On Jun 29, 7:20*am, Tony wrote:
On Thursday, June 28, 2012 9:43:36 PM UTC-5, Karen wrote:
Simple question, but why are tow hooks marked, "1200 lbs Max weight",
like the Schweitzer type release, towing big heavy 21M ships, *ships
with water, Grobs and others over 1300 lb gross weights? Actual
pulling weight? Is there an FAR? Thanks.

1200 lbs on the towhook refers to the maximum rope strength, not the maximum glider weight.

And if you trace it back far enough, it probably stems from an old
NACA study on glider towing loads from the 1930s where they said "We
don't think there is ever a case where you could apply more than 1200
lbs load to a glider tow hook." And thus, we in the US are saddled
with a tow hook limitation from the days of 800 lb max weight two seat
gliders from the 1930s.