Originally Posted by Ann T. Cate
And yet our 36 footer once did 159.5 nautical miles per day between Vanuatu
, [I]average speed[I] so, as me mum used to say," circumstances alter cases." That boat had a 29 foot waterline, and was heavy by the racing
standards of the time. So she had a theoretical hull speed
of 7 knots, and that average was 6.65, which is fairly close to the hull speed
. It will all depend on your boat, and how hard you decide to drive her. FYI, I used 1.3 for my calculation.
With that boat, we counted on an average daily run of 140 n. mi. And over the years, that was quite reliable. Which is why I was so pleased with the 159.5, and oh, how I wished it had been the magical 160!
That was good sailing! But I think your case is fairly typical -- people who sail well and do it for enough years might well remember one passage
-- "once upon a time" -- where they were able to average within 1/3 of a knot
speed over a whole day. That does not at all contradict my statement that such cases would be quite rare.
My "once upon a time" passage
was several years ago sailing downwind in a storm -- 40 to 50 knots of wind
-- with just a bit of headsail out. It was enough power for sustained surfing -- where all hull
speed bets are off -- and we did 55 miles or so in less than 5 hours, with long periods at 12 and 13 knots (hull speed of my boat is 9.3 knots). It was thrilling, although we did take a mass of green water
into the cockpit
, the only time that has ever happened on my boat.
I have never matched your feat of a whole day within 1/3 of a knot
of hull speed, although my boat, with a bulb keel
and fairly aggressive hull form, can be driven to a knot over
hull speed without too much drama, if there is enough wind
. But as you know, it is really hard to turn high speeds into sustained averages over long periods of time. I have managed 9 knot averages on Channel crossings -- but just a couple of times out of dozens of crossings, despite the fact that we are blessed crossing the Channel with what is usually a beamish reach in 20 to 25 knots of wind. My last crossing in September was a really good hard one -- a beam reach in what turned into a F8 at the end. We sailed hard, and the average speed was 8.3 knots, although we had long periods at just under 10 knots. The little lulls and deviations really knock down the average. That kind of fits with my thesis that an average of one knot below hull speed is a really good, fast sail over any longish passage, which would require driving the boat at hull speed for long periods at a time. An average of 1/3 knot below hull speed would be an exceptional day, and a whole day at hull speed would be more or less impossible on most boats unless they are surfing.