Motion In The Ocean...

[scarlet]

(peaked your curiosity with THAT title, didn't I?? lol)

So, we just came back from our first charter on a catamaran. I've sailed on Cats multiple times, but this was the first charter and first time with that much sail time. I was very surprised at the motion of the boat whist sailing through the waves. We were in about 3-5 foot "chop". (hope that's the right word.. the waves were pretty close together..) And the motion of the boat was really herky-jerky, rocking like one of those "tilt-a-whirl" rides at the carnival. In fact, it was pretty difficult to move around without getting knocked on my butt. (winds were 15-20 mph and we were sailing pretty consistently at 6 kts.) Absolutely NOTHING like those youtube videos that show a couple sailing in rough weather, whilst drinking wine and not spilling a drop!!!

We were with another couple that were REALLY experienced in monohulls, and I felt they were very good sailers. But this was their first cat charter. I'm much less experienced than they are, but my instincts were telling me to make some adjustments for a smoother ride..(fall off the wind a bit, put in the first reef, or sheet out the main a bit) but, would that have even helped? or is that the expected "motion in the ocean" with Cats.

I have a friend who has done a LOT of ocean sailing on both mono and multi-hull boats, and she says it is much smoother with a multi. But a few years ago I talked with Liza Copeland and she said she would never get a multi hull because of the herky-jerky motion. She says with a monohull, you get in a groove... and it's much smoother

Anyway... can someone tell me if this is normal, or if it was sailing error? or perhaps it was the type of cat we were on? (Lagoon 38)

[Steadman Uhlich]

Howdy.

I just finished a 620nm offshore voyage on a 52' cat.
Mostly "upwind" or to windward, and often against the current and waves.

When going to windward, against the 3' waves (short period waves), we had the same kind of quick, jerky, motion. At some times, it was noisy, and difficult to stand or walk, as the two hulls bounced. I have read how others tried to describe this motion on cats. To me, it felt very much like riding a truck over a long series of speed bumps in a street, just a little too fast for comfort, with abrupt shocks or bounce and a quick, snappy side to side motion in addition to the pitch.

Later when I went off watch, I went below to my cabin and tried to get some sleep after a four hour watch at the helm. As I lay there, I noticed the noises of the hulls, the loud wave slaps, and the quick side to side motion (jerky).

Winds were 15 knots and we were making 7 knots SOG (Motorsailing).

So, to answer your question, that can be what you feel. It was what I felt, and since I had a few days earlier made a very similar voyage in similar conditions, on the 53 foot monohull, my "muscle memory" and "sound memory" were acutely tuned to the experience and I was able to get a good sense of comparison.
___________

On the other hand, for other points of sail, the catamaran was much smoother ride than a 53' monohull I had recently sailed in similar conditions and on the same route (e.g. Off the New Jersey coast heading north to NYC). I remarked to the owner that I could understand the appeal of a big cat if one wanted a smoother platform for sailing (without so much heel).

Going to windward, I suspect the ride on the monohull would be preferable, to many people, due to the motion. While a monohull will still pitch, and the ride can be rough, the motion seems to be more to pitch and less yaw, while the multihull felt like pitch and noticeable yaw (jerky to the side). It might be a generalization, but I think the monohull moved more in one plane (one axis) while the multihull moved in two planes (axis), and that creates the difference in apparent feeling for the crew.

After several days of sailing like this, my body felt tired as different muscles in my torso were being used to compensate for the various motions. Some might call that "being beat up" and it can lead to fatigue.

When the wind was behind the beam, the cat had a smoother ride, even surprising me, because of what I noticed.

For example, there was a large shallow bowl of fruit in the galley that did not spill the stacked up contents out of the shallow bowl that was on a counter (apples and oranges, etc.). However, when going to windward, some items moved, and at least one apple escaped the bowl to land on the sole. Other items that were standing upright (e.g. A bottle of shampoo in the head) stayed upright, not falling over as they would if the boat heeled like a monohull would on similar point of sail and similar conditions.

Consequently, I can see why big Cat owners may want to have their boats delivered by professional crew when they need to make long distance sails to windward. To be fair, monohull sailors and owners tend to avoid going to windward whenever possible too.

The owner of this cat is very smart, and he hired crew to take the boat north (delivery) and had his wife and children fly to the destination port to join him later after the rough ride was over. I think that was a very good decision.

Much better to "go with the flow" than against it.
_______________

Since this is the Multihull Forum, I don't want anyone to mistake my message here. I enjoyed my time on the catamaran, and noticed a very positive difference in 'ride feel' when sailing off the wind. I look forward to sailing on more cats in the future, and can see the appeal they have (for various reasons).

[a64pilot]

I don’t have a lot of time in Cats, but ANY boat, ship whatever is affected by the motion of the waves, some more than others of course.
We spent s week on the Dive Boat AquaCat, a large power Cat and while it didn’t really roll that much, it’s motion was unpredictable and jerky.
I come from a mono hull powerboat background, and those can roll so bad that it will make you sick.
Our Mono sailboat when sailing will heel some, but usually much less than 15 degrees, at that point I reef, but thank God it doesn’t roll, unless running direct downwind, which I avoid if possible. Motion is smooth and regular, unless it gets real bad, then once in a while she will come off a wave and slam, if your in the fwd bunk, you will go weightless for a second as she falls off of the wave, but that is rare, and the weather is so bad, your not having a good time.

I think the heeling of a modern cruising mono hull is overblown. I have seen lightweight high performance tender monohulls, rail in the water, but my boat doesn’t sail well when overcanvassed like that, it actually sails just as fast standing up if you will.

Only way you can guarantee a smooth ride, is never leave the Marina.

[fxykty]

Probably a combination of being on a relatively small cat in particularly awkward sea conditions. But the reality of most catamarans is that they sail on top of the water rather than in the water, so they do bounce and jerk. Usually not so much that you can’t stand as you describe though.

You were already relatively slow so I’m not sure reefing would have helped, in fact more power helps to press the leeward hull down and steady things. But certainly changing your angle to the waves would ease the movement (most of the videos you’ve seen are running downwind - reaching and upwind are more like your experience). But of course if that takes you off your course to your destination that doesn’t really help.

Was the boat lightly loaded? Full tanks and a bit of weight can help to steady the motion.

Longer cats and heavier cats are less susceptible in mild conditions like you describe. Many of the catamaran YT’ers are on 44+ foot cats.

[belizesailor]

Depending on the boat and sea state, cats can indeed have an awkward motion caused by two hulls moving thru different phases of the wave train(s). I describe the motion of monos vs multis in such circumstances as "rythmic" vs "arythmic".

[scarlet]

Steadman, what a great opportunity for you to compare mono vs multi. I would have loved to do that back to back.

I wonder a bit if we had too much sail out. As multihull sailors know... you can't "reef by feel" because multis don't heel.. you have to go by wind speed. So, on our boat it said that once you hit 15 knts you needed to reef. Our skipper didn't want to do that, and showed me in the manual for the boat that you didn't need to reef until after 20+ knts. I probably would have reefed earlier had it been me. Our skipper also liked to have his sails trimmed in pretty close to center, even when reaching. On our little monohull, I handle my sails much differently... I usually trim them out further than our skipper does. But that's my preference..

Fxykty.. our boat was not heavily loaded. We did have full water tanks and gas tanks.. but other than that... it was a charter, and we each brought one soft sided bag.. and some groceries. So.. really not very heavy at all.

A64Pilot... you described it exactly... unpredictable and jerky. That's what Liza Copeland said as well. On a mono you set in a groove, and you can deal with that.. but on a cat.. it's unpredictable.

[scarlet]

Originally Posted by belizesailor

Depending on the boat and sea state, cats can indeed have an awkward motion caused by two hulls moving thru different phases of the wave train(s). I describe the motion of monos vs multis in such circumstances as "rythmic" vs "arythmic".

Is there a way to minimize that movement on a cat? There's part of me that believes that we exacerbated it somehow by the way we were sailing, or trimmed, etc...

(just as a note... we all managed the motion well... but I just would like to know how to smooth it out in case we are crossing, and someone needs to sleep, or we have guests who might be susceptible to motion sickness, etc.. )

[a64pilot]

As you know it’s not always like that, just going to windward I suspect with some angle to the waves, what you feel of course is the two hulls penetrating the wave at different times of course as the hulls are not centerline, they will impart a little yawing moment.

But mono hulls have their bad spots too, like going DD with a large following sea. To me that is worse, much worse than the jerky motion of a Cat.

If you were making 6 kts, I wouldn’t think you were in need of having to reef, although my Avatar picture was taken by a friend on their lagoon 380, we were working back and forth across the bay, an upwind leg and a downwind of course. They were worse upwind than we were, and an IP is not known for its prowess to windward.

[fxykty]

Originally Posted by scarlet

Is there a way to minimize that movement on a cat? There's part of me that believes that we exacerbated it somehow by the way we were sailing, or trimmed, etc...



(just as a note... we all managed the motion well... but I just would like to know how to smooth it out in case we are crossing, and someone needs to sleep, or we have guests who might be susceptible to motion sickness, etc.. )

The easiest way is to turn down wave. The next easiest is to slow down.

It does sound like the boat was over-trimmed, but easing the sails would have not as much effect as the first two things.

[JPA Cate]

scarlet,

Fwiw, my body just doesn't like jerky motion. That means, upwind, we slow down so I can hack it. We've always had monos, and I've watched corkscrew motion on a cat who was sailing in company with us, and I couldn't have tolerated that motion either.

With a mono, she'll heel and then you only have to cope with the heel angle, combined with an up or down, and the jerkiness of that, you can control with the measures you mentioned.

The guy with the 55' Outremer probably has the right of it for cats, but at 55', the length of his hulls will smooth out close-together wave patterns better than the Lagoon 38. Also, the Outremer is a little more a performance cat, they are nicely set up to sail, imho, more so than the Lagoons I have seen. The Lagoon is heavy for its length, and then, depending on tank size, the water is, too. Lots of times you can't turn down and go with the waves, for instance, if you have to get the charter boat back to the outfit from whom you rented it. Also, during the process of turning down, when it comes onto its beam, it will accelerate.

Ann

[james247]

Originally Posted by JPA Cate

scarlet,

Fwiw, my body just doesn't like jerky motion. That means, upwind, we slow down so I can hack it. We've always had monos, and I've watched corkscrew motion on a cat who was sailing in company with us, and I couldn't have tolerated that motion either.

With a mono, she'll heel and then you only have to cope with the heel angle, combined with an up or down, and the jerkiness of that, you can control with the measures you mentioned.

The guy with the 55' Outremer probably has the right of it for cats, but at 55', the length of his hulls will smooth out close-together wave patterns better than the Lagoon 38. Also, the Outremer is a little more a performance cat, they are nicely set up to sail, imho, more so than the Lagoons I have seen. The Lagoon is heavy for its length, and then, depending on tank size, the water is, too. Lots of times you can't turn down and go with the waves, for instance, if you have to get the charter boat back to the outfit from whom you rented it. Also, during the process of turning down, when it comes onto its beam, it will accelerate.

Ann

The draft and subsequent centre of gravity has so much to do with the ride. A smaller monohull dingy sailboat bounces about like a cork. Forward momentum causes a boat to bump and crash.
Personally I find a 50 footer with 10 foot of draft much more relaxing that one with 6ft. The pressure of sail and keel on a monohull lock the forces of physics together. This works well in cruising boats. Notwithstanding this 7 days going to windward is debilitating.
A cats physics are different as there are different and many forces causing the boat to move more aggressively in a short sea.
Dropping off a large sea in a monohull is unpleasant and can be controlled largely by working the boat through the seas. It is difficult to do this in a cat creating this jerky motion.
In similar conditions the cruising cat and the mono hull seem to have similar speeds when going hard to wind. Off the wind the cat has some advantage dependant on sea conditions more than anything else.

[BigBeakie]

Scarlet,

Now you have found out that there is more to "comfort" than wide cupboards, big showers and lots of aft cabin floor space.

There are things that do matter if you enjoy good "sea keeping" qualities in rougher conditions. And they are well worth considering if you plan to do a decent amount of passage making.

Things like hull design issues eg. fine cut-water bows together with a decent Lwl/BH ratio; progressive nacelle buoyancy; weight kept centrally instead of in the ends of the hulls; correct amount of rocker in the hull shape; bridgedeck clearance; the height of the center of effort of the sails & the weight of the rig and sails; using double dagger boards to smooth out quick motion, etc. can all make a significant difference.

While beating will never be as comfortable a point of sail on a cat, even a well designed and sailed cat, it can be quite tolerable for long periods. It can be intolerable for long periods on some boats however, so make sure you test sail under those conditions and points of sail if at all possible.

It is also usually not as "jerky" when passagemaking if the swell is longer, and then working to windward can be very rewarding in a good cat.

[JPA Cate]

Big Beakie has the right of this, that the distance between the seas has a huge effect on how the boat behaves, mono or cat.

Ann

[mark_morwood]

In my experience, that is not an uncommon general experience in those conditions - a corkscrew motion that some find quite disconcerting if going upwind into a steep, short chop. One theory is that it is related to the leeward bow hitting the wave after the windward bow that causes the jerking motion.

In your particular case, 6 knots in that much wind seems slow so you were probably over-sheeted and/or pointing too high. In any case, you can often get a much more comfortable ride with a better VMG by falling off a bit. We would always experiment. In our case even with that motion we could happily leave cups on the saloon table, it seemed that people were more impacted than things.

And I guess slightly for your encouragement here are a few videos, the first two of us sailing upwind at 8 knots in 20 to 25 knots of breeze in the middle of 5 days upwind sailing between Bermuda and the Azores - the most upwind we did in the 3 1/2 years we were out cruising.

https://youtu.be/TWEUyKMk0z4
https://youtu.be/rY4-lNKxF4E

And the last one is of the sailing you want, going 7 knots in 8 knots of breeze heading from Panama to the Galapagos Islands:

https://youtu.be/uLkOWqehUCs

Mark.

[Catapault]

"Short Sharp Chop" and going into it, is the one point of sail that we find pretty nasty on the Cat. It tends to jerk around to the point of being uncomfortable.

Same wind and sea height, but longer wavelength and it is much nicer.

There is certainly a suitable speed vs waves and can try speed up or slowing down some to adjust the 'jerkyness' a bit. I find we can almost hit a Harmonic of wavelength vs hull length that makes it especially nasty if the swell is coming in from 45deg off the bow, or anything in that region.

Where possible, I try and 'go someplace else' rather than beat into a short chop.

Most other conditions, Our Cat clips along beautifully with low motion and very comfortable.

Mark.