On Jan 5, 6:51*pm, ProfChrisReed wrote:
I'm still not convinced by those who propose that the wings of the
glider generate no extra lift (or even generate less lift) when
climbing on tow.

We know that on a winch launch the glider climbs because the wings
generate more lift than in level/descending flight. This must be true
because there is nothing pulling it up.

However, we are told that on aerotow the wings generate the same (or
less) lift as in level/descending flight and the tug just pulls the
glider up the slope.

Does this mean that the tug climbs in the same way, i.e. wings
generate only enough lift to carry the weight of the tug, and the prop
drags the tug up the slope? This doesn't match what I've read about
how aircraft work. L=W only in level flight. I think the tug's wings
generate more lift than its weight, and thus it climbs.

If this is true, the same must be true for the glider behind it.

Bring on an aerodynamicist to show me I'm wrong.

Chris.

Winch towing is different than aerotowing on a couple of points. On
winch the glider goes through a couple of accelerations (change is
airspeed and or direction)..."arcing flight path". The glider also
must carry the weight and drag of the winch cable.

But the glider climbs on winch tow because the winch is imparting
energy to the glider. "thrust" if you will.
A glider climbs on tow only because of the energy imparted into it by
the tow plane.
A towplane climbs because of the energy inmparted into it by the
engine, from the fuel.

Its a study of potential energy (fuel) being converted into kenetic
energy (thrust) being converted back into potential energy (height)

A glider can only climb due to the following........

Tow plane
Winch
Thermal
Wave
Ridge lift
Its own power source (motorglider)
Being carried up a hill by a human (hang glider)

Etc

these are all external sources of power.

To climb we need "excess horsepower".....not excess lift

Excess lift will cause a change in flight direction and or change is
airspeed.

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