Thank you Bernard, I fly 55 and the tail was where I hoped the air was leaving the glider. Really the only option I guess.
Cheers Paul On 24 February 2011 15:14, Future Aviation <[email protected]> wrote: > Hello Paul > > The reason why I had reservations entering the debate in the first place > was concerns about > a large number of e-mails that need answering. I will answer yours but ask > for everyone's > understanding that I can not continue to do so! > > 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. > Even a partial sealing of these openings causes a large reduction in > ventilation airflow. > But not only that - it is also detrimental in terms of performance as the > air attempts to > escape in other (less desirable) places. > > I trust this helps. > > Kind regards to all > > Bernard > > ------------------------------ > *From:* [email protected] [mailto: > [email protected]] *On Behalf Of *Paul Bart > *Sent:* Thursday, 24 February 2011 2:18 PM > > *To:* Discussion of issues relating to Soaring in Australia. > *Subject:* Re: [Aus-soaring] Air vent > > 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 >> > > > _______________________________________________ > 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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