Posted by Andy G on November 14, 2005 at 11:55:21 from 130.159.248.44 user AndyG.
In Reply to: Re: Well? Re: Arthur Ransome and S&A in Wikipedia posted by Robert Hill on November 12, 2005 at 00:35:54:
As I was taught it, a centreplate is normally taken to mean a vertical, usually parallel-sided board which is lowered into a slot at the top of the centreboard well, in order to provide sideways resistance when beating and reaching. The centreplate (also known as a dagger board can be removed completely from a boat with ease (as in, for example, the Mirror and Laser dinghys). Depth of the plate, and therefore the amount of resistance available, can be reckoned from what's left stickin' up. Running aground with a centreplate is no fun.
A centreboard, however, is pivoted on a bolt which passes through the fore-end of the centreboard case, and is lowered by degrees to provide variable resistance. Running aground is more of a warning (the board pops up) than a disaster. When up, the centreboard tends to fit wholly in the centreboard case - though in many boats the trailing edge of the board will sit above the top of the case (as in an Enterprise or GP14, for example).
Here's a photo of Mavis' centreboard:
The discussion in S&A regarding the bowels of the Amazon suggests that that boat has a centreboard, presumably a heavy one, held up by tackle when not required. Mavis clearly shows a similar arrangement, though unlike most modernish dinghies, the top of the centreboard case is covered and not open. Nancy's comment about an iron keel therefore sounds very much like the Amazon has a galvinized iron centreboard**. (In more modern dinghys the centreboard is often wood, which makes keeping it down harder - often there's a split pin which passes through both the centreboard case and a hole in the back edge of the board to prevent the board from floating up.)
I've barked my shins and knees on wooden centreboard cases for ages - I'd be very wary of the metalwork at the aft end of Mavis' case. It looks deadly!
A note to potential duffers: removing a centreboard requires you take out the bolt - which is under the water level when the boat's afloat. :-)
Andy G
** That said, an iron rubbing strake is common under wooden keels in small boats.