Light air performance of different multihulls?

[mglonnro]

Originally Posted by barnakiel

I am not sure why you get hung up on comfort?

For my part I was just asking what else matters IF the long term average speed is the same. The first two things that came to my mind were: a) am I motoring or sailing, and b) is it 'comfortable' or not.

There are obviously a bunch of them (safety, cost, build quality, how easy to service, sail, etc), and a lot of them are very subjective, indeed.

If I got hung up on something, it was the 5 knots!

[wingssail]

Originally Posted by mglonnro

I guess you didn't buy a boat to maximize your discomfort either? The most common comfort requirement I've heard is that it's good to be able to move safely inside a boat without being thrown around and hitting sharp edges. (Sorry for oversimplifying everything to a glass of wine on a table )

Love of sailing is as good as anything, obviously!

So, if all boats end up going five knots, which questions might be asked to figure out what boats best satisfy the love of sailing?

Comfort is important to me as well but I have my own requirements to be comfortable:

• A quiet place to sit and read (or nap) with well placed intimate lighting, quiet, good quality music, etc
• A roomy bed with good ventilation
• A nav station with a comfortable seat and a big nav table where I can sit and use the computer (for navigation or entertainment), will all the electrical and electronics at hand
• Clear cabin sole, spare bunks and other horizontal surfaces to maintain a feeling or room and tidiness, which brings peace to me
• A good galley with a good stove and counter space and a refrigerator and freezer and running hot and cold water
• Heat, sufficient to keep the boat at 70 when it is below freezing outside and air conditioning to keep it below 80 when it is 95 outside
• A separate shower, a changing area, and a vanity area with mirrors in front and behind
• A work shop so that I can have a boat project without parts being strewn an the salon table
• Tons of accessible storage so that I can carry all my provisions, spare parts, tools, sails (14) and all the sailing gear not is use at the moment
• Storage for all my clothing, warm weather and cold, as well as foulies, and a hanging looker for a few business suits for each of us
• Room for records storage, so that the key documents of my life can be carried with us
• A good wine and liquor locker as well as fine glassware, flatware and excellent gourmet cooking utensils and good storage for them all
• And a place to put my wine glass if we are heeled over and charging to windward in rough weather

Beyond comfort, (and actually taking a higher priority), are sailing characteristics, because I'm not out here for comfort, I'm out here for sailing.

• Good performance in all wind strengths and every wind direction
• Surperb windward performance
• Surperb down wind performance
• Total all weather safety and capability and safety from the consequences of sudden knockdowns in the middle of a squally night
• Ability to easily heave-to or forereach in a storm
• Easily and safely handled by two persons, yet fit for a full racing crew
• Totally set-up for crew efficiency meaning big winches, direct leads, low forces on lines and handles, room to work and work together
• Clear decks for easy on deck crew work, sail handling, and visibility
• Great instrumentation and computer supported navigation and tactics
• Full protection for on deck crew in all weather conditions

There is a lot more, but I think you get the idea.

I do worry about being tossed around, but plenty of handholds in the right places prevent that (and the muscles needed hold me in place get some exercise, similar to calisthenics).

As for the 5 knot average for all boats? I don't buy it. We commonly exceed that. For example when crossing the Indian Ocean in 2020 we sailed 2790 miles to Mauritius in 442.3 hours which is an average of 6.3 knots and that passage had a lot of calm periods in the first half, yet we did not use the motor much, putting 24 hours of motoring time in the log.

I might like to have a nice, high performance, catamaran, if it could meet all my criteria, but I don't have a million dollars to spend on a boat.

Meanwhile I have a great monohull which is comfortable, fast, and affordable. I can race it and do well, while living aboard, as we have for 34 years.

And show me a liveaboard multi that meets my criteria, above, that can do this upwind.

[smj]

When one brings up comfort the first thing that comes to my mind is motion, both while at anchor and while sailing.
Even if the boat is huge with all the comforts of home, if the motion is uncomfortable so is the boat.

[mglonnro]

Originally Posted by wingssail

There is a lot more, but I think you get the idea.

Great lists! It was deeply satisfying to read your post.

As for the 5 knot average for all boats? I don't buy it. We commonly exceed that. For example when crossing the Indian Ocean in 2020 we sailed 2790 miles to Mauritius in 442.3 hours which is an average of 6.3 knots and that passage had a lot of calm periods in the first half, yet we did not use the motor much, putting 24 hours of motoring time in the log.

Yes, sounds reasonable to doubt this as a universal truth. It was funny, however, that my log was so spot on, but I will do my best to change it

I might like to have a nice, high performance, catamaran, if it could meet all my criteria, but I don't have a million dollars to spend on a boat.

Meanwhile I have a great monohull which is comfortable, fast, and affordable. I can race it and do well, while living aboard, as we have for 34 years.

And show me a liveaboard multi that meets my criteria, above, that can do this upwind.

Here is the reason I wrote this post in the first place. Never having sailed on a performance catamaran, I'm trying to figure out whether it's worth dreaming of one day having one.

[barnakiel]

Originally Posted by mglonnro

(...)


If I got hung up on something, it was the 5 knots!

Imho, very rightly so, as there is much more to talking about averages and light wind performance, than light wind performance and comfort.


Thinking of average of speeds (say: average of speeds of various cat designs in light winds) we will quickly discover while averages are a kind of tool, we gain much more insight from looking not at averages, but rather from thoughtful analysis of the distributions. Questions about the tails of the curve, about standard deviations, of skew, etc. bring us much better understanding of what sails and what does not, in light winds.


My favourite example goes something like this:


Take three identical cats, let them be Lagoons 38.


1) Empty one, rip out furniture, send engines to scrap metal shop, leave anchors and chain on the dock.


2) Leave one as is.


3) The last one load with typical cruising c(--)p - ribs and oversized outboards, 1kW solar on arch, 20 diesel jugs just in case the wind drops below 10 knots ... ah, yes, a genset and a full kit of spares for the genset, two engines and 40' inch plasma TV set... to name a few 'must have' cruising items. (Damn, forgot about air-con! sorry)



Now seal lock their engines ... and sail the boats on any long passage. NOW calculate the averages.


Without any magick skills, the average is ... 5 knots. The fast one (no engines) made it at 7 knots, the normal one at 5 and the one with extra diesel jugs at ... YES 3 knots.


If you let them use engines, the average pops to 6 knots! But only the speeds of the bottom two boats changed.



Etc. You are already seeing my drift. Averages are ... well.


The real thing is to ask oneself - on which tail of the bell curve I want to sit?


Surprisingly, I would take the engine-less boat.


Because the thread goes performance of cats in LIGHT AIR.


BTW, my biased view is an average of 5 knots is ... slow - given what an average cruising boat today is! (40'+ easily)



If your boat is like ours, 25' on the water then 5 knots is very nice. If, however, your boat is about 36' on the waterline, or longer .... sorry, but you are sailing a tub.


!!!


++Hugs,

barnakiel

[mglonnro]

Originally Posted by barnakiel

Surprisingly, I would take the engine-less boat.


Because the thread goes performance of cats in LIGHT AIR.


BTW, my biased view is an average of 5 knots is ... slow - given what an average cruising boat today is! (40'+ easily)



If your boat is like ours, 25' on the water then 5 knots is very nice. If, however, your boat is about 36' on the waterline, or longer .... sorry, but you are sailing a tub.


!!!

Or sailing it like a tub!

It's hard enough to dock under sail with a monohull. I wonder, do many people do it with Lagoons?

++Hugs,

barnakiel

Hugs!

[barnakiel]

Yes. Docking less easy.


Classe Mini racers are towed out and into berths. They do not have an engine. One of the factors why a 6 meter boat can cross the Atlantic averaging 11 knots ...


!


b.

[dustman]

Everyone says that monohulls have way less surface area for the size. I don't think that's the case. When you think about it, for a given length the catamaran weighs much much less because it doesn't require almost half the boat weight in ballast. Then, even though the monohull seems to have much less wetted surface area at a given displacement, the monohull cannot have a surface area optimized hull, such as circular, because it would be extremely unstable. Most monohulls have a broad, relatively flat midbody which has to be overly wide for stability. Then, most monohulls seem to have a large keel with a lot of surface area.



I would surmise that most monohulls/catamarans of similar performance/size don't have drastically different wetted surface areas. And that difference could be made up for easily by the low wave making and form drag of the catamaran. On many monohulls those factors become quite significant at just a few knots.



My two cents. Would love to see some data.

[Mr B]

Cats sit on top of the water, Not in it, like mono's do,

So the drag is less, FWIW,

[wingssail]

Originally Posted by dustman

Everyone says that monohulls have way less surface area for the size. I don't think that's the case. When you think about it, for a given length the catamaran weighs much much less because it doesn't require almost half the boat weight in ballast. Then, even though the monohull seems to have much less wetted surface area at a given displacement, the monohull cannot have a surface area optimized hull, such as circular, because it would be extremely unstable. Most monohulls have a broad, relatively flat midbody which has to be overly wide for stability. Then, most monohulls seem to have a large keel with a lot of surface area.

I would surmise that most monohulls/catamarans of similar performance/size don't have drastically different wetted surface areas. And that difference could be made up for easily by the low wave making and form drag of the catamaran. On many monohulls those factors become quite significant at just a few knots.

My two cents. Would love to see some data.

I don't know who says that mono-hulls have "way less" wetted surface than catamarans.

I have just been looking at the weights of a few boats for comparison, a Jeanneau Sun Odyssey 44, a Lagoon 43 and an Outremer 45 and I don't see huge differences on weight. The Sun Odyessy is 18.8k lb the Lagoon 16k lb, and the Outremer, the lightest at 13.5k lbs. Maybe older boats would show more differences.

So we would expect that if the hull shapes were similar, the wetted surfaces would be proportional. But they are not. The shape of the monohull is close to being semicircular, with the addition of the keel. The Lagoon has two, relatively semicircular hulls, and two keels as well. The Outremer, with narrower hulls, and boards, will have somewhat more wetted surface for its weight by virtue of it's deep, narrow, hull shapes, but will offset that by having less wave producing, shapes and lighter weight.

All in all, I'd guess that the sail areas would have more to do with light air performance then the relative wetter surfaces for these boats.

That, and how much weight is piled on. If you put 4000lbs on the Jeanneau it increases the weight 21% The same weight on a Lagoon is a 25% increase, and on the Outremer, that much load is close to 30% increase over light ship.

If you also consider that for cruising the builders of catamarans tend to keep the sail areas down, for safety, it is not hard to see why some people think that catamarans look sticky in lighter airs.

Personally I'd like an Outremer 5x. I don't know how it would feel sailing, I'm sort of used to powerful monohulls, and anyway it's way out of my price range., so never mind.

But back to the topic. For sure, it you took an Outremer or other light weight performance cat, without over loading it with cruising and liveaboard weights, across the ocean, it would, or could be, very fast. Wetted surfaces would not be a major factor.

It would probably leave the Jeanneau in it's wake. Lets all recognize that.

But I doubt if the owners of that high performance cat will be living on it after it arrives at it's overseas destination. After a few weeks on the sun they will be flying home. These are not well suited for long term liveaboards, in my opinion. Maybe I'm wrong.

But take a normal 40+ foot Lagoon, FP, Catana or any of the British or South African cruising cats, load it down with 4000lbs of gear, and send it across the same ocean, and it would not be a rocket ship. It would not be much faster if at all, than the Jeanneau or any other cruising monohull of comparable size. And any of them, mono or multi, will make good liveaboard cruising boats.

So when it comes to light air performance, sail area and weight count. And for average boats, there might not be a whole lot of difference. between one kind of boat and another.

[fxykty]

Originally Posted by wingssail

...



But I doubt if the owners of that high performance cat will be living on it after it arrives at it's overseas destination. After a few weeks on the sun they will be flying home. These are not well suited for long term liveaboards, in my opinion. Maybe I'm wrong.



...

I expect you are wrong by your own example - you live aboard a racing monohull perfectly happily as you’ve told us. Why would it be any different for a performance oriented catamaran?

How is a performance cat not well suited?

I look at ours (albeit 53 foot long) and she has everything we could possibly want for two of us and occasional crew or guests.

[jdmuys]

Originally Posted by wingssail

And show me a liveaboard multi that meets my criteria, above, that can do this upwind.

I surmise a Marsaudon, either TS5 or TS42, depending on how much space you want.

The price will depend on the options, but you can reach $1 million on the TS5 if you select many carbon options

As they say, fast, comfortable, cheap - select any two.

[fxykty]

Originally Posted by jdmuys

I surmise a Marsaudon, either TS5 or TS42, depending on how much space you want.



The price will depend on the options, but you can reach $1 million on the TS5 if you select many carbon options



As they say, fast, comfortable, cheap - select any two.

Go used and save 60%-70% of that million (USD I assume). You get all three! Not everything has to be bright, shiny and new.

[Tupaia]

Originally Posted by wingssail

But I doubt if the owners of that high performance cat will be living on it after it arrives at it's overseas destination. After a few weeks on the sun they will be flying home. These are not well suited for long term liveaboards, in my opinion. Maybe I'm wrong.

I think you are wrong.

[mglonnro]

Originally Posted by Tupaia

I think you are wrong.

I, too, wonder why an Outremer 5X wouldn't be suitable for living aboard? I'm running out of dreamboats soon if it is!