<<If you decide to go with one central controller for two
working units you also need two sources of input for heading and
possibly wind direction.>>
Arto,
You might be right. I actually started to write something up
yesterday and then figured I'd already spent too much time on forum
posts.
But today is a federal holiday here, and none of my clients are
calling me, so why not ponder the electronics.
I'm a big fan of the Tack Tick wireless instruments. It's just
great not to have wires running everywhere, particularly on a boat
that can be folded and demounted. Plus it's neat now they just all
work together. After I connected my Tack Tick system to my NMEA
bus, the instruments automatically knew the difference between true
north and magnetic north based upon the GPS location. When I added
in the mast rotation sensor, they automatically subtracted out the
rotation to give me true and apparent wind speeds, regardless of
how quickly I mess with the mast. Having them be solar powered and
waterproof is also a plus.
At first I thought I'd be able to get away with just a second
speed transducer because things like the fluxgate compass and depth
sensor wouldn't care where the boat was pointed. But then reality
set in and I realized that while I'd get an accurate wind direction
and speed even in reverse, the autopilot wouldn't be able to use
that data, and the instruments themselves would be a bit confused.
That would mean either converting to a heavy-duty autopilot that
can be reprogrammed, which is expensive, heavy, and hydraulic, or
sticking with the tiller pilots and either switching inputs or going
with two full systems.
Two wind sensors also wouldn't work because the system will only
recognize one, and because it's wireless, you can't switch it.
This is one of the few times that a single-ender seems attractive
to me -- no worries about any of the electronics, controls, sensors,
or lights.
---
1) One thought is to put the wind meter on a separate mast,
possibly on the windward hull, which will rotate through 180
degrees. Rotating the mast on each shunt would change the wind
direction and compass direction mechanically as the mast moves, as
well as switch the internal connections for the speed transducer,
autopilot mechanism, and nav lights. (Did someone else suggest this
a few years ago?)
That way there's only one instrument system and the only
redundancies are a second autopilot tiller mechanism (single
controller), a second speed transducer, and a second set of nav
lights.
It still seems kind of complex and cumbersome, though. Plus, the
wind sensor wouldn't be of much use of sailing with the ww hull to
leeward in very light winds.
2) The other thought is just dual systems, with instruments on the
aft-facing side of the cockpit visible while sitting on the
forward-facing side. Then everything just works as intended, from
the mast heads, without having to remember to switch inputs on each
shunt. Nav lights could even be auto-controlled with a sensor that
flips a solenoid any time you're going in "reverse" at more than 2
knots. Or at least sounds a warning buzzer if you haven't flipped
the switch.
But that's another $10k expenditure, give or take. The plus side
is the "simplicity" of not having to rotate a mast that itself can
fall in a wind shadow, along with having redundant online
replacements if anything of the instruments were to fail. The
downside is all that money for something on which we shouldn't rely
on too much in the first place.
3) So perhaps I should call it a day with a mechanical windvane.
---
Nah. Save $100k on the boat so I can go overboard with the toys.
;-)
Plus the windvane, of course.
- Mike
If you decide to go with one central controller for two working units you also need two sources of input for heading and possibly wind direction. May be a switch for them too? Or easier to just have two of each?Arto
From: Mike Crawford <mcrawf@nuomo.com>
To: harryproa@yahoogroups.com.au
Sent: Monday, January 21, 2013 12:23 AM
Subject: [harryproa] Re: Survey/build/feature discussion - Rudders/foils
How many autopilots? Good question.
One central controller with two separate mechanisms, using a simple switch to change between the two? Just one autopilot, which might work the same in both directions if you use a Speer section and keep the tiller on the same side? Or just get two complete systems so that you have some redundancy?
I think any of the above could work. Like you point out, the huge savings (when compared to buying a new or even a used F36) would cover the second autopilot. And then you'd the extra it if you needed it.
- Mike
Gardner Pomper wrote:
Mike,
AUTOPILOT.
As for an autopilot, I'd use a Raymarine ST-4000 tiller pilot. The control goes inside, or at least at the cockpit, and just the mechanical portion sits out, the base connected to the leeward hull, the end connected to the tiller (not the extension). I use one of these on my catamaran with great success. If patched into the nmea system, you can even have it steer to GPS waypoints, or to the average wind direction of the last minute.
So, would you just have 2 autopilots? One for each tiller? I guess that would be simplest, and somewhat affordable, since we are saving so much money on the boat <grin>.