The powers in the know seem to indicate that just cutting a hole in the
back may not be the solution, it is important to figure out the way in
which the air re-enters the airflow.
The theoretical advantage of not having air spilling around the canopy
edge is easy to understand. How to quantify this advantage and how many
seconds of flying with the wrong flap setting this may buy you is
another question.
However, after having flown the JS1 most recently, let me add the
following observations:
The cockpit is very quiet and the ventilation is excellent, with the
adjustable air nozzle providing all the comfort you would need in a hot
day. There is a marked advantage compared to the already good (and in
other ways identical) Schleicher setup.
In fact, the ventilation is so good that there is no need to ever have
the side vent open on the Mecaplex sliding panel. To my initial surprise
JS have now discontinued the Mecaplex vent altogether. This provided no
discomfort, even on takeoff on a hot African day. Whatever the
performance gain of the air extractor, not having to open the side vent
offers an additional advantage.
I reckon the "shark gill" must have about 30pts of value on a comp day
based on psych factor alone. Just be sure to polish it thoroughly while
on the grid.
Alexander Georgas
On 15/12/2013 20:01,
wrote:
Noticing all the openings behind the cockpits of mainly Schleicher gliders such as -27 and 29's I'm asking myself if this is a real drag reducer or a placebo. For those unfamiliar: people have been cutting 4x2 openings into the fuselage about 8" behind the canopy cutout and put air vents - some with funnel-like contraptions on the inside of the turtle deck into their gliders. The funnel seems to suggest to the air molecules "this way out", some pilots may put arrow stickers on the inside so the air knows which way to flow. The whole thing is meant to avoid pressurizing the cockpit from the front air vent. Air leaking from the canopy seal would trip outside air flow to become turbulent.
Are there any serious comparison flights that were done following a scientific protocol to show the effect of such devices? Is this really better than putting a Tibetan prayer flag on the tail or a plastic Jesus on the glare shield? The latter can serve double purpose since I know where I would stick my transponder or PFlarm antenna...
Seriously, I'd be interested if anyone has found this thing useful beyond the statement that it must be good since all these hotshot pilots (insert call signs here) have one.
I'm waiting with jigsaw in hand for your responses, the LS8 rests uneasily in the basement!
Herb, J7