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Old 15-08-2015, 11:16   #121
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Re: AIS Do I Need It?

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Originally Posted by skipmac View Post
Pardon the drift, but since you bring this up, what type/model/brand reflector are you using?
This kind. It's 40ft up the mast, don't know the brand. It's the white gizmo above the radar.
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Old 15-08-2015, 11:47   #122
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Re: AIS Do I Need It?

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Originally Posted by Jon Eisberg View Post
Well, perhaps I've just had an extraordinary run of amazingly good luck, in all those years of sailing prior to the advent of AIS, and running boats without radar, or often even without so much as having a hand bearing compass on board… ;-)
As for me, being the Old School Wimp that I am, whenever I determine - sometimes with no more than a casual use of the naked eye, no less - I might be dealing with a collision course situation, I'll generally default to my trusty "I Think I'll Take His Stern" Mode…
It's worked fairly well for me, so far… Then again, perhaps I've just been Lucky
I'm shocked Jon. I wouldn't think of sailing without my Weems & Plath handbearing compass. One of the handiest tools a sailor can have. And back in the "old days" a necessity for coastwise navigation.

But as you say, its not difficult to take relative bearings by just sighting through your rigging. You may not know the exact bearing but you can tell if the other guy is going to cross ahead or behind or....

Don't know how I survived these past forty years without radar and AIS.
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Old 15-08-2015, 11:48   #123
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Re: AIS Do I Need It?

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Originally Posted by estarzinger View Post
Flat answer regarding 'Need' is NO. You can sail perfectly safely without if you are careful.

Whether it will be "very helpful" depends on where you will sail . . . higher shipping density will mean more helpful. Take a look at the follow picture . . .

Attachment 107319

Your immediate part of the world I would characterize as 'medium density' and you will probably find it occasionally useful. But if you go into asia (especially around Japan) or toward the red sea, you will find it rather useful. In the south pacific . . . not so much. Below 40 S, pretty much not at all.

Regarding what to get - you have two options to consider: (1) is transmit or not . . .I would suggest you definitely want to transmit. You want them to see you so they can take avoiding action. (2) black box or with own screen . . . It just depends on how your nav station is set-up. If you already have a good plotter screen which you can feed AIS info to, then go black box . . . if you don't have such a screen get an AIS with one. The Vespers have excellent models of both.

DH . . . you know I am a fan of AIS . . . . but IMHO you are being unreasonable saying that people CANNOT do collision avoidance by eyeball. It may well be harder, but people did it for years (before AIS and also before recreational radar) and many still do it . . . and collisions with ships are extremely rare (and almost always happened when people were not paying attention, rather than because they were paying attention but 'could not' make an accurate assessment). When using eyeballs you simply take earlier and more significant action when you judge there is the risk of a collision.

I might note that the use of AIS actually increases the risk of two types of collisions. (1) people with AIS tend to use smaller margins of error and if something completely unexpected happens may well not have enough margin to recover; and (2) people are sometimes (often when tired at 2am) for get that the screen does not reflect full reality and stop looking around at the real world, and hit something not showing clearly on the screen (perhaps not showing on either radar nor ais screens). Both of those are 'operator error' and not truly the 'fault' of the equipment, but the equipment does allow/encourage that sort of sloppy behavior.
Zinger, very interesting pic. What surprised me is my little stretch of river is solidly in the orange range, a relatively busy spot, which sitting in my cockpit at dock right now, looking at the peaceful quiet river I would not have guessed.

So here is a new theory I'm working on. I keep my AIS CPA alarm set to .5 miles, any more just isn't practical in this neighbourhood.

When the alarm sounds, I go down stairs to see what the ruckus is all about to determine if its a real concern or just a ferry or tour boat (thankfully more yachts don't have them or the thing would never stop alarming).

If the alarm starts going off too frequently, then I call down the stairs for somebody to turn the bleeping AIS receiver off, I put away my pickles and pepperettes, pull my head out of my rear and start actively driving the boat. Its become too busy for the computers (AIS and Autopilot) to drive and a real person has to take over.

So maybe AIS is more useful in quieter waters when you're not expecting to meet much traffic.

Its just a thought I had, probably full of holes.

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Old 15-08-2015, 11:52   #124
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Re: AIS Do I Need It?

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Originally Posted by Kenomac View Post
During the past three years since we first installed our AIS receiver, we've only needed to contact another vessel one time. At night a large ferry appeared to be heading directly at us from 6 miles away, we first spotted the ferry 8 miles out on radar and began tracking it. The conversation basically confirmed what we already knew. When asked if they could see us.... "No problem, we see you just fine.... Please don't worry about a thing." And they passed us 1/2 mile off our stern.

With our radar reflector, we are very visible. Using only our eyes and radar, nothing sneaks up on us. We can tell if a vessel is going to pass us via the stern or off the bow without a compass using just our eyes and have plenty of time to take evasive action... Which is to always allow the faster, larger vessel to pass ahead of us. If AIS did not exist... I think we would be fine.
Hm... we contact most any large vessel (freighter, cruise ship, etc..) that is on AIS that may become an issue within an hour or so.

Even if its just "Have you gotten the latest weather" or "are you intending on staying on your course". They seems to appreciate it, know we are there because they can see us on AIS, usually confirm in the conversation that their CPA is about the same as our CPA, and establish a coarse solution very early on which makes both of us happy and is a professional experience.

If they need to later change course to adjust to a different, larger ship, then we have already established a friendly dialog and we can re-establish communications to settle on an updated course adjustment if one is needed.

We may talk to a half dozen large ships during our gulf stream crossings.
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Old 15-08-2015, 12:04   #125
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Re: AIS Do I Need It?

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Originally Posted by zboss View Post
Hm... we contact most any large vessel (freighter, cruise ship, etc..) that is on AIS that may become an issue within an hour or so.

Even if its just "Have you gotten the latest weather" or "are you intending on staying on your course". They seems to appreciate it, know we are there because they can see us on AIS, usually confirm in the conversation that their CPA is about the same as our CPA, and establish a coarse solution very early on which makes both of us happy and is a professional experience.

If they need to later change course to adjust to a different, larger ship, then we have already established a friendly dialog and we can re-establish communications to settle on an updated course adjustment if one is needed.

We may talk to a half dozen large ships during our gulf stream crossings.
Interesting, I don't ever recall calling a commercial vessel from my sailboat. Called a tow truck for a boost at dock once, but no commercial vessels. Water taxis I guess if I needed a lift to the mainland.

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Old 15-08-2015, 12:25   #126
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Re: AIS Do I Need It?

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Originally Posted by Kenomac View Post
This kind. It's 40ft up the mast, don't know the brand. It's the white gizmo above the radar.
Appears to be a Firdell Blipper...

While no doubt your 53-footer produces a pretty strong return as far as most sailing yachts go, you may not be getting as much additional benefit from that one as you might think...

;-)

"The poor performance of the Firdell Blipper was surprising, given its popularity and reputation..."

http://www.ussailing.org/wp-content/...or%20tests.pdf

"The Firdell Blipper 2107 narrowly failed to meet ISO8729 during this testing,
but showed good peak and average RCS performance. The Blipper is priced at
£130 and weighs 1.8kg; the main drawback was a RCS drop-off above an
elevation angle of 10̊."


http://www.ussailing.org/wp-content/...tor%20Test.pdf

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Old 15-08-2015, 12:43   #127
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Re: AIS Do I Need It?

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Originally Posted by onestepcsy37 View Post
I'm shocked Jon. I wouldn't think of sailing without my Weems & Plath handbearing compass. One of the handiest tools a sailor can have. And back in the "old days" a necessity for coastwise navigation.
Nah, I'll whip mine out from time to time, though I rarely remember to bring it along on a delivery... Probably just as well, since I'd be likely to leave it on the boat, anyway ;-) I need to learn to make a List, though most every pair of binoculars have a compass, anyway...

One of these old Autohelms is my favorite, a marvelous gadget, a shame they were discontinued so long ago... However, I probably use it more at anchor, than when underway... ;-)


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Old 15-08-2015, 13:00   #128
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Re: AIS Do I Need It?

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Originally Posted by FamilyVan View Post
Interesting, I don't ever recall calling a commercial vessel from my sailboat.
I rarely call a ship when we are close to land -- I figure that they have better things to do than chat with me. If there could be confusion about our crossing I will call to make sure, but otherwise I leave them alone.

When well offshore and it's been a couple of days between ship sightings, I might call to say hello. More often (especially since I installed the AIS Class-B transponder) the ships call me. They usually just want to say hello, make sure we are doing OK, tell me about their favorite sailboats, and casual stuff like that. It gets lonely halfway between the US West Coast and Hawaii!
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Old 15-08-2015, 13:03   #129
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Re: AIS Do I Need It?

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Originally Posted by zboss View Post
Hm... we contact most any large vessel (freighter, cruise ship, etc..) that is on AIS that may become an issue within an hour or so.

Even if its just "Have you gotten the latest weather" or "are you intending on staying on your course". They seems to appreciate it, know we are there because they can see us on AIS, usually confirm in the conversation that their CPA is about the same as our CPA, and establish a coarse solution very early on which makes both of us happy and is a professional experience.

If they need to later change course to adjust to a different, larger ship, then we have already established a friendly dialog and we can re-establish communications to settle on an updated course adjustment if one is needed.

We may talk to a half dozen large ships during our gulf stream crossings.
Sounds very annoying if you ask me. If I was on the bridge of a large commercial vessel, I don't think I'd like to be chatting with every pleasure boat within a one hour radius.

Besides... At the speed most of them travel, we only see them for 20 minutes or so after they appear over the horizon, which is why our radar is on the six mile setting. One hour? Ridiculous.
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Old 15-08-2015, 14:03   #130
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Re: AIS Do I Need It?



"I might note that the use of AIS actually increases the risk of two types of collisions. (1) people with AIS tend to use smaller margins of error and if something completely unexpected happens may well not have enough margin to recover; and (2) people are sometimes (often when tired at 2am) for get that the screen does not reflect full reality and stop looking around at the real world, and hit something not showing clearly on the screen (perhaps not showing on either radar nor ais screens). Both of those are 'operator error' and not truly the 'fault' of the equipment, but the equipment does allow/encourage that sort of sloppy behavior." --estarzinger

Unfortunately, it is so, that is why I called it "seductive." Thank you for stating it so much better than I. I'm going to cover the display up, and check it when it alarms. My own need is to maintain an attentive watch. I turn on and off whatever I need.


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Old 15-08-2015, 14:05   #131
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Re: AIS Do I Need It?

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With our radar reflector, we are very visible.
Don't bet your life on it--in heavy weather and/or heavy rain, you are just part of the clutter. A ship's detection of your AIS transponder is vastly superior to its detection of your radar return.
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Old 15-08-2015, 14:44   #132
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Re: AIS Do I Need It?

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Not at 5 to 8 miles out you can't. It's not easy even with a HBC. You can get the roughest approximation by using a stanchion as a transit, but the accuracy of that depends on a very steady heading.
Oh yes I can...

90% or more can be sorted and dismissed as soon as they appear at 10/15 mile or so simply by looking at the aspect. Those that can't be dismissed are watched....some time later its a simple matter to dismiss another 90%.
Then I start paying attention to them as are left...

Its all down to skill and experience.....

Sorry, Ann, couldn't help myself
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Old 15-08-2015, 14:48   #133
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Re: AIS Do I Need It?

Oh and also... some have said that when simply using a compass bearing you can't tell if the ship of interest is passing ahead or astern...yes you can.

Bearing opening... ( to use a simple example... opening from 3 points on the bow to 4 points) passing astern. Bearing closing.... ie from 5 points on the bow to 4 points on the bow.... passing ahead.
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Old 15-08-2015, 14:52   #134
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Re: AIS Do I Need It?

just as some fact(s) on this whole topic (from BoatUS claims) . . . collision ranks as a middling frequent risk (not in the top 5 major categories categories of claims but also not tiny) . . . . and most (+80%) of the collisions are with other pleasure vessels (this includes a decent chunk racing). second category after pleasure on pleasure is pleasure collisions with small commercial vessels - primarily fishing/lobster boats and interestingly official (police, DNR, and USCG) boats . Collisions with 'big commercial ships' are tiny.
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Old 15-08-2015, 15:10   #135
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Re: AIS Do I Need It?

Another little wrinkle.. if you have distant land beyond the ship you can watch how the ship moves 'against' the land.
Of course the closer the land the more you have to factor in a bit of 'fudge' but it still works to a degree.
Needs a bit of practice.
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