Max Tow Weight and Rope Strength

On Apr 14, 8:54*am, 150flivver wrote:
On Apr 14, 7:32*am, wrote:





On Apr 13, 9:32*am, 150flivver wrote:

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?

To repeat myself another way: You should look through the records for
the aircraft and determine where the limit on the placard came from.
It may be as simple as someone putting their own saftey factor on top
of one established by the hook supplier.
A 1000 lb limit seems really low. This would preclude towing most 2
seaters including *2-33's(1040 gross wt).
Having determined origin, it can be either corrected, or if not,
consider a hook installation more suitable for your needs.
If it is someone's home made hook, it may be placarded that way
because it was only tested to that force when it was installed. AC
43-13 specifies these testing requirements and is commonly used as
method of compliance by banner tow guys. The placard you describe
mentioning both makes me suspect this could be the case.
If it is not a commonly used glider tow hook(Schweizer type or Tost),
I would seriously consider going to a proven glider tow hook which has
been demonstrated to work at the expected loads and proven to release
when you need it to.
FWIW- the highest loads I've experienced have all been from hanging
the rope in the trees and getting the "big yank".
Good Luck
UH

Are any hooks rated to more than 1200 pounds?- Hide quoted text -

- Show quoted text -

Tost hooks go higher- not sure what limits are- Tim Marra would know.
What kind of towplane is this?
UH