Hi! Frans
I wouldn't be happy having rain entering the upper cowl when parked
outside for long periods.
However on my Jabiru installation I proved that Isolating all lower cowl
intake air such as for oil cooler allowed the down draught of general
cooling air to be more effective.
Regards
Bob Harrison G-PTAG
-----Original Message-----
From: owner-europa-list-server@matronics.com
[mailto:owner-europa-list-server@matronics.com] On Behalf Of Frans
Veldman
Sent: 17 October 2008 17:35
Subject: Re: Europa-List: Cooling & Cowling
<frans@paardnatuurlijk.nl>
[quote:022580b62a="Jeff Roberts"]Since I struggled with the cooling on
my 912-S Tri gear for so very
long I thought I'd throw my thoughts into this subject. I have found
the air cooling of the fins to be inadequate. If you look at the round
inlets in relation to where the top of the engine sits you will find
they are too low and too outside.[/quote:022580b62a]
While fitting the cowling and planning some modifications to the lower
cowling, I was also not happy about the position of the forward inlets.
Thinking about it I got the idea to make Naca inlets in the top cowling,
with a air flow promoting shroud, just above the fins, and close off the
standard forward inlets. (I do not literally mean just putting some bid
over it, but these positions can be used for other purposes, like
landing lights.)
These naca inlets in the upper cowl and closing off the standard inlets
would have the following advantages:
1) No path for the air to escape directly under the engine (instead of
over the engine). This air is not just lost, but also increases the
pressure under the engine, hindering the air flow through the fins.
2) During flight, air will enter here and finds its way down through the
fins to the exit at the rear of the lower cowling.
3) No more need for the (expensive?) Rotax shroud and the third nostril
(another drag creating hole).
4) No more need for the gills on the side. The naca inlets are in the
top, just above the fins, so warm air will escape naturally there once
the engine is shut down. The cowling won't heat up.
5) From the naca shroud It is easy to make a small bypass to cool things
like alternator regulator. There are direct and straight ways in the top
cowling to almost every part that needs to be cooled. All these ducts
can be glassed in the top cowling.
6) Lower drag. I believe the standard inlets are very draggy, with their
sharp endings, and there is no room to make a ramp to slow the air down
before letting it loose in the engine bay. With the naca inlets, there
is sufficient room to make a rounded expansion where the air can slow
down and expand, without creating much turbulence.
7) Easy to implement. Naca inlets can be bought, closing off a hole is
easy too.
I have yet to start with implementing this. Comments please, before I
start cutting something that I'm going to regret later. ;-) Do I oversee
something?
Frans
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