Use a Harken Carbo Air Block and it will pretty much never need lubrication
and it won't rust... Or conduct electricity... Or conduct EMF.
A 40mm may be big enough but the 57mm is a guarantee. Use the cheek
mounted style. I've provided a link below. ~$45.
This isn't for my boat, but it is about marine hardware, sort of...
First, background:
I have to hang a dipole antenna for our emergency management amateur
radio station. We're going to take advantage of some well placed
concrete light poles in the parking lot. The dipole must be able to be
