Tuesday, 16 February 2016

Cape Town to St Helena Passage Summary

Hi everyone,
We are now cleared-in to St Helena and had a quick look around Jamestown.  We returned to Zen Again to get to work on post-arrival boat work, one of which is this passage summary!

We had a great passage from Cape Town to St Helena.  This part of the South Atlantic is certainly gentler than the southern Indian Ocean.  This was in line with expectations.

First the usual plots…

Zen Again track

Zen Again speed

The track plot clearly shows how we gybed to and fro in the SE wind as we made our way NW to St Helena.  Initially we laid the course with a nice S wind.  The wind eventually settled in the SE and a-gybing we went.

The speed plot shows we made good average speed but our speed varied substantially all the time.  This was due to the wind being light and quite variable.  Compare the plot to those of our Indian Ocean crossings and you'll see the difference.  This plot also clearly shows how much we slowed down yesterday to delay our arrival to dawn today.

Here are the vital stats for the passage…
  • Distances/Speeds
    • Route Distance = 1700nm
    • Logged Distance = 2074nm
    • GPS Distance = 2010nm
    • Duration = 14 days 17 hours
    • Average speed = 5.8kt  (same as Reunion to Richards Bay!)
    • Average VMG = 4.8kt
    • Average day's run = 141nm
    • Best day's run = 151nm (6.3kt)
    • Minimum boat speed = 3 kt
    • Maximum boat speed = 8.5kt
  • Weather
    • Minimum wind speed = 6 kt
    • Average wind speed = 12 knots
    • Maximum wind speed = ~28kt (in one of several brief squalls)
    • Apparent wind angle range = 90 to 150 (we don't "do" running, choosing to broad reach instead)
    • Seas up to 2m
    • Swell up to 3m
    • Frequently overcast but some gloriously sunny days and starlit nights
  • Engine
    • Total = 12 hours
    • Driving = 2 hours (leaving Table Bay)
    • Charging = 10 hours (mainly to ensure good power for our HF net control work)
  • Consumption
    • Water = 110 litres
    • Fuel = 24 litres
    • Books = 7 (3 + 4)
  • Failures
    • None
  • Stars
    • The boat!
    • Aries vane gear (steered for 13 days non-stop)
    • Satphone.Me email system (over Iridium GO!)
    • PredictWind Offshore app (over Iridium GO!) for obtaining GRIBs
    • qtVlm GRIB viewer and weather-routing software
    • SeaIQ iPad navigation software
    • Icom HF/SSB radio

On departure from Cape Town we found the log was grossly under-reading.  I recalibrated it early in the passage by comparing it to our GPS Speed Over Ground.  I suspect the log is now overreading slightly since we ought to have had a little assistance from current.

There was steady commercial ship traffic for the first few days but that decreased rapidly thereafter.  We went for several days without seeing any traffic.  We saw one AIS-less fishing boat only.  It felt a little lonely out there at times.

The HF/SSB net worked pretty well.  We exchanged positions, courses, speeds and wind info daily between a flotilla of boats spread over more than 1500nm N-S.  The net controllers were communicating successfully over at least 1000nm despite it being a non-optimal time of day.

Overall it was a very pleasant passage.  It was our longest passage to date, both in terms of miles logged and its duration.  That record won't last long though!

We really enjoyed our time in South Africa but were ready to leave.  We are already enchanted by St Helena.  Jamestown is a very nice little town with many historic old buildings.  The people are all very friendly.  We expect to stay here for about a week.

Farewell Africa!

1 comment:

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