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Thread: AIS during the TP. Experiences?

  1. #11
    Join Date
    May 2009
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    Novato
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    122

    Default Essential

    I think AIS is an essential part of the safety gear. In fact I think all entries, whether or not equipped with radar, should be required to carry a transponder type 'B' unit and keep it turned on for the entire race, once beyond the ocean's demarcation line (inside the bay, forget it). Energy consumption is tiny. There are a ton of options now. Cost is really not bad, and it is still dropping.

    I think one of the things that made AIS so valuable for me was the ability to configure alert criteria and see a graphic display. I used a dedicated display by Watchmate because I didn't want to leave the PC on. It consumes practically nothing, has a totally configurable set of alerts, and the display stays off until a target fits the criteria you configure.

    Adam said that Blue Moon was a ship magnet. I encountered many also. But even if just one ship in 2200 miles happens to find your boat while you're sleeping, wouldn't you want to know about it, and better yet, wouldn't you want the ship to "see" you? You can forget about them seeing your (required) radar reflector until it's too late, if at all. On both legs I encountered ships whose CPAs stayed around 0 nm consistently, until one of us changed course. When well offshore I would set the "CPA" alert to 2 nm. That would result in an alert sounding over an hour before the TCA (time to closest approach), which gave me plenty of time to track the ship and decide if a course change or hailing them was necessary. I also set a "Range" alert that had priority over the CPA alert. I wanted to know every time a ship was inside of 6 nm from my position whether or not it was on a collision course. I frequently hailed ships (by name)... I enjoyed the conversation even if there was no danger of collision, and when there was, they invariably agreed to change course so I didn't have to. Oh... and what peace of mind I had when I saw them changing course real time.

    Paul/Culebra

  2. #12
    Join Date
    Sep 2007
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    448

    Default

    I've been watching the AIS Class B transponders and they are still rather expensive as safety gear goes - the unit I'm most interested in is the Comnav Marine X2 black box unit at $800 (which includes its own GPS antenna - you supply the VHF aerial). Based on a friend's usage, it draws about 1 Amp - which is a fair bit of power on a small boat.

    Note that the Comnav Class A transponder is $2700 - way outside my league.

    Do you have a particular piece of equipment you're looking at?

    I'm not convinced that a Class B transponder is essential.

    A receiving unit, given the relatively low price and power consumption, does not seem onerous - but adding the cost & power consumption of a transponder to a skipper's entry probably is. I see the value in having an AIS receiver, in particular one that uses a dedicated display other than a laptop computer - but is a receiver an essential piece of gear? If most entries already have one then I'd say so.

    - rob/beetle

  3. #13
    Join Date
    Sep 2007
    Posts
    577

    Default

    Quote Originally Posted by JakeinDenver View Post
    Are most folks using fixed or portable GPS connections for their AIS GPS positioning?
    Jake, I have a Navman 5500 (low end, fixed mount, grayscale display plotter) providing the GPS position to the NASA AIS Radar.

    I'm pretty much with Bob: CPA is interesting information, but the little tadpole tails on the NASA display are adequate to decide if there's a problem.

    My VHF uses the masthead antenna, while the AIS uses an antenna on the stern rail. So I'm not going to get AIS hits from ships 40 miles away, but who cares.

    Max

  4. #14
    Join Date
    May 2009
    Location
    Seattle
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    105

    Default

    I think an AIS RX is a no-brainer. It's relatively cheap and consumes very little power, while reducing the risk of collision and increasing situational awareness.

    My experience with AIS on the SHTP and return was kind of hit-or-miss. For the race, the software I was using kept giving me false alarms (GPS dropout due to a spinnaker pole and water sitting on the sails stacked on deck over the nav table). I ended up turning off the alarm, and looking at the screen before taking naps. I picked up Culebra and Kestrel nearby. Around day 3 I couldn't have cared less that I didn't have AIS, and slept for hours on end. One day about 800 miles out I saw a cargo ship, but that was it. After I lost sight of Warrior's Wish on the first night, the next boat I saw was a fishing boat 50 miles from Hanalei. Neither of these were transmitting AIS.

    For the return trip I fixed the software problem, and we saw significantly more ship traffic (did we see more because we had AIS and 4 eyeballs instead of 2 half-opened ones? probably.). AIS came in handy for one ship that was insisting on running us over until I called them by name. They then said "yeah, we see you and have you on radar. clear astern." I also did some maneuvering to try and stay away from ships, but I don't know if that really helped. It also gave me a false sense of security as we surfed down the Strait of Juan de Fuca at 10kts in zero visibility with Peter glued to the chartplotter. I kept thinking "there's no one else crazy enough to be sailing out here in a foggy gale at 2am on a thursday". 5 minutes later we pass by a sailboat motoring upwind. Not that I would give up my AIS in the fog...

    On a little ULDB at speed, running into a log, a whale, a container, a refrigerator, or a sailboat has about the same outcome as running into a container ship. A large part of singlehanded ocean sailing is mitigating the risk of losing the boat to a collision, but you're not going to be able to engineer your way to zero risk. If you want to sleep well on an SHTP at some point you have to come to terms with the fact that there are a lot of things to run into out there, many of which you will not see.

    That being said, next time I do something like this I'll probably have an AIS transponder.

    Adrian
    Idefix

  5. #15
    Join Date
    Sep 2007
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    3,688

    Default

    To put it in perspective, at eight miles all you'll see of a ship is a trail of smoke on the horizon. As Max suggests, if there's a ship 40 miles away I don't really need to know about it.

    I installed the splitter mostly because I wanted to clean up the back of the boat (Rule Four). Also the price was right.

  6. #16
    Join Date
    May 2009
    Location
    Seattle
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    Default

    I hate to revive a dead thread, but I hadn't got around to uploading this photo until today, and I think it makes a good case for AIS on a small sailboat.

    http://www.flickr.com/photos/adriancjohnson/5140308470/

  7. #17
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    Aug 2010
    Location
    Denver, CO
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    Default

    Wow Adrian... what an incredible shot. It would be funny if getting run over wasn't such a real threat. How long before you "saw" the boat did you know something was there from your AIS?

  8. #18
    Join Date
    Aug 2009
    Location
    Sausalito CA
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    Default

    Adrian..
    That pic is worthy of a "I heart AIS" sticker...I really don't like FOG. I bet you could hear the prop chugging through the water though...Yikes! Great pic!

  9. #19
    Join Date
    May 2009
    Location
    Seattle
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    Default

    Thanks,

    It was taken a little ways outside the entrance to Juan de Fuca. We spent 2 or 3 days bobbing around in the fog with wind oscillating between 0 and 25 knots, and the traffic was pretty continuous. I imagine SF bay gets to be the same way...

    We were usually picking up traffic around 20 miles out. They probably all had us on radar, but AIS allowed us to do our part by actively trying to stay out of their way.

    A little while later the wind was back to zero and we got passed by various sorts of traffic that did not show up on AIS...
    http://www.flickr.com/photos/adriancjohnson/5143552225/

    Adrian
    Idefix

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