Towrope tension??

On Mon, 15 Oct 2018 04:34:27 -0700, Retting wrote:

Looking for information covering tension applied to a towrope during tow
and any other maneuvers while on tow.

Here's the result of a spreadsheet calculation I did some time back for
my Libelle being flown by myself, so the weights are accurate. Of course
I still have the spreadsheet.

Libelle on tow
==============
Glider weight 216 kg
Pilot+parachute 73 kg
Flying weight 289 kg

Glide ratio 36
Drag at best glide 8.03 kg
Best glide 53 kts
Tow speed 60 kts
Drag at tow speed 10.29 kg

Climb angle 600 fpm (5.67 degrees)
Load due to climb 28.54 kg

Total tow load 38.83 kg

Explanation
===========
I calculated drag at best glide as all-up weight / glide ratio and then
scaled it for tow speed as (towspeed^2 / bestglidespeed^2) since drag
varies as the square of flying speed.

Load due to climb: I calculated the angle as asin(climbrate/towspeed)
where both speeds are in kts. The tow load due to climbing is
flying weight*(climbrate/towspeed)

So the load in the tow rope is drag + climbing load.


--
Martin | martin at
Gregorie | gregorie dot org