poor lateral control on a slow tow?

On Jan 6, 5:22*am, Eric Greenwell wrote:
On 1/5/2011 10:52 AM, Andreas Maurer wrote:





On Wed, 5 Jan 2011 09:23:29 -0800 (PST), Derek C
*wrote:

Gliders appear to get near to the stall during slow aerotows at much
greater than their normal free flight stalling airspeeds. I would
suggest that aerotowing must increase the wing loading in some way.

I have to admit that I didn't bother to read all the 120+ postings
about this topic, so please forgive me if the things that I'm going to
post have already been mentioned in this thread.

The main factor for the seemingly odd flying characteristics behind
the tow plane is the downwash of the latter.

Let me explain:
The downwash has a significant angle (the air is deflected downwards
behind the tow plane's wing to up to four degrees!), but due to the
larger span of the glider it only affects the inner part of the
glider's wing.

(big snip)

Andreas' posting was the clearest description for me of the wake effect.
I'd love to see "3-D" perspective view of the wake behind a towplane, as
I doubt I'm visualizing it well.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
email me)- Hide quoted text -

- Show quoted text -

One possible explanation for the slow tow effect is that although the
glider is (or should be) above the main wake and prop wash from the
tug, it is flying through air that has been pushed down by the tugs
wing. Hence it has to fly at a higher angle of attack to maintain
position. As this would only be a transitory effect that does not
extend too far behind the tug, using a longer rope should reduce this
effect. Certainly it seems easier to aerotow on a long rope than a
short one.

Derek C