Are Performance "Cruising" Catamarans Safe? - by Antares Catamarans

[jmh2002]

Antares Catamarans have posted up a new video which is bound to cause some controversy but also includes some useful discussion, data, and links.

I didn't want to derail other threads so I started a new topic with their video and included the links from the video description.


Have at it!


Are Performance "Cruising" Catamarans Safe? - by Antares Catamarans

Join us as we discuss the pros and cons of performance catamarans and dive into research done by the Univerisity of Southhampton, UK, about why multihulls capsize. Topics covered include catamaran stability, 2021 World ARC performance data analysis, and much more!


Link to catamaran stability:




Link to World ARC results:




Link to Definitions:

 

[jmh2002]

I will note that it is well worth reading through the 'Definitions' which contains a lot more information including all the formulas, plus additional notes.

For example:

III. Stability Indicators

SSpd – Stability Speed:

This figure is an indicator of the wind speed at which the windward hull of a catamaran, or the main hull of a trimaran, will begin to lift. The formula does not take wave action, shortening sail or hiking-out into account. This figure is an indicator of the wind speed at which the windward hull of a catamaran, or the main hull (vaka) of a trimaran, will begin to lift. This formula includes a 40% safety factor for wind gusts but does not compensate for wave effects.

Multihull Designs by John Shuttleworth Yacht Designs, 1998, p. 37.

SSpd. = 8.23805*((0.5*Bcl*Disp*2240)/(SA*HCE))^0.5

The result of this calculation could be used as the first reefing wind speed since it has a 40% safety factor for unexpected gusts.

*** See on Technical page for more on this subject

KSI: Kelsall Stability Indicator

= 13.73(D*Bcl/2SA*Hcl)^0.5

= 13.73(Displacement *half Bcl/SA*Hcl)^0.5


* A Note from Calvin H. Markwood:

Derek Kelsall says this is the wind speed, winds abeam and 100% of working sails or greater, in knots per hour at which the cat is likely to capsize. Many other factors a!ect the actual situation and hence he suggests that these figures are used for comparison of similar types only.

We do not include Hce in the list of specifications on the site, simply because we didn’t think it was important to all potential site users. It is used in the Stability Speed (Sspd) calculation, however.

The data readily available for boats rarely includes mast height, but does include sail area. Thus, I have derived a method to approximate Hce from boat length and sail area. The derivation is included in the article”Analysis and Comparison of Cruising Multihulls.”

The resulting equations are:

For boats up to 40 feet Lwl: Hce = 2/3*(SA/Lwl) + 0.25*Lwl

For boats 40 feet Lwl and greater: Hce = 2/3*(SA/Lwl) + 10

The “40% of mast length + height of mast base above the water” is probably a good way of estimating Hce. If the sail were a triangle, it would be 33%. Given the shape of current multihull main sails, the 40% is possibly a better number. However, as stated above, mast length and height of mast base above the water are not readily available.

 

[jmh2002]

Also of note (even if it's stating the obvious):

Chris White, “The Cruising Multihull”, (International Marine, Camden, Maine, 1997), states that a boat with a BN of less than 1.3 will be slow in light winds, and a boat with a BN of 1.6, or greater, is a boat that will be reefed often in o!shore cruising.

 

[jmh2002]

NB: I'll need to check further, but aren't the (supposedly 'heavy') displacement numbers given in the first table way off?

If yes, that would throw off all the other numbers too.

Not sure where that data has been sourced from, is it from the Multihull Dynamics site?

Multihull Dynamics, LLC – Multihulls by the Numbers

 

[RandallStephens]

“People want performance in their cruising cats now!”

”Do we have any models that fit the bill?”

”No.”

Design new models to give the people what they want, new moulds etc. etc.: costs loads of money and takes years.

Make video questioning safety of performance cats: pretty much free and can knock it out in no time.

 

[Rantifarian]

NB: I'll need to check further, but aren't the (supposedly 'heavy') displacement numbers given in the first table way off?

If yes, that would throw off all the other numbers too.

Not sure where that data has been sourced from, is it from the Multihull Dynamics site?

Multihull Dynamics, LLC – Multihulls by the Numbers

The Seawind 1260 is listed as 18077lbs on the manufacturer website, and Seawinds have consistently weighed in well above the manufacturer specs. The sail area of main and jib according to Seawind is 1014sqft, also well different to the table.
Whole table is worth what you paid for it

 

[Mambo Kings]

Antares Catamarans have posted up a new video which is bound to cause some controversy but also includes some useful discussion, data, and links.


Link to catamaran stability:

I suspect that Balance Cats will be surprised to discover that the waterline length of the B526 is less than the B486.

Whole table is worth what you paid for it

I dont think that @ol70 is going to cancel his order on the back of this startling new information.

 

[jmh2002]

Yeah, it's now clear that the table is a complete mess, which is a pity because the metrics and formulas side of things can be useful.

I threw up the links when I was busy with something else but after I started looking at the displacements noted in the table and even from memory began to think that these numbers just weren't right.

Does anyone have a membership to the Multihull Dynamics site to check if that is where the data has been sourced from - and Antares has just copied this incorrect data across? Or have they made these numbers up themselves?

In any case the devil is always in the detail and they should have cross checked the numbers before putting something like this out in the public sphere.


Antares may well have made complete fools of themselves...

 

[Mambo Kings]

Then look at the calculations done comparing the three Lagoon 42s and their different passage times.
The math is so flawed that you have to ask yourself......would you trust a boat designed by a team who are so number impaired that they verge on mathematically dyslexic?

I dont want to be cruel and I truly respect people who choose volume over performance for their particular needs...but this is a terrible piece of work.

 

[jmh2002]

I dont want to be cruel and I truly respect people who choose volume over performance for their particular needs...but this is a terrible piece of work.

Yes, agreed, terrible.

I'm all for comparisons and discussion, and especially with metrics and data - which is why I posted the video and tables for all of us to pick apart - but this is just a mess and will no doubt reflect very badly on Antares.

In fact the more one looks at all the provided data the more it looks like an epic fail

 

[Mambo Kings]

Somebody needs to save a version of this video before it is taken down,
Surely this ranks up there as one of the most embarrassing sailing videos of all time. Pure unintended comedy. Reminds me of the Monty Python sketch about Australian wine.

But if you want a multihull video that was genuinely tongue in cheek....check this out.

 

[jmh2002]

Somebody needs to save a version of this video before it is taken down,
Surely this ranks up there as one of the most embarrassing sailing videos of all time. Pure unintended comedy. Reminds me of the Monty Python sketch about Australian wine.

But if you want a multihull video that was genuinely tongue in cheek....check this out.

Yep, already downloaded...

(this is the tool I used if anyone needs it: https://en.savefrom.net/383/)


And yes, already watched the Outremer video when it came out. I was surprised that it provoked some negative reaction. I thought it was absolutely brilliant. Some people clearly have no sense of humour. Given that it was Women's Day it seemed clear to me that Outremer were taking the piss on purpose ('le piss take' ?).

Well played to them for trying to raise a worthwhile topic without being boring and dry about it

PS: I guess those who were upset may not have read the video description from Outremer:

Sailing, A Woman’s World: Outremer turns tables for International Women’s Day

Outremer is proud to support women in sailing, and has launched a campaign to celebrate International Women's Day and the ongoing success of its dedicated "Ladies Only" programs. The campaign features a short series of entertaining videos that looks at men and women in sailing, and the biased narratives that sometimes exists between them.

The videos humorously deflect the socio-cultural prejudices that women can face in the world of sailing: women often excluding themselves in certain situations.

Thank you to our clients that accepted to be in this video

 

[smj]

Yeah, it's now clear that the table is a complete mess, which is a pity because the metrics and formulas side of things can be useful.

I threw up the links when I was busy with something else but after I started looking at the displacements noted in the table and even from memory began to think that these numbers just weren't right.

Does anyone have a membership to the Multihull Dynamics site to check if that is where the data has been sourced from - and Antares has just copied this incorrect data across? Or have they made these numbers up themselves?

In any case the devil is always in the detail and they should have cross checked the numbers before putting something like this out in the public sphere.


Antares may well have made complete fools of themselves...

I checked Multihull Dynamics and they pretty much accurately quoted their site except for the Antares 44 lwl/bh which they have as 11.2 but is actually 9.2, how convenient.
I’m guessing the Mulitihull Dynamics site is of on the Balance 526 as it also stats loa at slightly over 47’.
If anyone is seriously looking to purchase a cat I can’t see why they wouldn’t shell out the yearly $12 and become a member of MD. I guess their info isn’t always correct, and a lot of the info has been gained from the builders so should be taken with a grain of salt.

 

[ol70]

I suspect that Balance Cats will be surprised to discover that the waterline length of the B526 is less than the B486.


I dont think that @ol70 is going to cancel his order on the back of this startling new information.

Canceled this morning...I wish someone would have explained to me earlier that I picked the Corvair of catamarans. Unsafe at any speed! LOL.

 

[SSolo]

IMHO this is one of those 'esoteric' conversations that are worthless.
if you are pushing HARD when racing or being plain stupid then you can capsize any multihull but usually there is significant contribution of human error / over confidence involved allowing the boat to be overpowered leading to a capsize
As i said on 'how to keep your multihull upright' thread have a reefing plan and stick to it. It is simple.

If you want to take on the racers, practice practice practice.. but don't believe you can balance a boat on one hull as well as they can, without lots of practice

I used a beach cat in my early multihull days and sailed like a insane nutter in club races, until I could reliably balance it right on the limit... then I applied that skill and knowledge to racing the offshore boats
even then i have flipped a few times... each time, it was my error that was the major factor

 

[MultiThom]

It is best when viewing pretty much anything on line (political, advert, performance....) what is said about figures and statistics. "There are lies, damned lies, and statistics." "Figures don't lie, but liars figure" Yah, my name is Thomas and I do doubt everything.

 

[smj]

So what’s safer, a lightweight performance catamaran making 8 kts boat speed in 20kts of wind with just a 300sq ft roller furling jib up, or a heavy catamaran making the same speed in the same winds with over 1000sq ft of working sail flying?
i know which cat and crew will have less stress on them.

 

[socalrider]

What a dumb video. Just because you have a lot of sail area doesn't mean you have to use it all. If you re-ran the calculations with a reef in for the performance cats you could equalize the stability numbers.

Reminds me of arguments in the motorcycle community, with Harley guys saying their bikes were safer because they were heavy and underpowered.

Edit: Just to be clear, there are plenty of reasons *not* to go with a performance multihull, just like there are plenty of reasons to enjoy a Harley. But the inherent safety argument is not a good one.

 

[smj]

A good read.

Considerations for Seaworthiness

Yacht Designs. Safety at sea, construction, seaworthiness, Multihulls, Catamarans, Trimarans. Sail. John Shuttleworth, Capsise, stability, performance, racing, cruising

shuttleworthdesign.com

 

[PIL66 - XL2]

IMHO this is one of those 'esoteric' conversations that are worthless.
if you are pushing HARD when racing or being plain stupid then you can capsize any multihull but usually there is significant contribution of human error / over confidence involved allowing the boat to be overpowered leading to a capsize
As i said on 'how to keep your multihull upright' thread have a reefing plan and stick to it. It is simple.

If you want to take on the racers, practice practice practice.. but don't believe you can balance a boat on one hull as well as they can, without lots of practice

I used a beach cat in my early multihull days and sailed like a insane nutter in club races, until I could reliably balance it right on the limit... then I applied that skill and knowledge to racing the offshore boats
even then i have flipped a few times... each time, it was my error that was the major factor

100%

What a dumb video. Just because you have a lot of sail area doesn't mean you have to use it all. If you re-ran the calculations with a reef in for the performance cats you could equalize the stability numbers.

Reminds me of arguments in the motorcycle community, with Harley guys saying their bikes were safer because they were heavy and underpowered.

Edit: Just to be clear, there are plenty of reasons *not* to go with a performance multihull, just like there are plenty of reasons to enjoy a Harley. But the inherent safety argument is not a good one.

There are no reasons to enjoy a slow, heavy HD (Hardly Drivable) bike.... lol
I've had them and it's a scene..... Try BMW GS 1250 and it's like someone turning the light switch on.......... Thank F#ck we are all different..... Check out "Million Dollar Bogan" on youtube if you like Harleys. He takes them places they shouldn't go

Great video @Mambo Kings .....