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Old 16-02-2011, 15:10   #1
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Ocean-Going Catamaran Size and Bridge Deck Clearance

I'm a tall guy and currently looking for a catamaran to cross oceans.

Firstly, I had a look on a 35' Wildcat. Impressive, huge beds, sufficient standing headroom, great layout (only some space for the workshop is missing.
Downside, low bridge deck clearance and limited storage, not too much payload.
Good second hand prices due Charter Cat South Africa is out of business.

Secondly, a 36' and a 40' Dean, Impressive huge salon and cockpit, again workshop is missing and similar downsides for much more money.

Thirdly, I learned that bigger and more beam is safer. Beside that room and payload is much more and getting used ones doesn't cost a fortune more although I'm aware that maintenance will be much more.

Fourthly, a Prout Quasar Espace 49 (the one with close to 24' beam). Decent
salon with galley up, queen size beds, room for workshop, engines more a midships, solid and proven design. Downsides, engines not very powerful.
However, I couldn't find bridge deck clearance. Somebody knows?

Fifthly, CPA Cataclub 48. Huge salon, 3' more beam than the Prout, tons of overhead bins and lockers, one electric winch for the huge main.
Downside low bridge deck clearance from 2'4" to under 2'.
Current owner circumnavigated.
However, I couldn't find nothing about Multicoque Diffusion the French builder,
but I was told it is hand layed up fiberglass with Airex foam above the waterline and although 16 years old no signs of delamination obviously a good job and the reason that they seems to be no longer in business.

Finally, the first two boats - both ocean proved - are less than 150k and the second two are under 240k and ocean proved of course.

I'd like to learn about the importance of bridge deck clearance and safety of bigger catamarans. A friend of mine -a live aboard - told me that he never experiences bad weather on his 46' Privilege and asking him why, he said I'm sailing away always! Another plus of a bigger cat - or?

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Old 16-02-2011, 15:58   #2
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A good read on bridge deck clearance.

Bridgedeck Clearance Catamaran Concepts

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Old 16-02-2011, 16:33   #3
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I will paste this from a previous post:
With any multihull you need to bear in mind its true pros & cons.

In cats, I feel that you need at least enough wing clearance to drive your inflatable through the wing tunnel, (ducking of coarse), a low cabin and center of gravity, and full visibility forward when under sail... IF you want a true blue water boat that can carry a load and be driven to windward.

If one is content with protected, and/or carefully chosen downwind cruising, then the wing clearance can be a bit less, but you still need to see where you're going... The Catalac may be right for you, but these are things to bear in mind in your search.

For "serious" cruising, the less accommodation the better, if it buys you more wing clearance, better visibility forward, and a low COG! Many custom "one offs" were built to a better design.


PS... for crossing oceans, Here is an example of a seaworthy small cat. My Australian friends had this small flush deck 28'er extended to 32', and had a light weight cabin added with 4' 6" head room. With a roller furling boom, keeping the boat light, and a lifetime of sailing skill, they sailed it around the world over a 10 year period, with no major damage and no disasters. It had a VERY low center of gravity, was wide, and had about 2.5' of bridge clearance! With a small high clew jib, they could see forward as well.

In crossing oceans, It doesn't pay to ignore the laws of phisics...

Until you get to around 40', most production cats are giving up too much seaworthiness in order to pack in accommodations. Most folks don't cross oceans, and accommodations are what sells boats. There are some exceptions among production boats, only a few. There are better tris in this size range and price, but if you prefer cats, in this size range, look for sitting head room if necessary, but do NOT sacrifice wing clearance!
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Old 16-02-2011, 17:06   #4
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I did my circumnavigation on a Privilege 39, and but was told that anything under 40 feet was unseaworthy. We went anyway, and we had a great time.
Dave -Sailing Vessel Exit Only
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Old 16-02-2011, 17:18   #5
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Another thing to keep in mind as it pertains to bridge deck clearance is the fact that many catamarans that advertise a relatively high bridge deck clearance on paper, in reality have a much lower clearance when loaded down with cruising gear. I've seen some moderate to large cats drop 6 inches when loaded with only a modicum of cruising gear.
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Old 16-02-2011, 17:50   #6
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The smallest cat I would like for ocean sailing would be the size of FP Athena or thereabout. Been on one Privilege 36/7 and she looked very respectable.

The bridgedeck clearance - can go without, but it will be noisy. IMHO the more the better.

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Old 17-02-2011, 10:19   #7
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The Admiral 40 has a lot of headroom (to much for me!) and good bridgedeck clearance.
Catamaran "Burnout"
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Old 26-02-2011, 06:55   #8
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Maine Cat

The Maine Cat 41 fits most of your criteria. It is an open bridgedeck design but with a foldable enclosure. It is light, fast and has daggerboards. It gets great reveiws and apparantly cruises very well. Not sure about headroom or the ability in rough conditions. Interesting, though. I'd like to try it out.
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Old 26-02-2011, 07:20   #9
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Re: Ocean-Going Catamaran Size and Bridge Deck Clearance

Regarding bridgedeck clearance: Recommendations vary, but the consistent advice from most sources is along the lines of "the bridgedeck shouldn't slap on the wave crests". Clearance of 6 to 7 percent of the waterline length or 20% of the tunnel width (whichever is greater) should be enough to keep most waves from hitting the bridgedeck in typical conditions, ie. 29 to 34 inches clearance on a 40' LWL cat; more is better when things get rough. A clearance of less than 5% of LWL, or a bridgedeck that extends forward into the first 1/4 of the boat's length, is likely to cause problems.

Clearance should be measured with the boat fully loaded for cruising, with her standard crew complement on board. Reporting clearance in light-ship condition is misleading unless it's accompanied by a pounds-per-inch-immersion figure. If there are lumps or protrusions that intrude on the tunnel, such as flared-out sections to fit double berths, the clearance to these is also important.

Regarding size and stability: Chris White's long-standing recommendation of a minimum 30,000 / 41 kN.m righting moment (with 100,000 / 136 kN.m being ideal) is, IMHO, grounded in good physics and statistics. A rough approximation to RM is to multiply the boat's displacement by half the hull-to-hull centreline distance. Going smaller is possible, but very dependent on seamanship, as a cat with very low RM may not be able to take care of herself when the sea state picks up.

Also worth noting: Excessive beam relative to length can be dangerous; such a boat might stuff the leeward bow (causing a pitchpole) when overpowered, rather than lifting its windward hull while maintaining level fore-aft trim. A heavy cruising condomaran won't do either, but it's a concern with lighter and more powerful long-range cruising cats.
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Old 26-02-2011, 09:04   #10
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Mainecat 41 revisited

Just checked the website and it says they have " 6'9" headroom in the hulls. The highest in their class". BOB
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Old 26-02-2011, 10:35   #11
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Re: Ocean-Going Catamaran Size and Bridge Deck Clearance

Well, I did research for more than a year, trying out different cat's to find one suitable for long time live aboard, with homey feeling and not all plastic inside, sea worthy for ocean crossing, galley up for social and as I see it practical reasons, roomy to have a couple of guests without being crowded and at not to high cost.

Pretty soon I fell for the Prout 50 Quasar because of it's shape (slim and not looking like a large white box with high freeboards), well documented quality and the other aspects I looked for. I read Charles Kanter's evaluation of the Quasar, which also told me I was on the right track.

Finally I purchased one in Florida and sailed it home to Sweden in the summer of 2010, together with three of my kids, with stops on Bermuda, Azores and Jersey (not New Jersey though) and finally Swedish West coast where I live. The journey took two months and gave me a good evaluation of the Quasar when it comes to the demands I had had on the cat I bought.

My conclusion was that I still like the type BUT there is one thing that at times was very frustrating and that was the under bridgedeck slamming. The table in the saloon was jumping up and down and it was no chance what so ever to get any sleep in the forward beds, since the slamming hit just under them and it was lika a Mike Tyson punch at every slamming.
Actually i mailed from the boat to a friend of mine, who also owns a Quasar and was on his way to meet us in Azores, to ask him if this was normal and if the boat could break. No problem he replied, in certain waves they slam quite a lot, they are built strong enough to deal with that. That was comforting but still no chance to get any sleep when slamming.

The sleeping problem I fixed when I came home, by building a frame in the beds and putting a board on top, to let the mattresses come up 0-5" (0-8cm), and at the same time levelling the bed. It turned out perfect.
The slamming issue for me at the Atlantic crossing could partly have a reason in the well loaded boat, which also had about 400 litres of water in the aft collision compartments, which made it even lower in the rear part. When taking out all the stuff in the boat, together with the water, she raised almost 4" (10cm) in the rear.
Never the less the Quasar is still quite low when it comes to bridgedeck clearance, but I can cope with that since most other parts on the boat are good. It is a solid boat no doubt.
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Old 26-02-2011, 16:06   #12
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Re: Ocean-Going Catamaran Size and Bridge Deck Clearance

Extra comment...I purchased the older and more narrow beamed Quasar, meaning that the forward beds were a bit short for me and my boys, being 6'4, so I had the lengthen them. No problem.
On the wider and newer Quasar Espace the forward beds are long enough though.
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Old 27-02-2011, 10:11   #13
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Re: Ocean-Going Catamaran Size and Bridge Deck Clearance

Hi Tolly,

thanks for your helfull comments.

I like the Quasar 50 for the same reason you described. What is the clearance measured? May be 3' more beam may help a little bit due canalizing the waves.

The load you described seems to me quite normal for a cruising cat and even with a water maker you'll carry water to have a reserve. In principle weight distribution isn't bad due the engines are located more forward than the standard.

How much power has your Prout? How many miles did you on an average for the crossing?

Sure, some of the newly built cats have more but the majority doesn't have. The price for it is high windage and the height above the waterline accesses 13'.

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Old 27-02-2011, 11:53   #14
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Re: Ocean-Going Catamaran Size and Bridge Deck Clearance

I am not sure about the measured clearance but I can check it out if you want to. I don't think it's more than 50cm though. I can not slide the rubber dinghy under it (which I'm glad for).
About the slamming. I read Charles Kanter's check on one Quasar, saying that he had no slamming at all, even though there was a lot of waves. I guess he was just lucky. But in fact, we had no slamming at all on the way to Bermuda, and on the rest of the trip only at certain waves (on the Atlantic they can come from every place at the same time). When fixing the bed problem at home, it should only be disturbing slamming under the saloon table, and I feel that that's more of a psychological than practical problem, since it doesn't effect the cooking and not the seats around the table...just the table and floor around it. But it's quite loud when it's bad.

I have two Yanmar 40HP engines new 2006 (boat is 1980), which is power enough. We had hardly any wind on our way to Bermuda, so it was mostly motoring then and also on half of the way between Azores and Jersey.
Occasionally we had 25-30 knots of wind and we almost always had all three sails fully set. Top speed about 14 knots. Average speed for the whole trip was little more than 6 knots, but we burned almost 1500 litres on the whole trip of fuel because lack of wind.

I did quite an excessive check on the Quasar's ( for sale around the world a year and a half ago when I was searching, of which some still are for sale. I have been onboard the two still for sale in England, of which one is a good buy (Starlight), and the other one is godbye(LOL) (Cheep's Clothing), a total wreck.
I didn't buy Starlight then since the owner, though a very nice and reliable man, at that time wanted to much for the boat. Now he has lowered the price to more reasonable level well worth considering.
There is one Espace for sale in Greece, but I'm afraid it's something wrong with it, since I believe it's to old to be an Espace, which could mean that it is one of the few Quasar's built just between the first Quasar model and the Espace, and these few models I have heard wasn't good at all.
If I'm wrong in this, the price they want for that one is very good.

Anyway, good luck.
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Old 04-10-2014, 23:43   #15
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Re: Ocean-Going Catamaran Size and Bridge Deck Clearance

Hi Tolly
Thanks for the great posting on Prout Quasar's in general and the underwing slamming issue you have experienced.
Im also looking at a Prout 50 "quasar" but im uncertain of its origins?
Its a narrow beam build of 6.5M to its 15M length and looks quite low on the water for clearance. It was apparently purchased in the UK in 2010/2011 and refitted quite extensively? But alas .. this will never fix the bluewater wave issues.
The owner cant tell me the build date/year of his boat? he insists 1990 but im not sure of when they stopped building the narrow beam version.
Do you have any design details for the model ?

Thanks and regards

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