| Subject: |
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Re: Weir collapse on Kennet and Avon |
| Name: |
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Alan (Hawksmoor) |
| Date Posted: |
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Dec 20, 06 - 9:39 AM |
| Email (optional): |
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lorraine.sencicle@tesco.net |
| Boat Name: |
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Hawksmoor |
| Message: |
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Howard says "With all respect to Alan, pilots are employed for their local knowledge and although it is perfectly possible to make this passage given reasonable experience, the cost incurred in buying that local knowledge will make it well worth the money for the extra peace of mind".
Having carried out a little more research I withdraw my offer of pilotage!
First of all the logistics are more complex than anticipated mainly due to the large tidal range in the Severn estuary which means in effect there is a very limited time 'window' available for the passage. (a) you must reach Sharpness Basin before high water to guarantee passage through the lock into the canal (b) you cannot leave Portishead until there is sufficient rise of tide to lock out.
With only 5 hours of 'flood' in total, there will probably be less than 3 hours to cover 20 miles or more from Portishead to Sharpness?
There is a 'Catch 22' situation with regard to neap tides as against springs. Spring tides will result in a fast and exciting passage, too exciting for the majority, neap tides make it more difficult for a slow vessel such as a narrow boat to arrive in good time at Sharpness?
I have looked at Reed's Nautical Almanac where it is confirmed that the tidal stream runs at up to 8 knots through 'The Shoots' in the region of the Severn Bridges. I was surprised to read that even on neap tides the tidal range is around 30 feet (42 feet on springs). This implies that even on neaps the tidal stream in this area will be around 6 knots or almost 7 mph! With rates of this order you really have to be spot on with your navigation to keep clear of the shallows.
I had also anticipated that insurance companies would make the use of a pilot mandatory before providing cover.
I think I will start a new thread on the slightly less problematic passage along the tidal Trent!
Alan |
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