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tigermullet
04-09-2007, 10:46 AM
In casual conversation the subject of using the constant bearing strategy for avoidance of collision was raised.

I was surprised to learn, from that conversation and others that followed, that it seems to be a little known.

Do you use the strategy?

Bats do, so do pilots using VFR rules. I thought it was well known and that every boatie would know about it. It takes seconds to learn the constant bearing decreasing range strategy and really should be part of learning before licencing.

Chimo
04-09-2007, 11:10 AM
Probably many do it without the jargon.

http://www.bsos.umd.edu/psyc/batlab/kaushik/sfn_2005.pdf

Cheers
Chimo

peterbo3
04-09-2007, 11:15 AM
Tiger,
The problem seems to be that many operators do NOT look anywhere except directly ahead. Or at their GPS without employing a designated lookout. If some bozo is too stupid or lazy to check 360 deg every couple of minutes, they are certainly not going to see or react to an approaching vessel on a relative angle that remains constant.
If you go for a heavy vehicle licence & do not check your wing mirrors EVERY 30 sec, you will fail, regardless of how well you can drive. It is all about situational awareness.

runci
04-09-2007, 11:34 AM
does that mean that everyone is responsible in a collision ......

thats what i was taught.... whereas there are rules of the water it is everyones responsibility to avoid a collision

revs57
04-09-2007, 12:17 PM
Constant Bearing Strategy? No idea, even read Chimo's link, still didn't get it! As Peter said, its all about awareness, and as runci said, In my thinking everyone is responsible! Every eye is on the lookout! I inform my crew that I only have one set of eyes and need their help, not to assume anything because that can make an ass-out-of-u-and-me.

I tell every passanger, even though I'm the skipper and responsible, we play as a team

I suppose if we see a boats lights at night and everyone is informed and got their heads up, (sometimes they pick things up before I see them, they are a well trained lot!) Then I slow down until we can determine which way its heading, I've even slowed down for bright stars before, thinking it might be a mast light on a yacht.

Once I've determined the direction of travel by the red or green light, or that its anchored, I will correct my course accordingly and keep a close eye on the vessell and proceed cautiously.

If we see a boat during the day, from the port or starboard, I begin to calculate where that boat will cross my course, make adjustments for their course, considering they maintain both speed and course, and adjust my course accordingly, to pass behind the approaching boat.

Very rarely will I ever speed up and attempt to cut in front of a boat, unless I've made prior preparations with the crew so everyone has their heads up and have plenty of space to do so. To me plenty of space is at least 100 metres when in open waterways as the wake usually dispersed by then too.

The team approach has taken a lot of guess work out, and save our bacon more than once. One night coming out of Mooloolaba with no moon, very dark, we were just out of the entrance and I nearly ran over an unlighted tinnie, one of the crew caught a glimpse of his sounder, the bloke shone a torch at us, it was so close, there are some idiots out there!

The water is no place to be playing chicken!

Cheers

rhys

tigermullet
04-09-2007, 12:25 PM
Chimo. Did I use jargon? Must be getting edumacated in old age;D

tigermullet
04-09-2007, 12:34 PM
(quote)
If we see a boat during the day, from the port or starboard, I begin to calculate where that boat will cross my course, make adjustments for their course, considering they maintain both speed and course, and adjust my course accordingly, to pass behind the approaching boat.


That's it, Revs! - Constant bearing, reducing range. If the bearing is constant and the range reducing collison is inevitable unless action is taken by one or both.

charleville
04-09-2007, 01:52 PM
Yep - that is what they taught me when I did my boat licence course and it is what I practise.

If any doubts are in my mind about the other boat giving way rightfully, I slow up and pass behind them.

This especially applies when I see bigger boats.

Fish Guts
04-09-2007, 02:49 PM
what i was shown in the coxswains course was if you saw a boat that you thought was going to eventually cross your path, the easiest way was to line it up in a section of your windscreen for example the bottom left corner, top corner, right corner ect, and if it remained there for a period of time in that same spot, without moving, there was a likelihood of a collision. pretty simple. you can take bearings of it to make it more accurate, but have found to put the other boat in a section of your windscreen really easy

d-man
04-09-2007, 02:52 PM
Yep - that is what they taught me when I did my boat licence course and it is what I practise.

If any doubts are in my mind about the other boat giving way rightfully, I slow up and pass behind them.

This especially applies when I see bigger boats.

Exacerly! That's what I practise too. :o
Was taught that a collision is imminent when the bearing and range are constant and closing.

Gill
04-09-2007, 02:57 PM
Power driven boats crossing
The boat approaching from starboard ( right ) side has right of way.
How ever, if the other boat does not give way, the boat with right of way must take action to avoid a collision.
Same direction crossing paths

SgBFish
04-09-2007, 03:12 PM
Fish Guts

Another way to do it is using the boat against the land mass behind it.
If the land is moving backwards against the other boat you will pass in front of the other boat. If the other boat is making ground on you he will pass in front if he is neither making nor losing ground evasive action is needed. Sailors use this all the time. Racing yacht navigators use hand bearing compasses in a similar way to see if the bearing to the other boat is changing.

Never underestimate the speed of Ships. It’s not uncommon for them to surprise the inexperienced by there speed.

Rhys is spot on with his comments. Current navigation tools are never a substitute for the human eye or a few of them. Even inexperienced people can see crab pots, un-light boats and maintain a lookout.

As a professional driver once said to me, ‘treat them all like idiots and you will never be surprised”.

Scott

FNQCairns
04-09-2007, 04:22 PM
Nothing worse than a boat that has the right of way slowing down, speeding up, changing course slightly....being courteous. All that does is force a game of chicken on the other boat if he is to say within regulation If a vessel has right of way hold course and speed until near the last sensible moment, otherwise the regulation goes to potty!

One of my recreational boating pet hates.

cheers fnq

Deiter
04-09-2007, 05:25 PM
Well said Rhys, and in particular FNQ. It only causes confusion when the boat with right of way starts to give way. I believe that if you know the rules. stick to them until you think you are going to be run over. Similar to waiting in your car at an intersection for the other car to go, coz' you know he/SHE has right of way. Then you wait, and wait,.........and wait, then realise the other driver has no idea. This is when you start to hesitate - start to move, then they start to move, so you stop, and b4 you know it, both cars are in the middle of the road and still giving way!!!

Damo

mirage
04-09-2007, 06:51 PM
Fish Guts has the simplest explanation. Doesn't matter if you are flying, driving or boating if an object is staying stationary in the windscreen you are 100% going to hit it and it is going to hit you.
For example, when boating, if the other boat is not moving left or right relative to a fixed point on your widscreen (like an insect splatter) then eventually you will hit it. Doesn't matter what size it is, how fast it's going or what direction it's going if it aint moving in the windscreen you'll both have an unhappy ending.
That is the constant bearing strategy being talked about.
Cheers, Scotty.

rat_catcher
05-09-2007, 08:15 PM
Current navigation tools are never a substitute for the human eye or a few of them.
Exactly..........the old Mark 1 Eyeball! That is the first thing I was taught when I was in the Navy working on the bridge of a warship.