re. the speed: unless you were planing it is unlikely those speed figures are true. "Maximum" hull speed is calculated by the equation A*square root(waterline length) where A is a constant typically taken to be 1.34 (if waterline length is in feet and the speed in knots). For a 23' boat that gives 6.4 knots. However the value of A varies depending on the hull shape and could be as high as 1.5 which gives 7.2 knots maximum. For a BC23 something between 6.5 to 7 seems likely which fits with Andy's experience.
The "maximum" hull speed can be exceeded by using lots of power, or by having a very fine hull design (think rowing eight, kayak, catamaran, etc.) or by planing. The limit is imposed by wave making effects. When you see a tug or fishing vessel using full power and creating a huge trough behind the bow which the boat is sitting in, together with a huge wake, you know it's going at around hull speed and wasting power making all those waves
For a displacement sailing boat it also follows that once you are getting up to maximum hull speed you may as well reef because extra sail area is only making the boat less comfortable.
Any log which measures the flow of water past the boat needs calibrating since there will be regions beneath the hull where the water is flowing faster than boat speed and regions where it is slower. On Seatern the paddle wheel log placed to one side of the outboard well read low on one tack and high on the other. I gave up with it in the end. I now use GPS which has shown Seatern achieve a gratifying 10 knots and more (well, there might have been some current!).
Peter
