My task is simple: navigate a 37' sailboat up the South River without grounding us using only a 100 yard sphere of information from the outside world, a chart, some basic tools, and my skill as a navigator.
|Courtesy of NOAA|
At the beginning of this exercise, the Fl (2+1) R 6s* buoy off of Saunders Point was directly off of our port beam and we were in 18 feet of water. Our boat draws about 6 feet of water, so my goal is to keep us in waters deeper than 10 feet; this not only allows me some margin of error, it also allows me to roughly follow the 12-foot depth contour on the chart if need be. I spend a moment looking at the chart and devise a plan. I need visible landmarks to verify our position, so I decide to plot a course that takes us close to navigational markers as we move up the river.
My first waypoint is the #4 red buoy (Fl R 2.5s), which is to our north near the mouth of the river. The water shallows up very quickly beyond the buoy so to allow for some margin of error I plot our course to pass slightly west of the buoy. According to my calculations, it should take about 9 minutes until the buoy is visible.
With our course plotted and the instructions relayed to Andy, all I can do is wait. To help pass the time, I inquire occasionally as to our depth but in this region the bottom is relatively flat so it varies little as we progress. 9 minutes come and go and there is still no sign of the buoy. My heart starts beating a little bit faster and I quickly review my calculations. Had I forgotten something? Were we off course?
Before I start to doubt myself too much, Andy yells down to me that he sees the buoy just off of our starboard bow, right where it should be. I make a quick mental note of the extra time it took; was that due to tidal currents, which I hadn't accounted for, or was it just an error in estimating our initial position? But those matters would have to wait because I needed to relay our next leg to Andy, which takes us northwest straight to the #5 green buoy off of Turkey Point.
There is a shallow bar between our current position off of red #4 and the next waypoint. My first instinct is to plot a course around the bar, but instead I plot a course right over it. Placing faith in our depth sounder and the quick reflexes of our helmsman I decide to use the bar as a way of establishing our position. We are only making about 5 knots through the water, so once our depth sounder reads 10 feet Andy can simply turn us to starboard to clear the bar. After we round the bar we'll have a reasonably good fix on our position.
At least, that's my plan.
Andy steers his course to the Turkey Point buoy, and I wait. After a few minutes, the water beneath us starts shallowing up.
10 feet. As per my instructions, Andy turns us 10 degrees to starboard to clear the bar.
9 feet. I have Andy turn us another 10 degrees.
8 feet. I have Andy turn us another 10 degrees, and I start to wonder if my plan to use the bar as a fix was too bold of a move. If we are further south on the bar than I planned we would have to make a much larger course correction than I had allowed for.
12 feet. I have Andy begin to turn us to port to resume our course to the Turkey Point buoy and breathe a quiet sigh of relief. My plan had worked, we were back on course, and I now had a much better fix on our location.
This goes on for another several legs and we make it about halfway from the mouth of the river to the bridge at Edgewater. Over time, Andy & I fall into a steady rhythm and sailing the boat blind seems almost natural. My calculations get more and more accurate so that we hit our last waypoint almost exactly when I think we should. At this point, Mark comes back the cockpit from his position on the bow and congratulates both of us on a job well done.
It's not actually foggy out; it's a perfectly clear day and Mark & Andy both had well over a mile of visibility and access to a GPS chartplotter in the cockpit. Mark isn't just a crew member keeping watch, he's a Royal Yachting Association sailing instructor and Andy & I are his students. This whole experience had been a teaching exercise meant to simulate sailing under poor visibility conditions with limited outside information. I can't speak for Andy's experience on the helm, but this certainly increased my confidence as a navigator.
If you are a sailor and ever have occasion to try blind navigation under good visibility conditions, I highly suggest that you try it. It is a bit stressful, but also very rewarding.
*This is nautical chart lingo for a buoy with a flashing red light that repeats a 2 + 1 flash pattern every 6 seconds.