Light air performance of different multihulls?

[wingssail]

Don't get me wrong jdmuys, I know that the fastest sailing boats are multihulls, but my point, and I think that the ARC results show it, is that for normal cruising boats, multi's don't cross oceans any faster than monohulls. There is a lot more going on besides flat out speed.

Originally Posted by jdmuys

Of course: you are cherry picking. You exclude the fast cats just to support your hypothesis...

No, I am not cherry picking. you'll notice I also excluded the fast monohulls, as well as the slower examples of both types.

I was trying to show how cruising boats compare on crossings.

As far at the Marsaudon TS5, I watched a video of them sailing that boat it is was not two old cruising couples, they were keen, aggressive, and knowledgeable sailors, and it was light and lightly loaded, so that is not a typical cruising boat.

[smj]

Originally Posted by arsenelupiga

obviously you have not heard of CF member Django with lagoon 38 that won both ARC races and left behind many racy boats that you promote, couple years ago.



Unfortunately for 'cat performance pushers', cruising cats like lagoon provide way more value for money and more comfortable drive. You can have appartement on water or/and fast passagemaker if you put effort into it.



Now feel free to start crying.

Here’s my crying....[emoji23][emoji23][emoji23]so funny it brings tears to my eyes!!!!

[wingssail]

Originally Posted by barnakiel

But now. This is a simplification.
Certainly, but often concepts can best be illustrated in simple terms

A wide boat can do without ballast. A narrow one cannot. Hence the wide one will only weigh (ha ha, another simplification) some 50% of the heavy one.
Wide boats cannot do without ballast and require similar amounts of ballast. For example, compare a narrower boat the Santa Cruz 52 with a new, wide, Beneteau 55.1: The Santa Cruz is 14ft wide weighs 21000lbs and has 9100 lbs of ballast. The Beneteau is 16.27 ft wide and weighs 37000, has 9300 lbs of ballast. The wider boat has MORE ballast.

Now draw those hulls again, now measure their wet area.
Sorry, you can draw them

You used same weight, but narrow and wide weight will NOT be the same weight. Ballast normally is range 50% of the weight, and ballast is OPTIONAL in a wide boat.
Ballast is not optional in a keel boat.

Ballast is also optional in a cat ... ;-)

There is also one more factor. Assuming wide hulls are sailed flat. They are not. Look at Comanche again THEN watch Ken Read talking about Comanche becoming a mono-maran when heeled. A canting keel is such a nice device ... it works both ways!

Never the less, Wild Oats is considered to be faster than Commanche in light air due to the reduced wetted surface. But normally, cruising boats don't have canting keels, and in light air there is not enough wind to heel a wide boat enough to reduce the wetted surface.

Bottom line, wider boats of similar displacement have more wetted surface and are slower in light air than narrow boats

b

But in the case of catamarans, which was the original point of discussion, no catamarans that I know of have wide hull shapes with greater wetted surfaces like the wide monohulls. Semi circular shapes typical of normal catamarans will have less wetted surface than skinny hulls typically seen on the higher performing cats, for the same weight. But the ones with narrow hulls are also lighter. Narrow hulls means less wave making and lighter means faster, so they are fast. But make the hulls fatter, to fit more interior, and they will have more wave producing shapes and generally more weight, so even if the hulls have less wetted surface, these boats will generally be slower.

In both monohulls and catamarans, narrower hulls are better in light air, though for different reasons.

[barnakiel]

Originally Posted by wingssail

But in the case of catamarans, which was the original point of discussion, no catamarans that I know of have wide hull shapes with greater wetted surfaces like the wide monohulls. Semi circular shapes typical of normal catamarans will have less wetted surface than skinny hulls typically seen on the higher performing cats, for the same weight. But the ones with narrow hulls are also lighter. Narrow hulls means less wave making and lighter means faster, so they are fast. But make the hulls fatter, to fit more interior, and they will have more wave producing shapes and generally more weight, so even if the hulls have less wetted surface, these boats will generally be slower.

In both monohulls and catamarans, narrower hulls are better in light air, though for different reasons.

OK. So me have a challenge for the cruising multi - to get a long narrow option the boat needs to be big, for otherwise all the cruising gear will not fit.

Or we need to accept a bit less light wind potential in return for load carrying capacity.


Interestingly, older Outremers had long narrow hulls, newer ones have much wider hulls. Today it seems that Marsaudon took up the fast cat niche, while Outremer went towards the center line - remaining light, but not narrow. (not as narrow as before)


And once we have the best hulls for the job we also have to walk into that loft and write a $$$ check for lightwind sails.


Because regular cruising sails are next to useless in light wind sailing.



b.

[barnakiel]

Originally Posted by Mr B

My Gemini weighs 4.5 Tons,
Its a cork, It sits on top of the water, not in it,
It needs 3 knots to move on the 150 Genoa,
It sails usually 2 knots under wind speed,
I like to sail between 5 and 10 knots,

I spent 7 days sailing (motoring) in Bass Strait, I had one day with wind,
9 Knots of speed, 3 metre waves,
The rest of the time it was dead calm and no wind,
The Genoa hung on the boat like a wet rag, The rest of the time,

We have either no wind or screaming winds,

This sounds exactly like summer sailing in Scotland - either flat and motoring (good!) or else (tied to a dock listening to the blow). Next week good weather returns again and we can go sailing ! (=motoring)


Also sailing out from Darwin towards Christmass there is a 400 to 600 miles flat patch - it blows maybe 10 knots but more likely 5 knots there a few hours each day. Then it is flat the rest of the time. An amazing light wind sailing exercise.


Also the area between Panama and Galapagos. Some 800 miles of light winds. Good if you are a light wind sailor, but nerve wrecking for the rest. Most boats will power thru the whole patch.


For unknown reasons (which I interpret as civilisational anxiety) many cruisers hate light winds. But there are also some that enjoy it all the way.


Cheers,
b.

[mikereed100]

Originally Posted by wingssail

The result of this is that the cats don't normally have faster crossing times. Of course a high performance cat crewed by keen sailors will be faster on an offwind passage.

Normal cruising boats? The passage times will often not be shorter.

I am reminded of an informal survey of fellow cruisers that the Pardeys did some years ago. They asked something to the effect of, "What is your average speed, year in and year out." The answer, regardless of length and number of hulls was about 5 knots. My MFD has been keeping track of our average speed over the past 10 years and 30,000 some miles, which includes a lot of motoring, as well as trade wind passages. Interestingly, the average is exactly 5.0 knots.

[NaClyDog]

Originally Posted by mikereed100

I am reminded of an informal survey of fellow cruisers that the Pardeys did some years ago. They asked something to the effect of, "What is your average speed, year in and year out." The answer, regardless of length and number of hulls was about 5 knots. My MFD has been keeping track of our average speed over the past 10 years and 30,000 some miles, which includes a lot of motoring, as well as trade wind passages. Interestingly, the average is exactly 5.0 knots.

Time is the great equalizer!

[zboss]

Originally Posted by mikereed100

I am reminded of an informal survey of fellow cruisers that the Pardeys did some years ago. They asked something to the effect of, "What is your average speed, year in and year out." The answer, regardless of length and number of hulls was about 5 knots. My MFD has been keeping track of our average speed over the past 10 years and 30,000 some miles, which includes a lot of motoring, as well as trade wind passages. Interestingly, the average is exactly 5.0 knots.

That's true for us as well but one thing is for sure: the folks with the longer hulls or multiple hulls has a more comfortable passage at 5 knots.

[mglonnro]

Originally Posted by mikereed100

I am reminded of an informal survey of fellow cruisers that the Pardeys did some years ago. They asked something to the effect of, "What is your average speed, year in and year out." The answer, regardless of length and number of hulls was about 5 knots. My MFD has been keeping track of our average speed over the past 10 years and 30,000 some miles, which includes a lot of motoring, as well as trade wind passages. Interestingly, the average is exactly 5.0 knots.

I took some measures from our own database. There are millions of data points of us not moving (in marina, anchored), but to make it simple I included just the data points where we're moving >= 1.5 knots.

- 20.5M data points
- average speed 5.06 knots
- 0.5% percentile median: 5.05 knots

Funny

[jdmuys]

Originally Posted by wingssail

Don't get me wrong jdmuys, I know that the fastest sailing boats are multihulls, but my point, and I think that the ARC results show it, is that for normal cruising boats, multi's don't cross oceans any faster than monohulls. There is a lot more going on besides flat out speed.

indeed, if you restrict yourself to Lagoons or similar. I never claimed otherwise. What I am claiming, is that the claim you make - about catamarans in general - is not supported by the evidence you manipulated.

Originally Posted by wingssail

No, I am not cherry picking. you'll notice I also excluded the fast monohulls, as well as the slower examples of both types.

That you *also* excluded other [possibly irrelevant] data points doesn't make it any less cherry picking. At the very least, any point you may have made concerns only "catamarans-that-you-haven't-excluded", which is not entirely convincing to say the least.

Originally Posted by wingssail

I was trying to show how cruising boats compare on crossings.

As far at the Marsaudon TS5, I watched a video of them sailing that boat it is was not two old cruising couples, they were keen, aggressive, and knowledgeable sailors, and it was light and lightly loaded, so that is not a typical cruising boat.

Yes they were knowledgeable (I wrote "competent"). Aggressive? I suppose that's true, since they won. Light and lightly loaded? Yes of course. That *is* the point. Choose a light catamaran (ie built for speed as I wrote), and you will be able to go fast (should you decide to do be "agressive"). Choose a condomaran, and you will not have that option.

I can see 3 sets of catamarans and crews:

- those who can and do, such as Regis Guillemot on his TS5
- those who can and don't (because they don't care at that moment, or whatever)
- those who can't (eg Lagoon owners, or TS 5 owners who are not competent enough - such as myself if I had one)

Now if you want to compare what happens in aggregate compared to monohulls, depends largely on the sizes of the pools you compare, unless you want to engage in more sophisticated analysis, which remains to be done.

I don't know anything about that. And I don't care about who decides to do what (if they can). Some even bring down their sails at night. I care about what the options are. Not who decides to do what. But claiming that a Lagoon 38 can be as performing as a TS 5 (which you did not, but kind of implied) is an extraordinary claim that would require extraordinary evidence.

[mglonnro]

Originally Posted by jdmuys

I don't know anything about that. And I don't care about who decides to do what (if they can). Some even bring down their sails at night. I care about what the options are. Not who decides to do what. But claiming that a Lagoon 38 can be as performing as a TS 5 (which you did not, but kind of implied) is an extraordinary claim that would require extraordinary evidence.

It's interesting to think about what the right questions are?

For argument's sake, let's say everyone in the long run (Lagoon or TS 5) really ends up having travelled at 5 knots average. My next questions would be:

- How much diesel was used? Percentage engine hours/total time at sea?
- Of all the meals eaten (at sea), how many times could I leave the wine glass standing on the table without worrying about it? Or some other better way to measure the comfort of it all ..

[wingssail]

Originally Posted by mglonnro

It's interesting to think about what the right questions are?

For argument's sake, let's say everyone in the long run (Lagoon or TS 5) really ends up having travelled at 5 knots average. My next questions would be:

- How much diesel was used? Percentage engine hours/total time at sea?
- Of all the meals eaten (at sea), how many times could I leave the wine glass standing on the table without worrying about it? Or some other better way to measure the comfort of it all ..

Measuring how much comfort I'd have is not how I choose a boat. I didn't buy a boat to maximize my comfort, I bought one because I love sailing. Sitting on a couch with my wine glass on a table nearby? That can be done in a condo ashore and it is not what I hope to be doing at sea.

Of course we all have our own priorities.

[mglonnro]

Originally Posted by wingssail

Measuring how much comfort I'd have is not how I choose a boat. I didn't buy a boat to maximize my comfort, I bought one because I love sailing. Sitting on a couch with my wine glass on a table nearby? That can be done in a condo ashore and it is not what I hope to be doing at sea.

Of course we all have our own priorities.

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?

[jdmuys]

Originally Posted by wingssail

Measuring how much comfort I'd have is not how I choose a boat. I didn't buy a boat to maximize my comfort, I bought one because I love sailing. Sitting on a couch with my wine glass on a table nearby? That can be done in a condo ashore and it is not what I hope to be doing at sea.

Of course we all have our own priorities.

we all have our own priorities, _and_ Our own scenario. Having a condo ashore is [usually] not an available option when sailing around the world. In this kind of scenario, where your only accommodation is the boat, comfort starts to deserve some consideration, some of the time.

But pleasure sailing, is very important to me too :-)

[barnakiel]

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


Comfort on all cats I have been on was great. And twice so in light airs.


If somebody sails only short stretches or is very young and can take a lot of discomfort, that's fine. Let them be. It is nice to be young, and nice to sail inshore. And we each have different comfort / discomfort tolerances.


Comfort in a cat in light winds is great. There is nothing to argue here.


b.