed with his new found power, he'd doing just fine. Just to be=20
> sure that we're all talking apples, I can confidently quote him at 28=20=

> in^2 inlet for coolant, which I believe is half of what you recommend=20=

> above. Reality isn't meeting theory at eye level here, and everyone=20
> will be much better off if we know why.
>
> --=20
> This is by far the hardest lesson about freedom. It goes against
> instinct, and morality, to just sit back and watch people make
> mistakes. We want to help them, which means control them and their
> decisions, but in doing so we actually hurt them (and ourselves)."
>
> Exactly the point I have been making for a long time.  The formulas=20
> that determine intake size cannot be right because we have examples of=20=

> systems functioning well enough with much smaller inlets.  In fact,=20
> for most of  us,  if the inlet size rule was not violated, we would=20
> have to go back to air cooled engines because there is simply not=20
> enough room for the intake let alone the even larger outlet.

Ian apparently was able to cool his engine in a very hot environment=20
(Australia) using two evap coolers of only a core volume total of 400=20
sq in.  The rads were  perpendicular to the air flow just behind the=20
cheek inlets and the ducting looked well designed in the photos.  This=20=

establishes a minimum size that we know works that is far smaller than=20=

the formulas call for.

With our airspeeds almost never below 100 mph, we have so much cool air=20=

available that smaller inlets and radiators have proven to be adequate.=20=

  The real issue is duct design.
Jerry
>


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