[Rhodes22-list] Reconnecting the Tabernacle Screws Following Sacrificial Failure

[Chris on LBI]

Roger,

Thank you for that thought regarding uneven loading of the screws. I suspect
that you are correct that the screws would actually fail in some sort of
sequence. It sounded like a single "pop" when they gave way, but it easily
could have been three pops almost on top of each other.

Unfortunately I don't really have a target pullout force to base the design
of the repair around. As I speculated in the original thread, under normal
mast stepping/unstepping process, the screws should never have any upward
force acting on them; it should all be shear force when the mast is
horizontal. So I don't know whether 70, 210, 500, or 1500 pounds is "right".

All I really have is a guess at how the factory may have constructed it to
begin with (how long were the factory screws? what diameter were the factory
screws? was the fiberglass hole larger than the screw itself?) and my boat
with 1" screws and oblong holes that are larger than the screws. I don't
know if or how many times my boat has already been through previous repairs.

Also, I don't know what the designer's (Phil Rhodes?, Stan?) original
motivation was for this sacrificial joint. Was it intended to fail safe to
protect the cabin top (and what would be the maximum allowable force) or to
protect something else that finds itself in the path of the lower half of a
descending mast?

Thanks,
Chris






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