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post #21 of 26 Old 2 Weeks Ago
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Re: Upgrade Autopilot on a PSC34

Hello,

Is it necessary to have the instruments networked together? No. It is nice? Absolutely.

Are your Raymarine instruments networked to your Autopilot? IE do you have two separate networks, one for the Raymarine gear and another for the Lowrance? Or perhaps the Lowrance isn't connected to anything else? Either way, here are some advantages of having instruments, Plotter, Autopilot, VHF all communicating:

True / Apparent wind:
With standalone instruments maybe you can get true and apparent wind, maybe no. With networked instruments you DO have true and apparent, and you can display that information on the plotter, and send that information to the autopilot. This allows the pilot to steer to a wind angle. Personally I like this function and use it frequently if I am just out for a few hours sail with no real destination. I pick a wind angle (usually 60 degrees apparent), engage the AP on that wind angle, trim the sails, then relax. I can do anything I want and the boat will stay on the wind angle and the sails properly trimmed.

Instrument data display on plotter:
My instrument displays are mounted on the bulkhead next to the companionway (the previous owner mounted them there). If I have guests aboard they frequently will sit where the instrument display is blocked. Since I can display any information I want on my plotter (Vulcan 7) I don't need to constantly tell my guests to move. Of course if I'm racing the crew knows to stay out the way, but for sailing with guests I want to nice to them (most of the time).

Navigating to a destination:
As previously described, the plotter can provide instructions to the AP. This can be for a single waypoint or many waypoints along a route. This is nice if I'm doing a long delivery.

VHF:
All current VHF radios include DSC. The radio must be GPS information for DSC to work. There many ways to accomplish this, including VHF w onboard GPS. A VHF w NMEA 2000 networking makes this super easy. Many new VHF radios include an AIS receiver as well. My Simrad RS35 does and I can see AIS targets on my plotter, including information on range, bearing, speed, CPA, etc.

If it were difficult or expensive to network different units together I would not do it. However, since Raymarine has the Seatalk to Seatalk NG kit available, all you need is the kit and some cables. For under $100 you can have all of the instruments networked.

Barry

Quote:
Originally Posted by olson34 View Post
I have not felt a need to try to interface it with anything. We also have a late model Lowrance hi-def radar and 9" plotter at the helm. Wonderful stuff, especially the radar with its ability to resolve small targets.
Our older Raymarine ST-60 instrument cluster is on its own separate network.

It would be fun to tie this stuff together someday with a 'black box' interface, but there's just no need to do so.

Barry Lenoble
Deep Blue C, 2002 C&C 110
Mt. Sinai, NY

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post #22 of 26 Old 2 Weeks Ago
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Re: Upgrade Autopilot on a PSC34

I wonder about instruments displaying True Wind data when underway.

The only data that the wind instrument sends is APPARENT and they called AWI for that reason - Apparent Wind Instrument.

The angle is relative and set by the use relative to the bow.

When in motion the TRUE wind SPEED is a calculation using data from the Speed Log. If it is fouled or not properly calibrated or properly aligned... or there is current... the speed DATA is in accurate.

The fluxgate compass data likewise requires calibration to the ship's CL.

TRUE WIND "values" are computed and only as reliable and accurate as the calibration of the transducers. Currents are tough to isolate because the transducer doesn't "see" current... unless the boat is stopped at anchor

Steering information needs to be confirmed by observing the TRACK on a plotter. This may mean that a skipper needs to COMPENSATE for inaccurate computation by the instruments. Basically the track doesn't lie and it needs time to mean anything.

pay attention... someone's life depends on it
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Re: Upgrade Autopilot on a PSC34

To add clarity -
Our Raymarine ST-60 instruments display true wind or apparent with a button push. Having added an ST-60 repeater at the nav station, and also (invisibly...) shrunk the holes in the cockpit bulkheads for the then-new Raymarine instruments, I will repeat that process only when I have to do so.

Good point about having DSC. Our late model Simrad VHF is wired into the Lowrance bus and provides DSC on our chart plotter. Between DSC and Radar, I would choose 'both' !! (If *really* forced to choose, tho, I would go with Radar.)

As stated, we monitor our course by watching our chosen AP track. There are too many solid things to dodge off the Oregon and Washington coasts to leave navigation completely up the multi-waypoint functions one could link to the AP.
What with fog, ships, many small fishing craft, and logs... The Straights and Puget Sound also discourage us from turning over course changes to the electronics. Other mariners look at risk differently than do I. They are not in any way 'wrong', but they do not have my particular viewpoint and my boating history, either.
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Re: Upgrade Autopilot on a PSC34

With regards to the CPT

While I did occasionally use the wind tracking feature of the st4000, I do not find that I miss it much with the CPT. The simplicity of the system makes up for the lack of that feature. If the wind shifts, you will know it and can simply alter course or trim to the new wind angle. I can see very little point in an auto pilot that sails to way points and then changes course. Usually someone is on watch to make course corrections. When I want to sail to a wind direction I will of course use the windvane. On the last few thousand miles of my pacific crossing, we dealt with very light winds and also did allot of motoring. This is when the autopilot becomes much more valuable than the windvane. I love my monitor, but in reality, it is usually easier and simpler to just use the CPT.

Grant

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Re: Upgrade Autopilot on a PSC34

Quote:
Originally Posted by BarryL View Post
True / Apparent wind:
With standalone instruments maybe you can get true and apparent wind, maybe no. With networked instruments you DO have true and apparent, and you can display that information on the plotter, and send that information to the autopilot. This allows the pilot to steer to a wind angle. Personally I like this function and use it frequently if I am just out for a few hours sail with no real destination. I pick a wind angle (usually 60 degrees apparent), engage the AP on that wind angle, trim the sails, then relax. I can do anything I want and the boat will stay on the wind angle and the sails properly trimmed.
Another advantage is that some AP's will automatically change from using AWA forward of the beam to TWA aft of the beam. This prevents unintentional jibing with wind shifts or sudden changes in boat speed off the wind, and makes for a steadier course into the wind.

Quote:
Originally Posted by SanderO View Post
When in motion the TRUE wind SPEED is a calculation using data from the Speed Log. If it is fouled or not properly calibrated or properly aligned... or there is current... the speed DATA is in accurate.
Some instruments can use SOG in lieu of STW for TWS.

Quote:
Originally Posted by granche1 View Post
I can see very little point in an auto pilot that sails to way points and then changes course.
I don't know of any autopilot that allows significant automatic changes in course without human intervention. Ours allows a maximum of 30* automatic change in course, and comes with this feature turned off as the default.

This point often gets lost in these types of threads: just because a feature can be used doesn't mean one is forced to use it. It is silly to avoid a type of AP altogether just because it has features that could be used, but that one doesn't want to use.

Mark
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Re: Upgrade Autopilot on a PSC34

As a non technical whiz I accept the fact that the data from transducers is not going to be accurate... whether it's fouling, or calibration or friction. The values I see on my displays are close enough for me to make informed decisions.

I do use the AP almost all the time and use a dial to set the heading I want. My decision is informed by the wind instruments and my track on the plotter where I can see the local environment and the mark I am trying to make. I both tweak the twim and alter the course as need be. The plotter will calculate a TTG or time of arrival and small changes do often show up in TTG or time of arrival. Trimming and dialing in the course changes manually is how I sail and what works for me. Usually I can't sail a rhumb line to a mark... and it may not be the shortest trip.

pay attention... someone's life depends on it
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