Wind and Waves

Now that you hopefully have a better understanding of following seas, let’s define a few more terms and procedures.

If I say the winds are westerly, that means they are from the west.  Generally I speak of wind direction in relation to the direction we are trying to go.  So, for example, when we left Cape Cod, the Azores and Europe were to our east, so we wanted to set a course to the east, therefore westerly winds would have been good, as they would have produced a following sea and all would be happy.  As it was, many of you already remarked, that we did not go east, as the winds were actually quite strong from the southwest forcing us to take a more northeasterly course.

This morning, the winds in Horta are howling, that is faster than strong, but not quite a gale!

I use knots to measure speed, as a knot = 1 nautical mile per hour, a nautical mile (nm) is about 1.12 statute miles.  We still use nautical miles because it turns out there are exactly 60 nm in one degree of latitude and since 1° of latitude equals 60 minutes, one minute of latitude = one nautical mile. It makes looking at charts and estimating time very easy.

So the Bost scale of winds:

  • Light and variable, less than 5 knots (6 mph) and from any direction. They are light enough, the direction doesn’t matter.
  • Light winds, 5 to 10 kts
  • Moderate winds 12 to 16
  • Strong, 18 to 25
  • Howling 25 to 35, (so today the winds are blowing 15 to 20, with gusts 37)
  • Gale 38 to 45
  • Storm faster than that.

Directions.  In general, directions like easterly, means in relation to a real map, so USA is west, Europe is east and South America is south.  On a boat, there is one other direction we look at, the apparent direction.  The  boat doesn’t know which way it faces, it just knows that the winds are on its nose (bow), that’s 0°, coming at a right angle to the boat, is on our beam, the starboard (right) beam is 90°, the port beam, (left) is 270°  All of these directions are relative to the boat. On the diagram I drew I added two more directions, the right and left rear quarters.  Basically, I try to keep the winds between 135° and 225°, and the more near 180°, the better.

 a wind diagram in relation to the boat

a wind diagram in relation to the boat

How the Boat handles in Winds and Waves

In calm weather and flat seas, I would normal run Dauntless at 1600 rpm, which would produce a speed of 6.2 knots and consume 1.5 gal of diesel per hour or 4.13 nm/gal.  Now how does this change with wind and waves?

If at the same 1600 rpm, if I was running into a 10 to 12 knots on the bow, or they are at 0°, dauntless would probably slow to about 5 knots, as this wind would probably produce waves of about 2-3 feet and we would start to pitch up and down (all wave heights mentioned are an estimate and an average, if the waves are 2 ft., there will be some 1 ft. waves, some 3 ft. waves and an occasional 4 ft. wave.  Think of it as a bell curve with the average being in the highest point of the curve, but there are extremes on both sides).

If this same wind were on the beam, our speed would stay the same, we would not slow down, but we would roll and 15° to each side. This is without the paravanes.  It would be uncomfortable.  And as you can see, a 10 to 15 knot wind is really normal, so the paravanes were really important.

From the stern, this same wind would add a few tenths speed and the ride would be ideal. That’s how we got the saying, “May You Have Fair Winds and Following Seas” I smile even writing it.

Now, if the wind is blowing 20 knots for any length of time and the seas have had the time to build, those winds would produce 5 to 8 ft. waves.  Going into them, our speed would be reduced to half, if they were on our beam, with paravanes, our roll would be one third of what it would be without, so about 10 to 15° with, without almost 40° (yes, I have done that, no, I won’t do it again. I never felt unsafe, but it’s miserable).  Larry Polster of Krogen told me he has had his 42’ roll as far as the cap rails.  I’ve never got that far (that I know of), probably only a foot below.

So the lesson here is that as the winds increase above 15 knots, it really limits ones course.  Therefore, when we left Cape Cod, while we wanted to head east, as the winds keep getting stronger and stronger from the southwest, it made os take an ever more northerly course and essentially pushed us to Nova Scotia.

So again, I am always trying to keep the winds in the rear of the boat.  We spent days and days just trying to get further south, but the winds and the waves they produced were not allowing it.

We only had two nice weather days.  I had been hoping that most of the trip would be under the influence of the Bermuda and Azores high pressure areas, giving us light winds, sun and very small seas, less than a foot.

But alas, it was not to be.

Also dauntless’ normal speed of 6 knots is about a third to a quarter of the speed of a low pressure system across the ocean,  So even as one storm passes, the next one will catch up to us in a few days.

One of the reasons we only saw whales and turtles once, was that it takes calm seas to notice a turtle floating near you or to see a whale surface.  We only had two days without white caps and those were the days we say the whales and turtles.  The first few days Julie and I wanted to see whales so badly, we were imagining them everywhere, but it was only the waves tops.

A distant TCU

A distant TCU

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