Hello all
I'm sure Mike doesn't mind if I point out the following:
A) The openings for the rudder cables could be much smaller if they
would not serve the dual purpose of extracting the ventilation air.
B Mike also forgot to mention that there is another point where the
ventilation air is meant to escape. This is on top of the fin where
the elevator joins the tailplane.
I'm surprised by his statement that "The location is known to be bad as
the pressure there may even be above static." Perhaps his research is
more thorough and more trustworthy as the work done by the Schleicher
design team.
Kind regards to all!
Bernard
PS: Members of this list are welcome to ring me on 08 84492871 if they
want to discuss the issue further but I ask for your understanding
that no further correspondence will be enterd into.
-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of Mike
Borgelt
Sent: Thursday, 24 February 2011 7:22 PM
To: Discussion of issues relating to Soaring in Australia.
Subject: Re: [Aus-soaring] Air vent
At 03:14 PM 24/02/2011, you wrote:
>You are right - the ventilation air needs to escape again and this
>needs to be managed. For this very reason there are several openings
>(call them air extractors if you like) at the tail end of a glider.
No they aren't. These are usually there because the rudder cables need
attachment to the rudder. The location is known to be bad as the pressure
there may even be above static. A triumph of hope and misunderstanding of
aerodynamics that persisted because the glider manufacturers were too bone
idle to do it properly. Even after some of the designers had visited hot
countries. The less said about the Schleicher underwing NACA duct intakes
for the vent system the better. Bad idea putting these in a low pressure
area. Caproni did the same for the jet engine intake on the A21J (top of
fuselage - where were we talking about putting extractor vents?). Mike Burns
figured this out which is one of the reasons why the jet at Toc performs
much better than the factory prototypes (ie the entire production run -
just like every glider ever built).
Mike
Borgelt Instruments - manufacturers of quality soaring instruments since
1978 phone Int'l + 61 746 355784
fax Int'l + 61 746 358796
cellphone Int'l + 61 428 355784
email: [email protected]
website: www.borgeltinstruments.com
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