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From: David Straton (no email)
Date: Fri May 12 2006 - 17:18:07 EDT
OK troops,
Here are the results to the Cyclone survival exam.
> ------------------------------------------------------------------------
> Hey there cruisers,
>
> With Cyclone Larry just ashore with winds of up 300kph it is a timely
> moment to revise matters to do with meeting a cyclone at sea.
>
> Imagine this....
>
> You are sailing somewhere between the Solomons and Queensland. You hear
> of a cyclone building over the SPCZ. The wind starts to build. Waves get
> higher, and one dumps in the cockpit of your catamaran, sending water
> inside, killing all your electrics, weatherfax, radio, radar, GPS,
> laptop, EPIRB, the lot.
>
> Bugger!
>
> You only have left a compass and a barometer.
>
> Exam:
>
> A) If you face the wind, the cyclone eye is:
>
> * 1. On your left. CORRECT*. In the southern hemisphere the cyclone
> goes clockwise. Buys Ballot rule says: If you Look into the wind, the
> Low is on your Left.
> 2. On your right
> 3. Straight ahead
> 4. Looking at you.
>
> B) You measure the direction of the wind as 270şM. After 30 minutes it
> is 280şM.
>
> 1. The wind is backing.
> *2. The wind is veering. CORRECT*. The magnetic dial goes
> clockwise. An increase in bearing means a clockwise shift. Veering
> means a clockwise change. Backing means going backwards
> (anti-clockwise) round the clock or compass.
> 3. You are in the Dangerous Semi-Circle.
> 4. The compass is deviant.
>
> C) You measure the barometric pressure as 1005 hectopascals. After one
> hour it is 1000 hectopascals.
>
> * 1. The eye is approaching. CORRECT.* The barometric pressure is
> dropping so the centre of the cyclone is getting closer.
> 2. Who's worried, you still have a grand of hectopascals left.
> 3. You must be in the Dangerous Quadrant.
> 4. You will go down the plughole clockwise because of the Coriolis
> effect.
>
> D) You establish that the wind is veering and the barometer rising. You
> should:
>
> 1. Reach on the starboard tack.
> *2. Reach on the port tack. CORRECT.* See diagram in link below.
> 3. Run down wind with a drogue.
> 4. Call for help on your Hadley cell phone.
>
> E) You establish that the wind is veering and the barometer dropping.
> You should:
>
> 1. Reach on the starboard tack.
> * 2. Reach on the port tack. CORRECT. *See diagram in link below.
> 3. Beat to windward on the starboard tack.
> 4. Set a course for the Madden Julian Oscillation.
>
> F) You establish that the wind is backing and the barometer rising. You
> should:
>
> 1. Reach on the starboard tack.
> *2. Reach on the port tack. CORRECT. *See diagram in link below.
> 3. Beat to windward on the starboard tack.
> 4. You are in the Navigable Semi Circle.
>
> G) You establish that the wind is backing and the barometer falling.
>
> 1. Reach on the starboard tack.
> 2. Reach on the port tack.
> * 3. Beat to windward on the port tack. CORRECT.* See diagram in
> link below.
> * 4. You are in the Dangerous Quadrant. CORRECT.* See diagram in
> link below.
>
>
> ------------------------------------------------------------------------
Diagram to explain answers.
http://www.psyberspace.com.au/Cruising/Images/Cycloneevasion.jpg
Unfinished met site.
http://www.psyberspace.com.au/meteorology/
One thing I have learned from this exercise is the importance of a
default plan involving the *PORT TACK* (in the southern hemisphere). Its
actually obvious when you think about it. As the Buys Ballot rule says:
'If you LOOK into the wind, the LOW is on your LEFT.' From which it
follows that the port tack will take you away from the low and a
starboard tack will take you towards it.
I can remember that my slightly modifying the way I remember right of
way. 'Boom on the right, keep out of the light', becomes 'Get out of the
light with the boom on the right.'
Options 1 and 3 in the attachment involve a fine port reach. Option 2, a
port run or reach, but its in the safe semicircle, so a fine port reach
would be OK, just not as fast to get away. Option 4, in the Dangerous
quadrant, involves a port beat.
Thus a good default plan is a fine port reach, until you can work out a
better plan.
I imagine this will carry implications for sails, reefing sequence, etc,
to cope with a building sea breaking over your port bow. Possibly
reefing the main, and then dropping it, and just sailing under the jib
gradually being roller-reefed.
I think it also carries implications for a plan to stow and launch a
sea-anchor. You are likely to be on a port tack at the time. I would
like to be able to drop it over the side as safely as possible. Maybe
stow it in the port forward locker.
Remember that everything is the opposite way around in the Northern
Hemisphere.
More to think about.
Cheers
Dave
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