Center or aft cock pits

[Montanan]

Originally Posted by S/V Illusion

As I said earlier, it all depends on the size boat. Smaller LWL center cockpit boats look like bathtubs, have a high freeboard and suffer from more movement.

Our CC suffers none of those traits simply because it is designed as a CC, not an unintended consequence of marketing to the CC lovers.

Parenthetically, we have a huge salon, huge aft cabin and room for 10+ people in the cockpit. It’s all about length, not cockpit location.

Quote:
Originally Posted by wolfgal View Post
this thread is very informative!

for those who have commented, i'm curious to know:

i once read that the higher centre of gravity in some CC's (the ones in which the cockpit is high up) can make for seasickness. can anyone comment on this?




Center cockpit tub boats can indeed look like tubs, very beautiful and inviting tubs; but their tub architecture can retain very low centers of gravity and with their low freeboard, you sit not just low and near the water but even IN the water. As to whether sitting in the water induces more seasickness, well that may occur with some persons, but more likely you will become prunish before you become sickish. As to how many persons can occupy the cockpit that is primarily a matter of the yacht's size, length and beam. And such center cockpit tubs never have any issues with water coming aboard because the water is already aboard.

Better a tub, than a tug.

[zippy]

One thing I haven’t seen being mentioned is the low seat backs on many center cockpits. They look uncomfortable without some type of back support system. I enjoy lounging on an aft cockpit bench with my back resting agains the cabin. It’s comfortable and protected, and not available on the CC where you seem perched on the boat rather than in it. Haven’t sailed on a CC so I would like to know if this is an issue.

[wolfgal]

All very interesting comments here... much appreciated.

Yes, s/v Illusion, your CC sounds quite wonderful... i'm searching for a much smaller boat, one that is small enough for a solo girl that has enough "home-space" to fit my liveaboard/cruiser ambitions.

actually, these days, i'm very curious about a particular tub-of-a-cc, not one with enough length to bring the freeboard down.

Yes, Dan, i imagine that the high freeboard makes for motion. this is my concern... on a tub-version, i read that not only do they tend to not point so well, but they can dance at anchor. i read somewhere else about a wife who felt seasick in the high-cents-of-gravity CC...

but Skipmac says that the motion was ok on his CC's. Skipmac, do you mind telling me what kind of CC 34' you had so that i can peek at its proportions?

Montanan, forgive me, but i'm a bit lost... are speaking of boats like the Seadog 30 that have a low set cockpit and high combing? if so, i imagine that these would provide for a decent ride, yes. i've seen a few boats like this in the UK

Reefmagnet, are you out there? Reefmagnet has a 33' CC...


wolfie

[Tillsbury]

It’s certainly true that some CC designs are too high up, and/or have short backrests (for the same reason), but that’s a specific fault of the design, not of CCs generally.

Also re: cockpits “filling up with water” - a CC can only get rid of this water through its cockpit drains. That would worry me, as these things do have a tendency to fill with junk. My AC has an 18” square hole in the transom at floor level. If my cockpit were to be entirely filled with a wave it’d be gone in a couple of seconds, whether or not my cockpit drains were blocked. Of course, this boat only has cockpit drains because the CE regs demand them — they’re entirely pointless on a well-designed cockpit.

[MartinR]

Originally Posted by Jim Cate

A point I have often made...

A huge aft cabin means a smaller saloon and galley area, and this is where one spends the majority of one's conscious hours below decks. The giant aft cabin is only used when asleep, and for sleeping one does not need all the volume.

And I have yet to be washed out of any of the aft cockpit boats I've owned or sailed on. That's a red herring if ever there was one!

Jim

Jim is right. A center cockpit is not safer than an aft cockpit. It may feel so, but in reality there is little difference.

The location of the cockpit is not very important to me. Great cruising boats have been built with both. Bad boats have been built with both.

For CC I like the boats with no passageways better. This makes for great cockpits, nice sheer line, and good privacy. This, of course, if you mostly sail in warm climates. The Freedom 40 is a good example of this.

Swan built some yachts with dual cockpits, aft cockpit for sailing and forward for guests/relaxing.

And there is the Aleutian 51, which is a center cockpit boat, but has a small private aft cockpit for the enjoyment of the owners

[MartinR]

Originally Posted by zippy

One thing I haven’t seen being mentioned is the low seat backs on many center cockpits. They look uncomfortable without some type of back support system. I enjoy lounging on an aft cockpit bench with my back resting agains the cabin. It’s comfortable and protected, and not available on the CC where you seem perched on the boat rather than in it. Haven’t sailed on a CC so I would like to know if this is an issue.

Yes, on some, but not on all.

[Reefmagnet]

Originally Posted by wolfgal

All very interesting comments here... much appreciated.

Yes, s/v Illusion, your CC sounds quite wonderful... i'm searching for a much smaller boat, one that is small enough for a solo girl that has enough "home-space" to fit my liveaboard/cruiser ambitions.

actually, these days, i'm very curious about a particular tub-of-a-cc, not one with enough length to bring the freeboard down.

Yes, Dan, i imagine that the high freeboard makes for motion. this is my concern... on a tub-version, i read that not only do they tend to not point so well, but they can dance at anchor. i read somewhere else about a wife who felt seasick in the high-cents-of-gravity CC...

but Skipmac says that the motion was ok on his CC's. Skipmac, do you mind telling me what kind of CC 34' you had so that i can peek at its proportions?

Montanan, forgive me, but i'm a bit lost... are speaking of boats like the Seadog 30 that have a low set cockpit and high combing? if so, i imagine that these would provide for a decent ride, yes. i've seen a few boats like this in the UK

Reefmagnet, are you out there? Reefmagnet has a 33' CC...


wolfie

I hear my name, lol.

Yes the wife and I do have a 33 foot cc called a Nantucket Island. It was her that fell in love with it originally and she still maintains we are never allowed to replace it with anything but another cc if we were ever to upgrade. This boat makes exceptional use of internal living space below decks for the size and there's plenty of room in the cockpit. Bad points are the low coamings which is resolved with a comfy bench seat built into the pushpit and sport-a-seats in the cockpit, high freeboard to length which is really only a hassle with marina docking and a lack of decent external storage, which is my greatest bugbear as stuff needs to be stored in the cabin instead. It doesn't point that high, but gentleman should never sail to windward anyway. As with every aft cabin ever made, the companion way steps are more of a ladder so it takes more care to ascend and descend on them in rougher weather.

Even though I've heard they can sail around at anchor, ours has always been rock steady which may be due to the stern mounted solar arch more than original design. Rolling motion in the cockpit is no worse than any other boat, and I've found it to be very dry ride thanks to the higher freeboard and forward cockpit. It's also a flush deck boat, so airflow via the aft cabin hatch is fantastic and we have a readily available dance floor for those enchanted evenings. The aft cabin with walkthrough access has a pullman bed which is reportedly queen sized which we find more comfortable than a vee berth arrangement.

Not a pure blue water cruiser by any means, but certainly comfortable and capable for one or two aboard for lengthy periods of time.

[wolfgal]

Hey Reefmagnet, amazing how you can hear your name from half way around the world and down under too!

yes, your cc has the higher cockpit, with higher centre of gravity. do folks (guests) feel queazy there?

i've never heard of a solar arch creating more stability at anchor. this is interesting; i wonder if anyone else has this impression...

many thanks to all in this discussion!

wolfie

[roland stockham]

i've never heard of a solar arch creating more stability at anchor. this is interesting; i wonder if anyone else has this impression...

wolfie[/QUOTE]


Yes this ageneral principle in boat design. Increasing weight eway from the centr of motion increases moment of inertia and role reaistance. Generally this tends to be thought of in terms of weight in the rigging since that has the longest moment. Increasing, for example wire size, will slow the motion and increase resistance to a knockdown. The negative aspect is that it makes the boat more tender and reduces ultimate righting moments so there has to be a balance. A stern arch will have some effect, probably more on pitching than role as it is only going to be 3-4m above the roll center but well aft of the center of pitch.

[Montanan]

Originally Posted by wolfgal

All very interesting comments here... much appreciated.


Montanan, forgive me, but i'm a bit lost... are speaking of boats like the Seadog 30 that have a low set cockpit and high combing? if so, i imagine that these would provide for a decent ride, yes. i've seen a few boats like this in the UK

wolfie

Wolfie

Ha, an example of Poe's law. Just having a bit of fun with the whole cruising tub concept and how many persons you wish to share your tub with.

Beauty is in the eye of the beholder and the reality is that when you are on a boat you don't get to view the boat from afar, so it becomes much more how the boat looks, feels and operates when you are on it. Take for example, an unpainted aluminum / aluminium hull, it oxidizes over time to a functional dull grey, [fifty shades of grey], some people dislike the appearance, others recognize the awesome benefit of protective oxidation and greatly appreciate its becoming an important feature of the boat and the lack of need for expensive painting and the self healing property of the material, scratches don't matter. And no bright work to attend to.

But as to there being an issue with potentially having a modestly higher positioning above the center of gravity of the vessel for crew in a CC versus an AC, the CC will be at the midpoint of the length boat and thus prone to less pitch due to being the fulcrum location. Yet a CC may have a higher degree of roll rotation athwartship.
There being the wise reason why one chooses an unglamorous cabin aboard a cruise liner at the lowest level and mid ship so as to minimize motion, similarly as to choosing which sleeping location particularly when making passage, or in a rolly anchorage. A centered berth is peaceful and side berth less so, unless you enjoy being rocked when you sleep which some do.

A CC will tend to derive less pitch and possibly more roll. Yet, I have seen CC that are lower than AC as to height above the vessels center of gravity and / or the water line and CC's lower than AC.

Much depends on the nature of the seas one is experiencing in the moment, because such seas induce the moment. Seas coming from a beam induce mostly roll, seas from the bow or aft, induce pitch.

The Moment of a force is a measure of its tendency to cause a body to rotate about a specific point or axis. This is different from the tendency for a body to move, or translate, in the direction of the force. In order for a moment to develop, the force must act upon the body in such a manner that the body would begin to twist. This occurs every time a force is applied so that it does not pass through the centroid of the body. A moment is due to a force not having an equal and opposite force directly along it's line of action. What are the Elements of a Moment? The magnitude of the moment of a force acting about a point or axis is directly proportional to the distance of the force from the point or axis. It is defined as the product of the force (F) and the moment arm (d). The moment arm or lever arm is the perpendicular distance between the line of action of the force and the center of moments.
Moment = Force x Distance or M = (F)(d)

The Center of Moments may be the actual point about which the force causes rotation. It may also be a reference point or axis about which the force may be considered as causing rotation. It does not matter as long as a specific point is always taken as the reference point

There being much more important factors in boat architecture as to motion stability than where the cockpit is installed. The location of the helm doesn't much change the rocking forces and reaction of the vessel, but it does change your reference point of experiencing such Moment.

There being those times when the sea gets harsh and you need to respond to ease the forces and thence need to have someone fulfill your request to Hold My Beer so as to lessen such shared Moments. [Note with my typical crew, the request begins with: Hold my beer. And explicitly followed by: Don't drink my beer!]

The AC of the ship imaged below will comparatively experience both pitch and roll. But it likely will not be pooped by a trailing sea wave.

[exMaggieDrum]

Our Whidby 42 had a great center cockpit. One time we had 13 tightly packed in the cockpit, all sitting down next to each other, but we had margaritas to make everyone friendly. It was much dryer in rough seas, especially following seas. It was a great liveaboard and it allowed access to the engine room (yes room) a pleasure compared to most 42's. I would go with a CC anytime. I admit it does not have the sleekest lines for the traditionalists but that is a personal point of view.


One of the things I really liked about the cockpit was the length of the P&S seats, and high coaming when sailing with some heel, they were my preferred place to nap on the downhill side. If I was green around the gills (I do get seasick sometimes) it was better up in the cockpit than down below even if I may have felt some more moment athwartships than down below.

[Reefmagnet]

Originally Posted by wolfgal

Hey Reefmagnet, amazing how you can hear your name from half way around the world and down under too!

yes, your cc has the higher cockpit, with higher centre of gravity. do folks (guests) feel queazy there?

i've never heard of a solar arch creating more stability at anchor. this is interesting; i wonder if anyone else has this impression...

many thanks to all in this discussion!

wolfie

What can I say? It's like a sixth sense


Anyhoo, I don't think the small additional height of the cockpit adds much, if anything, to inducing sea sickness because even though the roll is amplified, pitching decreases so it's kind of a "swings and roundabouts" comparison. The cabin of any boat is far more likely to induce queasiness when the boat is in motion then the cockpit. The cabins on all our boats have always been affectionately referred to as the "cabin of doom" when things get boisterous; The cockpit is always the best spot to be! Perhaps the only negative with the higher cockpit is that it does move faster if the boat is rapidly rolled like when caught by the odd wave in rough and confused sees.



I based my remark about the arch (which I don't technically have, it's more a mish-mash of different bits) on the theory that the windage acts as a riding sail. I had heard that the NI rides around at anchor, but ours has always been rock steady, for which I attribute to the steadying effect of the wind resistance from davits, solar panels and radar pole at the stern.