Towrope tensions....Part II

On Monday, October 15, 2018 at 11:59:23 AM UTC-4, wrote:
On Monday, October 15, 2018 at 10:20:53 AM UTC-4, Retting wrote:
Looking for towrope tensions information applied during a typical AERO tow. Singles and twins up to 600kg/ 1500#.
Perhaps testing was done back in the 60’s before Al Gore invented the internet. Prefer some numbers over methods of achieving.
The Uganda Information Award is still in play .... this thread only .
Credible Best Wag will be considered.
Civil disagreement with counter points encourage.
Numbers boys numbers.

R

Retting, you didn't make it clear whether you want the rope forces in the air, or in ground roll, or both.

Some months ago I landed my Russia (total flying weight about 250 kg) at another airport and got an aeroretrieve. Thought I'd try the low tow position for a change (always done high tow before). Once I got stabilized below the towplane's wake, the rope shape was very different from what I expected: it went horizontally away from the towplane, then down to the nose of my glider at a steep angle. When my speed or position changed a bit, the rope sometimes looped back over the nose, trying to kiss my yaw string. I did not like that at all, so went back to high tow. Possible explanation and connection to this thread: 250 kg divided by a lift-to-drag ratio of about 25 at that speed means a rope tension, in level flight, of about 10 kg. With such a light glider the rope tension was so weak that the air drag on the rope in the propwash behind the towplane was stronger, keeping the front half of the rope horizontal.

If the loop was as described you almost certainly were flying the low tow too low.
I point out to my students tat if the rope goes up when you release from low tow you are too low.
FWIW
UH