Stabilised mono hulls/ or catamarans?

rustybarge

rustybarge

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Hi all,
Just read Mby dec. issue, reviewing stabilisers for mono hulls. Zero speed fins cost about £96,000 fitted. Gyro's about half that much.

Why? Who can afford to run their 40' cruiser at 20kts, costing £700 to go 100nm.(1 mpg). Because fuel has gone up 5* in the last decade, even if you are multimillionaire, it would be impossible to justify that sort of expenditure.

Hence Wally's new 86' displacement super yacht, costing £5m, but capable of returning 2.3mpg at 8kts........wow. (12kts max)Twice the length, half the consumption. It is fully stabilised to stop sick inducing rolling.

Me, I'm a normal mortal, looking at boats in the 10 mtr range. So how is the ordinary boat that planes at 15 kts going to behave at 8 kts? I guess it's going to roll a lot.

Cue Bright idea.......How about a 10 mtr catamaran. Doesn't need stabilisers. I've always wondered why catamarans are so unpopular.

The Rnli don't use them, so maybe their sea keeping isn't great. the very latest lifeboat just off the plans, is a Shannon class boat, water jets, mono hull.

Can anybody answer this question...what's wrong with cats?
 
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rustybarge said:
Hi all,
Just read Mby dec. issue, reviewing stabilisers for mono hulls. Zero speed fins cost about £96,000 fitted. Gyro's about half that much.

Why? Who can afford to run their 40' cruiser at 20kts, costing £700 to go 100nm.(1 mpg). Because fuel has gone up 5* in the last decade, even if you are multimillionaire, it would be impossible to justify that sort of expenditure.

Hence Wally's new 86' displacement super yacht, costing £5m, but capable of returning 2.3mpg at 8kts........wow. (12kts max)Twice the length, half the consumption. It is fully stabilised to stop sick inducing rolling.

Me, I'm a normal mortal, looking at boats in the 10 mtr range. So how is the ordinary boat that planes at 15 kts going to behave at 8 kts? I guess it's going to roll a lot.

Cue Bright idea.......How about a 10 mtr catamaran. Doesn't need stabilisers. I've always wondered why catamarans are so unpopular. The Rnli don't use them, so maybe their sea keeping isn't great.

Can anybody answer this question...what's wrong with cats?
Click to expand...

Nothing but they still roll, and have a motion which does make some people sicker than on a mono.
 
Hi maxi,
Aaah, I didn't know that. I was told they pitched more than a monohull because there is very little bouyancy in the forward sections of the hulls.

How do you like Portugal...I've been to Traviera lots of times.......pretty unspoilt and the ria formsa is amazing place to keep a boat.....fantastic beaches as well.
 
Hi rivonia,
What sort of fuel economy do you get at say 8 kts? Do you get a quasi rolling movement like maxi says? Does your cat handle short chop?

I' m on a live aboard as well..........18mtr barge on river mooring, but I want to go to sea!
 
I have 18000 miles on the log of my cat. I'm so used to its motion that I get sick on a mono. It's not worse, just different. Women tend to prefer the no-heeling aspect. In an anchorage with a little swell rolling in, the cats will move a little as a wave passes under them whereas a mono can build up a rhythmic roll.

Research has shown that any vessel can be capsized by a breaking sea from the beam where the height of the sea is >= the beam of the boat. My 23 ft beam puts me at a distinct advantage. Capsizes tend to occur through over-confidence and pressing on in heavy weather. Tris tell you when they are over-pressed but the signs are harder to spot on a cat and can result in inexperienced skippers carrying sail too long. It has been said that in a cat you should reef for the gusts while in a mono you reef for the steady wind.

The RNLI take self-righting in extreme conditions very seriously. Cats are very difficult to self-right but then very few modern monos are equipped with RNLI style self-righting equipment. The capsize scenario is the one that multihull sceptics latch on to but realistically it is no more of a bogey than sinking for a ballasted mono. A 2" diameter hole below waterline admits more water per minute than any bilge pump can cope with and if it is in an inaccessible area where it can't be plugged it is terminal. A leak on a cat is not life threatening (inconvenient and messy of course) as the boat isn't going to sink.

Fuel economy: I get 7 mpg at 8.5 knots (2.5 litres per hour from each engine). Probably 12+mpg at 6 knots.

The biggest reason, apart from the perception of capsize risk, that people don't buy multis is the cost of parking. In the Caribbean they are overtaking monos in popularity. Capital cost of the boat is pretty comparable to the cost of a mono of the same speed and accommodation.

Incidentally, a capsize is not as terminal as everyone assumes. Self-rescue is possible if pre-planned but is pretty difficult. It is not necessary to have a humungous floating crane, an inverted cat can be righted by another boat of comparable size if you know the technique.
 
rustybarge said:
Hi rivonia,
What sort of fuel economy do you get at say 8 kts? Do you get a quasi rolling movement like maxi says? Does your cat handle short chop?

I' m on a live aboard as well..........18mtr barge on river mooring, but I want to go to sea!
Click to expand...

Hi,
To do 8 knotts with engines on we would have to do 2500 rpm's and that would use 2lts of fuel per engine per hour If motoring we usually only motor at 1500 to 1700 rpm and get a return of 1.5 ltrs per hour at 5knotts.

Very economical We have VP MD 2020 engines.

Peter
 
rustybarge said:
Hi maxi,
Aaah, I didn't know that. I was told they pitched more than a monohull because there is very little bouyancy in the forward sections of the hulls.

How do you like Portugal...I've been to Traviera lots of times.......pretty unspoilt and the ria formsa is amazing place to keep a boat.....fantastic beaches as well.
Click to expand...

Because the amount of roll is limited by the shape you feel the pitch more in a catamaran. Basically if you float a box on a liquid and disturb the surface of the liquid the box will be disturbed. The motion of the box varies depending on the shape of the box and other outside influences such as sails.

Portugal is very nice and I am looking forward to getting back next week. We live inland and find it very comfortable, the locals are very friendly and Mrs Maxi feels quite safe there on her own.
 
Hi Snow,
Thanks for v.usefull info. I'm guessing your cat is around 20mtr with a beam of 23', thats fantastic fuel economy, 7mpg is about 1 euro a nm, (at inflated med. prices)
It means that you can actually make seapassages instead of sitting in a 'floating weekend cottage' 'cos the running costs are so high at 20kts.

Rivo's consumption figures also match up......I like the idea of wafting along at 1500 revs sipping diesel!

The purchase price of new cats does seems to be about 50% more than equivalent monos, but then you're getting two hull instead of one.

Next question for me is sailing or motor cat.
 
Hi maxi,

I tried out a motorcat in the Iow , and was very impressed with the soft ride. Main prob. Was that it had outboards, where do you get petrol in a marina? Long walks with jerry cans is a bit off putting.

I did notice the different motion straight away, even at rest. I reckon it's far superior to a rolly-polly monohull at displ. Speeds.
 
Oh you silly saussage... the gulf between MoBo's and raggies is nothing as that betwixt Cat people and dog,,,,, sorry mono, people... you have opened a can of worms...:D

It is interesting to note that almost all workboats used to move people to and from the various windfarms around the East Coast are Cats... most have jet drives and are made of aluminium.. They have to work in all weathers when needed ..The Dutch pilots also use them... .. So I am guessing that powered cats are pretty good... Now when it comes to sailing cats....!!!

Not that I am biassed...(see my profile:))
 
Hi tomahawk,

I guessed from your profile that you sail a cat, but one would imagine that the workboats that service the wind farms would be sail boats, for purely ecological reasons.
It would make very interesting training tacking around the pylons.

Maybe the 2016 Olympic team should train on the new wind farm off the needles.

But seriously, is your cat better than an equivalent monohull?
 
There isn't really an equivalent mono to our boat. Nearly all boats fall into two categories.. racing and cruising.. The cruising types go huge on luxury with sailing performance as an afterthought... The racing jobs are stripped out with minimal inside fit and need a big crew to make them go...(as well as keep them upright). You vey rarely find comfortable boats that sail fast with lively performance but do not need a big crew...

I suppose ours is the sailing equivalent of a sports car.. We have to keep weight down and it is small inside compared to other cats of the same lenght. but she sails very well and with deep daggerboards points well and at 40 feet the rig is not so big as to need superman to handle it...

The biggest difference between a mono and a cat is what I call twitching... They pitch fore and aft with a short rocker movement.. then you get a double twitch as waves pass from one side to the other... Of course there is the pleasure of your wine always being where you left it when you tack:):)
 
Thanks for all that info. It's exactly what other cat owners have told me. Given that all engineering solutions are a massive compromise, I think would prefer twitching To heeling or rolling. Landlubbers are quoted as saying ' going very slowly heeled over at 45* , soaking wet and coughing up your guts doesn't sound like much fun'

Do you find that marinas charge a surcharge because you're a cat.....+ 50%?
 
cat surcharge?

Somem marinas do
Some don't.. I nave not yet found a global rule..

However another nice bit about a cat is that you have space to carry a decent tender and it is very easy to deploy it and recover.. If you go for a more cruising type you can carry the weight of generators so you don't really need to be in a marina...
 
Hi Rusty

we are also Cat people... our first sail boat is a Gemini 10.5, and like Tomahawk are on our way to the med!... Small world!

We had motor boats for 15 years before deciding to take a couple of years out and travel to the med.... no real experience of sail boats of any sort, but doing a bit of research and looking at loads of mono's came to the decision that a Cat was probably the best compromise for live aboard...

We chose the Gemini based upon level of comfort vs size vs supposed performance ( bear in mind our last boat was a 33ft power boat with twin 275Hp any sail boat was going to be a bit slower :-) ) vs condition vs what we had to spend!

I have to say we are very pleased we went down the Cat route... The Gemini's are built to a price, but the accommodation we get on a 35ft cat is great... starting with a queen sized bed and a full sized fridge and a hammock seat at the back... performance given our very limited experience seems good, if F4 and 5s we seem at least as fast as similar sized mono, maybe even a bit better, especially if the wind is on or behind the beam.... and its great being able to slide past a 38ft mono sitting down with a nice cup of tea watching the mono boys sitting glumly on the rails... Still to be fair my mono mates say I don't get the same level of "feel" pounding up wind... no idea what they mean.


Another nice thing with our Gemini is that for a Cat is is narrow at 4.3 meters. beam, this has allowed us to cruise along the Midi on the way to the med... something that a barge boy like yourself might appreciate?

best of luck with whatever you decide to do

Stu
 
Monos generally look prettier, and i would have though it easier to build a bombproof mono with self righting than a cat with that sort of ability. However, tomorrow i am off round the Cape of Storms in a cat on which i'v done bout 70,000nm so er, let's hope it's ok
 
Hi stu,

Have a look at these cat designs from Nz for home building in alloy......10m*4mtrs. I'm going to stick with Diesel engines. From info on this blog most 10-12m cats seem to get around 7mpg at 8kts, works out as cheap as sailing.








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Ever considered a trawler yacht - at 14M LOA, we run at about 6.5 to 7 knots, consume about 1.5 gals/hour in calm water and about 2gals in rough. We have enough range for over 3000NM so only buy fuel at the right price i.e 50-80 euro cents a litre. For stabalizing we have sails to ease the motion and/or flopper stoppers (which also work at anchor).
It works out more economical than sailing and when the weather gets yukki, we shut the wheelhouse doors.
www.lesbirdsnest.com
 
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