yachtmaster

Fireball - you would do all of that agreed but my point is that in 10m visibility, no radar, no plotter usinf DR and depth soundings, it would be dangerous to use aim for buoys, Increase visibility and yes, its fine but not in 10m - it just cannot be,
 
OK, before knocking the whole exercise as flawed, try it once your boat is one the water. Or come out with people who are used to doing it. Much better than theoretical meanderings.
 
yes - because, as you've stated - DR (and y DR ... not EP ??) is not 100% acurate so the chances of getting that close to the buoy are so remote that you would be unlucky to hit it - afterall, they are comparitivly small on a big bit of water... ... and if it is really that bad that I couldn't alter course in vis (bear in mind I can motor at 1-2knots through the water) I'd be dropping in and out of gear as I approached where I thought the target was (see my other post)
 
10m is the length of my boat ... having had quite a bit of practice I know I can alter course significantly with 10m notice ... if travelling slow enough.
 
Gludy
As already stated, if you wish to blind nav to a buoy you do not take a bearing staright for it. It is not that accurate, you would almost certinly miss it. Likewise if yu wish to find a harbour entrance you do not aim for it, if you miss you wont know which side of it you are. In a nutshell you aim to deliberatly miss by a fair amount. You knowthat the buoy is on (say) the 10m contour so if you aim to the east of it on a CTS when you reach a depth of 10m you turn to the west and follow the 10m contour. Using time speed distance or log and tide to calc EP's at regular intervals. When you think you are there you tell the examiner who then lets you see where you actually are. If it comes within the theoretical vis then the examiner will usually assume it has been seen and tell you. If you can follow the contour then you will find it.
You state you have done the theory courses, well I am afraid they do not include blind nav. This you will only practice on the theory couses.
 
IMHO this is where experience really counts as well...... in picking the right buoy... eg one that is on an easily followed contour.....

As an example, try this technique immedately off Harwich and you'll struggle, as the whole area is very similar in depth..... but go just a little further north to the main shipping channel markers, and the depth change is more rapid...... and hence a clearer contour, and you can then buoy hop along the southern/Eastern side of this channel quite safely...
 
Brendan

There you go again refusing to see the facts right in front of your nose and just restoring to personal smearing......... what i amsaying is not theoretical - it is practical, its simple physics and we all have obey the physics.
 
"yes - because, as you've stated - DR (and y DR ... not EP ??) is not 100% acurate so the chances of getting that close to the buoy are so remote that you would be unlucky to hit it "

I agree with you again. BUT I am being told they aim to one side of the buoy using DR!!!!! So I am being told that its so accurate they aim to one side and when the spot the buoy off the port bow they confrim position ...... I am sure they do this but not in 10metre visibility!!
 
what smearing? Go out with an instructor and learn the basics if you think it's so difficult you'll have a problem with it.
It's a practical exercise. Do you really have an issue with that?
 
"Gludy
As already stated, if you wish to blind nav to a buoy you do not take a bearing staright for it. It is not that accurate, you would almost certinly miss it."

I agree with that - Then in 10m vis you would not hope to spot it.


"Likewise if yu wish to find a harbour entrance you do not aim for it, if you miss you wont know which side of it you are. In a nutshell you aim to deliberatly miss by a fair amount. You knowthat the buoy is on (say) the 10m contour so if you aim to the east of it on a CTS when you reach a depth of 10m you turn to the west and follow the 10m contour. Using time speed distance or log and tide to calc EP's at regular intervals."

Understand and agreed.

"When you think you are there you tell the examiner who then lets you see where you actually are. If it comes within the theoretical vis then the examiner will usually assume it has been seen and tell you. If you can follow the contour then you will find it."

Again agreed - no problem with any of that

"You state you have done the theory courses, well I am afraid they do not include blind nav. This you will only practice on the theory couses. "

No I have done the thory exam - what i stated was that I have in real life been down to zero visibility - not seeing the bow of my own boat (Princess 385 at the time) and been in low vis like 20 and 30 m on a number of occasions.

I have however, always had my radar.
 
So which bit are you arguing about ??

I've suggested that your nav (or mine) isn't acurate enough to actually hit the buoy
It has been suggested that in practice you'd go for a contour (helps if the buoy is on one !!)

The actual practice will depend on what instruments and senario you find yourself in.
The YM prac (and y don't you do CS prac first?) aims to see if you can actually navigate acurately in a theoretical situation.
 
I have an issue with what you say.

I have done a practical exam - you telling me what to do, you are handing out advice based not on what i say but on your assumptions which are plain wrong.

I have given you timings for how little time you would have to miss a buoy and you have simply ignored the facts, ignored the physics, ignored the bery practial points that that demonstrates and then resorted to infroming me in genral terms of my ignorance of this or that ...... none of which is to do with the points.

Tell me how many seconds do you think you should have to avoid a solid obstacle in front of you when travelling at 5 knots with a visibility from the hel of 4 to 10 foot in front of your bow and a lookout on the bow? That is the issue, deal with the issue and please stop telling me to do this or that.
 
Fireball.

What I am saying is very, very simple. Its is this:-

In 10 metres of visibility:-

1. I do not accept that at 5 knots speed you can be so accurate as to be within 30 foot of a buoy and so aim not to hit it....... I bleive in that visibility you should aim to avoid it.

2. If you are aiming for it in the above vis and speed then you have only a few seconds to avoid hitting it should you be lucky enough to be doreclty onto it.

3. If you accept the lack of accuracy then there may be little point in aiming for it as you would not see it anyway.

Thats really it.

Nobody has attempted to answer those direct points or deal with the few seconds of warning.
 
Brendan

Over 5 miles do you think that you should fail if you cannot navigate to within 30 foot using only compass, speed and depth contours with a knowledge of the tidal streams?

My view is that such an accuracy claim is absurd.

It may be possible to get onto a depth contour and follow it to a buoy but to do that with only a few seconds warning of the need to take avoiding action and not hit the buoy would be irresponsible.

Do you agree? Because that is what we are talking about in this example.
 
I'll repeat an earlier post as you seemed to have missed it.

[ QUOTE ]
you would know when you're in the vicinity from your EP .... so you would take appropriate action before you get too close ... wouldn't you ??
eg - if you assume 100m error on a short buoy hop ... then as you get to the 100m radius from target you'd be more cautious - slow down and if the target has a sound signal, even stop the engine for a couple of seconds to try and hear where it is.

100m is a pure guess - but depends on your start point, distance to target, wind and assumed tidal effect ... oh and the accuracy of your helming ... (difficult to hold to specific courses by hand ...)


[/ QUOTE ]

Bear in mind the colregs here too ... which state:
[ QUOTE ]
Every vessel shall at all times proceed at a safe speed so that she can take proper and effective action to avoid collision and be stopped within a distance appropriate to the prevailing circumstances and conditions.

In determining a safe speed the following factors shall be among those taken into account:

(a) By all vessels:

(i) The state of visibility;

(ii) The traffic density including concentrations of fishing vessels or any other vessels;

(iii) The manageability of the vessel with special reference to stopping distance and turning ability in the prevailing conditions;

(iv) At night the presence of background light such as from shore lights or from back scatter from her own lights;

(v) The state of wind, sea and current, and the proximity of navigational hazards;

(vi) The draft in relation to the available depth of water.


[/ QUOTE ]

The bit in bold is my edit ... but shows that if you were in reduced vis you wouldn't be going that fast ... if you can only see 10m then you'd be going at a speed that allows you to stop in 10m (with someone on the bow I hope!) ... otherwise you might hit someone else who is also blind nav.

In practice You'd also have everyone on deck lifejackets on with flares to hand, liferaft ready to deploy and a sodding great fog horn.

In the YM prac it doesn't matter if your vis is reported to be 1m, 10m or 100m ... you (the navigator) cannot see anyway so you just have to be good at nav.

In my DS prac we had to sail to pic up a buoy (in good vis) the instructor was happy when I had the boat nearly stationery at 1m from the buoy ... I finished the manouver at 6" off the buoy - just shows that what they are after is a demonstration that you can carry out the required task competantly (unlike my spelling ... but I've cut my finger so typing is reduced /forums/images/graemlins/frown.gif).
 
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