The centreboard version of the Tonic 23 draws 0.71 m with the plate up and 1.37 m with it down. Everything that makes that possible lives in a slot you cannot see from the outside.
Getting the boat where you can work
The plate drops out downwards, so the boat has to be high enough to swing it clear — on a trailer that usually means lifting the hull off the bunks onto trestles. Support the stub keel, never the plate.
Freeing the pivot
The pivot pin corrodes into its bushes rather than wearing out. Soak it, work it back and forth, and resist the temptation to drive it out hard: the load goes straight into the laminate around the slot.
Warning: never lift the boat by the keel once the pivot is out. The stub carries the ballast, and nothing is holding it to the plate any more.
Cleaning up the plate
Cast iron weeps rust through whatever is on top of it, so take it back to bright metal wherever the coating has lifted, prime the same day, and build the antifouling up from there.
Reassembly and tension
Set the pivot with sealant rather than grease — grease washes out and leaves a path for water. Then set the lifting tackle so the plate stops just short of the slot: metal on laminate is what wears the slot oval.
Tip: mark the tackle at the fully-down position with a whipping. From the cockpit you can then tell at a glance whether the plate is really down.
What to check every season
Play at the pivot, wear in the slot, the condition of the lifting wire and its terminal. Ten minutes ashore, and it is the difference between a boat that takes the ground gently and one that does not.
