very basic; mooring to a harbour wall question.

What I occasionally do when moored alongside a ladder is to rig a snatch block to run up and down the shroud and rope that to the ladder. So if you enter at high water the block is at the bottom of the shroud and the rope is horizontal. As you drop, the block runs up the shroud. This is in addition to fore and aft lines but it stops the boat from ranging about.
 
Have you really got 8m of drop? Most in the bristol channel only have a few metres of water at high tide, once you drop 2m the harbour is dry and the rest of the tidal drop doesn't matter.

Where are you cruising with 8m high harbour walls?
 
steve yates said:
I cant seem to get my head round this.

q1) If I come alongside a harbour wall at high tide, tie up, and bugger off to the pub, how exactly do I arrange the mooring ropes and springs to cope with the 8m difference at low tide?
I can't leave 8m of slack or the boat will be all over the place, but if I snug her up tight, she'll be left hanging in air, suspended by her cleats, if I'm lucky!
Its obviously something done all the time by you guys, but I can't figure it out!

q2) With a large tidal rise and fall, on a small 18ft boat, for tying to a harbour what kind of length mooring warps and springs should I be looking at?
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Yawn, it will get worse.

Your lines have to be the hypotenuse [c] of a right angle triangle. The other two sides are the height of the fall [a] [so to speak] - that is how far you will fall when the water goes out and the horizontal distance [c] of your chosen point on the harbour wall from the point where your cleat lines up with the wall.

We all know that a squared plus b squared is equal to c squared.
So since you can know what a and b are then you can work out what c is

Keep up at the back....

Example:

Depth the boat will fall is [a] 6m [ seems a big number, even for someone who sailed the Bristol Channel] and you put your line 8 metres along the harbour [that is b], from your cleat

Then c, the length of line you need to allow for the rise and fall is the square root of 6x6 plus 8x8.
Those of you comfy with numbers will know that the answer to this is 10metres.

The really observant will have noticed that this an example of a 3,4,5 triangle.
So if you can divide the height by 3 the result multiplied by 4 to find where on the harbour wall to fix your line and then multiply the same number by 5 to get the length of line you need to set.
This is a piece of 'horse-back' arithmetic that you can use, without warranty or guarantee.

Personally I might go to the pub and come back from time to time just to see what is happening.

Managed to park a boat on a training wall no one told us about through rushing to the pub and not back from it. More amusement for the locals.

All of this maths came to me after a liquid evening on a minor Channel Island when we returned to the dinghy well fed and watered to find it suspended several metres from the now completely dry harbour. The ensuing cabaret kept several locals amused and they probably tell their grandchildren of our antics.

Any questions, see me after prep and before cocoa.
 
steve yates said:
From tide-forecast.com.. "Maryport Tide Chart. The largest known tidal range at Maryport is 8.98m 29.5 feet " Obviously not always, but today for instance high tide is 8.01m and low tide -0.55m.
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But the harbour wall at Maryport has a drying height of 6 or 7m, so even if you go in at high tide you will only drop a few metres, never 8m
 
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birdseye said:
What I occasionally do when moored alongside a ladder is to rig a snatch block to run up and down the shroud and rope that to the ladder. So if you enter at high water the block is at the bottom of the shroud and the rope is horizontal. As you drop, the block runs up the shroud. This is in addition to fore and aft lines but it stops the boat from ranging about.
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But what the feck does it do to your rigging?
 
As Dylan has said: weights in the middle of (long) fore and aft lines have much merit. Similar principle to using an angel on an anchor catenary really. Works in settled weather, but could be problematic in a blow. Personally I'd prefer to be aboard to monitor things!
 
SteveSarabande said:
But the harbour wall at Maryport has a drying height of 6 or 7m, so even if you go in at high tide you will only drop a few metres, never 8m
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Ok, so maybe that's why I can't get my head round it? The chart shows Maryport harbour drying and has a sounding of 2.2, which I am presuming means you would touch bottom when the tide still had 2.2m to fall? Anyway, that still leaves 6m, a fair amount? And Maryport was just an example, I have no idea what I'll find on my travels, but I'm sure I'll find more extremes than that.

Maybe the question should be simply how do I tie up against a harbour so the boat stays there at high tide and sits comfy on the ground at low tide?
And how do I know what that difference will be? If my assumptions and calculation above is wrong.
 
steve yates said:
Ok, so maybe that's why I can't get my head round it? The chart shows Maryport harbour drying and has a sounding of 2.2, which I am presuming means you would touch bottom when the tide still had 2.2m to fall? Anyway, that still leaves 6m, a fair amount? And Maryport was just an example, I have no idea what I'll find on my travels, but I'm sure I'll find more extremes than that..
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Then take off the distance from bottom of keel to the deck, another 2m, so we are down to 4m.
 
in this case the only option is to tie up to a ladder or how are you going to get back on the boat??.. if the tide is falling you need a slip rope through the lowest rung of the ladder that one can poss reach ....allow one rung per pint
 
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TonyBuckley said:
And yes many boats moor against the walls. As someone said, if you can get your lines wide, that helps but the answer is to come back frequently and adjust; there is no easy answer and no long term solution.
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+1

You don't always have to adjust, but you need to check.

Lines as long as possible (lines wide).

Don't be fussed about having the boat tight up against the wall (different if you expect to dry out) especially mid-tide when it is falling or rising rapidly.
 
prr said:
in this case the only option is to tie up to a ladder or how are you going to get back on the boat??.. if the tide is falling you need a slip rope through the lowest rung of the ladder that one can poss reach ....allow one rung per pint
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Would never tie directly to a ladder. You can grab a loose spring and haul the boat in when you want to get back on board.
 
The only non drying harbour I know with that sort of range is Port St Mary on IOM. I have experienced mooring on a big spring tide a couple of times. I remember being rafted out three or four deep and the only shore lines that could reach were climbing ropes!
 
steve yates said:
It seems to me, most fishing boat owners in small drying harbours.
Maryport has numerous fishing boats and a few leisure yachts tied up against the walls. None of those leisure craft have moved that I can see for the last 6 months.

I'm sure it's not unique?
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Have you looked to see how they are tied up? Maybe they are on rings that run up and down rails or on a pontoon that raises and falls.
 
l'escargot said:
Have you looked to see how they are tied up? Maybe they are on rings that run up and down rails or on a pontoon that raises and falls.
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Pretty sure it's just bollards and large rings on top of harbour wall, but will take a loser look. Definitely no floating pontoons in Maryport, or indeed in the average small harbour, on the west coast at least.
 
TonyBuckley said:
8m is nothing compared to the Channel Islands.

And yes many boats moor against the walls. As someone said, if you can get your lines wide, that helps but the answer is to come back frequently and adjust; there is no easy answer and no long term solution.
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I haven't read all these but its simple as has been said you use an "Angel" A heavy weight in the middle of either the front or stern line...This keeps it tight and its totally a long term and easy solution used by many boats all year round.
 
steve yates said:
That's one of my destinations, so worth knowing, thanks.
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How good are you with heights as the ladders up the wall are very difficult to negotiate especially over the top.

If you or your sailing partners suffer at all use your main haliard as a safety line!

My lady admirable refused to climb them!

Much easier to moor up to a fishing boat but don't expect a lie in as you wont be able to avoid an early morning shuffle!
 
I seem to remember being in a harbour with a significant tidal range where I saw rings in the wall just about at water level low tide. The idea was that you loop a line through this ring first chance you get (don't tie it off there unless you plan on leaving at low water) and the two ends of the line are then made fast to a bollard immediately above it at the top of the wall. You do this twice, one for the bow, one for the stern. You then pass your respective mooring lines around these vertical lines and make fast. As the vessel rises and falls on the tide your mooring lines simply slide up and down your vertical ones.
 
Many, many years ago, when I was a member of the local constabulary, we got a call to go to a fishing boat at the harbour. When we got there we found an inebriated fisherman, and a fair sized trawler suspended from her mooring warps. The fisherman had been left on board as a watchman, and he decided to go to the pub for a pint, one became several, and when he returned to the boat the tide had gone out. We decided it wasn't a police matter, and called the skipper, I'm not sure what happened, I know we didn't want to go near the warps, you could heard them humming with the strain. I guess the choice would be an axe, or simply wait for the tide to come back in. I often wonder if any damage was done.
 
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