Pontoons in a blow

[Rob_Webb]

A friend's boat is in moored (port side to) in the marina nearby and has been buffeted about by the screaming winds we've had here recently, up to 60kts. At times the wind has been on the beam pushing him against the pontoon and because his freeboard is very high compared to the height of the pontoon there is a tendancy for his hull to roll towards the pontoon and try to roll up on to it.

We were wondering about running a masthead halyard down to a pontoon on his opposite (starboard) side to try to keep him bolt upright and prevent the roll to port - any thoughts on whether this is a sensible technique and anyone tried it before? Presumably it wouldn't overstress the rig (heavy ketch rig)?

To put it into context the boat is LOA 84ft and 80 tons.

Cheers
Rob

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[BrendanS]

What I'd worry about is snatch. Rigs take fairly steady loads, very different to a large heavy boat possibly rolling all the way towards the halyard, then rolling back against it. You'd want a shock absorber in that system.

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[TheBoatman]

Don\'t do it!

Rob
You’ll probably rip out any cleats that you attach the line to, bust the line or worse still damage the rigging.
80 tons of boat just moving up and down on a swell would put a huge strain on any line especially if it’s snatching.
IMHO the only solution would be very large fenders fitted not only to the boat but the pontoon itself.


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[Rob_Webb]

Thanks, both good points. In case it makes any difference, the water itself is pretty flat and the boat isn't rolling in any swell, it's purely the lean that comes from blowing hard at even at bare poles.

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[BrendanS]

Wind is never steady nor constant in direction. Once rigged, you will stand the danger of snatching if anything changes even for a few moments

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[MainlySteam]

Hi Rob

It is common practice here (and in other windy places) to run lines from the masthead to ground when the boat is ashore in a cradle. Obviously, in that case, the cradle also provides a good deal of support from overturning but in the end, when sailing the heeling force from the wind is taken by the rig. So I suspect that all would be well.

How the boat would react in the water though I do not know, but the restraint may introduce snap type forces into the rig if the boat has a tendency to roll back to windward then to leeward again, or has enough freedom to surge, to be arrested by the line to the mast.

I assume an anchor is out of the question due to neighbouring boats or their access needs?

We, fortunately, are in a marina which has piles just in from the outer end midway between each neighbouring berth ie Pontoon>Boat>Pile at Outer End>Boat>Pontoon>Boat>Pile etc so there is a pile which the facing out end of the boat is sprung out from the pontoon to and, of course, the inner end of the boat is sprung out from the pontoon alongside by the forward mooring lines onto the main pontoon walkway. Maybe he can get a pile driven /forums/images/icons/smile.gif.

On the weekend an about 35 foot yacht had taken shelter in a berth across behind us and was just moored up to the pontoon without springing himself away from it and although the wind was about 60-70 degrees away from abeam, so close to stern on for him, on several occasions I saw his mast almost hit the rigging of the yacht on the other side of the pontoon against which he was berthed as the wind laid him up against the pontoon.

Regards

John

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[TheBoatman]

Rob
You didn't say if the boat was alongside a straight pontoon or if it was in a finger berth?
If it's in a finger berth could you run lines out from the opposite berth to pull the boat off the pontoon?

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[Rob_Webb]

Hi John

Well, it sounds best to leave things as they are and just rely on good fendering. And with an 80 ton aluminium hull it looks as though the pontoon will come off worse anyway!

How is your sailing going these blowy days? Someone here at the office said that we've got a cyclone forming over the tropics due to come our way and bring some nice big NE's by the weekend - that'll make a change then!

Rob

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[MainlySteam]

Rob

I had wondered about the safety of the pontoon itself.

On the sailing side we are not into day sailing and trying to fit in longer is a bit troublesome with flying backwards and forwards to Australia - and seems I have another new build to start over there in a month or so for me to look after. We do have to take the boat to Nelson to be lifted before end of autumn and tentatively planning that after Easter. But will be just across, have the yard turn us around as quick as possible, and back again. Still, it is a very nice trip, providing the weather is ok, which it almost always is once one gets through French Pass into Tasman Bay, and Nelson is a pleasant place.

Seems as if you have moved into luxury vessels - is that so??????

Regards

John

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[boatmike]

This is a "little ship" problem which is never very evident on smaller boats but is recognised as something to be avoided on superyachts and even small patrol craft and minehunters all of which I have been involved in either building or crewing. Superyachts, where an Awlgrip paint job can cost £500K for a 40 metre vessel are particularly vulnerable and sensitive to paint scuffing. (you can repaint a Minehunter for a fraction of this without taking her out of the water).
The solution is simple but could be expensive. A floating sausage type fender the length of the pontoon, moored to it. Large ones are called "Yokohama" fenders (not sure why, probably another Japanese invention) As the ship rolls the "Yoko" revolves or just dunks itself a bit avoiding the tendancy for the ship to climb the pontoon. To make it work however the "Yoko" needs a number of vertical bearing points on the pontoon that it can ride on like little piles or it will end up sitting on top of the pontoon itself!
The principle is to create a cylindrical floating fender parallel to the WL somehow. I have seen all kinds of jury rigged ways of achieving this but they all rely on having some vertical bearing points to stop the fender itself climbing the pontoon. I don't know the specific situation of course but if you were able to create 3 or 4 vertical bearers which can sometimes be achieved by weighting the end of a short plank and hanging it vertically over the side you might (subject to hull shape and gunwale height above pontoon) get a large cylindrical fender between the hull and the plank. Ideally this fender needs to float not be hung clear of the water.
The bottom of the planks can be tied together at the bottom (sometimes by chain) and a line from bow and stern will then keep them vertical. All a bit involved I am afraid but only you can see if it might work in this case. Either way the normal sausage fenders hung vertically are often worse than useless when the displacement of the vessel is greater than the pontoon.
Whatever you do I agree with others who have said don't run a halyard to the other pontoon. Allow the boat to roll and find a way of getting the fender to roll up and down the ships side rather than grinding up and down between the pontoon and the paintwork!
Hope this helps....

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