MILTON MEDICINTEKNIK KB wrote:

> Another basic principle is to have a tank - as large as possible - and
> look at the air-flow out of it (ascending) or into (descending).

  I remember that one from 20++ years ago, for gliders.  Two thermistors
(bolometers) back-to-back on a strut across the nozzle to the tank.

> Most likely too bulky for a small airborne gadget.  :=)

  Why?  Don't assume the tank must be metal (though an aluminium can or
similar nosepiece comes to mind) or that it must be round.  A closed
cavity (bulkhead) anywhere in the model can be used.

  Note: sensitive to solar heating.
--
  Cheers,
        Paul B.