Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 16-08-2015, 09:00   #166
Registered User
 
MYTraveler's Avatar

Join Date: May 2010
Posts: 166
Re: AIS DO I NEED IT.?

Quote:
Originally Posted by Dockhead View Post
In open water you must use at least a hand bearing compass, in order to detect a risk of collision in time to do anything about it - in cases where difference in speed is double or triple or more.
You don't need to know a bearing with precision to determine risk of a collision course -- all you need to know is whether the bearing is changing. For that, a hand bearing compass is not necessary or even particularly useful. If the other vessel appears to maintain a constant bearing, it should be regarded as a collision risk. Knowing that the bearing is actually changing, imperceptibly but for the hand bearning compass's precision, does not add useful information, in my opinion.
__________________

__________________
MYTraveler is offline   Reply With Quote
Old 16-08-2015, 09:03   #167
CF Adviser
 
Pelagic's Avatar

Cruisers Forum Supporter

Join Date: Oct 2007
Boat: Van Helleman Schooner 65ft StarGazer
Posts: 6,895
Re: AIS Do I Need It?

Familyvan I honestly never do that.... My simulator training discouraged making assumptions and that was
reinforced by reading so many formal reports of casualties caused by failure to properly assess a changing situation

My working philosophy..... , both my eyes (if in sight) and electronics must fully agree with my desired CPA until the vessel is well clear.

By setting that formal example, it was the only way I could teach my officers to be good watchkeepers when working on my ship.
__________________

__________________
Pelagic is online now   Reply With Quote
Old 16-08-2015, 09:04   #168
Registered User
 
MYTraveler's Avatar

Join Date: May 2010
Posts: 166
Re: AIS DO I NEED IT.?

Quote:
Originally Posted by DotDun View Post
I despise sites like MarineTraffic/Shipfinder/Vesselfinder making money off my information.
I don't think the commercial users are paying to get your information -- they want to know where their fleet is.
__________________
MYTraveler is offline   Reply With Quote
Old 16-08-2015, 09:12   #169
Registered User

Join Date: Apr 2006
Posts: 4,413
Re: AIS DO I NEED IT.?

Quote:
Originally Posted by MYTraveler View Post
You don't need to know a bearing with precision to determine risk of a collision course -- all you need to know is whether the bearing is changing. For that, a hand bearing compass is not necessary or even particularly useful. If the other vessel appears to maintain a constant bearing, it should be regarded as a collision risk. Knowing that the bearing is actually changing, imperceptibly but for the hand bearning compass's precision, does not add useful information, in my opinion.
This correct and Dockhead is all wet about this.
__________________
Sandero is offline   Reply With Quote
Old 16-08-2015, 09:26   #170
Eternal Member
 
monte's Avatar

Cruisers Forum Supporter

Join Date: Jul 2011
Location: Australia
Boat: Lagoon 400
Posts: 3,650
Images: 1
Re: AIS Do I Need It?

The reason a hand bearing compass is useful is because it can be rotated to determine the other vessels bearing. Line up the lubber line with the ship and monitor. Obviously not needed if the other vessels course is clear using less finite techniques, but definitely more accurate than an eye through the rigging of a moving sailboat, unless of course your sailboat doesn't move...
__________________
monte is offline   Reply With Quote
Old 16-08-2015, 09:35   #171
Registered User
 
MYTraveler's Avatar

Join Date: May 2010
Posts: 166
Re: AIS Do I Need It?

Quote:
Originally Posted by Jon Eisberg View Post
Do you mean to say you wouldn't even bother to take the trouble to place a DSC call to the ship in question, for the purpose of determining the precise location of its transponder, "in order to more accurately assess the situation" ?

That could make all the difference in deciding whether to cross ahead, or to chicken out by taking his stern, no?

;-))
Transducer location is part of Class A info.
__________________
MYTraveler is offline   Reply With Quote
Old 16-08-2015, 09:42   #172
Registered User
 
MYTraveler's Avatar

Join Date: May 2010
Posts: 166
Re: AIS Do I Need It?

Quote:
Originally Posted by monte View Post
The reason a hand bearing compass is useful is because it can be rotated to determine the other vessels bearing.
How does that help? For making contact -- if the other vessel is AIS equipped, you can hail by name or DSC. But if it is useful, wouldn't it be easier to add or subtract 180?
__________________
MYTraveler is offline   Reply With Quote
Old 16-08-2015, 10:38   #173
Registered User
 
FamilyVan's Avatar

Join Date: Nov 2014
Posts: 1,779
Re: AIS Do I Need It?

Quote:
Originally Posted by Pelagic View Post
Familyvan I honestly never do that.... My simulator training discouraged making assumptions and that was
reinforced by reading so many formal reports of casualties caused by failure to properly assess a changing situation

My working philosophy..... , both my eyes (if in sight) and electronics must fully agree with my desired CPA until the vessel is well clear.

By setting that formal example, it was the only way I could teach my officers to be good watchkeepers when working on my ship.
Fair enough. We know doubt have identical simulator training because I believe we're both Canadian, good chance we even studied at the same schools if that's the case.

However, our background prior to that training may have lead to different philosophies. I was a quarter master (wheelsman) for well over a decade before ever standing a navigational watch, as I'm sure you're aware, a wheelsman generally isn't permitted the use of electronics beyond a Gyro or FOG.

The result of that background for me, is that I've never had much use for electronics, for me I just used them to verify my evaluation. I was popular with many skippers because I didn't rely too heavily on electronics. When I became skipper myself, I didn't care what any one else though

I am definitely not trying to contradict you or challenge your philosophy in any way. I'm just explaining mine.

Sent from my XP7700 using Cruisers Sailing Forum mobile app
__________________
FamilyVan is offline   Reply With Quote
Old 16-08-2015, 11:34   #174
Eternal Member
 
monte's Avatar

Cruisers Forum Supporter

Join Date: Jul 2011
Location: Australia
Boat: Lagoon 400
Posts: 3,650
Images: 1
Re: AIS Do I Need It?

Quote:
Originally Posted by MYTraveler View Post
How does that help? For making contact -- if the other vessel is AIS equipped, you can hail by name or DSC. But if it is useful, wouldn't it be easier to add or subtract 180?

Being able to rotate the hand bearing compass allows you to compensate for your own vessels course deviation and monitor the true bearing.
__________________
monte is offline   Reply With Quote
Old 16-08-2015, 13:09   #175
CF Adviser
 
Pelagic's Avatar

Cruisers Forum Supporter

Join Date: Oct 2007
Boat: Van Helleman Schooner 65ft StarGazer
Posts: 6,895
Re: AIS Do I Need It?

I agree that experience does help you to anticipate traffic and I credit my early days working the west coast especially fog bound BC and Alaska with honing my use of Radar techniques in a fairly well organized environment.

But as I ventured more into heavily congested Asian waters... the locally trained mariners on coastal freighters, would often surprise me with their aggressive actions on poorly equipped ships and fishing boats.

This developed my style of maintaining a very formal bridge team at all times and verifying escape corridors by ARPA Trial Maneuvers and the use of True Motion.

Insisting on a focussed bridge did not make me popular with the new watchkeepers at first.... but years later after they had experienced their own commands..... they thanked me for it.
__________________
Pelagic is online now   Reply With Quote
Old 16-08-2015, 13:50   #176
Senior Cruiser
 
Jim Cate's Avatar

Cruisers Forum Supporter

Join Date: May 2008
Location: cruising SW Pacific
Boat: Jon Sayer 1-off 46 ft fract rig sloop strip plank in W Red Cedar
Posts: 11,461
Re: AIS Do I Need It?

In my experience, use of a HBC is the only non-electronic method that works when one's own boat is not steering a steady course, something that happens in any sort of big seas. When your boat is yawing about, the canonical "sight over a stanchion" sort of technique doesn't work, but noting the compass bearing to a distant ship does.

The interesting discussions above with professional big ship skippers are based on the stability of such big ships, something that yachts often lack in reality.

Jim
__________________
Jim and Ann s/v Insatiable II , lying Port Cygnet, Tasmania once again
Jim Cate is offline   Reply With Quote
Old 16-08-2015, 16:15   #177
Moderator
 
Dockhead's Avatar

Cruisers Forum Supporter

Join Date: Mar 2009
Location: Cowes (Winter), Baltic (Summer) (the boat!); somewhere in the air (me!)
Boat: Cutter-Rigged Moody 54
Posts: 19,751
Re: AIS DO I NEED IT.?

Quote:
Originally Posted by MYTraveler View Post
You don't need to know a bearing with precision to determine risk of a collision course -- all you need to know is whether the bearing is changing. For that, a hand bearing compass is not necessary or even particularly useful. If the other vessel appears to maintain a constant bearing, it should be regarded as a collision risk. Knowing that the bearing is actually changing, imperceptibly but for the hand bearning compass's precision, does not add useful information, in my opinion.
The purpose of a HBC in collision avoidance is to detect CHANGES in bearing which are imperceptible to the naked eye. No one cares about the bearing itself.

If you can't see a changing bearing with your naked eye, this does not mean necessarily that you're on a collision course. He could be passing a mile ahead, or a mile behind. Maybe he already maneuvered to set up a safe crossing. Or he might be about to run you down. You can't tell. And lacking this information, you don't know what to do. Maybe he's passing behind, but since you can't tell, you make a hard turn to starboard - right under his bows. If you were using the hand bearing compass properly, writing down the bearings every two minutes for a while, you would have this information, and you would know the correct maneuver - which is often to hold your course and speed.

Sent from my SGP521 using Cruisers Sailing Forum mobile app
__________________
"Parce que je suis heureux en mer, et peut-Ítre pour sauver mon ame. . . "
Dockhead is offline   Reply With Quote
Old 16-08-2015, 16:26   #178
Moderator
 
Dockhead's Avatar

Cruisers Forum Supporter

Join Date: Mar 2009
Location: Cowes (Winter), Baltic (Summer) (the boat!); somewhere in the air (me!)
Boat: Cutter-Rigged Moody 54
Posts: 19,751
Re: AIS Do I Need It?

Quote:
Originally Posted by Sandero View Post
Obviously you can't observe north with your naked eye because it is impossible to see! It's a construct. You can observe the motion of vessels and fixed things in the water with your eyes. And you can make judgements if your vessel is going to have a (too close) encounter...
A bearing is just as much a construct as is North. You cannot observe it directly, but only in relation to something fixed and far away (preferably as far away as the magnetic North Pole). In open water with only your stanchion as a reference, which is not fixed, but rather slewing around, and besides that, is only a couple meters away at best, you can see only enough to recognise courses very far from collision courses.

Sent from my SGP521 using Cruisers Sailing Forum mobile app
__________________
"Parce que je suis heureux en mer, et peut-Ítre pour sauver mon ame. . . "
Dockhead is offline   Reply With Quote
Old 16-08-2015, 16:57   #179
Registered User

Join Date: Apr 2006
Posts: 4,413
Re: AIS Do I Need It?

Quote:
Originally Posted by Dockhead View Post
A bearing is just as much a construct as is North. You cannot observe it directly, but only in relation to something fixed and far away (preferably as far away as the magnetic North Pole). In open water with only your stanchion as a reference, which is not fixed, but rather slewing around, and besides that, is only a couple meters away at best, you can see only enough to recognize courses very far from collision courses.

Sent from my SGP521 using Cruisers Sailing Forum mobile app
Boats are moving platforms to make observations from... including celestial which is not easy on board in a seaway. However I, sitting in cockpit can pretty effectively site a vessel's "progress" by comparing it to a fixed stanchion for example on my boat and make a reasonable assessment of whether it will pass my bow or stern... or YIKES. If there is any doubt I take the stern and have had no problems with this approach in coast waters and between NE and the Carribean. I do recall being driven nuts by a vessel looking for a ESA launch first stage near the Amazon which was doing some sort of search pattern which I later figured out. It was dancing like a butterfly ;-) and I took a course well clear of its maneuvering.

I think we want to hone and keep sharp are basic seat of the pants tried and true low tech navigation skills and not lapse into relying on these fabulous high tech devices. I learned to DR, worked with paper charts and did offshore passages without GPS and I now use plotters all the time and my charts are not see the top of the chart table much. I am not averse to high tech.

I don't think MOST boats in most situations *need* AIS. And of course they did fine without it a number of years ago. It would be interesting to know if we have fewer accidents / incidents since the introduction of AIS? And where these changes were.

Keep it simple.
__________________
Sandero is offline   Reply With Quote
Old 16-08-2015, 20:23   #180
Registered User
 
El Pinguino's Avatar

Join Date: Aug 2013
Location: Punta Arenas ahorra
Boat: 39' Westerly Sealord
Posts: 3,957
Re: AIS Do I Need It?

Quote:
Originally Posted by Jim Cate View Post
In my experience, use of a HBC is the only non-electronic method that works when one's own boat is not steering a steady course, something that happens in any sort of big seas. When your boat is yawing about, the canonical "sight over a stanchion" sort of technique doesn't work, but noting the compass bearing to a distant ship does.

The interesting discussions above with professional big ship skippers are based on the stability of such big ships, something that yachts often lack in reality.

Jim
True enough.... we have/had access to toys smallboat sailors could only dream off ... 25 kW radars for one.

However , watching the compass bearing of another ship was - for me at least - a big ship practice..... eyeballing the relative bearing is a small ship skill ... you learn in time to factor in any yaw..

When anything gets half close to me the bearing better be altering pretty substantionaly.......

A thort.... when taking a bearing of a big ship do you take the bearing of the front, the middle, or the back end?

Close up you can have an opening bearing on the bridge and a steady bearing on the bow......

Ping... waiting on epoxy to go off....
__________________

El Pinguino is online now   Reply With Quote
Reply

Tags
ais

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
AIS AIT2000 from Digital Yachts with GV30 GPS+AIS Antenna SFH Marine Electronics 1 16-02-2014 17:19
For Sale: AIS-MULTI AIS Receiver with built in Antenna Splitter kokomodenny Classifieds Archive 1 17-09-2013 09:53
For Sale: Standard Horizon Matrix AIS+ GX 2150 VHF Radio/AIS Receiver with CMP30 Ram3 Second St westsailwill Classifieds Archive 6 23-04-2013 19:21
AIS Simulation - Run VDR to play AIS Nmea file rgleason OpenCPN 16 12-01-2013 11:28
Can You Get Radar & AIS Overlay on Laptop ? AIS Transceiver Recommendations ? lunasea.ds Marine Electronics 22 27-12-2010 14:06



Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 04:57.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.