The Offshore Voyaging Reference Site

Mono- or Multihull?

As I have said many times before, I’m agnostic about the number of hulls a cruising boat should have. There are benefits and drawbacks to one, two, or three.

That said, I do have a soft spot for some boats with three hulls, but that’s another post.

Anyway, I came across this good article comparing the options that’s worth a read.

I think the author does a very good job of pointing out that condo-cats are great for hanging out on, particularly in rolly anchorages, but if we want a cat or tri that sails well, we gotta keep her light, and if we are not willing to do that, the overloaded multi will have a hard time keeping up with a similarly loaded mono.

That was certainly our experience over the years we sailed our McCurdy and Rhodes 56, and is also why our friends Steve and Linda Dashew turned away from cats (their first love) in favour of long thin monos.

Real selection criteria to think about, instead of engaging in the silly which-is-best argument.

Much more about how to cut through all the noise and blather to end up with the right boat for our needs.

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Drew Frye

The “no difference in speed” thing is true for most cruising catamarans. In fact, I never found a cruising cat on my home Chesapeake that I could not easily catch with my PDQ 34 cat, including many that were 10-15 feet longer (a few Gunboat exceptions!). Why? Because they are underpowered to keep inexperienced crews safe. Because they were over loaded. And because my PDQ was mildly turboed both above and below the waterline. Not particularly light, but no dragging transom either. Unless you have expereince with performance boats and preferably performance multies, that conservative rig is probably right for you and you shouldn’t be pushing it. For example, if it is gusty, if you are above hull speed, or if there are sqauls in sight, there must be someone at the helm and accesible to the winches. A different mentatility than monos on autopilot. Personally, I believe a long beach cat apprenticeship is very wise. Then you will know how they feel before things go pear shaped.

Yes, the motion is worse. Or maybe different is more descriptive. It is quicker, but there is no roll off the wind and no heel. Different.

I would not say which is better, lacking offshore miles in a mono. But I am sure that when powered up they require a closer watch. When there is no watch is when you hear of capsize. They will only go faster IF you are ready to dedicate the attention. Otherwise, you reef early and the speed is the same.

Stein Varjord

Hi Drew,

I agree with every word you say.
I have sailed a lot on both monohulls and multihulls of all kinds, including professional racers. I’ll try to explain my experiences on the sailing motion comfort issue. Your description is correct and fair: “Different” is a key word. Still, my observations do give well designed cats a pretty big advantage in flat out life quality while sailing in significant wind, no matter which direction.

One trip was especially illuminating. I was on a TRT1200 catamaran, which is a cruiser, but VERY light and fast compared to most cruising cats, incl carbon mast, carbon daggerboards, etc. Basically a 40 foot beach cat with 4 double cabins and good comfort level. I’ve sailed one across the pond and another time averaging 23 knots over about 2 hours, which was pushing the limits more than a bit, but shows that this was no condomaran. One would expect a cat like this to move quite quickly and perhaps uncomfortably, especially upwind in waves.

One time about 20 years ago we were 8 people aboard sailing south along the Swedish west coast. Just 2 of us had ever been in any type of sailboat before, the owner and me. Thus, we had 6 total newbie guests. The weather was pure blue sky and about 28 degrees Celcius (perfect summer) but over 20 knots from dead ahead, increasing a bit. We left the harbour around 11. We had a party the night before. Our monohull friends in 3 boats had left around 7. We had agreed to meet quite a bit further south, in Smögen.

We sailed about 5 hours. during the trip, the 4 newbie sailor girls insisted on cooking an fancy brunch, and serving it with champagne in tall glasses in the cockpit. We sat around the cockpit table (has no edges to stop things falling off) going at a good rate full upwind in open waters and noticeable waves, perhaps 1 metre 3 feet. Now and then some spray coming over the bows. The newbies were ecstatic about how wonderful this sailing thing was. Zero seasickness. We arrived at the destination before 17, all aboard smiling like a sun and ready for another party, looking for our friend boats.

Two of them arrived a while later, after over 10 hours sailing. Nobody had been able to eat anything. They were all soaked, cold and all had been seasick. One had damaged a sail. All relationships on both boats were hanging on a thin line. One wife insisted that they were going to sell the boat the next day. Not totally serious, but still not meant to be funny. She did leave on a bus later. The last of the 3 boats had gone to another earlier harbour. They all agreed that it had been the worst “storm” and a horrible trip. These were far from hardcore sailors, but none on these boats were newbies. The wind was at its strongest around 13 to 15, when we were all out there.

All the newbies on our boat looked at each other like they thought the others must be insane. We had a beautiful and smooth day on the water. “One of the best days of my life”, was said. How could the others have hated it so much and taken more than twice the time (they had tried more sheltered waters inside some islands) with about the same size boats? Why didn’t we have that “storm”?

Is any cat always more comfy in a seaway than any mono? No, absolutely not. Again we need to remember the word “different”. Cats and monos do their jobs with different tools, resulting in different behaviour. Cats barely heel, which is a massive comfort factor. They roll little, usually significantly less than the actual wave contour. Monos usually exaggerate the wave contour significantly. Cats also usually pitch a bit less and much softer, because of their fine entries and twin bows and sterns. Each motion is faster, but dramatically smaller.

On average, this translates to a dramatic improvement in motion comfort, but there are also some situations when it’s hard to walk normally on a cat. That can usually be remedied by a small course change. I know that many competent sailors claim they think the motion on cats is too jerky and that monos are better. I find no place to put that type of statements. Maybe poorly designed or poorly handled cats? I don’t know. My 50 years of sailing and 40 on multihulls, including designing and building some, tell me that cats and tris usually, when all is counted, have far more comfortable motion than monos. This is perhaps one of the best reasons to sail them.

Terence Thatcher

See also: the new article in Practical Sailor about the bulkhead failures in the Lagoon 450. Drew and his crew over there did a powerful expose’, marred only by a conclusion that seems too generous to Beneteau. Until the PS article, I did not understand the high stresses to which cats are subjected in a seaway.