Saturday, February 6, 2016

Manzanillo to Ixtapa, Passage Planning

We’re setting sail from Manzanillo to Ixtapa this afternoon, an approximately 36 hour non-stop, overnight passage. This isn’t a particularly difficult trip, although it is along a stretch of coast that is distant from law enforcement and some reference sources warn of risks associated with this. My own research indicates that thousands of boats have made this journey and there have been no significant incidents reported in the last three years and only a few before that. I think the coast road might be a bit sketchy for driving along, but I'm confident the sea route should be plenty safe.

I thought it might be of interest to some of you who read this blog for me to summarize the approach I’ve developed over the past few months to planning a passage such as this one.

First I take a look at the large scale paper charts that we have for this area. This provides a good overview of the coastal waters and their major landmarks, lights and navigational hazards. Coastal navigation is mostly about knowing where you shouldn’t be, e.g. aground on a shoal, as it’s pretty easy to figure out where you are, using your eyes, dead reckoning, GPS and/or radar.

Then I read the Sailing Directions for the area, which summarize the major features and hazards along the coast and the cruising guides we have on board.

Armed with this information, I plot a route on my iPad using the Navionics Boating app. Usually this involves entering waypoints for the route’s start and finish and then setting intermediate waypoints to stand off coastal landmarks a desired distance. For this passage, we’re going to stay out about 5 nm from the coast to avoid some currents and waves around a few points along the way and to be beyond the comfortable range of local small craft, but inside the main shipping lanes.

I pull the latitude and longitude coordinates from key waypoints and enter them into our PredictWind Offshore software to look at weather routing options for different departure dates and times. PredictWind gives us graphic and tabular data of the winds, swells and weather we are likely to encounter along our route based on the estimated speed under motor and sail.  We time our departure accordingly and so as to reach our destination during daylight hours. For this passage we’ll be leaving around 4 pm so as to be approaching Ixtapa around sunrise on Monday, slowing the boat down in early morning hours if we need to.  During the passage, I download updated forecasts by satellite using our IridiumGo! about every six hours. We have found PredictWind’s forecasts to be quite accurate within 24 hours, even along the coast where land affects the wind.

For passages over 24 hours, I send an email to my dad and brother letting them know our starting place, destination and estimated time of arrival. They are both listed as contacts for our EPIRB (emergency beacon) and for our IridiumGo! satellite device’s SOS button and having this information could be helpful if we are ever in distress. I email them progress updates during the trip and when we have arrived safely via satellite, as I don’t want them to be sitting around wringing their hands worrying about us for this job for which they were conscripted.

I then transfer the route on the iPad wirelessly to chart application on our Raymarine multifunction display (MFD). Now we have the route available on both MFDs located at the helm. When underway during daylight, we normally have one MFD chart set at short range to see nearby detail and the other at long range to see the bigger picture. At night we usually have one MFD set to display radar and we zoom in and out of the chart on the other MFD as we go.

I typically start a new track on the MFDs to record where we have sailed from, so that we have “bread crumbs” to follow back if we need to turn around. This is really useful for getting out of or back into an anchorage at night.

We keep the iPad Navionics app running in the background while underway, so that we have a redundant device isolated from the boat’s electrical system and Raymarine data network. We also note our position, course and speed every hour in the log and have the paper chart open on the salon table so that we can revert to good old fashioned paper navigation if World War III starts while we’re sailing and the GPS satellites are knocked out.

This approach has worked out really well for us and we’ve grown very confident and comfortable in  applying it to our passage making.  However, our passages so far haven’t really been at all difficult, so we’re not going to get complacent and I expect we’ll find ways to augment and improve as we start sailing in more challenging waters.