Kedging off when aground

[qsiv]

Re: Rigging strain

ooh, I dunno - if you think of the angle that the cable emerges from the water to the stemhead fitting when you are anchored - it's pretty steep, so you wouldnt need much extra to allow for the height of the mast.

I'd agree with you in respect of the loads and leads - and just add not to use a masthead spi halyard unless the boat is masthead rigged.

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[Twister_Ken]

Prolific beer drinkers

May need to pump bilges while suspended, which is going to play havoc with the angle of dangle mathematics.

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[jimi]

Re: Rigging strain

I wonder but don't know if I'd be brave enough to try it on my own boat, if when getting a pull off, the towboat could be attached to a spinnaker halyard ? Perhaps if there were wtwo two boats one could have the normal towrope and the other the halyard. TCM you're chartering something in May, fancy some fun?

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[tcm]

Re: eek.

No problem. I will whack it up the bramble bank and have a play. No matter that in towing off the load is zero followed by almost-instantly-applied-massive load , i am just sure that the mast will take it.

Reminds me, this summer, we saw a benny go too close under a superyacht bowsprit in a marina - his mast bent and collapsed in double as though made of cheese.





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[sailbadthesinner]

Re: Rigging strain

nah
you get them to set the halyard and the tow rope so that boat starts tilting as the tow boat pulls you off then towingline kicks in.
we were in mud and angle was about 30 deg then tow ropes taut and away we came.
no damage but a bit of power needed as we were well stuck.

the main problems
1. releasing the halyard so it did not ricochet into the boat and take someoene's 'ed off.

the boat lurching about a bit as the halyard came slack

was getting our kedge out. we had to transfer a line attached to our kedge line to the stinkie whilst NOT putting our selves back on the mud bank and not fouling anyone's props.

oh plus all the kedge chain and warps got covered in mud so the boat was a stinky mess .

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[qsiv]

Re: Rigging strain

Without specific details it's difficult to answer ...

Lets assume the boat pulling you off had about 40 HP with a 14" pitch prop that equates very roughly to a peak bollard pull of just a shade over 1000 lbs (about 1013 in fact). Being conservative lets up that to about 500 Kg.

Now consider the load on your spinnaker halyard ..

asuuming that 'you' are a 30 something foot yacht, then the spinnaker halyaard is likely to be in the region of 12 mm (1/2 inch) braided rope - this has a breaking load of more than 3000 Kg (even 6mm has a breaking load of more than 1000 Kg).

Empirically I would suggest that the load your kite puts on the masthead is likely to be more than the boat towing you would exert.

If the 'tug' is a motorboat with big engines, then there is scope for higher loads, but the props are likely to be pitched for high speeds, and so they are not going to have enough grip to generate huge loads.

As for the shrouds - if they cant stand these loads, you probably shouldnt be at sea anyway! As a broad rule of thumb, and assuming a 6 tonne displacement with little or no sweep to the spreaders, single spreader with lowers and cap shrouds, I would expect the wire to be sized with a breaking strain comfortably in excess of 3 to 4 tonnes. There will be some pretension of course, but the rig should be quite able to stand the loads.

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[TheBoatman]

Re: Rigging strain

Whenever I've seen boats being pulled by their rigging very little seems to happen, yes you heal the boat, but thats about all?
If you have a "tug" available then you must get the stranded boat facing bows to the tug and open water, then start pulling.
To try to drag a keel sideways through the sand/mud is a waste of time, you must pull directly down the line of the keel. That normally means that you have to take a turn around the bows and spin the boat round, afterall the direction he was heading only lead him aground? Best to try to pull him back the way he came in!
If you have to pull them off backwards then position the tug so that a line can be taken across the cockpit to the far cleat, this will automactically heal the boat when you start to pull, but a word of warning, tell the crew that this healing will take place and watch the tow rope, otherwise you'll decapitate the helmsman<s>
Another tip is when (pulling them off bows frst) you start the pull get the helmsman to drive the casualty ahead full and push/pull the tiller/wheel from side to side to "wiggle" the boat off.

Always worked for me?

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[qsiv]

Re: Rigging strain

I wasn't particularly commenting on the effectiveness - just tying to put some figures across to allay peoples fears over the stresses and strains, and that they were likely to be within ordinary limits.

What others were suggesting were to use one boat too heel the grounded vessel, with another pulling the boat off. Whilst heeling will (depending on the hull form of the casualty) reduce the draft I fully accept that the boat will come off most easily when towed for or aft.

A couple of years ago at the AmCup celebrations in the Solent Dennis Connor put his boat (Extra Beat - quite gorgeous) aground on Lepe Spit (how could one know it was there, it's only on the charts and bouyed), but came off quite quickly by running 30 odd crew out along the boom, backing the jib to turn her beam on to the gentle breeze, and then sheeting everything home to add heel and power. In the fifteen minutes or so he was out of action most of the fleet sailed past him...

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[janie]

Whilst living in Annapolis and sailing 22' keel boat without engine on shallow Chesapeake Bay, we became expert at kedging off. Don't go too hard aground, back the jib/main, depending whether you're going upwind, or downwind, chuck out just one anchor to pull the bow around, and we could get it done in no time. I guess it depends how big/heavy the boat is.

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[Oldhand]

If you go sialing when there is a good breeze, where do you think the heeling moment on the hull is applied from? The mast rigging of course, so why shouldn't it take the load of being heeled over by a tow?

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