Thursday, February 11, 2010

Construction, Misconstruction, Tempests and Teapots

Even when there is no sailboat on the horizon no sailor travels alone.  My last post attempted to demonstrate this by including examples of recent expressions of concern by others for our welfare and of concern by us for others.

The examples were fairly humourous excerpts demonstrating the fairly direct way in which sailors communicate.  Terse and to the point.  This is contrary to the way in which some of us blog.

Well, haven't we had fun since that post.   So  today's topic will be all about how, on Meredith, we deal with the following:
  • sailing in the face of unsettled weather forecast
  • Wiring a Chartplotter into an autopilot, and 
  • Why was I such a cheap (&*^# when I bought the first chartplotter
First the weather:

Sailors in Florida are a cowardly lot.  Most are old and retired, a slice of demographic pie heavily flavoured with the timidity that grows on aging frames like moss on old growth trees.  Many have arranged a slip in the Abacos for 3 or 4 months.

These people are not a good source of sailing advice.  They are too cautious. 

Meredith likes to see for herself.  If a forecast is closed we don't go.  We like to think we are prudent just not stupidly overcautious.  If it looks like a weather window might open up we will go see.  We do not huddle with the rest of the pensioners waiting for the perfect forecast.  This has worked for our boat in the past.

What we do is set a "go - no go" point.  At any point up to the GNG we turn around when either of us says so.  No questions or comments.  We set the GNG well along any intended path so everyone can take their time and get settled in before deciding to bail. 

This approach has seen us make a number of passages in comfort days and in one case weeks before others with whom we had been travelling. 

All this system requires is a willingness to admit things did not work out as planned.

I loved Heather Loveridge's rebuke.  Her open and direct nature immediately endeared her to the crew of Meredith.  Unwilling to interfere with others' plans she waited until we admitted defeat before commenting.  

As for wiring Chartplotters to Autopilots Wade is absolutely correct that no sailboat should even bother to consider such lunacy.  Sailboats do not sail direct from one waypoint to another, not even when under power.   Having point to point navigation control is silly and could prove harmful.   For the record Heather agrees with Wade as do many others.  Sailors all.

To the powerboaters (fewer in number but unanimous) who expressed the contrary view you are also absolutely correct - for powerboats point to point navigation makes good sense much of the time. 

Example: crossing the gulf stream.  A powerboat travelling at 25 knots will make the trip from Florida to Bahamas in under 2 hours.  If you assume an average current for the stream of 3 knots across the Florida Straits this means a powerboat will be carried 6 miles offcourse during its trip.  This requires a 15 minute maximum correction.  It is not worth allowing for so the power guy just pops in a waypoint and pushes the button on his twin 400 hp whatevers and by the time his coffee is done he is already at his destination and looking for his VISA card to pay the fuel jockey.

A sailboat will take 10 to 12 hours.  The 3 knot current will, without correction, take the sailboat 30 to 35 nm north of this boat's intended destination.  This is almost as far as the entire east/west trip.  A sailboat cannot steer point to point.  We must plot the effect of tide and current and leeway and choose a course that, when you look at it, will take us far south or our intended destination.  We steer 15 or 20 degrees or more south of the course we need.  That way we end up where we want to go.  Our VISA cards are reserved for the bar.

Even powerboaters will not use an autopilot coupled to a chartplotter in the ICW (like Meredith was doing when its chartplotter kicked the bucket).  The navigable channel in these parts is only 100 feet across.  Most chartplotters or GPSs will only give accuracy to 75 or 100 feet.  If your chartplotter shows you in the middle of the 100 foot wide channel you only have 50 feet of water on either side.  If the gps is off by 75 feet you should not be surprised to find yourself 25 feet in the mud.

So why did Meredith, a sailboat, couple its chartplotter to its autopilot and then use it in the ICW?  Huh?  Why?

We were sitting in Vero Beach, bored out of our skulls.  We had cleaned and vacuumed very square inch, we had gone up the mast to install a new windvane, we had rewired the fuel pump, the engine room blower and the macerator pump, we had changed the Y valve for the head and even some of the hoses.  We had done every dirty stinking rotten job on our boat that had been waiting to be done.  And still there was time to put in. 

I like to tinker with things electric.  Wiring the chartplotter to autopilot seemed like a good afternoon's entertainment and the project went well.  Once done of course, the project must be tested.  A proof of concept sort of thing.  Just to see if it works and if it does what can you do with it.

This afternoon I am upgrading the wiring by adding opto isolator circuits I picked up at Radio Shack.  And looking forward to it.

Or maybe I will dinghy over and spend time with Frank on Melodeon who is still adjusting the mockup of his new anchor roller before sending it off to the machine shop. 

He has this really cool idea that just needs a little bit of tweaking...

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