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Date: Mon, 04 Apr 2005 20:23:58 -0400
From: Ernest Christley <echristley@nc.rr.com>
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To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Subject: Re: [FlyRotary] Re: Cooling Inlet Areas/Bernie's RV9
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Al Gietzen wrote:

> Doug;
>
> I agree with your ‘rule-of-thumb’ numbers. My analysis came up with 
> coolant inlet area in sq. in. of 1/3 the HP (.33) for climb out on a 
> 90F day. It assumes a 120kt climb speed for my Velocity. I used 45% of 
> that additional for the oil cooler. Assumes scoop efficiencies of 85% 
> or better.
>
> Al
>

snip

> Second, even if cooling can get out, if it can't get in, it can't be 
> there to cool the heat exchangers. Rule of thumb: 0.3 sq. in. of 
> cowling inlet air opening per HP. 200 HP x .3 = 60 sq. in. Note: This 
> assumes a reasonably shaped inlet cowl which has been discussed online 
> often. IMHO: Berni's plane inlet shape and inlet cowl is fine, but I 
> question his inlet opening _area_.
>
snip

> Don't mean to start another stream of threads on an old subject, but 
> we sweated over this one for 3 months and 3 systems and one might save 
> a lot of time by comparing ones system to these simple "works great" 
> rules of thumb which are the result of LOTS of technical and 
> 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, but 
Ed is running with half the inlet area, and unless something has changed 
with his new found power, he'd doing just fine. Just to be sure that 
we're all talking apples, I can confidently quote him at 28 in^2 inlet 
for coolant, which I believe is half of what you recommend above. 
Reality isn't meeting theory at eye level here, and everyone will be 
much better off if we know why.

-- 
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)."