Med Mooring in heavy surge

[monte]

Telling the op to move is a bit pointless. I'm sure he's considered that option and would prefer stay and moor safely. Thousand of yachts are left stern to through winter with tidal surge situations, it's not that big a deal so long as the mooring, lines and cleats are up for it. Tighten the lines, double up if necessary, rear cross braces, make sure you don't get closer than 1m to the hard stuff and relax.

[vtomanov]

Originally Posted by monte

Telling the op to move is a bit pointless. I'm sure he's considered that option and would prefer stay and moor safely. Thousand of yachts are left stern to through winter with tidal surge situations, it's not that big a deal so long as the mooring, lines and cleats are up for it. Tighten the lines, double up if necessary, rear cross braces, make sure you don't get closer than 1m to the hard stuff and relax.

There are places in Greece where the Ferries generate HUGE serge... once I was about 3 meters from concrete in Simi and the Ferry managed to hit my stern to the concrete with HUGE 2m wave - luckily I had e about 5 fenders on the stern as there was one at the side of my boat.. and I did not suffer damage...

Another time on Paros/Paroikia - the boat was like alive constant huge serge waves 1-1.5 meters all night everything squishing and squashing I had lines about 6-7 meters long to shore and the night was really uncomfortable.. I will I was not so lazy and had went for Anchor in teh bay

anyway this si just my experince

[boatman61]

Originally Posted by CookiesnTequila

So do you make them as tight as possible, but just enough to ride the surge?

A little less than tight as possible.. enough for the lines forward to pull her a couple of feet further than you can comfortably stretch step.. and doubled up.

[Rapanui]

When this happened to us, used single not doubled shore lines to the bow cleats as well as the normal stern shore lines and then slacked away the stern shore lines until there was no snatching. That way you get lots more stretch maybe 6 times compared to the shorter doubled stern lines or more if you use thinner warp which you can do with impunity as even if they break it will be no drama.

[CarinaPDX]

I don't know where the idea of springs and snubbers got started, but in my experience they are a disaster. I spent a year in Marina Bay, Gibraltar, which had concrete piers and random powerful surges, and the springs just made it worse. They also were prone to breakage, which is a testament to the high loads that the springs themselves create! Rubber snubbers are better, because they are less efficient springs (i.e. they turn the energy into heat). Best to avoid the lot.

To explain: springs are energy storage devices. As they are compressed or stretched they absorb energy, which they release when the external force is removed. In this case an incoming surge will cause the boat to compress the spring before stopping; when the surge reverses the force of the surge is augmented by the energy stored in the spring, which accelerates the boat more than without a spring and stretching the lines even more in the opposite direction. If there is a second or third surge the energy will continue to build, often leading to hitting the quay. This works much like pushing a child on a swing, increasing the movement with each oscillation. It is a really bad idea, but admittedly sounds plausible.

Most Med harbors offer "slime lines" to fixed moorings for holding boats off. Where using an anchor is necessary I use a polyester line to a short length of chain and a Danforth anchor. I do not use nylon because the last thing I want is stretch in that line! With at least 100' of rode out and the bow only 3-4' off the quay I can't afford much stretch in the rode.

Greg

[hamburking]

Long lines!

Short, tight lines are asking for trouble...all that energy has to go someplace.

Long lines allow the boat to go up and down without moving forward or aft. Long lines can be very tight.

[captmikecoin]

See what the local fishermen do. In my experience they leave everything as slack as possible, if necessary pulling well off the quay and using long lines. However local conditions may require something different depending on the swell or surge direction. In the past I have tied a long spring from the bow to the quay on the windward side and let go (left the lines slack) the stern so the boat turned into the wind and waves and was riding to the mooring and the spring.

Mike

[sy_gilana]

We have done that for many winters.

Forget the springs, or the rubbers, or any patent solution.

There should be sets of lines going to the bollards ashore.
They should all be Nylon.
The splices should all be shoreside (so that you can cast off and leave in a hurry)
You should have a 1/2" four as the tightest set.
These should go direct ashore from the outboard cleats, and across each other on the inner cleats, or "v" to a center bollard if you have two slips.
A 3/4" four, and hanging about 30-40 cm below the previous four, also straight and crossed.
A 1" or larger pair last, hanging 30-40cm below the previous, but not crossed.

Adjust them carefully, and the thickest lines should only take strain on the most violent surges.

If your front lines, going to the main-chain are also Nylon you might land up boinging around like a toy. We prefer a chain pulled tight there, where weight is less springy than a Nylon line.

Never tried this but, would you be able to point your rudders in opposite directions? This could arrest surge quite well.

We also always fender off to adjacent boats really well and tie off to them too. You want to surge together, and not have relative motion. We spring and tie to both sides, and the whole dock should be snugly tied to each other....if a storm rolls through, and the boats are surging contrarily, huge damage can occur in a short time....

[Michele iCan]

Where are you in Crete? It's better to share this information, the place seems to be not very comfortable

[Visarend]

Had same problem when keeping the boat in Marina di Carrara, Italy, years ago. The only way to dampen the wild jumps and stops was to keep the boat some 3 m.away, and to put weight in the middle of the mooring lines. A lot of weight: I found in the nearby boatyard old discarded lengths of chain, and put some 60-80 kg on each line, hanging exactly halfway from stern to pontoon. This way it worked.

[chuckr]

Originally Posted by CookiesnTequila

I feel very silly!

20 minutes snugging lines (should have gone with my first instinct instead of listening to others!) and we are riding quieter than we have all day!

The answer certainly seems to be as tight as possible - just room to lift with the swells.

Thank you all! I may actually be able to sleep tonight!

YEP --

[Palarran]

One advantage you have with your cat is the ability to have crossed spring lines off your sterns that are fairly long. I use these as the primary dampening for surges. So if you can be a minimum 3 or 4 feet off the quay, tighten the springs and leave the two outer stern lines looser. Also, on Palarran I don't use my normal anchor bridle (of course) but a very long snubber on the chain. it is actually around 20' long and that takes a lot of stress and movement off the chain.

FYI, I was driven into the quay on Poros by a set of huge ferry wakes and didn't have enough fenders - it was painful watching my swim ladder and fiberglass get torn up right in front of me. This year Yeloya is installing a hydraulic passerelle for me so now Palarran can be 5 to 6 feet off the quay with no problems. Expensive upgrade and I wish I'd done it 4 years ago, but will enjoy it this year for sure.