Thursday, August 20, 2015
Swells
The ocean is a new experience for Charlotte and I. Carrie Rose has been on the ocean with her previous owners but now it is our turn. The ocean presents a different set of challenges from the Great Lakes, rivers, and canals we have been travelling over for the last four years. Planning the next leg of the cruise requires the usual chart review, and besides the different weather patterns there are tides and currents to consider.
Part of the process is listening to the NOAA weather forecast. This in itself is not unique but part of the forecast is. NOAA weather forecasts cover a lot of ground both figuratively and geographically. The radio is turned on and the first thing to do is confirm that the forecast is relevant to the area we are in. There are, in many cases, multiple stations broadcasting.
Then we figure out where in the forecast the human or computer generated voice is. If the relevant part is missed, it could be another 5 minutes before it comes up again in the endless loop of the NOAA radio forecast.
It is common to lose focus, as the mechanical voice drones on about statistics, and miss the important part. So with pen in hand we concentrate. The part of the forecast that differs in the North Atlantic is the use of the term swell. This is not heard in the Great Lakes and their tributaries.
Swell is described in two ways: direction and period. Direction is which point on the compass the swell is coming from, and period is the time it takes for two peaks to transverse a stationary point. NOAA may say the swell is from the southeast with a period of 8 seconds. I make a note of this along with the wind blown wave information and think, what does this mean when I come out of the harbor mouth.
Many years ago, a friend who sailed the Newport to Bermuda race said that he was surprised by the ocean’s waves. He was expecting there to be long swells that even though large, allowed the boat to sail up and down them with more ease than the short choppy waves on the Great Lakes. In reality, the waves were from many different directions. The boat was being hit from all sides. He found it a most uncomfortable experience.
This was on my mind as Carrie Rose turned towards the North Atlantic. Our initial venture was from Jersey City, NJ to the first viable inlet at Manasquan, NJ. That day the wind was a steady 15 knots and started to gust to 20 as the day wore on. Since Carrie Rose was heading south, the NE waves pick up her stern and allowed her to surf down the front of the wave until the wave caught up and passed under us.
Picture this, first the left rear portion of the boat raises in an odd way for a 17,000 lb. boat. But let us not dwell on that. Remember when I said the boat surfs along with the wave until the wave catches up, well then the boat feels a bit like it is going to be flipped over but the wave passes under and instead of flipping over the bottom drops out. Now the front of the boat rises as the rear end sinks. Add to this an infinite number of variations of wind, wave and swell, and it keeps me riveted to the helm.
This brings another concept to mind. A boat steers because the rudder exerts a force on moving water. A boat travelling with the waves will on occasion match the speed of the waves and if the rudder loses traction the boat will fail to respond to the helm. When this happens the bow starts to turn sideways into the trough of the wave. This sideways turn needs to be controlled.
Carrie Rose, as boats go, is small, but she is a superbly designed craft based on the fast fishing boats in the Northwest. She has a long keel and a large 4-blade propeller driven by a big truck engine. If left on her own she usually does quite well with the autopilot steering. If not I take over steering and correct for this tendency. After many years playing in the waves I am better at anticipating what is needed to keep the boat safely on its heading.
Remember when I was talking about the waves coming from different directions, well that is what happened that first cruise south on the New Jersey coast. With the wind coming from the NE, short choppy waves were striking the rear of Carrie Rose. This was expected but there was something else going on in the waves that I did not realize until I started to steer.
Carrie Rose was being lifted from the stern by the northeast waves while riding up and down the long swells from the southeast. This odd mix of wave and swell combined on occasion to join forces and broadside the boat with a big whack and an impressive spray.
This was confusing the otoliths in my semi-circular canals. My vestibular system began to send caution signals to my gut. In the background mal de mar waited for its chance, which it never got. Steering the boat and concentrating on the waves helped stave off the effects of motion sickness.
The next time we ventured out into the Atlantic was to go from Atlantic City to Cape May, NJ. The wind was 5 to 10 knots from the northwest and the swell was from the south. I decided to stay close to shore to mitigate the effects of the northwest wind and because of this, the effect of the swell was noticeable. The autopilot had no problem steering us the 40 miles to Cape May. I sat back and watched Carrie Rose gently glide up and over each oncoming swell.
The ocean is now not a new experience. On a rudimentary level, my store of cruising knowledge has been enlarged. I would say that is a good trade for a few queasy hours in the waves and swells of the North Atlantic.
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