Surprising results looking at Catamaran Performance Numbers

[rexripley]

I'm planning to buy a cruising catamaran this year, with the goal of starting a circumnavigation in 2023, after spending 2022 training my crew (family). I'm moving from a monohull, mostly weekend racing, background.

So I've been doing research on every catamaran I can find, and trying to resolve the apparent conflict between "condo cats that can't sail" and "performance cats with no accommodations."

I considered the possibility that a larger, older cat might be a good solution. After all, the DLR of a given brand stays the same across the line.

So if you determine you need a base speed of 10.5 knots to have the weather routing safety margin necessary, then you can get that with a slow boat -- eg, high DLR and low SAD-- that is just longer.

So, for instance, a Christ White Atlantic 42 has a base speed of 10.73 but is limited in accommodations, while a Leopard 50 with possibly too much accommodations has a Base Speed of 10.65. These are close enough to be worth the tradeoff.

What I realized is that there doesn't really need to be this tradeoff. It is possible to have hulls that are neither obese nor anorexic.

But it appears that the market has mostly bifrucated-- Outremer is making the 55 and Catana is making the 51, which are performance cats with a cruising approach, but they are too new (I'm looking to buy used.)

But I did find one brand that does surprisingly well in this by-the-numbers comparison.

And that brand is Bali. Their hulls are slim (though I'm just looking at Base Speed, SAD and DLR) and their accommodations are clearly charter oriented. But by the number these do well.

One other consideration that doesn't play into these theoretical discussions is availability. A Outremer 55 might be the perfect boat, but for many people it is out of their budget and not available for 12-18 months assuming they can afford it.

I believe a large part of the reason people are buying charter cats is not just because they can afford them, but because they are available. They are clearly produced in much larger numbers.

Anyway, I have my reservations about Bali and am leaning towards another brand, but they really did hit the compromise on accommodations and performance that most others have missed.

[rexripley]

Here's a screenshot of the spreadsheet:
https://imgur.com/a/6IQVPn4

[Tin Tin]

Where did you get that data from? The website multihull dynamics gives the base speed calculations for a number of cats and they are different to yours.


You want a faster than average very comfortable boat - older Lagoon 500. Has the waterline advantage over most fin keeled mid 40fters. Of course not quite as fast as a 45ft Outremer but carries twice the load.



This is all good in theory, the problem is what happens in practice in real life crossing oceans. Seeing you are a spreadsheet guy, get the results of the ARC rallies across the Atlantic, both ways. Then divide elapsed time (not handicap time) into the miles traveled for all the different cats and see what the answers are as average speeds, many will be below your target. The engine hours are also there to make adjustments.

[NevilleCat]

Pretty hard to find any affordable boat that would be able to average over 10kn realistically on any sort of passage with varying weather conditions. That would assume many miles of speeds in the very high teens etc. Certainly we've all had great sails where that seems achievable but does anyone actually do a loaded passage plan expecting a 10kn average?
Actually that would be an interesting thread...what passage speeds folks work on...after all with Predict wind etc it can be make or break with planning to get over a weather event etc. How accurate have your Polars proven?
10+ kn, maybe if you could find a cheap Chris White Hammerhead 54 tri.....but I'm prepared to be surprised.

[fivecapes]

Originally Posted by rexripley

Here's a screenshot of the spreadsheet:
https://imgur.com/a/6IQVPn4

You need to dig a little deeper and go beyond the surface.


eg. you've used max upwind sail areas for all the Bali's when the others are using working jib areas.
ie Bali 4.8 upwind sail area is only 118m2, not 179m2

[Palarran]

It's useless to look at that chart without the price being in the first column. It's always been the same and there is no change now, low price/comfortable/fast - pick two.

[fxykty]

Originally Posted by NevilleCat

Pretty hard to find any affordable boat that would be able to average over 10kn realistically on any sort of passage with varying weather conditions. That would assume many miles of speeds in the very high teens etc. Certainly we've all had great sails where that seems achievable but does anyone actually do a loaded passage plan expecting a 10kn average?
Actually that would be an interesting thread...what passage speeds folks work on...after all with Predict wind etc it can be make or break with planning to get over a weather event etc. How accurate have your Polars proven?
10+ kn, maybe if you could find a cheap Chris White Hammerhead 54 tri.....but I'm prepared to be surprised.

There’s a reason that 200 nm is an offshore passage target that not many cruising boats can consistently achieve despite only needing 8.3 knots average. You needs lots of waterline and decent sailing qualities, you want a boat that can easily sail in the mid-teens, so that you can be reefed down and sailing comfortably without fear nor pressing the boat.

The easiest way to get decent speed without blowing money way up is to decrease accommodation space (that does not need to mean less comfort, as any tiny house and smaller boat aficionado will attest) and add age. With fibreglass boats the consumables all have a 8-20 year replacement cycle, so you can easily go 10-15 years or 25 years old hull for similar refit cost as a younger hull and much less money than new or near new.

[Fore and Aft]

Rexripley I wonder why I don't see these Bali cats or other cats dominating the local sailing races?
No doubt some of these cats can do your 10 knot average but I would be prepared to rip out the interior, get used to eating dehydrated food and sleeping/living on a bean bag.
I have seen the Leopard cats hull thickness and nothing about it says speed to me.
Cheers

[Dave852]

On our St. Francis 50 “Ovive” we had some 240 mile days but it always averaged out to 200 mile days once you accounted for all weather conditions over a 3 to 15day passage. So 8 knots. Some days faster than others. https://youtu.be/WFqm48C2BPk

[Simon.Sails]

There should be much more data collection and sharing by cat owners. The available data from ACR races and anecdotal evidence just isn't enough.

[Heath68]

Following

[django37]

The weights and sailareas given by designers or boatbuilders are not usefull in such calculations. We (designers and boatbuilders) are all optimist with weights - some more than others, and sailareas are given/measured differently. Use result from weighed and rated boats, or use results from many races - yes not only the ARC. I have an Excel file with 98 cruising cats in 39 races, but its 498 kb, so it cant be uploaded here

[UFO]

Originally Posted by Dave852

On our St. Francis 50 “Ovive” we had some 240 mile days but it always averaged out to 200 mile days once you accounted for all weather conditions over a 3 to 15day passage. So 8 knots. Some days faster than others. https://youtu.be/WFqm48C2BPk

Very Nice to average 200miles per day Even on my best day I only ever hit 190 and averaged out over an 8 day passage 150 Miles per day, But the Lagoon 440 is not renowned for speed, but even in 43 knots and a 7m swell (downwind) I could still brew coffee with the peculator which barely stood on the gas ring

[Dave_S]

It's an interesting conversation.

I look at Roam a Spirited 480 and they aim to average 200nm days, sometimes they do better, sometimes not but sail with a fair pinch of reserve.

The temptation must be, with more accurate weather windows, to pick a safer more comfortable run. I'm sure if they needed to out run weather they could pick up the pace.

I've imagined, when my day to cross oceans comes, I would look for a window without any motoring but long enough to sail in light winds for some part of it. So I think the ability to make meaningful ground in light winds may be equally important.

[Dave852]

Originally Posted by UFO

Very Nice to average 200miles per day Even on my best day I only ever hit 190 and averaged out over an 8 day passage 150 Miles per day, But the Lagoon 440 is not renowned for speed, but even in 43 knots and a 7m swell (downwind) I could still brew coffee with the peculator which barely stood on the gas ring

I hear you about the coffee, we are on our third cat and could never go back to Rolling downwind.