Hello Gary, hello all
I wasn't going to enter the debate but now I feel that it is about time to
put the
record straight.
A) The "Mandl air extractor" is anything but new. Schleicher experimented
with
a similar device more than 20 years ago and so did Dick Buttler in the
US.
B) If my information is correct both parties have found that considerable
drag is
created where the (almost stationary) ventilation air is meeting the
free airflow
again.
C) Statements such as "The size and geometry of the extractor lower the
pressure
level inside the cockpit to ambient levels and allow the ventilation air
to
seamlessly re-enter the external flow outside the fuselage." can only be
regarded
as an attempt to mislead the gliding public.
No air extractor known to mankind can accelerate the ventilation air
without causing
severe turbulence and hence create considerable aerodynamic penalties.
D) If I remember correctly onother manufacturer has claimed that his "air
extractor"
improves the performance of his glider by 3 or even 4%. Claims like
these are utter
nonsense! They were even privately disputed (laught at) by a member of
his own
design team.
E) There are a number of disadvantages with another opening in the fuselage
and
the ingress of moisture is only one of them.
I hope this brings the debate back to a rational level. Please let me
appologise upfront
if I have hurt someone or destroyed previously held beliefs.
Kind regards to all!
Bernard
-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of
[email protected]
Sent: Wednesday, 23 February 2011 9:18 PM
To: Discussion of issues relating to Soaring in Australia.
Subject: Re: [Aus-soaring] Air vent
Mike,
I am deleting old emails.
I came across this one of yours.
Re rain ingress - you are an inventive sort of person -do you have any
suggestions?
I note you did not suggest anything at the time.
Is it a problem, other than if the glider is tied down outside?
Have you further considered the matter? If so what did you conclude?
Has anybody else given the matter any thought?
Gary
----- Original Message -----
From: "Mike Borgelt" <[email protected]>
To: "Discussion of issues relating to Soaring in Australia."
<[email protected]>
Sent: Friday, July 30, 2010 6:14 PM
Subject: Re: [Aus-soaring] Air vent
>
>
> When we were discussing the DG Mandl extractor air vent some time
> ago I think I mentioned that the best location would be on top of
> the fuselage in the low pressure area.
>
> It seems either somebody saw that or had the same idea. Blending the
> vent tangentially to the rear was always a good idea and is commonly
> used in engine cooling. Nice touch to add the louvre. This looks far
> better than the relatively crude DG vent. Might want to organise
> something so rain doesn't get in though.
>
> http://www.streckenflug.at/news/js_communication_2010_07.pdf
>
> 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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