The 5.5 and 5.7 has the same mast except for the lowbudget external halyard and halyard lock of the 5.7.
I suggest you upgrade with the 5.5 top fitting with sheave, hook and ring. I have the top fitting and hook lying around, unfortunately shipping from Sweden might be a problem?
I mill my own out of delrin. But, I would agree with upgrading to the hook. If the sail is built right and everything lines up, it hooks and unhooks like a dream. Very simple.
-- Scott
Prindle Fleet 2
TCDYC
Prindle 18-2 Mod "FrankenKitty"
Tornado Classic "Fast Furniture"
Prindle 19 "Mr. Wiggly"
Nacra 5.8 "De ja vu"
Nacra 5.0
Nacra 5.8
Tornadoes (Reg White) --
Here is what came on my 1983 Nacra 5.0 which uses the same mast head setup as the 5.7.
I tried every sheave Murrays and others had, but could not find the correct size. I was just about to have a set custom made, but found out that the 5.0 (an upgraded version) is still made in Australia that uses the correct sheave. I ordered it from:
The only difference between this new sheave and the old originals is that it is supplied with a spacer to get the ID down to 1/4", the width and outer/inner OD are the same.
Hope this helps.
Enjoy
-- Hobie 16 (3 formerly)
MacGregor 25 (formerly)
Chrysler Dagger 14 (formerly)
NACRA 5.0 (currently)
High Point, NC --