Catamaran vs Monohull... advantages, disadvantages?

[Tupaia]

Originally Posted by double u

as expected the "discussion" has heated up!
It would be well if we agreed on the parameter by which we compare cats & monos!
LoA?
Displ.?
payload?
PRICE?

(& boatie, your mentioning "Cooking Fat" as an example is highly demagogic, as you well know! You would have to add where the name come from...

You missed one : Engine Hours?

[letsgetsailing3]

Is there somewhere a list of objective preferences, and which is better based on those preferences?



Because this is all about those.


This really is no different from the Bene/Cata/Hunt vs old school threads, where everyone advocates for whatever it is they currently have. Which kind of makes sense, as you've made a choice and put your money down already.


It's also like the "my car is better than your car" threads in the car forums.

[valhalla360]

Originally Posted by double u

agreed! one can sail the cat into one, the mono into the other- rather difficult...

Depends on the cat. Most are pretty hard to sail into a capsize outside the more extreme performance models.

Of course, broaching in a following sea and filling the cockpit is far more common with monohulls but as mentioned...it's a silly argument. If you are half way competent in a properly maintained boat, both situations are extraordinarily unlikely.

If there is a difference, an upside down cat makes for much better internet fodder than an open sea with a monohull on the bottom out of sight.

[AuChante]

How big to waves have to be to flip a boat? From what I gather from watching boat fail videos is that there are two failure modes.

1: The bow submarines into a wave: Conditions are exponentionally worse than the boat is designed for.

2: a near-breaking wave lifts and flips the boat over: The boat is just too small.


It seems like everyone is worried about the boat surviving a "level 10" see, but debating the seaworthiness of "level 7" and "level 8" boats. When someone mentions a flipped cat, I'm imagining that either the captain was asking to be flipped (not reefing when the most boat-illeterate person would want to reef), or it was out in torential seas that only the most seasoned sailors in the most bulletproof boats would have survived... Of course I have no idea what a typical rough sea is out there.


On the other hand, I do know that on my beachcat in high wind and sea, flipping was catastrophic and sudden. Can be cruising along, seemingly fine, then everything is upside down. Of course that was the goal with that boat. I loved sailing on that line.

[chrisr]

Originally Posted by valhalla360

If there is a difference, an upside down cat makes for much better internet fodder than an open sea with a monohull on the bottom out of sight.

if only due to the fact that a floating upside down cat is something for the media to show on tv, where as a sunken mono is just...waves

cheers,

[Tupaia]

Originally Posted by chrisr

where as a sunken mono is just...waves

cheers,

And, sadly nobody to tell the tale.


I personally know of two who were never found.

[Spokey Doke]

So lots of folks think cats are a bad choice for big seas/weather...lots of cat folks say "no", or "it depends on the cat"

Fair enough...

So if we are open to the idea that cats can be a fine choice in serious waves/weather at sea...what are the primary characteristics of a cat that is particularly good in this context?

[chrisr]

it was explained to me once (by a chap who has done 4 america's cups) that the ideal cat needs to be able to plane sideways

ie when hit by a big wave the boat is shoved away without resisting / tripping over. this i think is the essence of the difference...mono's fight the ocean...cats just bob around waiting for conditions to improve

cheers,

[donradcliffe]

There is no clear cut answer; what you are getting is both mono and cat owners justifying their purchases.

There are several categories of cats. One kind is go go fast on, and another is to take you and your toys safely over oceans. With higher performance you get less safety and less load carrying capacity.

If you want to go fast on weekend afternoons and stay within VHF range of rescue, get a performance cat and you will not be bored.

If you want to cross oceans and sleep well off watch, get a mono or a condo cat.

The mono will buy you a lot more boat for the money.

[Tupaia]

Originally Posted by donradcliffe

If you want to cross oceans and sleep well off watch, get a mono or a condo cat.

The mono will buy you a lot more boat for the money.

Completely WRONG. A performance cat with boards has significant advantages over its keeled condo siblings when crossing an ocean.

Firstly it will be less exposed to heavy weather with faster passages and even the chance of outrunning storms in certain conditions.

In heavy weather a lightweight performance cat with boards up can simply lay a hull sliding sideways if hit by breaking waves. A heavier cat with keels is much more uncomfortable and could conceivably trip over the leeward keel especially if it has a high freeboard and multi level coach roof as is the case of condo cats.

A cat with boards can use their adjustable nature to balance the boat when fore reaching, the multi equivalent of being hove to. Such an adjustment is not available to cats with fixed keels making it much less stable.

Running downwind in heavy seas in front of a storm a cat with boards up will remain under control, even under autopilot because the CR is very far aft by the rudders and there will be little or no tendency to broach. The rudders acting like a drogue. A keeled cat under similar conditions particularly if the rudders are small can be prone to doing a 180, multi equivalent to a broach, around the keels if the rudders are small and cavitate at the top of a wave crest. Putting it broad side to the wind and waves during the turn. A condo cat is more akin to a mono under similar conditions that must relay on a drogue to maintain steerage. The cat even with keels will still benefit over the mono as it will ride on top of the waves rather than suffer being pooped but at the same time will present huge bluff transoms to the full force of the waves if it stops in a wave trough. Good seamanship would require deploying a parachute sooner rather than later.

A good performance cat will enable you to keep sailing in all but the most extreme conditions when laying a hull or deploying a parachute would be a last resort.

Completely RIGHT monohulls are cheap to buy. A cat is more expensive a good performance cat is very expensive.

[malbert73]

Originally Posted by donradcliffe

The mono will buy you a lot more boat for the money.

Not really. Only if you are comparing by LOA. Like I’ve said comparing a 40 foot cat to a 40 foot mono is completely invalid.
It would be like me bragging to an owner of a 30 foot mono how much better/bigger/more comfortable my 40 foot mono is.

Cats are “bigger” boats LOA per LOA- and that includes price. Side by side comparisons by build quality, age, and price yields much longer monos and then the difference is less about better/worse but rather about “different”

very few people downsize cruising yachts and that’s probably one reason folks stay in catamarans from monos- because they universally all have upsized in switching. The other one is lack of heeling which is the only clear cut winner in this discussion.

[fxykty]

Originally Posted by Spokey Doke

So lots of folks think cats are a bad choice for big seas/weather...lots of cat folks say "no", or "it depends on the cat"

Fair enough...

So if we are open to the idea that cats can be a fine choice in serious waves/weather at sea...what are the primary characteristics of a cat that is particularly good in this context?

One that has prioritised design for sailing performance rather than for accommodation.

Very rare these days, but rather more common in designs from the 90s and early noughts. Other than the self build plans from several Australian designers there aren’t many examples in the current crop of ‘performance’ cruising cats - many of the production and semi-custom performance cats have become too heavy and have too large rigs to compensate.

The reality of a well-sailing cruising cat is relatively limited load capacity. That’s a trade off that not many are willing to make, hence the lack of new boats that sail well without needing clouds of sail.

[Simi 60]

Originally Posted by fxykty

The reality of a well-sailing cruising cat is relatively limited load capacity. That’s a trade off that not many are willing to make, hence the lack of new boats that sail well without needing clouds of sail.

And why we went with option 3

Comfort and load carrying ability were not being given away
And a cat that spent a lot of time motoring to maintain 7.5 knot averages in light air seemed a pointless and expensive proposition.

The powered cruiser can often be bought for a lot less coin and savings pays for a hell of a lot if not a lifetime of fuel.

[conchaway]

Here's the TRUTH-- In a monohull, in a storm, you'll "rock and roll' but if you get knocked down, you'll come up. In a "Cat", if you go over, you STAY over.

[Tupaia]

Originally Posted by conchaway

Here's the TRUTH-- In a monohull, in a storm, you'll "rock and roll' but if you get knocked down, you'll come up. In a "Cat", if you go over, you STAY over.

You will of course know that a modern broad beamed monohull has a righting moment circa 35% which means if she is rolled will have considerable negative stability so is very unlikely to come back up and unlike a cat will sink because of the big chink of lead.