Can a ship tow a sail boat?

[MarkSF]

Originally Posted by senormechanico

Multihulls.
Mine planes at about 12 knots. Even equipped with lots of cruiser stuff, I've sailed it over 17.

How is the planing speed of your multihull relevant to the hull speed of the monohull we're discussing?

[neophytecruiser]

Just as a point of interest, the strongest point of attachment for most sailboats, with keel stepped masts, is the base of the mast, itself. This won't allow for towing at 14-knots, but can provide a strong point which is more robust than most undersized cleats found on many sailing vessels. For successful towing, a bridle system would have to be in place to keep the towed vessel directional.

[guyrj33]

Originally Posted by KTP

Right but that is the water pushing your boat from underneath, over a large surface area.

Imagine tying a 2 inch diameter rope to your car fender and then attaching it to a Boeing 747. What do you think would happen? Would your car go 300mph or would your fender fly off?

Like I said it's not that simple.
The water wasn't pushing my boat from underneath, relatively speaking the water was moving up and down.
My boat was being propelled by gravity and the wind.
The car analogy, nice try but doesn't apply.
Yes, I can tie a tow line to my sloop in a way that will not destroy the boat at 14 knots.
And like I said it's not something i'd like to try.

[a64pilot]

I feel sure the ship Capt. knew it wouldn’t work, but was nice enough to demonstrate it, no one can say he didn’t try. The line parted it seemed.

[Jdege]

Saw this, yesterday.

https://youtu.be/uJHRzqB-TZI

[guyrj33]

to rephrase the original question.

How does a sailboat with a displacement hull behave when exceeding hull speed under tow?

[roland stockham]

About 4kn is the practical limit on a sea tow so if the ship is prepared to slow down to that speed and you can pick up a towline without getting sunk (not that easy with a ship!) the yes it can be done. The issue is not how fast the boat can go it is the turbulence generated behind the ship. With something like a large rib you can go twice as fast.

The only time I would contemplate a sea tow if I had no steering or no means of moving AND imminent danger from a reef or something. If you have any means of moving in a consistent direction you are much better off getting extra supplies and limping in on your own. If the hull is compromised and wont stay afloat then it is not going to survive a long tow so you may as well abandon now.

[MJH]

Originally Posted by ericoh88

My friend who left Langkawi for Bali/Indonesia and his boat got into trouble after Batam. He and his best friend had been hand pumping for days and ran out of drinking water. Called for help and was picked up by a container ship.

I felt sorry for his loss. I was on his boat when he install the new solar panels. Boat was found later - obviously stripped clean.

Is there really a way for a ship doing 14kts to tow a sailing yacht ?
What do you think?

Eric

After my experience I don't recommend it.

I was once towed by the USCG out of the Gulf of Mexico and they would not honor my request to slow down (they probably had a party to go to that night). It took the breaking of their tow line to give us time enough to cleanup some things before starting again. My boat was jumping from wave to wave for about 10 hours at speeds 10+K and it turned the inside of the boat upside-down. Lost some equipment including a stainless steel anchor with some damage to the bow. I and my mate just hung-on wedged in some corners of the cabin. The anchor chain moved itself from the anchor well through the door and through the sail compartment into the forward stateroom and against the entry door. Consider your options and think twice before getting towed by the CG or other large vessel.

~ ~ _/) ~ ~ MJH

[Brewgyver]

Originally Posted by guyrj33

to rephrase the original question.

How does a sailboat with a displacement hull behave when exceeding hull speed under tow?

The simple answer would be "badly." But again, it's not likely to happen in the first place.

So, for the hypothetical, how badly would it behave? I think this is how it would go:

Given the specific case of a conventional monohull sailboat
Given an attachment point of infinite strength on the bow of the sailboat
Given a tow line of infinite strength
Given a towing vessel with infinite propulsion power (granted, a large container ship has enough)
Then, as the sailboat exceeds hull speed and starts to rise above the surface, the ballast is no longer effective, the boat loses its righting moment, it falls to one side or the other, and is destroyed.

[redneckrob]

Originally Posted by guyrj33

to rephrase the original question.

How does a sailboat with a displacement hull behave when exceeding hull speed under tow?

I was on a 110' Coast Guard WPB in Alaska and had to tow a small fishing vessel some distance back to port. The hull speed on the boat was something like 5 knots and our clutch-in speed was something like 7 knots. When we tried to tow at 7 knots the towed vessel veered wildly from side to side and would almost certainly have parted the tow line or whatever it was attached to if we'd continued. So we had to clutch in and clutch out about every 10 seconds for 18 hours to maintain our speed at 5 knots. Very painful!

[KTP]

A container ship might have $100 million in cargo onboard (who knows? containers packed with Mercedes). I don't think they really care about a $30,000 sailboat.

[roverhi]

Modern ships apparently can't slow down enough to tow a sailboat at a survivable speed. Don't know what their lowest speed is but they have to have a tug pulling backwards against the forward thrust of the ship to slow down enough to meet speed requirements in SF Bay.

[jmschmidt]

Everyone posting to this question has hit the nail on the head.

This reminds me of my dad, back in the 1950's had the idea that a friend, who owned a tug and barge operation could successfully to tow Dad's 21' ChrisCraft cabin boat down the Columbia River to the ocean for the fall fishing derby. Since the tug owner was also going down to fishing from his tug, it seemed like a good idea. After the first mile all the cleats, bollards and pulpits were ripped out of the poor little cabin cruiser.

[MarkSF]

Originally Posted by guyrj33

to rephrase the original question.

How does a sailboat with a displacement hull behave when exceeding hull speed under tow?

The answer is, it depends - on the hull design. To exceed hull speed significantly, the hull needs to plane. To do that, it needs planing surfaces - flat ones carried aft usually, that develop lift.

Most monohull sailboats have little or no planing surfaces. They are purely displacement. Some of the lighter, race-orientated monohulls do have some - and you will see, and hear, of them reaching high speeds, especially downwind.

If you have no planing surfaces, and you try to exceed hull speed in a purely displacement hull, you get the opposite of lift - suction. The boat is literally sucked under water.

The boat in the video has about as much chance of planing as I have of going to the moon.

So, assuming you can find an attachment point strong enough to pull it at 14 kts, it will sink. But you probably couldn't. Whatever point you attach to will probably be ripped out, or snap.

[David M]

Not from a financial perspective. Most ships are on time schedules and quite literally cannot afford to slow down to tow a boat at its hull speed.