BRISTOL SAILING ASSOCIATION

Newsletter April 2013

Contacts:Kath Liddiard (Commodore)01443 227928

Jock Playle (Secretary)0117 973 8855

Jane Jenkyn (Treasurer) 01275 880318

As some of you know, Mike Berry underwent a serious operation last month. He initially made a good recovery and returned home on April 25th, but had to return to hospital again for observation. Jeff and Gordon visited him this week and found him to be much improved and about to go home. Mike says he is feeling well, and hopes to come to our June meeting. We wish Mike all the best for a speedy recovery.

Future Trips

As we were unable to source a suitable boat from Plymouth available for racing, both the Helford – l’Aber Wrac’h and PASAB race proposals have been cancelled.

1.1Jeff Birkin will skipper a weekend trip from Plymouth on May 31 – June 2. This will be on a Bavaria 44, and is fully booked at a cost of £128 per person. Final payments of £78 are now overdue.

1.2Jeff will skipper another weekend trip from Plymouth on July 5 – 7. Since payment of the deposits there has been one cancellation, so one place is now available. It will cost £117; final payments of £67 are due by Tuesday May 21st.

1.3Jeff will also skipper a cruise from Milford Haven, hopefully to southern Ireland, for a week Sunday July 14 – 21. This is fully booked and will cost £203.50 per person for the 7-day charter. Final payments of £153.50 will be due by Wednesday June 12th.

1.4We have some interest in Bill Barnes’ suggestion of a warm weather charter (Caribbean, Seychelles?) next Christmas. Please let us know if you are interested in this.

2.News and notices

2.1Colregs discussion. At the meeting on May 13 Alan Howells will lead a talk/discussion on the ColRegs - not the basic steering and sailing rules, but the ones that cause confusion especially in fog – for example the whole of Section II does not apply in restricted visibility, which most people don't realise. We have had arguments in the past about 'who was the stand-on vessel' and Alan will concentrate on this.As with last year's pilotage and ropework sessions, we can split the meeting with those who want to take part in this at one end and those who are happy to drink and chat at the bar end.

2.2First Aid

A number of us took the RYA one-day First Aid course on board Sabrina on Sunday May 2nd 2010. As this is valid for 3 years, the certificates have now expired. Brian Howell, who took the 2010 course, will again be our instructor for a day course on Sunday May 26th (the only May Sunday for which he is available) on board Sabrina. It will cost £25 (compared to the usual commercial rate of £75) and will be from 10.00 am – 4.30 pm. I will collect the fees on the day from each member who has booked and pay the total to Brian.

Will those going note that the bar on Sabrina will not be open, so you need to bring your own drinks and lunch.

2.3GPS warning.

The RYA has issued the following warning about degradation or even loss of GPS signals due to solar activity this year. This has also been aired on BBC Radio 4.

According to scientists the Sun is gearing up for its most active phase (solar maximum) of its 11-year solar cycle this year. Experts predict that the peak of the current maximum could happen anytime from May this year which will impact on the availability and performance of GNSS, with performance degradation likely until 2014, due to increased ionospheric scintillation and signal propagation delays.

During the solar maximum sections of the solar system intensify, making our ionosphere denser and thicker.

Higher solar activity; sunspots and solar flares increase ionizing solar radiation creating more free electrons in the ionosphere and cause sudden variations in the density of the ionosphere, causing the GPS signals to scintillate (as a twinkling star).

Impact on marine navigation

The impact of the ionosphere on GNSS performance can be significant due to the propagation effects on the GNSS signals as they pass through the ionized ionosphere at altitudes above 50km from the earth’s surface.

The most significant errors experienced by GNSS are due to the effect of solar activity on the ionosphere.

The magnitude of the effect of the ionosphere varies in both time and spatial extent.

The effect is much greater during the day than during the night and will vary with latitude, season and time of day (the hours soon after sunset being most affected).

The effects of the ionosphere can introduce measurement errors of greater than 10 m (even for DGPS users) and in severe conditions, the receiver can lose lock on the signal. Users of dual and multiple frequency GNSS receivers may be less affected. Adverse conditions can persist for several hours, thereby presenting a significant issue for navigation.

Skippers should be able to maintain the vessel’s estimated position through periods of GPS outage provided a decent log is kept, but the accuracy we now expect from GPS derived positions will degrade gradually the longer the outage continues.

Skippers should be aware that at the end of the outage, when a GPS position is restored, some onboard systems may require manual intervention to reinitialise.

It is also worth noting that during the last solar maximum the level of dependence on GNSS was much lower than it is now.

Marine navigation warnings

The Space Weather Prediction Center (SWPC) in the United States of America provides alerts and warnings on their website which show GNSS users where problems may occur and the potential effects on their operations.

The UK Hydrographic Office (UKHO) will issue navigation warnings on the basis of information provided to them by the SWPC or the UK Met Office.

An example of the type of warning if as follows;

NAVAREA XX XX/13SPACE WEATHER1. STRONG SOLAR RADIATION STORM IN PROGRESS UNTIL 081000 UTC JAN. RADIO AND SATELLITE NAVIGATION SERVICES may be affected.2. CANCEL THIS MSG 081100 UTC JAN

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3.Recent Trips

At the April meeting we had reports from Sue Fowle and Phil Steele on the PYC yacht trips on Spellbinder (skippered by Gordon on March 18-20) and Quartette (skippered by Phil on March 20-22. Bob Buchanan reported on his latest sail on Lady Emma. Here are these reports:

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Trip on Spellbinder, skippered by Gordon Ogden

Trip on Quartette, skippered by Phil Steele

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Trip on Lady Emma, skippered by Bob Buchanan

BSA April 2013- 1 -