deep snow at home didn't stop us from heading to Lymington for the next stage in our preparations. Joy from Scorpion www.scorpionribs.com had come in to see us on Sunday (thank you Joy) and Matt at the Haven Boatyard was ready to help get the snow off the cover and launch Black Gold.We now have new straps everywhere: more in the aft locker securing the spare engine and its full fuel tank, straps in both directions in the console locker and most importantly of all, foot straps for the driver and navigator!We had drawn round our feet last weekend with a pencil and we now think our feet are in the right place according to the instructions from the seat designer, Dr Ullman.
The big interest for this trip, the last before our big run to Plymouth
and back next weekend, was to evaluate another propeller. Last week we had done six runs on the measured mile in Southampton Water, fed the results back to Scorpion. This is not perfect science, but there are several web tools to help you with these decisions and one "propslipcalculator" at www.mercuryracing.com was helpful for me as a guide.The reason it isn't an exact science is that there are so many variables (changing fuel load and boat weight, atmosphere, wind and sea conditions, height of engine on transom, engine leg angle and more).
What we were trying to do was reduce these variables and run at similar boat weights,
constant shaft angle, two way runs on the same water and of course, noting everything. We also decided to stay with the same make of propeller as we were happy with the boat's behaviour and just wanted to evaluate the pitch (angle) the prop. Needless to say our snowy weather meant that Southampton Water was bitterly cold as we ran one way into a 20 knot plus NW wind and the opposite effect the other way. The sea had also become lumpy which adds another set of variables. Two runs in the freezing cold and lunch in the Jolly Sailor in Bursledon with friends seemed like a good idea. The promise being that we came back to finish the job when the wind and tide were going in the same direction (this makes the water smoother).
We completed the runs after our roast lunch in the pub and then coffee on
board our friend's well heated Oyster sailing boat. I wouldn't say the results were of great scientific merit, but we had knocked 300 rpm off our previous weekend's top end runs and gained some knots while still being able to reach peak power on the engine's power curve.
Another good day's work and Paul, Nicholas and I drove home on less snowy roads with the car heater set at 22 degrees...
Next weekend we go on our first big run, which I guess for Roger and me will be more of a test of the crew than the boat.
Gavin
April 6th, 2008
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