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post #31 of 54 Old 03-07-2008
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I've seen monohulls get nearly knocked down at anchor because there were some swells coming in...they just started rolling, and kept rolling more, and more and more... they finally left the anchorage, probably to find someplace without the swells that were causing them problems. My boat, my friend's trimaran and another catamaran didn't have any problems at all. It was fun to watch the guys on the monohull scurry around on a rocking boat, like ants in a kicked anthill though.
I'm calling you on this line. Any anchorage that is lumpy enough to put a monohulls beam ends in the water is also miserable for a multihull. Either that, or the story is complete BS. When the waves are coming in, both types of hulls roll. Monohulls probably roll less because the great chunk of lead wants to stay pointed down. The multihulls want to sit flat on the water, so when the water is tilted (like on the side of a wave) so is the multihull. Think of a weighted log in the water versus a sheet of plywood. The log moves up and down on the wave, the plywood tilts with the surface of the water.

There is a tide in the affairs of men,
Which, taken at the flood, leads on to fortune;
Omitted, all the voyage of their life
Is bound in shallows and in miseries.
Shakespeare, Julius Caesar IV, iii, 217
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post #32 of 54 Old 03-07-2008
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Plumper, hate to break it to you, but monohulls, especially narrow older style ones, will tend to start rolling if the wave period is right...kind of like a kid pumping his legs on a swing... and they'll start to roll more and more..

Yes, multihulls want to sit flat on the water, but if the wave period isn't too short and the wave height too tall...it really doesn't bother the multihulls...since they are just moving to with the water, not exaggerating it as a monohull rolling can.

The weighted log analogy pretty well sucks, since it doesn't have a keel and a righting moment, the way a keelboat does, so it won't start to build up rolling momentum the way a keelboat can.

It doesn't happen all that often, but it does happen.

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You know what the first rule of sailing is? ...Love. You can learn all the math in the 'verse, but you take
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her going when she oughta fall down, tells you she's hurting 'fore she keens. Makes her a home.

—Cpt. Mal Reynolds, Serenity (edited)

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post #33 of 54 Old 03-07-2008
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I'm still calling you on that story. The other reason it is not credible is that in a very rough anchorage, the boats would normally be pointing into the sea unless the wind is from another direction. If the wind is from a different direction than the giant waves you mentioned then everyone has a challenge keeping the head of their boat into the sea. If the wind is from the same direction as the waves (likely) then rolling is not the issue, pitching is, and monohulls or multihulls of the same length pitch the same.

By the way, I don't want you and the others here to think I am anti-multihull. Quite the contrary, modern multihulls are the bleeding edge of sailing. I would love to own and cruise/race one but can't afford it (more to purchase, more to moor, less accessibility to marinas). It is not my intention to slam multihull sailors, but I do enjoy watching them squirm when anything controversial is said about their boats.

There is a tide in the affairs of men,
Which, taken at the flood, leads on to fortune;
Omitted, all the voyage of their life
Is bound in shallows and in miseries.
Shakespeare, Julius Caesar IV, iii, 217
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post #34 of 54 Old 03-07-2008
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Plumper-

The waves weren't very big, probably no more than 2-3'... but were just enough to get this monohull rolling... the wind and waves weren't aligned from what I remember, since IIRC, the waves were refracted waves, not direct. 2-3' over 18' of beam is very different from 2-3' over 9' of beam, especially with a heavily weighted keel to multiply the rolling motion.

BTW, I've seen some coves, like Tarpaulin Cove on Nashuon Island here off of Vineyard Sound, where boats anchored in different parts of the cove will be pointing in very different directions.

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You know what the first rule of sailing is? ...Love. You can learn all the math in the 'verse, but you take
a boat to the sea you don't love, she'll shake you off just as sure as the turning of the worlds. Love keeps
her going when she oughta fall down, tells you she's hurting 'fore she keens. Makes her a home.

—Cpt. Mal Reynolds, Serenity (edited)

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post #35 of 54 Old 03-07-2008
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If any boat starts rolling and doesn't seek the upright position very quickly, there is something wrong, especially if it gets to the point where it is "almost being knocked down." Keels and masts don't accentuate the roll but dampen it. That is why figure skaters pull there arms in when they want to spin faster. Many dismasted sailors tell of how the motion on there boat got worse when dismasted even though the boat was more stable. Losing the mast takes away part of the dampening effect. If the single boat you now say you saw (vice "I've seen monohulls get nearly knocked down at anchor because there were some swells coming in") was increasing its roll in the waves, then it had other stability problems. It may have had lots of topside weight or half empty tanks or something else causing it to be in a state of loll. Normal boats, properly loaded, always seek the stable upright position (except wide boats that are more stable upside down - like multihulls, dinghies and poorly designed monohulls.

There is a tide in the affairs of men,
Which, taken at the flood, leads on to fortune;
Omitted, all the voyage of their life
Is bound in shallows and in miseries.
Shakespeare, Julius Caesar IV, iii, 217
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post #36 of 54 Old 03-07-2008
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Plumper—

If the wave period is right, instead of keeping the boat upright, it will start rolling side to side...and get worse as time goes on. It's basic physics... It doesn't mean that the boat has a stability problem necessarily. This is generally more true of older boats, which have narrower wineglass hulls rather than more modern boats with wider, flatter bottom hulls—which have much more form stability, as do multihulls.

Why do you think they sell Flopper Stoppers??? They aren't selling something to solve a problem that doesn't exist.... Must be an awfully lot of really poorly designed boats out there if someone had to invent these to sell... and must be a market for them.

Quote:
At last! Stop rolling at anchor. These roll control panels are constructed from solid stainless steel to last longer than any other system. Easy to assemble and easy to install. On sailboats, just move your main boom to the port or starboard; on trawlers, rig a pole over the side. Attach the panel to hang 8-10 fee below the surface and the roll is stopped. As a swell hits the boat, the panel opens and lets the boat roll a few degrees then it slams shut, stopping the roll. Two units, rigged on each side are twice as effective. First quality, guaranteed! Newly designed in 2005!

4 vane for boats up to 32' (shown on right)
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If any boat starts rolling and doesn't seek the upright position very quickly, there is something wrong, especially if it gets to the point where it is "almost being knocked down." Keels and masts don't accentuate the roll but dampen it. That is why figure skaters pull there arms in when they want to spin faster. Many dismasted sailors tell of how the motion on there boat got worse when dismasted even though the boat was more stable. Losing the mast takes away part of the dampening effect. If the single boat you now say you saw (vice "I've seen monohulls get nearly knocked down at anchor because there were some swells coming in") was increasing its roll in the waves, then it had other stability problems. It may have had lots of topside weight or half empty tanks or something else causing it to be in a state of loll. Normal boats, properly loaded, always seek the stable upright position (except wide boats that are more stable upside down - like multihulls, dinghies and poorly designed monohulls.

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You know what the first rule of sailing is? ...Love. You can learn all the math in the 'verse, but you take
a boat to the sea you don't love, she'll shake you off just as sure as the turning of the worlds. Love keeps
her going when she oughta fall down, tells you she's hurting 'fore she keens. Makes her a home.

—Cpt. Mal Reynolds, Serenity (edited)

If you're new to the Sailnet Forums... please read this
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
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Still—DON'T READ THAT POST AGAIN.

Last edited by sailingdog; 03-07-2008 at 03:23 PM.
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post #37 of 54 Old 03-07-2008
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I'm stopping here. My physics and yours don't agree nor does my experience.

There is a tide in the affairs of men,
Which, taken at the flood, leads on to fortune;
Omitted, all the voyage of their life
Is bound in shallows and in miseries.
Shakespeare, Julius Caesar IV, iii, 217
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post #38 of 54 Old 03-07-2008
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Well, apparently the physics in the real world, my experience and that of enough sailors does that they've developed a product to counter the problem.
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I'm stopping here. My physics and yours don't agree nor does my experience.

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You know what the first rule of sailing is? ...Love. You can learn all the math in the 'verse, but you take
a boat to the sea you don't love, she'll shake you off just as sure as the turning of the worlds. Love keeps
her going when she oughta fall down, tells you she's hurting 'fore she keens. Makes her a home.

—Cpt. Mal Reynolds, Serenity (edited)

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post #39 of 54 Old 03-07-2008
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You misunderstand the use of Flopper stoppers. They lessen the rolling. Of course boats roll. I agree. I am arguing with your bold claim that you saw boats whose roll, at anchor, increased so much that they were almost knocked down while you were sitting comfortably in your trimaran not subject to the same waves. The conditions for them (not you) were so bad that they had to leave.

A sea story? Maybe exaggerated, I don't know, but for me, incredible.

There is a tide in the affairs of men,
Which, taken at the flood, leads on to fortune;
Omitted, all the voyage of their life
Is bound in shallows and in miseries.
Shakespeare, Julius Caesar IV, iii, 217
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post #40 of 54 Old 03-07-2008
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And that boys is officially way off thread topic!

To bring us back... I saw some say "go below and ride out the storm". I've also heard it other places....

Are you seriously leaving the helm in rough weather and heading below and just monitoring a GPS or something?

I haven't dealt with this kind of weather at sea yet, but I'd have to assume I'd want to be somewhat steering the boat around white caps and such even while heaved to.... is it really safe to leave no man on the watch up on deck?

1976 25' O'day - "SeaWind"

Hello Sailor: "I've just learned that good boats, in good hands, are damned robust creations."

Last edited by Birdface; 03-07-2008 at 05:57 PM.
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