Friday, October 28, 2016

Boca Chica: Motorsailing Experiment, Clearing Out, Up the Mast Again, Wrapping Up Our Panama Cruise

We left Bahia Honda on Tuesday morning to sail back to Islas Secas a little over 30 miles to the northwest. It was a beautiful morning with a gentle wind blowing, perfect for sailing. Except that the wind was coming from the northwest. How does this happen? Is it a conspiracy of the oil companies to control the climate of the planet to force sailors to buy more diesel?

Later in the morning and through the afternoon, the wind shifted to the west so I unrolled the jib and began experimenting to develop a strategy for optimal motorsailing. Developing such a strategy under these conditions will likely prove helpful, since winds should be blowing from the southwest to west for most of our long passage to Mexico and the rhumbline for that passage is about the same as the course we were laying to Islas Secas. I have sadly concluded that Intermezzo, like many cruising catamarans, is so terrible at tacking upwind that there is no point even trying. Unless the wind is at greater than a 70 degree angle, we have to have an engine on to make reasonable upwind progress.

I created a custom display on the second chartplotter to display our velocity made good (VMG) to our destination, the ground wind speed and direction and the apparent wind angle (AWA) and apparent wind speed (AWS). VMG is the key metric, the rate at which the boat is making way to where we want to go. If we can point the boat directly at our destination, VMG would be the same as the boat's speed over ground (SOG). If the wind is coming from the same direction as our destination (the curse under which we suffer), we can only get their by motoring against the resistance of the wind. However, if we hoist sails and turn away from the wind until they fill, the motor gets a boost from the wind and our SOG increases. Since we are now no longer pointed directly at our destination, our VMG is less than our SOG because only some of our forward motion is towards our destination. Yet our VMG motorsailing veering slightly from a direct course can be greater than if we just motored directly because the boat is going faster. The goal is to find the optimal wind angle to maximize VMG.

My experiments on the way to Islas Secas were conducted while flying only the jib. I will conduct similar experiments while flying the mainsail as well, but I suspect that a jib-only motorsailing strategy will be better when tacking is taken into consideration, as I will explain later. I found that maximum VMG was achieved at an AWA of about 40 degrees. With a ground wind speed of around 12 knots, we achieved a VMG of about 6 knots, almost 20 percent faster than our direct fuel-efficient motoring SOG of around 5.2 knots. As we got closer to our destination our VMG decreased, as the course we were sailing diverged more and more from our intended course. It was only worth motorsailing if VMG remained greater than our direct motoring SOG.

If we were just sailing, without the engine, we would bring the boat across the wind and sail on the opposite tack, zig-zagging our way upwind. Intermezzo's tacking angle of about 140 degrees brings tears to your eyes when you do this, which is why we need to motorsail upwind. With a motor running, we can reduce this tacking angle to around 90 degrees. Plus, if the wind isn't coming exactly from the direction of our destination, one tack is more favorable than the other and we don't have to cross completely through the wind to fill the sails on the unfavorable tack. With the wind coming from the west and our destination to the northwest, the port tack was the favorable tack for motorsailing; crossing over to a starboard tack would actually result in a VMG of near zero. So when VMG dropped on the port tack to below our direct motoring SOG, we rolled in the jib and just motored directly to our destination. I'm not sure if having the mainsail up would have increased our speed enough to make it worth the effort of hoisting it and dropping it or the annoyance of letting it flap around luffing while we motored directly, compared to just unrolling and rolling the jib. That will be the next experiment.

So, it looks like a decent strategy for our passage to Mexico is to motorsail on the port tack at an AWA of about 40 degrees and then motor back directly to the rhumbline when we get too close to shore, an asymmetric zig-zag course up the coast. Looking at wind maps, it seems like heading further offshore might be beneficial, too, to try to catch more of the prevailing southwesterly winds and to give us more sea room for our motorsailing strategy.

Okay, enough with all my technical sailing musings. Back to the travelogue.

We arrived at the anchorage at the north of Isla Cavada just after 3 pm, the same anchorage where we had spent a few days at the beginning of our cruise. I really love this anchorage, definitely one of my favorites of the trip. I like the steep lush island, the little white sand beach, the gap through which you can see the windward sea and islands beyond, from which a nice cooling breeze often blows. When I get to posting pictures, you'll at least see what I mean; you will have to imagine the breeze, though. We enjoyed a very pleasant afternoon and evening there.

The next morning we weighed anchor to head to Boca Chica, where we hoped to officially check out of Panama and get our zarpe to Mexico, the vital document you need from the country you are leaving to enter another country from sea around here.

Boca Chica is a nice little bay with a small town with a few sportfishing resorts, a couple of small hotels and some nice residences around it. When we arrived we took the dinghy to town to do a brief reconnaissance of the docks and landmarks and then I got in touch with Moisés, the maritime authority representative from Pedregal, via cell phone. He told us he would drive all the officials required to check out and for our zarpe from Pedregal to Boca Chica and meet us at the town dock in the morning.

Sure enough, shortly after 10 am the next morning, Moisés, accompanied by representatives from immigration and customs arrived at the dock and 45 minutes, a sheave of papers and $95 dollars later, I had me my zarpe to Mexico.

Officially, we had to leave Boca Chica at 6 pm, but we knew there was nobody watching us to make sure we did. So we used the rest of day constructively to attend to boat chores. I went up the mast for the fourth time and, success! I finally replaced the main halyard and switched out the anchor light bulb for an LED. The main now raises and lowers much more easily and the LED consumes about 1/10th the energy of the incandescent bulb.

In the evening, we dinghied to the Hotel Boca Brava for dinner. It's a very nice boutique hotel with a decent restaurant. We shared ceviche and a fresh salad, I had "chicken pomodoro", a rough attempt at a light version of chicken Parmesan and Renee had a tasty grilled yellowtail tuna, all of which we washed down with a nice, crisp, chilled Argentinian white wine and followed with desert and locally-grown coffee. It was a very elegant way to end our Panama cruise.

We left Boca Chica early this morning just in case any officials happened to come by and headed to Isla Gamez for the day. We'll leave here around 3 pm to set sail for Golfito, about 15 hours away. It will be only a short stop in Gofito, just long enough to refuel and pick up a few groceries. We're going to come in "under the radar" as illegal aliens again.

We really enjoyed our Panama cruise. As with all good things, you feel a little sad when it's over. Yet mostly I feel excited about moving Intermezzo closer to its final destination and even more so about seeing loved ones over the holidays.

Our long slog northeastwards begins.