Max Tow Weight and Rope Strength

I am trying to find (remember) the standard formula for tow pressure on the
tow line in a standard smooth tow.
I forget if it is weight of the glider divided by L/d or a percentage of
L/d.

Initial tow pull to get rolling, is high drag on the line. I can tell when
the skid comes up on the 2-33 or when the 2-33/Grob/Janus break ground. The
reduction in rolling resistance can be felt in the tow plane, even on a
paved runway. We never notice a 1-26 on tow. Unless the weak link has been
further weakened by use, we normally don't break the link for training slack
line recoveries.

We have a Standard Schweizer tow set up on our Pawnee and it is placarded to
1200# Max.
Our weak links are to the about the 1000# configuration to fit the 80-200%
CFR requirement for most of our gliders. We routinely tow one glider at
about 1500# with no issues. This glider POH specifies a weak link tolerance
higher than our standard links and CFRs. We have a special weak link for
that one and still stay within the 1200# max.

Yes the Tow rating is limited to being able to effect a release if it had
the max pressure holding mechanism, as in the case of the glider kiting and
lifting the Pawnee tail.

B

"150flivver" wrote in message
...
On Apr 13, 8:01 am, wrote:

The basis of this specification, if I recall correctly, was force on
the release handle.
Rope strength is specified with limits related to the max certified
gross weight of the glider being towed, that is NTL .80 of gross wt
and NGT than 2.0 times gross wt. Weak links can be used, as
appropriate to saty within these limits.
If the approved installation of the tow hook has other limits, they
are in addition to those related to the glider defined limits.
If you are using a hook not produced for towing gliders(there are lots
of home made banner towing hooks made to AC 43-13 which may not be
suitable for glider towing), consider moving to a proven tow hook
installation.
Good Luck
UH

So in your example, a Schweizer hook is limited to 1200 lbs and it
would be acceptable to tow a 1500 lb glider as long as the rope (or
weak link setup) was rated at 1200 lbs? Unfortunately, the wording on
the placard doesn't refer to rope strength limits, but to maximum
glider weight. If it referred to rope strength, I could see it being
legal to tow a 1500 lb. glider by using a 1200 lb setup but because it
specifies a max gross weight for the glider/banner, wouldn't anything
heavier exceed the legal limit?