

16102014, 20:26

#1

Registered User
Join Date: Oct 2014
Posts: 20

Examination
Dear all,
I am Hongkonger, I am self study and will take a pleasure vessel certificate of competency in the coming November.
I have read a few books in library for instance the complete sailing by Steve Sleight, old books like Pass your Yachtmaster and Yachtmaster Exam.
In this moment, I am practicing mock exam paper. I have got some confuses for the calculation with almost reverse drift x knot with x knot boat speed.
Is it offset the drift speed by the boat speed directly or ......
My question is A to B the ground track measured by pointer on a chart is 6.5 knots, boat speed 5 knots with shipping course at 330 degree T, set 175 degree T with 1 knot drift. What is the position of boat abeam on the B point?
Hope you guys can help
Many thanks
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16102014, 20:34

#2

Senior Cruiser
Join Date: Mar 2008
Location: Calgary, AB, Canada
Posts: 4,851

Re: Examination
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16102014, 21:27

#3

Registered User
Join Date: Oct 2014
Posts: 20

Re: Examination
Dear Jackdale
Thank you for your advice. I did try your recommended method. The question was asking B point abeam of the boat. For your example of step 5, I can't extend the SMG from drift adjusted position and make a right angle from Isabella port. However I would like to travel to the port abeam as close as to the boat. I have two unknown information of what are the exact distances from the drift adjusted starting point by unknown travelling time, i.e., 65 mins or 70 mins.
The speed is 5 knots, SMG is 4.4 knots. If I want to take 6.5 knots. Should I calculate the travelling time by 6.5 knots distance over 4.4 knots speed, after getting the exact travelling time and then extend the drift (i.e. drfit and set are consistency after an hours) proportional by the calculated minutes. Afterward, reset the drift line to plot again to my destination.
Is it too complicated? or Just extend the SMG to be hit by the right angle of Isabella port to get the EP?
It is possible to get scores from the examination?
Appreicated
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16102014, 21:38

#4

Registered User
Join Date: Oct 2014
Posts: 20

Re: Examination
I am so sorry, I do the complete the example of EP based on current, let me finish beforehand.
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16102014, 21:58

#5

Registered User
Join Date: Oct 2014
Posts: 20

Re: Examination
Quote:
Originally Posted by ftkl
I am so sorry, I do the complete the example of EP based on current, let me finish beforehand.

Should I make the DR at closed to Isabella port and then draw the drift set distance to hit the right angle line from Isabella port?
Thanks, I practise the drawing to find out whether is the solution or not.
Thank you very much.
Regards
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17102014, 00:23

#6

Registered User
Join Date: Oct 2014
Posts: 20

Re: Examination
Any solution / calculatiin can have the 6.9 knots distance and 1.4 knots drift to get EP2?
Many thanks
Sent from my MI 2 using Cruisers Sailing Forum mobile app
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17102014, 08:21

#7

Senior Cruiser
Join Date: Mar 2008
Location: Calgary, AB, Canada
Posts: 4,851

Re: Examination
Quote:
Originally Posted by ftkl
Dear all,
I am Hongkonger, I am self study and will take a pleasure vessel certificate of competency in the coming November.
I have read a few books in library for instance the complete sailing by Steve Sleight, old books like Pass your Yachtmaster and Yachtmaster Exam.
In this moment, I am practicing mock exam paper. I have got some confuses for the calculation with almost reverse drift x knot with x knot boat speed.
Is it offset the drift speed by the boat speed directly or ......
My question is A to B the ground track measured by pointer on a chart is 6.5 knots, boat speed 5 knots with shipping course at 330 degree T, set 175 degree T with 1 knot drift. What is the position of boat abeam on the B point?
Hope you guys can help
Many thanks

Can you provide the exact wording of the question, please?
__________________
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17102014, 09:35

#8

Registered User
Join Date: Oct 2014
Posts: 20

Re: Examination
The question is extracted from sailing education center's exercise.
The question do not provide Deviation table, variation, and chart.
I try to translate the Chinese wording to English.
Q.3
A boat course at 330 degree T, found the same distances at 1.2 knots away from Peak (165) (22 degree 16.5 minutes N, 113 degree 53 minutes E ) and Chek Lap Kok beacon (22 degree 17.4 minutes N, 113 degree 54 minutes E)Q.5m3M. Find boat position.
If boat speed 5 knots, drift 175 degree T x 1 knot. Find boat position when abeam of boat in line with the position of WHITE ROCK (22 degree 21.5 minutes, 113 degree 52 minutes E)
Remark: Peak (165) I can't find on the chart, I just mark the position by the Latitude and Longitude.
Answer 1
The first position
22 degree 17 minutes 33 second N
113 degree 52 minutes 33 second E
Answer 2
Abeam of boat in line with the position of WHITE ROCK
22 degree 20 minutes 50 second N
113 degree 50 minutes 42 second E
There is a simple solution
Boat
Minute 60 Knot 5
Minute 30 Knot X
X = 2.5 Knot
Drift
Minute 60 Knot 1
Minute 30 Knot X
X = 0.5 Knot
The question did not mention any travelling time. Don't know why such solution.
Jackdale, I just want to know the way how to find the position not really get the exact position figures. The 6.5 knot distance mentioned above is measured by pointer, please ignore the value.
Thank you for your help.
Regards
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17102014, 15:21

#9

Senior Cruiser
Join Date: Mar 2008
Location: Calgary, AB, Canada
Posts: 4,851

Re: Examination
Here are the steps
1) establish a fix using 2 circles of position.
2) from that fix construct a set and drift, and determine course and speed made good.
3) go down the CMG line until White Rock is abeam (90 degrees) of your vessel.
4) determine the lat and long for the position when White Rock is abeam.
I do not have the chart so doing the assignment is a little tough.
__________________
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17102014, 16:08

#10

Moderator Emeritus
Join Date: May 2007
Location: Singapore
Boat: Maxi 77  Relax Lah!
Posts: 11,514

Re: Examination
Quote:
Originally Posted by ftkl
The question is extracted from sailing education center's exercise.
<snip>
Q.3
A boat course at 330 degree T, found the same distances at 1.2 knots away from Peak (165) (22 degree 16.5 minutes N, 113 degree 53 minutes E ) and Chek Lap Kok beacon (22 degree 17.4 minutes N, 113 degree 54 minutes E)Q.5m3M. Find boat position.
If boat speed 5 knots, drift 175 degree T x 1 knot. Find boat position when abeam of boat in line with the position of WHITE ROCK (22 degree 21.5 minutes, 113 degree 52 minutes E)
Remark: Peak (165) I can't find on the chart, I just mark the position by the Latitude and Longitude.
Answer 1
The first position
22 degree 17 minutes 33 second N
113 degree 52 minutes 33 second E
Answer 2
Abeam of boat in line with the position of WHITE ROCK
22 degree 20 minutes 50 second N
113 degree 50 minutes 42 second E
There is a simple solution
Boat
Minute 60 Knot 5
Minute 30 Knot X
X = 2.5 Knot
Drift
Minute 60 Knot 1
Minute 30 Knot X
X = 0.5 Knot
The question did not mention any travelling time. Don't know why such solution.
Jackdale, I just want to know the way how to find the position not really get the exact position figures. The 6.5 knot distance mentioned above is measured by pointer, please ignore the value.
Thank you for your help.
Regards

This is a vector problem. The first step is to draw a vector diagram on a plain piece of paper.
A line directly out from the front of the boat to abeam (draw the line past) WHITE ROCK. This is the 330 heading.
A second vector from the 175 degree is added  You must remember that 175 is true direction  the "relative direction" from the boat must be used  i.e. 330  175 = 155.
This is a quartering current  it will make the boat go "faster" so you need to know how much faster  the next step is to calculate boat speed (SOG)  This gives you time to get to abeam WHITE ROCK.
The final part is to calculate leeway/set/drift  how much you drift is dependent on how long you are exposed to the drift  that is why you need boat speed (time) to abeam WHITE ROCK.
Once you know how much time the boat is exposed to a 155 degree current you can calculate how far the drift is and then translate that to a plot on the chart.
These links may help explain better to you.
Speed over ground
Sailtrain: Navigation and Chartwork, Speed Over the Ground (SOG).
Leeway/set/drift
Sailtrain: Navigation and Chartwork, Leeway.
Online calculators for speed and drift  use "calculate speed" and 'current drift" to check you math.
Current Deviation Calculator
PS  Not to confuse you but be careful  most people don't actually want to drift off course. So the online calculators usually solve for "Course to Steer"  i.e. a course to steer so the the effect of drift is overcome  the CTS calculators in you case would give a CTS somewhat to starboard to overcome the drifting to port.



17102014, 17:12

#11

Registered User
Join Date: Oct 2014
Posts: 20

Re: Examination
Quote:
Originally Posted by ftkl
The question is extracted from sailing education center's exercise.
The question do not provide Deviation table, variation, and chart.
I try to translate the Chinese wording to English.
Q.3
A boat course at 330 degree T, found the same distances at 1.2 knots away from Peak (165) (22 degree 16.5 minutes N, 113 degree 53 minutes E ) and Chek Lap Kok beacon (22 degree 17.4 minutes N, 113 degree 54 minutes E)Q.5m3M. Find boat position.
If boat speed 5 knots, drift 175 degree T x 1 knot. Find boat position when abeam of boat in line with the position of WHITE ROCK (22 degree 21.5 minutes, 113 degree 52 minutes E)
Remark: Peak (165) I can't find on the chart, I just mark the position by the Latitude and Longitude.
Answer 1
The first position
22 degree 17 minutes 33 second N
113 degree 52 minutes 33 second E
Answer 2
Abeam of boat in line with the position of WHITE ROCK
22 degree 20 minutes 50 second N
113 degree 50 minutes 42 second E
There is a simple solution
Boat
Minute 60 Knot 5
Minute 30 Knot X
X = 2.5 Knot
Drift
Minute 60 Knot 1
Minute 30 Knot X
X = 0.5 Knot
The question did not mention any travelling time. Don't know why such solution.
Jackdale, I just want to know the way how to find the position not really get the exact position figures. The 6.5 knot distance mentioned above is measured by pointer, please ignore the value.
Thank you for your help.
Regards

Could you check any error on my steps
Firstly, I fixed the position 1.2 knots distance away from the given points. (no compass error occur)
After that, I plot a 330 degree T line from A point (1.2 knot away from both given points) to pass White Rock and use protractor to set a 90 degree linking to White Rock and across the ground track and can get the exact distance from A to the position plotted B i.e. 8 knots. (no CE too)
5 knots speed, 175 degree T set x 1 knot drift which I can find SMG (knot) by measuring the distance on chart i.e. 4 knots. (no CE)
If I travel 8 knots against the current, the actual distance should be
Boat speed
60 mins 5 knots
96 mins 8 knots
SMG speed
60 mins 4 knots
120 mins 8 knots
My actual travelling is 120 mins that is 10 knots on the course 330 degree T
60 mins 5 knots
120 mins 10 knots
So, I have got C point.
Theoretically, a new position D can be found by a line hit from C point with the set 175 degree T (no compass error occur too)
D position is the answer?
Thx
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17102014, 17:17

#12

Registered User
Join Date: Oct 2014
Posts: 20

Re: Examination
Just finish my hypothesis, hope to match your solution, go to study you one.
Thx
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17102014, 19:02

#13

Registered User
Join Date: Oct 2014
Posts: 20

Re: Examination
PEx  Calif, Just take a glance your method seems more easy on my way, I try practise again to make me sophisticated on the plotting skill. Should I concentrate to travelling time and distance not compass error because of none compass bearing mentioned in the question?
I did the above plotting for 45 mins, the period of time for exam is 1:30 for unknown long question. It is an official exam, can have exemption for RYA Ocean Yacht Master. I used to sail with dinghy and motor pleasure vessels, so, it is hard for me picking up my knowledge again at my age. I hope my holiday to ovrrseas trip not only eat and stay at hotel, I want do something on the way I were. Hope I buy a second hand yacht to meet you in Singapore one day in the future.
Appreicated to you guys
Sent from my MI 2 using Cruisers Sailing Forum mobile app
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20102014, 04:04

#14

Moderator Emeritus
Join Date: May 2007
Location: Singapore
Boat: Maxi 77  Relax Lah!
Posts: 11,514

Re: Examination
Quote:
Originally Posted by ftkl
PEx  Calif, Just take a glance your method seems more easy on my way, I try practise again to make me sophisticated on the plotting skill. Should I concentrate to travelling time and distance not compass error because of none compass bearing mentioned in the question?
I did the above plotting for 45 mins, the period of time for exam is 1:30 for unknown long question. p

Hi ftkl  As I explained in my PM testing is about doing things the long hand way and the "proper way"  In a long hand and proper way you start with the lat and long lines on the chart  these are True north relative.
Your exercise stops after calculating drift but the complete sequence (top of my head) is:
 Plot the true course relative to latitude lines using protractor
 Calculate boat speed based on current
 Plot set/drfit/leeway using true headings & speed
 Calculate set/drift/leeway angle
Note your question stops here so magnetic headings do not have anything to do with your question  the next steps are:
 Calculate True Heading to steer to avoid drift/leeway/set
 Apply magnetic variation to get magnetic heading to steer
 Apply compass deviation to get compass heading to steer
In the real world  enter waypoint in GPS steer accordingly  LOL.
In the real world method 2  Draw a liine from start to waypoint. Transfer angle from compass rose on chart (magnetic heading to steer), estimate drift (about 5 degrees), steer boat on course fudging compass error. Take a fix every 1224 hours, adjust course accordingly.
In regards to taking 45 minutes to pass this question. Sometimes you have to throw away a question if it takes too much time and come back to it if you have time.
This question has 2 answers only differing by how much leeway you make. i.e. final position.
The question gives you a 175 True current direction but you have to remember it is relative to the boat direction  hence I told you 155. I bet if you calculate the probelm with 175 and then again with 155 you will get the two answers given but one is wrong becuase you forgot to apply the current relative to the boat. This is how test questions are written to "get" you.
If you use 175 the boat will set to port less than 155 and go faster. Which ever question leaves the boat further to port is probably the right answer  Of course this is a complete guess on my part applying only what I know about how test makers try to get us.



20102014, 05:16

#15

Registered User
Join Date: Oct 2014
Posts: 20

Re: Examination
Lazy in the weekend, resume exercise tdy, i will take a detail look on SOG, and then do exercise again.
I am stupid at this moment after exercising more and more, hope to finish every question within 10 mins. Try hard
Sent from my MI 2 using Cruisers Sailing Forum mobile app
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