Mike,

If the tow line formed a 20 degree angle to the glider, (from tow plane
upward to glider) the glider would have to be 72 feet ABOVE the tow
plane.

Well, really allowing for the angle of climb, it would be 72 feet above
the "direction of flight" of the tow plane. If the tow plane could
climb at a 20 degree angle you would be level with the tow plane, but this
is not possible, If the tow plane climbed at a more reasonable angle of 5
degrees you would be 54 feet above the tow plane.

This, in my opinion, would be dangerous!

I like to tow with the tow plane's wheels sitting on the horizon. This
means that the glider is about 5 feet BELOW the towplane, and the angle of
the tow rope is about 1.5 degrees UPWARD from glider to tow plane.

I despise the term "high tow" as it implies positioning the glider
"high" and above the tow plane. I use the term, ""low tow" for
flying below the wake and the term "normal tow" for flying level with,
or slightly below, the tow plane, but above the wake.

In my opinion flying above the tow plane is forbidden!!

Cookie






At 04:07 15 March 2009, Mike the Strike wrote:
I took a good look at the geometry of my tow today. The tow line
appeared to be pulling down on the nose at about an angle of twenty
degrees. At 65 knots, the tow line formed a catenary to the towplane
with significant sag in the line.

It should be possible to model the angles of the line and angles of
attack of the towplane and glider, but I suspect some of the
simplistic arguments have not explained the phenomenon because they
haven't taken full account of the complex geometry of the tow.

At around 50 to 55 knots, I am unable to maintain high tow and sink
into low tow with no elevator authority and reduced aileron control.
My free-flight stall speed is below 40 knots. Gurus please explain.

Mike