Light air performance of different multihulls?

[mglonnro]

Originally Posted by Chotu

That’s what I was thinking.

Almost has more to do with the rig than anything else.

Data needs to be normalized by the square meter or square foot of sail area presented.

I think the source data is so general/anecdotal that it's not of much use to derive anything from that.

Furthermore, I wonder if constructing a synthetic figure by normalizing by sail area would answer the original question any better? I think it's more useful to know that this particular one boat usually gets up to 4.5 knots when true wind angle is this and true wind speed is this.

Having similar real world performance data from let's say hundreds of different catamarans (cruising) would be a good start to get some insights into what to expect, in general.

They are good follow-up questions, of course, when digging into the differences.

[mglonnro]

Originally Posted by smj

More accurate data can be found at
multihulldynamics.com
It’s not perfect but should give a good idea on a boats performance especially when compared to others

Yes! And it gives a lot of interesting calculations, but is there some way I get the required wind speed for the (cruising loaded) boat to get up to 4-5 knots (in different wind angles) from there?

I'm sure there is a mathematical way to solve this, since VPP diagrams do exactly that. Empirical real world data would be great, though, since the real world is more chaotic than polar equations.

[smj]

Originally Posted by mglonnro

Yes! And it gives a lot of interesting calculations, but is there some way I get the required wind speed for the (cruising loaded) boat to get up to 4-5 knots (in different wind angles) from there?



I'm sure there is a mathematical way to solve this, since VPP diagrams do exactly that. Empirical real world data would be great, though, since the real world is more chaotic than polar equations.

What I like about multihull dynamics is they come up with their performance and stability numbers using factory specs and the factory working sail area. A good comparison of boat to boat.
Once you start addIng specialty light air sails you really can’t get an honest comparison.
Also the one thing left out is the human factor. You could have 15 TPI Lagoon 42’s sailing together with Dennis Conner sailing the one with the oldest blown out sails and a dirty bottom and he may still outperform the others.

[Tupaia]

Originally Posted by smj

What I like about multihull dynamics is they come up with their performance and stability numbers using factory specs and the factory working sail area. A good comparison of boat to boat.

The only trouble with this is that the manufacturers specs are so for off reality or are tweaked for marketing purposes especially displacements; empty, light, half load, waterline, 30hp, 40hp or 50hp engine options, generator or not. Payloads are stated in round 1000's etc etc.



I think MD do a half way reasonable job and their understanding and analysis of various designs is pretty good but given the poor data they have to work with it cannot be regarded as defacto.

[smj]

Originally Posted by Tupaia

The only trouble with this is that the manufacturers specs are so for off reality or are tweaked for marketing purposes especially displacements; empty, light, half load, waterline, 30hp, 40hp or 50hp engine options, generator or not. Payloads are stated in round 1000's etc etc.



I think MD do a half way reasonable job and their understanding and analysis of various designs is pretty good but given the poor data they have to work with it cannot be regarded as defacto.

No doubt, that’s why I said it wasn’t perfect but as close as we may be able to get considering the challenge?

[mglonnro]

Originally Posted by smj

What I like about multihull dynamics is they come up with their performance and stability numbers using factory specs and the factory working sail area. A good comparison of boat to boat.
Once you start addIng specialty light air sails you really can’t get an honest comparison.
Also the one thing left out is the human factor. You could have 15 TPI Lagoon 42’s sailing together with Dennis Conner sailing the one with the oldest blown out sails and a dirty bottom and he may still outperform the others.

Yes, so it is. And, obviously, my summing up/interpretation of the posts in this thread is not pretending to tell the truth about anything.

I'm really interested in the empirical data, however. I think the theoretical estimation game is pretty advanced (with the VPP diagrams and the different comparison indices in multihull dynamics as good examples of his), but the empirical real world research a bit lacking?

And the configuration and human factor should be accounted for also, of course. It would be great to see the polar data of Dennis Conner sailing with a similarly configured boat that I have, in similar conditions

It all gets very complicated, I guess, but that's ok.

[barnakiel]

Originally Posted by mglonnro

I scraped together ROUGH numbers from the posts in this thread. I'm sure I misinterpreted something, but it's easy to fix.

"How much wind is needed to get about 4-5 knots of boatspeed?"

Upwind

Balance 526 4-5 knots
Outremer 5X 5-6 knots
Shuttleworth Advantage 6 knots
Gemini 105MC 34 foot 6-8 knots (?)
Serendipity 43 7-8 knots
Seawind 1160 Lite 8 knots
Hanse 388 8-10 knots
MainCat 41 9-10 knots
Lagoon 400 9-10 knots
Lagoon 42 9-10 knots
Lagoon 42 TPI -93 10 knots


Reaching

Shuttleworth Advantage 4 knots
Schionning Spirited 480 4-5 knots
Balance 526 4-5 knots
Outremer 5X 4-5 knots
MainCat 41 4-5 knots
46’ Custom Cat 4-5 knots
Searunner 38 5-6 knots
Lagoon 42 TPI-93 5-6 knots
Lagoon 400 5-7 knots
Hanse 388 6-7 knots
Gemini 105MC 34 foot 6-8 knots
Lagoon 42 8-9 knots

UPWIND, darling, UPWIND only VMG counts, so speeds without angles are oh I do not know oh I think I can say it - useless.


Or do all those boats are sailing to different targets???


NEITHER can I I see how a Hanse388 can sail 8-10 knots speed upwind. It sounds beyond the boats hull speed, or are you already on the plane?


https://nakedsailor.blog/2019/12/22/...ed-and-polars/



Good effort, but missed at places. Give us VMGs, and come to planet Earth with that Hanse figure.



b.

[mglonnro]

Originally Posted by barnakiel

UPWIND, darling, UPWIND only VMG counts, so speeds without angles are oh I do not know oh I think I can say it - useless.


Or do all those boats are sailing to different targets???


NEITHER can I I see how a Hanse388 can sail 8-10 knots speed upwind. It sounds beyond the boats hull speed, or are you already on the plane?


https://nakedsailor.blog/2019/12/22/...ed-and-polars/



Good effort, but missed at places. Give us VMGs, and come to planet Earth with that Hanse figure.



b.

Thanks for the 'good effort'

1) Yes, VMG, absolutely. Only one person offered their VMG numbers though (in this thread), so didn't have much to go on. But you are right!

2) Our Hanse is among the slowest in that list because the knots mentioned are not BOAT speed, but wind speed required to get about 4-5 knots of boat speed. So most of the other boats get there before we do...

[Dsanduril]

Polars and calculations are all well and good, but for empircal data, you can suss out a lot of information by asking "how much fuel does the boat carry?" A boat that is truly easily sailed in light wind tends, in the real world, to carry less. A boat that doesn't sail in light winds carries more.

Our vessel, as an example, carries enough, in tanks, to motor ~250 miles at optimum usage (that means ~4 knots). If we really expect to motor a lot we can squeeze another ~100 miles into cans. On a 4000 (or even 1000) mile passage that doesn't get you far.

As you putter around a cruising anchorage full of cats it's pretty easy to put together a list of boats on which it is easier to fire up the engine(s) than sail in light air.

For us, drifting along at 75 miles a day is a pleasure in its own right. Not a thrill, but a pleasure.

At the other end, every SoPac anchorage is full of cruising cats "capable of 20 knots" according to the marketing folk and yet I've never had a conversation in any of those anchorages about a 400-mile day. 200-mile days are pretty special. 150 seems typical. A lot of this comes down to sailing shorthanded and the effort and concentration required to handle a boat sailing > 8-10 knots.

[barnakiel]

Originally Posted by mglonnro

Thanks for the 'good effort'


(...)



2) Our Hanse is among the slowest in that list because the knots mentioned are not BOAT speed, but wind speed required to get about 4-5 knots of boat speed. So most of the other boats get there before we do...

a....hhhhh ...


In this case I must say, for many of the listed catamarans, the figures sound as something I would hear at a bar, not at any forum that is serious about boat performance !


Flat water, new sails, empty boat then maybe and only maybe (assuming a skipper who raced in light winds alot before he got himself a Lagoon). But cruising trim ? Ribs and 20hp outboards? Arches full of gear? Genset, aircon and freezer full of red meat and Johny Walker?



They are inflated. The numbers. By owner's pride factor.


b.

[Tupaia]

Originally Posted by barnakiel

a....hhhhh ...

In this case I must say, for many of the listed catamarans, the figures sound as something I would hear at a bar, not at any forum that is serious about boat performance !

Flat water, new sails, empty boat then maybe and only maybe (assuming a skipper who raced in light winds alot before he got himself a Lagoon). But cruising trim ? Ribs and 20hp outboards? Arches full of gear? Genset, aircon and freezer full of red meat and Johny Walker?

They are inflated. The numbers. By owner's pride factor.

b.

The polar I posted was made on passage using OpenCPN. The boat was fully loaded, had 2 RHIBs (lightweight), 2 outboards (again lightweight), complete dive rigs for two, dive compressor, genset (suitcase), tools, spares and food.

The sails were 4-5 year old Dacron and yes it was flat water because there was very light wind the whole point of the thread.

Like dsanduril we have tankage for 240litres that in optimal conditions on one engine gives us a range of about 450Nm. We only ever carry one 20 litre jerry for emergencies and have never needed it.

We are also content sailing 75Nm days, or stopping completely when there is no wind at all and and going for a swim. 190-210 days are common but not guaranteed and our best 24 hours so far is 254Nm.

A particularly relevant factor is that we can both sail and control all aspects of the boat single handed, without leaving the cockpit, so we remain rested on passage.

[tomfl]

Originally Posted by mglonnro

SNIP

And the configuration and human factor should be accounted for also, of course. It would be great to see the polar data of Dennis Conner sailing with a similarly configured boat that I have, in similar conditions

It all gets very complicated, I guess, but that's ok.

I crewed on a boat in the Baja Ha-Ha last year. The lady skipper kept repeating the same story about how she got her nails done at the same place where Dennis Conner had his hands manicured. Not trying to dis him as Conner was a first tier skipper in his prime; but he is in his late 70s now. Even in my early 70s I am no where near the sailor I was when I competed in one design and SORC races.

Maybe Loïck Peyron would be a better choice of a skipper on a multihull; or even a better choice Armel le Cléac’h.

[smj]

Originally Posted by tomfl

I crewed on a boat in the Baja Ha-Ha last year. The lady skipper kept repeating the same story about how she got her nails done at the same place where Dennis Conner had his hands manicured. Not trying to dis him as Conner was a first tier skipper in his prime; but he is in his late 70s now. Even in my early 70s I am no where near the sailor I was when I competed in one design and SORC races.



Maybe Loïck Peyron would be a better choice of a skipper on a multihull; or even a better choice Armel le Cléac’h.

Yes, but I would argue that Dennis Conner is much better known to the masses than the other 2 you mentioned, therefore the point more easily understood.
Also that example was brought to my attention years ago by I believe our beloved tomfl, and if Dennis Conner was good enough in your example it’s good enough in mine!

[KC375]

Originally Posted by tomfl

I crewed on a boat in the Baja Ha-Ha last year. The lady skipper kept repeating the same story about how she got her nails done at the same place where Dennis Conner had his hands manicured. Not trying to dis him as Conner was a first tier skipper in his prime; but he is in his late 70s now. Even in my early 70s I am no where near the sailor I was when I competed in one design and SORC races.

Maybe Loïck Peyron would be a better choice of a skipper on a multihull; or even a better choice Armel le Cléac’h.

Maybe give Peter Burling a try...he has youth and results on his side

[mglonnro]

Originally Posted by KC375

Maybe give Peter Burling a try...he has youth and results on his side

I vote for Jimmy Spithill, Ben Ainslie and the rest of Oracle Team USA to sail the heck out of a Lagoon 42 in light air conditions! Spectacular.