B - Classic)
Manfred,
For what it's worth - my opinion.
>
> * *
>
> * 1/.) I know the instruction on Mod 61B-Classic says that the hole of
> the stall warner should be 52 (1321 mm) out from the aircraft
> centreline, so far so good!/*
>
> */ I actually would like to know whether this point 52 is obligatory
> or could it be 70?? And if it must be 52 what is the reason for
> this exact point?? Does 70 from the aircraft/*
>
> */ centerline not work accurately? And why not? (Because I installed
> already an empty tube to the 70 point at the beginning when
> manufacturing the wing!!)/*
>
Wing section at 70" has slightly lower angle of attack than wing section
at 52" and stalls a little later, but I think it will work perfectly
well. Actually, on new build the postion is at least 70" out on the wing
(past the flaps I remember) and in addition XS wing twist could be
greater than Classic wing twist (?).
>
> *//*
>
> */2.) I understand that a vacuum appears on a special point _below_
> the leading edge if in stall configuration. /*
>
> */ But to my past knowledge in air-pneumatics on the leading wing
> edges there should still appear a pressure instead of a vacuum when
> the wing comes to the stall. I looked /*
>
> */ into many /*good aeronautical text books containing the theory of
> stall characteristics but I always found a pressure there!?//
>
> */ I would like to understand the airflow = pressure or vacuum = on
> the leading wing edge in stall configuration on our type of wing./*
>
> */ Could someone give me some hints, where I could see/read the
> theoretical background on this subject? Perhaps on the internet?/*
>
At high angle of attack stagnation point (pressure = dynamic pressure)
moves to underside of wing. Somewhere just below leading edge pressure
drops to below static pressure.
Stagnation point: see attached.
Interesting book including stall warner explanation:
http://www.av8n.com/how/
>
> *//*
>
> */3.) In the retrofit installation instruction (Mod 61b Classic) it
> calls at page 5 for a _W39 probe_ to be installed at a special angle
> as per the hole template!/*
>
> */ What kind of probe is that? Is it just a small brass or aluminium
> tube of 3 mm inside diameter, or is it a special manufactured probe
> with a sophisticated inside/*
>
> */ configuration? Is it a must buying it, or could I manufacture it
> myself?/*
>
Must be just an installation aid - on new build the probe is nothing but
a 5052 aluminium tube.
Inside diameter 3 or 4 mm, 1 mm is enough. Will allow tuning the hole
position up/down somewhat later.
Regards,
Jan de Jong,
filling the canoe of #461
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