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From: Dale Rogers <rogersda@cox.net>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Subject: [FlyRotary] Re: New Scoop
Date: Thu, 15 Jul 2004 10:00:17 -0400
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Steve,

   I hate being a nay-sayer, but I suspect you're making 
too big a project out of this, trying to "tweak" a system 
that has a major underlying flaw.

John Slade <sladerj@bellsouth.net> wrote:

> Steve,
> There is one other difference between our installations which might be
> relevant. Mine is a 3rd gen engine, yours is (I think) a 2nd gen. The 3rd
> gen water pumps are different, and I think the oil galleries are bigger.
> Just a thought
> John (installing the pan gaskets I should have installed last year)
> 

   There is one other difference, and I think it is not 
trivial.  Looking at the two systems, John's radiator is 
mounted at an angle to the air flow that requires 
considerably less than a 90* turn of the airflow.  Yours 
requires considerably more than 90* - it actually forces 
the air to travel slightly forward again, in order to get 
through the radiator.  The new scoop offers a slightly 
wider radius in which to do so, but at the cost of 
significant drag.

   Also, the gap between the oil cooler and the radiator: 
how has it been sealed? - or has it?  You have high velocity 
air going into a plenum; it will take the path of least 
resistance to get out.  If there is _any_ way easier than 
going through the heat exchangers, you lose cooling capacity.

   Finally, there has been considerable talk here, in the 
past, regarding the relationship between the intake size 
and the radiator area; there have been fewer about the 
relationship of the outlet size.  You have heated air 
exiting your heat exchangers, that means it's expanding.  
You need enough outlet area to keep from bottlenecking 
the airflow _after_ the rad, or you'll lose pressure 
differential right when you need it the most.  That outlet 
area has to take into account ALL the sources that are 
adding heat to it - engine radiation, exhaust ...

My tupence,
Dale R.