A Tale of Two Takeoffs

Many a tow pilot has wondered, "why are they all whining about 60 knot tows, when that's well above their stall speed, even ballasted?" The answer is that gliders following the towplane are in the downwash of the wing -- not the propwash, the downwash -- but the wingtips are not. So, the wingtips are operating at a larger angle of attack than the main wings. They will now stall first.
Even if the wingtip doesn't stall, the aileron does -- you get the aileron response of ragged edge of stall though the main wing is flying. That's why gliders get wallowy and hard to control on tow behind slow towplanes. This has caused crashes. That's also why it's especially a problem when the towplane takes off, gets up to speed, and then heads for the sky, losing speed, as quite a few tow pilots seem to do. Now the glider is slow, stuck in ground effect, well below the towplane, and deep in the downwash. Yes, airspeed indicators are off, but it's not that hard to be aware of the issue, and ask the first few pilots for a calibration. I think the larger problem is we all get used to towing dry, and the higher speeds just don't feel right.. It's a worse problem for standard class, since they're stall speed challenged to start with and many flaps typically allow a little more twist.

10.6.2.9 ...Towplanes will tow at 80 miles per hour (unless otherwise requested) in a pre- selected pattern to an altitude of 2000 feet AGL (or as specified by the CD).