Earlier, Wayne Paul wrote:

Is the Applebay hook similar to the Schreder design?

I think it's similar but not identical. George has said that he's not
familiar with the Schreder hook design. My memory of hooking up Z2 at
Sky Sailing (we're talking 1979 or so) is that the Applebay hook is
similar on the outside to the Schreder -455 hook, but I have no clue
what's on the inside.

By the way, one of the Schreder apprentices (I can't remember which,
though it might have been Australian Ross Nolan) once told me that Dick
saw the -455 hook in a dream, and drew all its parts out that
afternoon. That would have been between about 1958 and 1962. Dick used
that exact hook design in all subsequent HP designs through about the
HP-20 in 1984 or so. About five years ago I sold one of the SparrowHawk
guys a set of drawings for the -455 hook. They seem to have used that
same basic design, though resized and optimized for their lighter
weights and lower loadings.

Thanks, and best regards to all

Bob K.
http://www.hpaircraft.com