Heavy Monohulls vs Light Catamarans

[smj]

Originally Posted by wingssail

I am sure your tri is fun to sail, and I think I might have a hard time beating it on most passages, short or long, but I might be able to. I have a really good record beating multis of all sorts, excluding big cats on a reach, especially on point to point day sails.



However, the question is comfort at anchor. I sort of doubt that the light tri you pictured would have a great motion in a rolly anchorage, with one ama after the other touching. Seems like it might be sort of jerky.



Then there is the accommodation issue. Can you live on board with two people for extended periods? Can you even stand up? How about provisions and spares?



A good, heavy, monohull (such as my 18000lb sloop) is reasonably comfortable in a rolly anchorage, due mostly to a very tall mast and a very deep keel. I've yesterday gotten back from a three month cruise where ALL of the anchorages were exposed to the Pacific swell, and we were never thrown out of our beds. OK, twice we had to put our wine in tumblers instead of long stemmed crystal.



Yet, with all that, we are fast, and we have tons of room and load carrying capacity for cruising and living aboard.



So, comfort is not a simple multi vs mono discussion. There are more factors at play.



Which would you choose if you were going to sail and live on for twenty plus years?

From my perspective, there is no such thing as a reasonably comfortable monohull in a rolly anchorage.
The main reason we switched from a monohull to catamaran was the rolly motion of a monohull.
I’m sure there are a great number of people that enjoy the rolling of a monohull and I appreciate that, but personally I would much rather have the jerkier motion of a lightweight multi. That motion I have no problem handling but I’m sure there are others that don’t enjoy it.
There is no perfect boat designed for all, but no doubt if I had the choice between sailing and living on your performance mono vs our performance catamaran? It would be our catamaran.

[Joli]

Hard to determine what is comfortable, it's so subjective. We sail a big, heavy mono that was designed and built 50 years ago. We're comfortable on passage and anchored but it's a motion we both like. We've sailed big light cats that upwind in a sea state can have a pronounced cork screw motion, it doesn't bother me but my wife becomes deathly ill from it. The same sea state on our heavy mono is very comfortable for her.

Speed with a heavier mono is fine. Waterline and the ability to press allow for average days of 180 miles but we often make 200 miles, our final day into Charleston last month we were on a 230 mile pace. We're probably similar in speed to an Outremer 51 on average. Up or down I think we're quicker, reaching, I think they would be quicker.

If we were to upgrade our boat it would probably be something like a ten year old Oyster 655 not a new Outremer 51. The money would be the same but I would be sailing alone,. The missus doesn't like cats.

[Dockhead]

Originally Posted by smj

From my perspective, there is no such thing as a reasonably comfortable monohull in a rolly anchorage.
The main reason we switched from a monohull to catamaran was the rolly motion of a monohull.
I’m sure there are a great number of people that enjoy the rolling of a monohull and I appreciate that, but personally I would much rather have the jerkier motion of a lightweight multi. That motion I have no problem handling but I’m sure there are others that don’t enjoy it.
There is no perfect boat designed for all, but no doubt if I had the choice between sailing and living on your performance mono vs our performance catamaran? It would be our catamaran.

I think it's hard to argue with that. The achille's heel of comfort on my boat is rolling. We have 2.4m of draft and we roll less than other monos I have owned or sailed on, but it can still be very uncomfortable both at anchor and underway.


I have not yet resorted to flopper-stoppers, but at anchor I do sometimes use an anchor spring line to tune the angle to the waves to find a non-resonant frequency. Sailing downwind the rolling can be awful; another reason why I tend to broad reach and gybe rather than sail at or near DDW (better VMG being the other reason). That way, a bit of pressure in the sails damps the rolling.


I think lack of rolling is indeed a big advantage of multihulls, and I think comfort at anchor of multis is head and shoulders better than any mono. On the other hand, you get that twitchy motion at sea, particularly sailing upwind in short head seas, with all the multis I've been on, which can be horrendous.



So it's probably yet another case of pick your poison. But right downwind or at anchor, give me a cat any day, as you said.

[Dockhead]

Originally Posted by Joli

Hard to determine what is comfortable, it's so subjective. . .

Well, whether a particular pattern of motion may be uncomfortable or not might be subjective, but there is an objective component of comfort, and that is acceleration. Hull form plays a certain role in this, but for boats of even vaguely similar size and hull form, acceleration in any given sea state will be an almost linear function of weight.

[Chotu]

For the sake of a data point, the mono I’m cruising in now is 50’ and 40,000lbs.

Almost as comfortable as a 50’, extremely lightweight cat at anchor and a dream at sea with a very smooth motion, little roll or excessive heeling and a nice, smooth ride sailing.

I never thought a monohull could be in the same league as a cat for comfort until this one.

[Dockhead]

Originally Posted by Chotu

For the sake of a data point, the mono I’m cruising in now is 50’ and 40,000lbs.

Almost as comfortable as a 50’, extremely lightweight cat at anchor and a dream at sea with a very smooth motion, little roll or excessive heeling and a nice, smooth ride sailing.

I never thought a monohull could be in the same league as a cat for comfort until this one.

Depending on the waterline length of that boat, 40,000 is probably not a heavyweight at all for a 50' boat.


My boat is 44,000 pounds, 47' waterline length, making DL of a little under 200, which is in the "cruiser/racer" category in the traditional scale. So rather on the light than the heavy side.



Compared to smaller monos, I would say the same about the motion comfort of my boat, as you did about yours. Certainly more comfortable than smaller catamarans under most conditions. But the roll is the achilles heel, and I have never met any monohull which didn't roll at anchor if the water motion matches the resonant frequency. Not even a Swan 90. Same thing for sailing downwind in quartering seas.

[MartinR]

Originally Posted by Dockhead

A boat with D/L of 400 is going to be slow, slow, slow -- it doesn't matter how much you tweak the hull form.

Not necessarily. You can overcome much of this by increasing the sail area. That is why boats formerly looked like this:



You need much sail area to get a heavy boat to sail. And modern rigs do not do well in this respect. If you would but a Bermuda rig on the boat above it would be a snail.

But of course, the gaff rig makes for much heavier sail handling. All compromises.

[Dockhead]

Originally Posted by MartinR

Not necessarily. You can overcome much of this by increasing the sail area. That is why boats formerly looked like this:

You need much sail area to get a heavy boat to sail. And modern rigs do not do well in this respect. If you would but a Bermuda rig on the boat above it would be a snail.

But of course, the gaff rig makes for much heavier sail handling. All compromises.

This is not exactly true. First of all, hull speed is higher for a boat with light D/L and/or more fine hull.

Second, you cannot just pile on sail area and get proportionately increased performance. You have to have righting moment to stand up to that sail area. So you would have to pile on ballast proportionate to the increase in sail area, to get the same performance, but oops, if you do that, then you are increasing the weight even more -- it's a vicious cycle. Even worse, very heavy boats generally have longer keels which have less righting moment and more wetted surface, per unit of ballast weight. So you have several factors all working against speed, with heavy boats.

So I will stand by my statement that very heavy boats are necessarily slow.


Looking at it from the other end -- by making a boat lighter, you are getting more speed due to the positive interaction of several factors -- less weight means you need less sail area which means you need less righting moment which means less ballast which makes the boat even lighter. A virtuous cycle.


Dashew used this effect with brilliant results, by making light, long cruising boats with relatively fine hulls. The length largely makes up for any loss of comfort you would have due to the boats being light, and he was able to design compact easy to handle rigs, and even modest draft, and still get brilliant performance.

[MartinR]

Yes, the whole thing is complicated. As for gaff rig, you can pile on more sail area without too much penalty. as the center of effort of the sail plan is lower. Also instead of increasing the ballast you can increase the beam to increase righting moment.

My pilot cutter had a D/L of around 300, and was no slouch. In real figures, she was probably some 40% slower than my current boat. But the experience was almost the opposite. In a good breeze there was so much power from the sails, the hull was throwing a big wave, everything was vibrating, alive. The forces on the tiller required lines to hold it. At 8 knots it FELT fast. The current boat at 11-12 knots is about as exciting as sitting in a train. No drama at all. I am not sure what I prefer.

[Davo666]

There's a YouTube video somewhere with a delivery skipper on a big heavyish cat in a bit of sea and a blow - circa 35-40kn I think in the Pacific NW. Looked quite comfortable. He said the lighter cats (Gunboat etc.) accelerate faster and decelerate faster and would be a very uncomfortable ride in the same situation.

[thinwater]

Originally Posted by slug

All I ever see is catamarans motoring

Not even motor sailing

From a distance they look like oil platforms

Most charter cats are intentionally under canvased to protect them from credit card captains. They are not sail boats. They are designed to be anchor platforms.


On the other hand, you would see performance multis sailing away from you.


And I mentioned tris. You see them motoring a lot less frequently than monos. I can't recall seeing an F-boat or Dragonfly motoring, other than in the harbor.


That said, I liked my PDQ for cruising. Comfortable and doubly digit speed, if you pay attention. And yes, it could be capsized in less than a storm by an inattentive crew. Oh well. But not as much pure fun to sail as my F-24. But a motor home is always less fun to drive than a sports car.

[Rapanui]

One factor regarding comfort has not been mentioned - sea sickness. Irrespective of whatever boat you are on, be it it heavy or light, being seasick is extremely uncomfortable. Rolling is a big factor in that. Given that a lot of people are sick on ferries and the ilk, particularly older designs with narrow beam and no stabilisation, even being excessively big and heavy does not seem to help much.

My wife who is a cat evangelist has in the past, invited 2 seperate mono cruiser couples where the wives suffered chronic sea sickness for a trial sail on our boat to experience catamaran sailing, both wives found it cured their seasickness and both couples ended up buying catamarans. It does seem from anecdotal evidence that people sailing cats are less prone to sea sickness. Having said that, I have sailed with a couple of girls on a small heavy cat and they were constantly sick - but I suspect they would have been sick on wet grass.

[Joli]

Originally Posted by Dockhead

This is not exactly true. First of all, hull speed is higher for a boat with light D/L and/or more fine hull.

Second, you cannot just pile on sail area and get proportionately increased performance. You have to have righting moment to stand up to that sail area. So you would have to pile on ballast proportionate to the increase in sail area, to get the same performance, but oops, if you do that, then you are increasing the weight even more -- it's a vicious cycle. Even worse, very heavy boats generally have longer keels which have less righting moment and more wetted surface, per unit of ballast weight. So you have several factors all working against speed, with heavy boats.

So I will stand by my statement that very heavy boats are necessarily slow.


Looking at it from the other end -- by making a boat lighter, you are getting more speed due to the positive interaction of several factors -- less weight means you need less sail area which means you need less righting moment which means less ballast which makes the boat even lighter. A virtuous cycle.


Dashew used this effect with brilliant results, by making light, long cruising boats with relatively fine hulls. The length largely makes up for any loss of comfort you would have due to the boats being light, and he was able to design compact easy to handle rigs, and even modest draft, and still get brilliant performance.

The Daschew boats we've seen out cruising don't seem to be especially fast. They have very small rigs and shallow keels so don't seem to be able to get upwind without motoring. Downwind they need a lot of breeze to get up and going.

We're a heavy boat, 65,000#'s, so will never plane but we do have a big rig. Down wind we set 5,000 sq ft of sail and easily pull the apparent wind forward. Doing this allows us to sail deep but avoid rolling because we're pressing the boat.

We're comfortable at anchor but we're heavy with a deep keel and a very tall rig. We don't roll much.

[rslifkin]

How a boat rolls can be a big influence on comfort. And it impacts different people differently. As an example, I've got one friend that gets seasick quite easily on sailboats with a slower, more gentle rolling motion. But no problems on my boat with a much faster, snappier roll (which I find unpleasantly harsh at times). Total amount of roll doesn't seem to be the issue there, it's just the difference in how the boat moves.

[malbert73]

Originally Posted by Dockhead

You would win that bet.


Cats are just like monos in that regard. For a cat to be really fast AND be pretty comfortable, it needs to be light and pretty big. I like the Atlantic 57's myself; that must be an absolute blast to sail.

I got to sail on one. Amazing boat. And surprisingly twitchy under sail because so light and powered up. So I wouldn’t call it comfortable. Of course we were going 13-15 knots....

(The one I sailed on later on got flipped by a sudden squall and possibly waterspout at night on a routine delivery by very experienced crew- FWIW)