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post #1 of 13 Old 03-07-2012 Thread Starter
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Film ****** Assistance

Hello there,

I would be very grateful if anyone can spare the time to answer two questions. I apologise in advance for the ignorance I will inevitably display - I am far from seaworthy!

1: If a sailboat becomes unmanned, with its sails fully hoisted, and with a strong wind at its back, what is the likely pattern it will describe?

2: I realise the above is dependent on a great many factors, so a further question would be - how would the unmanned boat need to be rigged for it to continue to travel unmanned with speed, however erratically, and what wind conditions would ensure this?

Any answers will be much appreciated, thanks!
John
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post #2 of 13 Old 03-07-2012
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Re: Film ****** Assistance

It depends but downwind a sailboat would likely continue on it's course or close to it after the sailor fell off.

I would say the "best" way to ensure this at least for a time is to have the boat sailing "Wing and wing" (main and foresail flying on opposite sides of the mast with boat going directly downwind)

or, foresail only, no main.

Eric
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post #3 of 13 Old 03-07-2012
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Re: Film ****** Assistance

Welcome to Sailnet!
Others can explain it better then me but, If the wheel or tiller isn't locked or on auto pilot. the boat will round up into the wind. depending on the blow it will wander at the mercy of the wind and current. The boom will slam side to side, boat may heel over.

Wind at the back is the most difficult to maintain course. Sailboats are like weather vanes but will be all over the place without steerage.

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post #4 of 13 Old 03-07-2012
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Re: Film ****** Assistance

John -
Too many variables for a truly accurate answer, but:
In your first case scenario the boat will probably describe wide variations in course, but will probably end up going in a downwind direction overall.
In the second scenario, having only a jib up will probably have the boat proceeding in a generally downwind direction due to the center of effort of the sails being towards the bow.
If there is some sort of self steering device rigged the boat could go in most directions, depending on which sails are used and how the self steering is rigged.
If you're trying to film an unmanned boat under sail, put somebody below decks with the remote controls for the autopilot.

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Last edited by FSMike; 03-07-2012 at 12:23 PM.
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post #5 of 13 Old 03-07-2012 Thread Starter
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Re: Film ****** Assistance

Very helpful answers, Eric, Denise and Mike, and fast too! That's all I really need for now, but I think I'll have to return here when things get more specific.

Thanks again,
John
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post #6 of 13 Old 03-07-2012
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Re: Film ****** Assistance

you're probably describing a broad reach with the wind behind but not directly behind, and if sailing some distance, likely with an autopilot steering the boat.

Fall overboard then, and the boat will keep sailing away on a broad reach.

No autopilot? then she'll round up to a reach, luff and spill most of the wind but not all, and make slow progress downwind as long as there's wind and searoom, until after a couple of months the sails start to tear and shred from all that luffing.

That help?
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post #7 of 13 Old 03-07-2012
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Re: Film ****** Assistance

For what its worth I snapped my rudder off, that's sort of like the skipper falling overboard, and the boat rounded up and tacked but by then I had loosed the sails we drifted until I was able to lower the sails.

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post #8 of 13 Old 03-07-2012 Thread Starter
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Re: Film ****** Assistance

Quote:
Originally Posted by nolatom View Post
you're probably describing a broad reach with the wind behind but not directly behind, and if sailing some distance, likely with an autopilot steering the boat.

Fall overboard then, and the boat will keep sailing away on a broad reach.

No autopilot? then she'll round up to a reach, luff and spill most of the wind but not all, and make slow progress downwind as long as there's wind and searoom, until after a couple of months the sails start to tear and shred from all that luffing.

That help?
That did help, thanks. In fact, I do have another, more specific question to the film.

If you were to fall overboard whilst the boat was stalled, and a strong downwind suddenly picked up, would the boat's acceleration be quick enough to preclude you getting back on board? I had presumed yes, but it would be nice to know more definitively.
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post #9 of 13 Old 03-07-2012
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Re: Film ****** Assistance

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Originally Posted by John Merrick View Post
That did help, thanks. In fact, I do have another, more specific question to the film.

If you were to fall overboard whilst the boat was stalled, and a strong downwind suddenly picked up, would the boat's acceleration be quick enough to preclude you getting back on board? I had presumed yes, but it would be nice to know more definitively.

If by stalled you mean stopped or drifting very slowly due to calm wind, then yes, wind resumes at say 10 knots, boat is on autopilot (or maybe even not) and begins to sail downwind at say 3 knots. Most average swimmers max out around 2 knots and can't sustain that for too long, so do the math...

But the boat would accelerate slowly, might take a half to a minute to reach that speed. So kind of a coin-toss whether Mr. Oscar Overboard could reach her before she got up to speed, depending on his distance off, was he injured in the fall, what's the water temp (hypothermia etc).

But a big factor is even if her could get to the boat, could he get back on board? Most offshore cruisers are quite high-sided, and if he hasn't left a ladder out, or a line trailing astern, your character could be plumb out of luck.
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post #10 of 13 Old 03-07-2012 Thread Starter
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Re: Film ****** Assistance

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Originally Posted by nolatom View Post
If by stalled you mean stopped or drifting very slowly due to calm wind, then yes, wind resumes at say 10 knots, boat is on autopilot (or maybe even not) and begins to sail downwind at say 3 knots. Most average swimmers max out around 2 knots and can't sustain that for too long, so do the math...

But the boat would accelerate slowly, might take a half to a minute to reach that speed. So kind of a coin-toss whether Mr. Oscar Overboard could reach her before she got up to speed, depending on his distance off, was he injured in the fall, what's the water temp (hypothermia etc).

But a big factor is even if her could get to the boat, could he get back on board? Most offshore cruisers are quite high-sided, and if he hasn't left a ladder out, or a line trailing astern, your character could be plumb out of luck.
Again, very helpful, thanks. Especially the half to a minute acceleration factor.
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