Why a Multihull?

[sneuman]

One thing is for sure - the AC33 races showed that the boats were fast. But from what I could see, the tacking angles were no better than 90 - racing monos would have no trouble beating that. Secondly the tacks were really sluggish, much slower than a IACC mono.

[44'cruisingcat]

So a boat going to windward at around 250% windspeed tacks through 90 degrees....

Any idea what apparent wind angle that would be?

Of course mono's would tack through a smaller angle. That would be because they would be sailing at less than 1/2 the speed. But they would take much longer to reach the windward mark...

Anyway, it's been done, a huge mono was built and raced against a cat 1/2 it's length. The mono was absolutely thrashed.

[bayview]

Originally Posted by 44'cruisingcat

Anyway, it's been done, a huge mono was built and raced against a cat 1/2 it's length. The mono was absolutely thrashed.

So where did all the cruising gear stow on "this" cat?

[Factor]

SAme place the mono did.

What a silly statement.

[hummingway]

I was looking at an ad today for a really big cat - about 120' or something - and it cost 20m so I figured if I saved I could own it like ... never. But still I thought that's cool and then I noticed it had a 9000 litre deisel tank. So I guess what you do is call up your buddy, who is the ceo of imperial oil, and ask him to send around a truck to fill you up cause I'm pretty sure if you pull up to my marina's fuel dock you're not going to get 9000 litres of fuel! Sure glad I don't have that problem.

[rocma]

Originally Posted by sneuman

Or, you could say the big difference is that multis stay flipped and most monos don't.

Having said that, however, I don't think a properly sailed cruising multi is any more likely to capsize than a mono.

I think you should rephraze that Sneuman: a mono is more likely to capsize than a multi AND multis might stay flipped, but will most likely not sink. Whereas the most stable position of a mono is on the bottom of the ocean.

Anyway, I am stopping all this. It will never change: you either pro or con multi's. There doesn't seem to be a grey area.

[44'cruisingcat]

Originally Posted by bayview

So where did all the cruising gear stow on "this" cat?

What on Earth are you talking about? Cruising gear on Americas cup boats?

Is this a natural talent or do you have to work at it?

[sneuman]

Originally Posted by Catcruiser

I think you should rephraze that Sneuman: a mono is more likely to capsize than a multi AND multis might stay flipped, but will most likely not sink. Whereas the most stable position of a mono is on the bottom of the ocean.

Anyway, I am stopping all this. It will never change: you either pro or con multi's. There doesn't seem to be a grey area.

More likely to capsize? Would you like to back that up with evidence or is this more mythmaking?

And of course there's a grey area - I'm in it. I have done as much or more offshore in cruising cats as monohulls. I owned and raced Dart 15s and 18s in Hong Kong. I have stated on this forum numerous times that multis have their advantages.

But, if you prefer to see it in black and white, that's not my problem.

[Jaywalker]

Leaving aside knockdowns, sinking, and racing, all of which I hope to avoid, I haven't seen any mention of the advantages/disadvantages of using outboards, such as http://www.cruisersforum.com/forums/...cat-20760.html .

sandy daugherty: why drag your feet in the water?

1. PDQ 36's with outboards raised are ONE KNOT faster than Diesels owing to the weight of the engines and form drag of the drive leg.

2. Solar panels and wind generators provide battery charging, at much less expense, simpler maintenance, and no fuel to run out of.

3. You can pull an outboard out in the sunshine, fix it with a few hand tools, pat it on its little powerhead and get back under way while enjoying a remote anchorage. Pay yourself whatever you think you're worth, and communicate with the repairman in your own language!

4. Eighty seven percent of all recreational boats in the US are gasoline powered. Insurance companies don't provide discounts for diesel boats. The threat of explosion is overstated, and practical precautions work.


So when do outboards not work for cats?

1. When you can't find them big enough with the features you need, such as shaft length, very low gear ratios, big slow turning props, remote controls, etc.

2. When they cannot be located close to the center of motion.

3. When you need to bolt on extra alternators, hydraulic pumps, refrigeration, etc.

4. When you can't carry enough fuel outside the living compartments to get where you want to go.

That means the practical size limit for outboard powered boats is about forty to forty five feet. "Big Foot" and "high thrust" engines aren't really ideal unless you can get close to a 3:1 gear ratio and have room for 12" or bigger diameter blades. That is why the Yamaha High thrust 9.9s are the almost universal choice. Not many bigger engines have been tried, and while the Yanmar Diesel outboards looked really good on paper and in limited practice, they were heavy, complicated and expensive.
when an outboard ets over about 150# its no longer easy to haul around a moving boat.

I'd love to see some "Down-under" wizzards modify a major manufacturer's 20 to 30 hp outboard to run efficiently at 10 knots, with a max output at 12 knots. That's asking a lot, but its what a light 45' cat would need.

Does this about cover it, or is there something missing? ( I have for instance, noticed a trend towards reports of unreliable outboards, sometimes blamed on the E85 gasoline/petrol.)

[44'cruisingcat]

Originally Posted by sneuman

More likely to capsize? Would you like to back that up with evidence or is this more mythmaking?

It's not mythmaking. For a similar length boat, a catamaran will have around 4 times the righting moment of a monohull.

The wider beam makes it less likely for a wave to capsize a catamaran.
You're unlikely to capsize until the wave height exceeds your beam.

In the Queen's birthday storm, several mono's were repeatedly rolled, losing their rigs, but the cats stayed upright, even after being abandoned.

[sneuman]

Originally Posted by 44'cruisingcat

It's not mythmaking. For a similar length boat, a catamaran will have around 4 times the righting moment of a monohull.

The wider beam makes it less likely for a wave to capsize a catamaran.
You're unlikely to capsize until the wave height exceeds your beam.

In the Queen's birthday storm, several mono's were repeatedly rolled, losing their rigs, but the cats stayed upright, even after being abandoned.

As for righting moment, no one questions that intial stability is greater on a multi. It's that way also for a bundle of logs. Ultimate stability is what's important here for capsizing and we know that a multi's drops to zero much lower on a curve than a mono. I am not saying that means that multis are more likely to capsize - it just means they are less "tippy" under anything less than survival conditions.

The Queen's birthday storm doesn't tell us anything at all here. Since the famous report only cites incidents where Maydays were called in. Because cruising multis were much less common then, it's quite possible that these two were the only ones out there - and they both called Maydays. Most of the monos, on the other, did make it through without calling a Mayday. We might as easily conclude that the report shows that multis had a rougher time of it. Now, I am not saying that, but it is one possible- and equally legitimate - conclusion from that incident.

[44'cruisingcat]

You could speculate all you like - I could suggest that many more monohulls may have been rolled over, but didn't issue mayday calls. That would be just as realistic as what you suggest.

In fact more so, since we actually know those weren't the only two cats in the storm. There was at least one other - "Fallado" which didn't need assistance.

What can be concluded is that a storm which rolled several monohulls didn't roll any multihulls, even though there were at least 3 present. No speculation involved, just a simple statement of fact.

It's also a fact that the wider the beam of a boat, the bigger a wave it takes to roll it over. And that is why a cat is less likely to capsize.

[sneuman]

Originally Posted by 44'cruisingcat

You could speculate all you like - I could suggest that many more monohulls may have been rolled over, but didn't issue mayday calls. That would be just as realistic as what you suggest.

In fact more so, since we actually know those weren't the only two cats in the storm. There was at least one other - "Fallado" which didn't need assistance.

What can be concluded is that a storm which rolled several monohulls didn't roll any multihulls, even though there were at least 3 present. No speculation involved, just a simple statement of fact.

It's also a fact that the wider the beam of a boat, the bigger a wave it takes to roll it over. And that is why a cat is less likely to capsize.

So, what you're saying is that 2/3rds of the multis called a Mayday and only nine (was it if memory serves?) monos out of perhaps several dozen did so? Yeah, I agree you can draw any conclusion you want, which is precisely why that report doesn't inform this debate.

[44'cruisingcat]

You don't seem to undestand the difference between speculation and fact. We don't know how many multihulls or monohulls were there. We don't know what proportion of either of them issued maydays. We also don't know how competent the crews were, of if the maydays were really neccessary.

What we do know is that mono's were rolled, multi's were not. We know that because it is a fact.

[sneuman]

I have read the report. To wit:

Heart Light, a 41-foot Catalac was "catapulted" and "knocked over on one hull" several times.

"They tied off the helm to port and slid sideways down waves. Despite being 'captapulted' (sic) through the air on many occasions and being knocked onto one hull several other times, she endured."

As for the seven monos, the report concludes that:

"had it not been for scuttling or collisions with rescuing ships, six of them would have continued to float. The age-old admonition to never leave a boat until it's underwater would seem as true as ever."

From the report: "Does this mean that multihulls are actually safer in very severe weather than monohulls? We ÷ who own both a monohull and a catamaran ÷ certainly wouldn't leap to that conclusion. After all, there were several other monohulls in the core area of the storm that didn't even issue maydays and survived the storm with very little damage."