Hi Gary,
I don't think that in flight it will be a problem. Hopefully air is
coming out at good speed. No worse than dive brake boxes on the
ground. Tape it up.
The air is going to come out somewhere if you let it in to the
cockpit. It may as well come out in one place rather than where it
can trip boundary layers, cause noise etc.
You must ventilate the cockpit for pilot comfort and safety
especially in warm climates. I can only ever remember being cold in a
glider once and that includes a ride to 24,700 feet in wave at
Minden. I could have gone higher but the non backed up constant flow
oxygen system and a decision before made long takeoff that 25,000 was
about the reasonable safe limit caused me to break off the climb
there. The cold incident was at Gawler one Easter. Jeans and T shirt
was quite comfortable on the ground but fairly extensive strato cu
cover and climbs to 6500 feet meant that it was near zero up near
cloudbase with little solar heating into the cockpit. I tried closing
the vent but the canopy instantly started to fog up so I ended up
trying to stay warm under a WAC chart.
I had an exit vent on my Mini Nimbus, a shallow blister with the back
end cut off and a couple of small guides for the flow. Located to one
side under the fuselage about in line with the TE of the wing.
If the glider is unsealed using an exit vent to reduce the internal
pressure can probably make a difference. At the very least it will
improve the cockpit ventilation.
Take a look at what John Murray of Eastern Sailplane is doing with an
exit vent kit for Schleicher gliders. Seems the right idea to collect
the low velocity air in the cockpit behind the pilot's head and
accelerate it to exit on top of the fuselage over the wing. Don't
forget the pressure difference on average between the top of the
glider and the bottom is equal to the wing loading.
The vent on the JS1 seems to be an attempt to cause the exit air to
flow parallel to the skin. I was not impressed by the internal part.
No attempt to gather and accelrate the flow inside the fuselage. When
doing this we must consider both external and internal flow. Ever
looked down the intake of an F86 Sabre? At least ther eis some
recognition of the need for exit vents now instead of the actually
wrong placements or accidental leaks of the past.
I'll have a bit more of a think about this. and try to model the
flows and pressures at least qualitatively.
Mike
At 08:48 PM 23/02/2011, you wrote:
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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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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To check or change subscription details, visit:
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