Hi Bernard Firstly let me say that I have no credentials in glider design, so please take my comments on that basis.
Clearly, with the vents open, there is a considerable inflow into the cockpit. That is only possible if an equal amount of air leaves the cockpit. So I am wondering, would it not be better if the outflow was managed? Perhaps it already is. Cheers Paul On 24 February 2011 13:35, Future Aviation <[email protected]> wrote: > 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]*<[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*<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* > > > > _______________________________________________ > > Aus-soaring mailing list > > [email protected] > > To check or change subscription details, visit: > > *http://lists.internode.on.net/mailman/listinfo/aus-soaring*<http://lists.internode.on.net/mailman/listinfo/aus-soaring> > > > -------------------------------------------------------------------------------- > > > No virus found in this incoming message. > Checked by AVG - *www.avg.com* > Version: 9.0.851 / Virus Database: 271.1.1/3037 - Release Date: 07/30/10 > 04:34:00 > > _______________________________________________ > Aus-soaring mailing list > [email protected] > To check or change subscription details, visit: > *http://lists.internode.on.net/mailman/listinfo/aus-soaring*<http://lists.internode.on.net/mailman/listinfo/aus-soaring> > > _______________________________________________ > Aus-soaring mailing list > [email protected] > To check or change subscription details, visit: > http://lists.internode.on.net/mailman/listinfo/aus-soaring >
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