Saint Croix to San Juan

Here's something of a trip report - my first sailing experience with celestial navigation.   It seems ironic that I teach a class called Primitive Navigation and have so little experience on board a sailing vessel.    

My opportunity came with an invitation from Erik Zettler, who is an associate dean with the SEA semester at sea program out of Woods Hole.   SEA runs programs with two working sailing vessels.   This particular outing was called a Colleagues Cruise, intended to expose faculty members to the programs they offer.   I leapt at the invitation, and saw it as a great opportunity to get some on-board experience.     As part of their program, SEA teaches celestial navigation, and their vessels are outfitted with a decent share of sextants and plotting tools. 

This cruise was with the SSV (Sailing School Vessel) Corwith Cramer, a 130 foot brigantine with a steel hull.   There were 18 of us academics and a generous complement of 16 crew members to introduce us to the programs.   

I brought with me a replica of a traverse board - a device used from about 1500 until the 1700's to keep track of dead reckoning.   It looks a bit like a board game, but I wanted to test its effectiveness under real conditions.   Since the Corwith Cramer also has a GPS onboard, I could readily check the results.  

Chart of the region of the cruise.   St. Croix (USVI) is at the bottom right and San Juan is at the top left.    Click on the image to enlarge.   On the chart, I note many of the prominent lighthouses and some lighted buoys. 

The cruise started on Jan 3rd out of Christiansted, St. Croix, in the US Virgin Islands.   I flew down on New Year's Eve to get a chance to look around the island.   January 2nd we went onboard and spent most of the day getting familiar with the vessel and safety procedures, with a short historical tour of the town of Christiansted.   

SSV Corwith Cramer in Christiansted, St. Croix.

Binnacle, wheel, and "doghouse" on the SSV Corwith Cramer.

Cannons in the Danish fortification in Christiansted. 

One big question in my mind had to do with seasickness.    I never get seasick when I kayak, and have been in some decently large seas, but I have gotten seasick during some recent charter-fishing outings.  In the fishing experiences, the vessel trolled lines in tide rips at low speeds - certainly not ideal conditions.   I was wary of getting a couple of days of that feeling and got both an anti-seasickness patch and some meclazine, an oral medication.    I was unsure which would be more effective, but finally opted for the meclazine, as I could control the dosage better than a patch (i.e. take more if I needed it).  

It turns out paying attention to sea sickness was a good call, as the weather forecast was for 25 knot winds and 8 foot seas.   The academics were divided into three watches along with the crew, and we were given our assignments.   My first watch started at 23:00 on the 3rd, stretching into 03:00 on the 4th.    The head of our watch was a woman named Sarah Herard, an alum of SEA with a considerable amount of sailing experience.   

Initially, I wanted to try to get some twilight shots both in the evening of the 3rd and morning of the 4th, but, alas, events conspired against me.   We set out of Christiansted mid-afternoon on the 3rd, with the first task to get a bottom sample while hove-to.   

I had brought a backpackers compass with me to try to get a point of departure from triangulation of landmarks on the island of St. Croix.    This was one of my first of several lessons:  it's tough to take magnetic bearings on a steel hulled ship.    I still wonder how the compass in the binnacle in front of the wheel is arranged to be free from magnetic deviation.   My own compass readings didn't make any sense, and I can only attribute it to local chunks of iron throwing things off.   I did see that the crew members took sightings from the compass on the binnacle all the time, which seemed like a sensible practice.   Well, if nothing, I was onboard to learn stuff, and this was my first lesson. 

After the bottom sample deployment, we then headed north in the direction of Saint Thomas.   At this point, despite the meclazine, I began to get seasick in the swells.  For better or worse, I wasn't the only one and a fair number of the academics were suffering worse than I was.   I accelerated my dose of meclazine, and Sarah suggested I might do well to get some rest before my midnight watch. 

My bunk was located next to the galley, which was close to the center of gravity of the Cramer.  This was a bit of luck, as I could lie there with minimal tossing around and it definitely helped the meclazine kick-in.   I decided to forego chance to do an evening twilight set of shots, as it seemed like I'd get more benefit from resting up.  

Around 22:30, I had a wake-up call.   I actually had dozed a bit, which was surprising.   Even more surprising, I had almost no seasickness at that point.   So, I had a cup of coffee and some cookies the stewards had put out for the watch and went up to the deck.   A second science deployment was scheduled for midnight.   I found that I was one of the few academics who wasn't seasick.   Some were in pretty bad shape and I felt sorry for them.   Going from nothing to 8 foot swells didn't give a person a lot of chance to make a gradual transition.  Actually, the seas got a bit calmer.  We were in the lee of St. Thomas, and I could make out the city lights of Charlotte Amalie in the distance.

In any case, I was put at the position of bow-watch.   The main assignment was to look out for vessels in the distance, squalls, hazards like rocks, and the like.   For the deployment, we turned south and Charlotte Amalie began to slip behind us.   It was getting cloudy, but we had a near-full moon, which sometimes poked through the clouds.   In the distance there were two flashing lights - one flashed every 10 seconds and I made it out to be the lighthouse on the island of Culebrita, off the northeast coast of Puerto Rico.   The other light was flashing every 6 seconds.   I wasn't sure what the identity of that light was, but later when I got hold of a chart, ID'ed it as the light on Punta Esta, on eastern end of the island of Vieques.   

Although I didn't triangulate off the two lights, they did give me a sense of position, as we hove to for the deployment and then began to sail again in earnest.   There was a large vessel passing by to our north - from the lights, I judged it to be a cruise ship.   The weather deteriorated some, with sprinkles, but nothing too bad.   

I have to say that that time at night on the bow of the Cramer felt joyous to me.   I wasn't seasick.   I could enjoy the view of the waves breaking, the moon occasionally breaking through the clouds, and the flashing lights became "friends" to me - their regularity somehow was reassuring and gave me a sense of position at sea.   

A bit before 1 PM, I was relieved of my bow watch and then assigned to steering.   I was surprised that the crew put that much trust in me, but it wasn't too difficult to get the hang of.   I was to steer a course of 320 degrees magnetic, or approximately NNW (true).   Sarah was very helpful on watch and agreed to help put the pegs into the traverse board.    The board is shown below. 

Left: traverse board, marked up from the midnight watch.   Right: Cramer crew member putting pegs into the traverse board.

The traverse board requires some explanation.  Back in the day, most sailors could neither read nor write.  Still, they had to assist the navigator by keeping track of the ship's dead reckoning.   How to do this?   Well, the traverse board was the answer.   There are two parts to the board.   The upper part is used to keep track of direction and the lower part was used to keep track of speed.   A four-hour watch was divided into eight half-hour segments.   

At each half-hour mark, one of the crew would put a peg into a hole in the upper part that represented the heading of the boat.   This was based on the 32 compass point system (North, North by east, northeast, etc).   Also for that half-hour period, a peg was placed in the lower rows indicating the speed of the vessel in knots.   At the end of a four hour watch, the navigator would note the positions of the pegs and then use this to figure the dead reckoning over that period.   

My aim was to see how accurate it was.   As part of the experiment, I asked the crew members to fill it in, so things wouldn't be biased by me.   

I was instructed on how to steer the ship.   At first, I just watched the compass, but I tended to oversteer, which is a typical rookie mistake.   It takes a bit of time to get used to the time it takes for the ship to respond to a rudder change.   Eventually, I used a bit of the rigging as a visual guidepost - sighting against landmarks in the distance.   At this point, we were beginning to sail into the Vieques Sound, with the island of Culebra to the northwest and Vieques to the southwest.   The lights on Culebra projected against some of the rigging gave me a good visual and pretty soon, I was steering better.   

After my stint at the wheel, I did a boat-check - basically an hourly round to make sure everything is working properly.   There were no problems of note.   I then returned to my bow watch.   Sarah told me to be on the lookout for a light that marked a small island and rocks that would appear off our starboard bow.   I strained my eyes, but, we were still too far away.   Finally at 03:00, I was relieved and gave the next bow-watch some things to look at for orientation and to be alert for the next light. 

Before heading back to my bunk, I asked the head of the next watch to continue to fill out the traverse board, which he did.   I snoozed a bit in the bunk.   

Close to dawn, I was awakened by people talking about passing Las Cucarachas (the cockroaches), a small cluster of islands off the NE tip of Puerto Rico.    I got up and saw both the main island and the small trail of islands just off. 

I retrieved my traverse board, which recorded our headings and speeds from 01:00 until 05:00.   The starting position was 18 degrees 10 min N, 65 degrees 11 min W, by GPS.   I took the readings and then figured our DR position.  I got an easting of -2.9 nm, and a northing of 6.9 miles, roughly consistent with a heading of NNW.    Comparing DR position, I got 18 deg 24 min N, while the GPS had 18 deg 20 min N, and I had a DR of 65 deg 25 W, while the GPS had 65 deg 27 min W.   

I didn't consider this too bad.   The two tracks, displayed as rhumb lines can be seen below.   The dotted is the track from the traverse board, and the solid is from taking the two GPS measurements.

DR rhumb line using the traverse board (dotted line) and rhumb line from GPS (solid).   Some of the difference may be due to leeway and currents, although the inherent imprecision of the travserse board should be considered.  The gray oval corresponds to the region where the Vieques light and the Culabrita lights were simultaneously observable - when I was on bow watch. 

In the above figure, I indicate the ranges of the Punta Esta and Culabrita lights as the dotted circles. The gray oval represents the range where both lights should be visible, and should correspond to the region when I was on bow watch - 23:00 Jan 3 to 01:00 Jan 4.

After passing between Las Cucarachas and the island of Puerto Rico, I went back to my bunk, with our next watch coming up at 13:00.    I got up at 11:00 and tried to get a line-of-position (LOP) from the sun, and convinced the crew to begin the traverse board exercise again.   

Around 11:20, I took a sun LOP with one of the sextants onboard.  The shot seemed consistent with our DR.    I wanted to get a LAN sight, but the shoreline of Puerto Rico to our south presented a conundrum - I could do a short-dip sight, but we were somewhere between 4 to 7 nautical miles to the north of the shore.   I used some of the tall buildings in San Juan to get an index correction of about 4 arc-minutes-OFF.   This seemed a bit high, but time was short and I didn't have the chance to take more checks of the index correction. 

I wanted to do a LAN sight, which meant I had to start doing sighting before local noon to see the sun's altitude increasing, and then see it decreasing.   Unfortunately I was back on watch at 13:00, which meant I was called to lunch around 12:15, very close to the time of LAN.   I ate as quickly as possible, but when I got on deck, it was already 12:30, which was after the time of LAN for that longitude.   Despite that, I seemed to get readings of a rising sun, and then a LAN time around 12:37, when the altitudes decreased.   At first I thought this was great, but I later realized that this didn't make any sense, as it would have placed me at a longitude of 68 degrees - impossible given our DR and possible speeds.   I finally realized that I was having problems with the coastline getting confused with the horizon.   

I had to eventually settle on a pseudo-LAN at 12:37 when the sun had already passed LAN, but was only at an azimuth of 182 degrees.   Given that the angle of 2 degrees was so slight, and our longitude was very close to 66 degrees, this gave a fairly reliable latitude of 18 degrees 38 min north.  I maybe should have insisted on eating my lunch later so I could get a reliable LAN, but it was a very busy cruise, with lots happening.

Close-to LAN LOP sight.

Plot of 12:37 LOP .

At 13:00, I was back on watch.   Sarah wanted me to take bow watch again.   I have to say that the bow-watch was one of the most pleasant parts of the whole trip.   It was quiet.   I could look for landmarks and vessels.   On the charts, I could see the mark of a lighthouse of 100 ft.   From quite a distance, I thought I saw a lighthouse, but as we got closer, I realized I was confusing a high-rise for a lighthouse.   As it turns out, the lighthouse was on top of the old fort - seen in the photo below.

Approach to San Juan Harbor, with the fort just to the left of the bowsprit. 

It's interesting to note my perceptions as we approached the coast.   At first I thought I saw a lighthouse indicated on the map, but it was just a high-rise building.   I also thought I saw a marina in the distance, with the masts of ships appearing, but in reality it was another cluster of high rises.  Finally, the old fort at the entrance to the harbor hove into view and things made more sense.  

To be helpful, Sarah indicated that she saw a vessel appearing on the radar, passing to our port-side.  Eventually I sighted that.   Then, later on, as we approached the harbor, she said that a small container vessel was departing from San Juan, and I should keep an eye out.   I saw this and reported it, but there were many pairs of eyes on the quarterdeck who also saw it.  

Finally, we made our way into San Juan and dropped anchor.   

It's tough to summarize the cruise.   It was altogether too short, and I could have used more time to work on my CN.   Still, given the crowded nature of the trip, I got some good experience in - finding things that were my own misconceptions and sorting out good from poor observations.   This is always the nature of navigation - whether real or metaphorical.