We just published another article on the importance of keeping drag low on our offshore sailboats.
Some may wonder why we make so much of this? Here are two (of many) reasons, which got cut from the article to keep the length reasonable:
#1 Fixed Props Suck
Back when I had my Fastnet 45 I had a great crew and we were pretty competitive racing inshore “around the cans”.
For one race we were in the process of having a new MaxProp hub bored for the somewhat idiosyncratic shaft, so I had taken off the old folding prop so the machinist could measure it, and substituted a spare fixed three-blade prop. We were granted the standard PHRF 12 seconds/mile adjustment.
We went from near the top of the fleet to DFL¹. We simply could not get out of our own way or sail to our handicap, even with the adjustment for the fixed prop. Not even close.
Being at the helm and trying to keep the boat moving as boat after boat sailed over us was heart breaking—I can still vividly remember the feeling 35 years later.
Yes, feathering props are expensive, but they also have one of the best cost benefit ratios of any piece of gear I can think of.
#2 A Clean Underbody is Vital
The summer we voyaged to Svalbard from arctic Norway we had been in the water for over a year and there was no suitable yard to haul the boat, so there was a thin layer of slime on the bottom (no shell).
On the way north across the notoriously bumpy Barents Sea I was horrified by how slow we were, to the point that before the return trip we spent hours building a scrubbing device to get the worst of it off while standing in the dinghy, and I even went over the side to check the cleaning and touch up (in a dry suit).
Lucky we did, given it was a five day stone-beat to windward across the cold, foggy, and bumpy five hundred miles back to Norway. I shudder to think how much longer that would have taken without the makeshift bottom scrubbing, even though we motor-sailed for much of it—you don’t hang around in the Barents Sea in late summer.
Just a thin layer of slime slows a boat a lot more than would seem logical.
Two Other Thoughts
In both cases the problem was not so much straight-line speed but it was the excessive deceleration in the lulls, slow acceleration in the puffs, and the loss of pointing ability that was so horrible.
And keep in mind that in each case there was only one slowing factor—fixed prop on the first, slimy bottom on the second—on otherwise optimized boats!