Narrow Channels

[Lucky Duck]

We spent one summer evening aground about twenty feet from the outer lock gates where the scouring action of the water leaving the locks create a hard knoll just opposite the knuckle on the outer waiting pontoon.

Sticking close to that pontoon seemed to avoid the worst of it.

 

[DAKA]

Rising or falling tide?

The last time at Chichester it was a rising tide, others in particular Northeny were falling tides which blocked the channel for a couple of hours.

 

[Boathook]

In my years at Chi I was one the few people who could still get in and out at most low tides so I'm something of an expert at pushing my luck in and out of Chi Marina.

There's the lock keeper settling down to read a book, Thinking they have a couple of hours of no boat movement due to LW, and then you turn up

 

[mrming]

I’m in a tidal marina with a very narrow channel and I get this all the time. Visitors and inexperienced locals are worried about touching some soft mud on a rising tide. I once asked a boat to move over, but the skipper was clearly too nervous to listen. Now I just get right over and stop, or squeeze around them if there’s room.

 

[dunedin]

Separate subject. Learn how do do simple tide heights. Walk. Then learn what other factors can alter the calculated height. Run.

But only a fool thinks a tide tables can get to within 1cm - that is dangerous

 

[dunedin]

Just seen this - those two factors were the exact reason I had less water than expected.

I am very rough and ready with tide calculations, with an approximate rule of 12ths at best. I find tides rarely read the tables in detail anyway.
But if approaching any critical depths, I try to go directly over a few chart soundings on the approach to seevwhat the ACTUAL height of tide is.

 

[Mark-1]

There's the lock keeper settling down to read a book, Thinking they have a couple of hours of no boat movement due to LW, and then you turn up

I think they were given tasks to do at quiet times so I'm pretty sure they had a long walk from the over side of the marina at times. I definitely felt like a celeb over my excentril arrival times. Which is odd because the ribs and lifting keel boats must have gone out at low tide from time to time.

Lovely place to keep a boat, just not a lovely place to sail from.

 

[Sticky Fingers]

I am very rough and ready with tide calculations, with an approximate rule of 12ths at best. I find tides rarely read the tables in detail anyway.
But if approaching any critical depths, I try to go directly over a few chart soundings on the approach to see what the ACTUAL height of tide is.

Yes that’s a good tip. At the time it was all a bit fractious what with the squadron of outbound boats, a rammed waiting pontoon and a stiff crosswind. Hindsight would say anchor for a couple of hours eg at East Head. Good learning experience.

 

[DAKA]

Hi Mark

QUOTE "
I'm pretty sure at Chi the lock cill is shallower than the channel so if they got over the cill they had way more than 2cm in the channel. Also the deepest part part of the channel is a few metres North of the posts, so that might be a factor.in them thinking it was shallower than they were expecting.
" END QUOTE


Very interesting observation regarding the cill , the following needs confirming by a local before anyone relies on it (no one take any notice of this until the theory is approved by a local )

Chichester Lock cill is concrete and at the Marina side (close to the pedestrian bridge) , there is a painted label on the wall .
As such you will never hit the cill as the lock is always full of water as you go over the cill , the only exception is when you have a really long boat in the lock or the lock is jammed with smaller boats and you are unlucky to be forced right to the pedestrian bridge end.

When boats ask the lock keeper whats the depth over the cill he will provide a depth of low water at the bridge end but there is always significantly more water at the sea end as erosion digs that end out.

The channel (lock fairway outside) should be dredged to the cill depth but it isn't dredged on a regular basis and can be less than the lock exit.

 

[Mark-1]

LHi Mar

QUOTE "
I'm pretty sure at Chi the lock cill is shallower than the channel so if they got over the cill they had way more than 2cm in the channel. Also the deepest part part of the channel is a few metres North of the posts, so that might be a factor.in them thinking it was shallower than they were expecting.
" END QUOTE


Very interesting observation regarding the cill , the following needs confirming by a local before anyone relies on it (no one take any notice of this until the theory is approved by a local )

Chichester Lock cill is concrete and at the Marina side (close to the pedestrian bridge) , there is a painted label on the wall .
As such you will never hit the cill as the lock is always full of water as you go over the cill , the only exception is when you have a really long boat in the lock or the lock is jammed with smaller boats and you are unlucky to be forced right to the pedestrian bridge end.

When boats ask the lock keeper whats the depth over the cill he will provide a depth of low water at the bridge end but there is always significantly more water at the sea end as erosion digs that end out.

The channel (lock fairway outside) should be dredged to the cill depth but it isn't dredged on a regular basis and can be less than the lock exit.

I know someone who was lowered onto the cill and wrecked his rudder. The cill starts at the end of the diagonal "wood" "cladding". (I went down there for a look when it was empty for repairs. Pretty sure I have a photo somewhere.)

 

[xyachtdave]

A friend of mine went into the Chatham MDL lock that was clearly showing 100mm less than the stated draft of his boat on the depth gauge.

He was surprised when he hit the cill as he thought they should allow a bit of clearance on the numbers on the wall, rather than start the tape measure from the bottom and give the actual depth of water.

 

[Sailing steve]

A friend of mine went into the Chatham MDL lock that was clearly showing 100mm less than the stated draft of his boat on the depth gauge.

He was surprised when he hit the cill as he thought they should allow a bit of clearance on the numbers on the wall, rather than start the tape measure from the bottom and give the actual depth of water.

Well hoping there's "a bit of clearance" when the gauge says no, actually there really isn't is asking for the day to not end well.

 

[benjenbav]

About 400m downstream of the Chichester marina channel I once engaged in some arm-waving and then felt very foolish.

Motoring past Itchenor and towards the marina I grounded almost at the bottom of a spring ebb. Possibly owing to a belief that there was a tiny bit more water there than there was.

No matter. Soon had the kettle on to show that I’d meant it. And I settled down for an hour or so’s worth of watching the world go by on what was a very pleasant evening.

Then, to my horror, I spotted a considerably larger yacht, single-handed, heading upstream apparently without a care in the world.

I hailed. I waved my arms. “Stop. It’s somewhat shallow here” called I.

And still the yacht came on.

As it drew level, the skipper raised his cap in acknowledgment.

“Southerly” he said, “Lift keel”.

And on he went.

And I went back to my tea, slightly wiser.

 

[Poignard]

When I first took my Twister out to the Vilaine River, Brittany, I hove-to in the estuary waiting for what I calculated would be sufficient height of tide.

A large French yacht, going very fast, shot past inbound.

Aha! says I - local knowledge, I must have made an error in my calculations, and I set off in pursuit.

I didn't know at the time it was an Ovni with a centreboard; very common in that part of the world.

I didn't get very far!

Fortunately, and thanks to the echo sounder alarm, I didn't ground but I had to retrace my course and drink some more tea until there was enough water.

My calculations were right after all!

 

[The Q]

I was sailing past Stokesby during the 3 Rivers Race, some years ago...
Then there was a rather large bang from behind me..
The boat following behind, hit the concrete slipway for the old ferry..
He drew 3ft, my boat drew 18 inches.. (bilge keeler).

As for tides, where the boat is moored, 19 miles inland by river, the tide is normally about a foot peak to trough.
But give us a spring tides northerly storm , low air pressure, and rain it in extremis can be +3ft on that.
A southerly wind for several days, high air pressure, no rain forecast weeks, it could be -3ft..

As for this year's 3 Rivers Race on Saturday/ Sunday, we've only just had rain for the last couple of days, having had none for months, Saturday is forecast to be little wind, and an incoming tide at the start..
I predict a slow race, many touching bottom, and at the start sailing backwards.

The start if it happens on time is 11:00 am 31st May 2025. On here HSC Club Front : Horning Sailing Club

 

[Sticky Fingers]

…

And still the yacht came on.

As it drew level, the skipper raised his cap in acknowledgment.

“Southerly” he said, “Lift keel”.

And on he went.

…

I had an identical experience, probably in much the same spot. Lovely Southerly, ‘Belfast Child’. Not smug. At all. Just very self assured.

 

[Chiara’s slave]

I had an identical experience, probably in much the same spot. Lovely Southerly, ‘Belfast Child’. Not smug. At all. Just very self assured.

Nobody is that surprised when we pull that stunt. Though not many people realise how hard it is to steer a tri with no centreboard and the rudder not balanced.

 

[The Q]

Narrow channel sailing boats from 14ft to 40Ft in this race..
the river

At the turning point its just under 120ft wide,, just before they come round the corner down the river it's down to 50ft wide...

 

[LittleSister]

But only a fool thinks a tide tables can get to within 1cm - that is dangerous

Oh, the tide tables can. It's just that the water often doesn't!

 

[SaltyC]

Unfortunately nature hasn't read the predictions and does what it thinks not what 'we' say it should.