J/30 Class Association Forums J/30 Forum The Boat, Sails and Equipment Cabintop opening for Mast

Does anyone have precise dimensions on the cabin top opening through which the mast is lowered to rest on the keel?

I have the kenyon mast dimension here.


But - how closely does it fit, and how closely does the shape match?

Looking to perhaps change my strategy around holding the mast when it's lowered, to using a U-section on top of a post down to the keel instead of a foredeck A-frame.

The opening size varies over the production run of the boats Most have about a 1/2" of clearance around the mast

Don't count on the opening being centered and symmetrical. I found this out when I centered the top of the mast over the bottom of the keel when the boat was out of the water. I poured Spartitite and found the mast was almost in the extreme stbd side of the cutout, leaving a larger gap on the port side. Fore and aft was about right when I set the front of the mast at 3505mm (11 ft 6 inches) per rule 5.7.3

I had the exact same result centering the mast relative to the chain plates, because it looks so odd I double checked a couple of times.

Thanks everyone.