Yachtmaster Question?

yes you are quite right, at 223C its 2 degrees west.
I still cant agree with their answer! see my reply to TCM

Barry


<hr width=100% size=1>I just want to retire with my boat to the Med!
 
Calling YM experts!

Well, the book's wrong or the question ain't what you say. If they give the compass deviation and chart variation, the course of the boat is then irrelevant.

Even people who pass or run YM courses don't know everything.

I can't get those numbers even by working backwards from the answer.

What book is it, so we can avoid?

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Re: slight correction

i wrongly used the word "variation" in place of deviation on at least two places in the post above. The compass's poxiness is always deviation. I knew that. But nonetheless, net the deviation and variation on chart to give compass error. The answers are stil correct- IMHO!

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Re: UNderstanding, not parrotting

As I said, knew add east, subtract west variation (declination) to take magnetic to true, I should I use it every day! Wasn't sure about deviation, now I am. Thanks Matt.

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CADET it is.....Compass to True...ADd East.....
Tut tut Clive....and you running a sea school too /forums/images/icons/laugh.gif ....good job you've got Phil Cool......

<hr width=100% size=1><A target="_blank" HREF=http://www.boatsontheweb.com/> Website, Photo Gallery, Chat Room, Burgees</A>
 
Is this not a deliberatly misleading question?

Deviation applies to the ship's fixed compass, not the handheld. That's not to say the handheld will not suffer from deviation, but it would have to be swung against its position of use (etc) which makes it impossible. Hence, knowledge of the devaition affecting the handheld is unknown. Also, the handheld should be used in places well away from possible deviation causing effects.

Therefore, I suspect the answer will be to do with the correction for variation, only.

<hr width=100% size=1>Piers du Pré
http://www.dupre.co.uk
 
Re: not according to the question

it says that the bearing were taken using the ships compass - not a handbearing compass. So deviation applies. Thiough as you say, it would not normally change. But only an exercise. Giving the wrong answers makes it all the more exercising!

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Re: awkward brigade

I agree, barry. Also, those questions when one train leaves Peterborough at 10.16 am and another leaves Euston at 10.27 - completely wrong timetable AND on the wrong main line station into London so they would NEVER meet. Also, the answer to most physics electical questions is "the voltage is zero, cos the battery is almost certainly dead - it would be if you used any of the batteries in our house".

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Re: awkward brigade

Think this is why doing the day skipper thingy drove both me and Tutts nuts. No wonder all the old saily boats ended up on rockes with all this iffy navigatory stuff. Now when was the last time you saw a star for instance, cant remember ever seeing one of those going to Guernsey. So a fat lot of good for navigating. And when doing dead reconning. Wheres the bit that tells you the formular for reconing the distance traveled when the fag fell on your lap and you jumped about trying to shake it off your d**k whilst going round in circles!!

<hr width=100% size=1> <font color=blue>No one can force me to come here.<font color=red> I'm a volunteer!!.<font color=blue>

Haydn
 
YM test for Hlb

H is hammering back from Guernsey to Plymouth at 22 knots, having set off at 12 noon local time. After one hour his starboard engine revs begin to drop off quickly, to only 1000 revs, giving 10 knots and eventuallty after an hour at that speed the stbd engine dies altogther, giving 8 knots on port engine alone. He explains the situation to Tutt, who takes over the helm, and he goes down to the engine room. He fixes then engine after exactly one and a quarter hours, and goes back on the flybridge.

He suddenly realises that Tutts has been retracing their course back to St Peter Port at 8knots. H enquires what the heck is going on? Tutts tell him to shut up, cos she is busy looking for those all-important "revs" for him, which he just said had fallen off the boat. Mind you,she wasn't sure what the might look like, but anyway she had already picked a lot of red and green floating things cos they looked a bit useful, were they "revs" then or what? H says that they are useless, but Tutt says they can't be blimmin useles cos even if they aren't "revs", he is always telling her to look for for red or green things, now they've got loads he's still in a blimming bad mood, ungrateful git. H and Tutts then spend 15 minutes having a bit of a row, but eventually chuck all the red and green floating things overboard, and head off again towards Plymouth. If closing time is 11pm in Plymouth - will they make it in time?

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Re: not according to the question

Perhaps I should RTFQ first! For the sake of another nmemonic (sp?) we were taught that when working from charts to compass, 'West is best, east is least".

<hr width=100% size=1>Piers du Pré
http://www.dupre.co.uk
 
This is a common problem on a steel boat. Steel boats can have large magnetic fields of their own, giving high deviations, so the steering compasses are corrected to bring their deviations down to a few degrees. Because the hand bearing compass is not held in any specific position, its deviation can't be properly corrected and it can't give accurate bearings. The usual way to do it is to use a pelorus, a sight which sits on top of the compass, is aligned with its target and is then read by using the steering compass scale. You may remember seeing someone take a bearing in that way in one of the WWII naval films.

Deviation can be thought of as the compass being pulled one way or the other by the boats magnetic field, and it depends on the direction in which the boat is pointing. So if you are using a pelorus (i.e. you are taking a bearing using the steering compass) then the deviation you should be using is the deviation for the boat's heading, not that for the resulting bearing. The question gives the deviations for each of the bearings in order to allow you to fall into the trap; it could be considered a 'catch question' except that so many people have fallen into the trap for real.

But for the question to work, it must also give the deviation for the ship's heading, and your version of it doesn't give this (although plotting the three values we are given makes it look as if it could be fairly small). If you aren't given the information, then the question is wrong anyway.

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If the variation is 8deg W and the deviation is 2 deg W then the total error is 10 degrees W. Westerly errors make the compass read more (Error West, compass best; error East, compass least) so the compass will be 10 deg higher than true. Hence 358C = 348T, 265C = 255T, 134C = 124T.

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Naa. Your all wrong. If you read the Returning Home for repairs thread. Our resident sea school advises we PM Coliholic with all our problems!!.............../forums/images/icons/laugh.gif/forums/images/icons/laugh.gif

<hr width=100% size=1> <font color=blue>No one can force me to come here.<font color=red> I'm a volunteer!!.<font color=blue>

Haydn
 
Re: UNderstanding, not parrotting

Yes but to get these answers you need to know that the deviation at 223° is 2° west.

then 358-2-8 = 348, 265-2-8 =255, 134-2-8 =124

The question is misleading by giving the deviations for the individual bearings but is in error in not giving the only relevant one for the ships heading. (you can use the figures given to draw a deviation chart, it's always a sine wave, but I dont think they really expected that!)

In answer to BarryH regarding taking bearings with the steering compass; it is done with a pellorus and probably a compass like a Sestrel Moore once popular on sailing vessels.
Alternatively you turn the ships head to point at each mark in turn and read the bearings diectly. In this case the three separate deviations would be used and the popular answers of 355°, 259.5° and 123° would be correct.

It seems that the questioner set out to be misleading, it is a Yachtmaster question not a comp. crew question, but cocked it up by leaving out the vital bit of info.

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