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Go Back   SailNet Community > On Board > Boat Review and Purchase Forum > Sailboat Design and Construction > Multihull
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Old 07-23-2012
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Thumbs up CATAMARAN DESIGN and BRIDEDECK CLEARANCE

Open for discussions and opinions


(1) Interested in comments from Catamaran owners re Bridge deck clearance. I have heard reports
about low bridge deck clearance causes Slamming and pounding of significant proportions when sailing to windward. Comments please.

(2) Some designs have .500m clearance others .700m and I notice the latest designs on some are rising to .950m and 1.2m
bridge deck clearance. Comments please.

(3) I have noticed quite a few catamarans stay in port while Monohulls make passage to their next port. When asked why they are staying in port
I,m told waiting for for less wind and a better wind angle. Supposedly this has something to do with Slamming and pounding? Comments please.

(4)Galley preference. Main bridge deck or hull. As a interested cook and have cooked on numerous vessels I ponder the merits in having the galley within the bridge deck. Re heat transfer- Condensation- Moisture- the heat generated from the galley causing condensation on the ceiling, moisture gathering in drapes, upholstery plus smells and vapours, books in library pages being affected and absorbing the moisture. As usually with most modern designs the chart table and electricall main board and electronics are also positioned in main saloon - bridge deck, I wonder the wisdom re this.
I would have thought the galley in the hull would be preferable with higher head room - hatches and extractions fans and more ventilation - thus removal and moisture control would be more efficient, plus providing a larger lounge area in the main saloon. After all the kitchen in most homes is not in the lounge. Plus normally in the tropics if one does not have air conditioning one gathers with chilled drinks in the cockpit area with sea breezes and a view and possibly to be a nosey parker while the cook cooks. Comments please.


Below are some hyperlinks to a new design with increased bridge deck clearance. How ever I,m would have thought for offshore passage and in moderate to heavy seas a clearance around about 1.6m to 1.8m
would be needed to avoid constant bridge deck slamming when going to windward or even slightly cracked
sheets. Comments please.

http://www.schionningdesigns.com.au/1700c


http://www.schionningdesigns.com.au/gforce-1800

http://www.schionningdesigns.com.au/1200

Thanks in anticipation.
http://homepages.ihug.co.nz/~philcla...0ETIQUETTE.htm--------------------------------------------------------------------------------

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Last edited by piclarke; 10-21-2014 at 11:33 PM.
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Old 08-06-2012
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Re: CATAMARAN DESIGN and BRIDEDECK CLEARANCE

Why wouldn't bridgedeck clearance be a function of size?
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Old 08-06-2012
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Re: CATAMARAN DESIGN and BRIDEDECK CLEARANCE

It's not a function of size, just look at some of the condomarans with 40' loa and 10 inches of clearance.

I seem to recall reading somewhere that the absolute minimum bridgedeck clearance you want is 19", from the lowest point of the bridgedeck to the water. This includes any Nacelle (spelling?) hanging down from the bridgedeck.

If you really want to understand this issue go to boatdesign.net and do a forum search, there is lots and lots of data, much of it from NA's and designers (richard woods posts there frequently) and you will get a fuller understanding of the issue.
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Old 08-06-2012
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Re: CATAMARAN DESIGN and BRIDEDECK CLEARANCE

I don't know enough about the bridge deck issue to comment on specific heights but insufficient height is a major problem from what I do know.

Regarding the interior, I'd favour a downstairs galley. My biggest complaint about catamaran layouts is the restricted seating space in the saloon where much space is taken up by the galley and/or nav station. Must say I do like the layout of the Schoening 1320 though I know nothing about the boat itself. The 1700 is for my money absurdly large, but then I only think about space for a couple plus very occasional guests.

The way I figure the galley is this. Down below gets it out of the way with one major drawback being heat in warmer climes. For me that is negated by the fact that in summer we always cook outside and with a cats cockpit even preparation outside is simple.

Others might say that the galley in the saloon allows more interaction twixt the cook and the crew. Fair enough I guess but I still don't think that outweighs the other issues.
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Last edited by tdw; 08-07-2012 at 06:26 AM.
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Old 08-07-2012
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Re: CATAMARAN DESIGN and BRIDEDECK CLEARANCE

Most any catamaran will pound in certain sea states.
If you're looking to eliminate pounding, buy a monomoran.
I dont have rules of measurement that I can help you with but common sense should prevail. If the bridge deck clearance looks low, its going to pound more that one that does not look low.
Galley down works for us. Its open and inclusive of folks working in the galley with those living in the saloon. When I was chartering catamarans for vacation sailing, I prefered galley up. Living aboard, galley up is a deal breaker. I dont want to cook in my living room. We comfortably seat 6. 8 is a push, but doable for dinner.
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Re: CATAMARAN DESIGN and BRIDEDECK CLEARANCE

[QUOTE=tdw;906246]I don't know enough about the bridge deck issue to comment on specific heights but insufficient height is a major problem from what I do know. {Thanks}

Regarding the interior, I'd favour a downstairs galley. My biggest complaint about catamaran layouts is the restricted seating space in the saloon where much space is taken up by the galley and/or nav station. [Agree my thoughts exactly] Must say I do like the layout of the Schoening 1320 though I know nothing about the boat itself. The 1700 is for my money absurdly large,[ I think you need it if your doing offshore passages and have extra crew to help with watches so one does not get tired and irritable, and depending on your age.] but then I only think about space for a couple plus very occasional guests.

The way I figure the galley is this. Down below gets it out of the way with one major drawback being heat in warmer climes. For me that is negated by the fact that in summer we always cook outside and with a cats cockpit even preparation outside is simple.[ Most boats these days have a BBQ,s hanging from the stantions or pushpit.]
Others might say that the galley in the saloon allows more interaction twixt the cook and the crew. Fair enough I guess but I still don't think that outweighs the other issues.[/QUOTE][ Good point agree.]

Oceancruiser.
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Re: CATAMARAN DESIGN and BRIDEDECK CLEARANCE

My comments about Bridge-deck clearance comes from the lips of designer comments I have read. They also come from a Cat sailor who owns a Catana 381 that has 2' 6" clearance and it does not slam, I know because I sail it like the Tornado Olimpis Cat I used to race.

I am just about to Launch my Website which tell you what Cat NOT TO BUY, depending on your requirements of course, if you want a Condo, have one, if you want to sail sideways have Skegs, if you like Hobby Horsing or slow Cats there are thousands out there, mostly from the Production boat department.

Watch out over the next few months when I launch my Web site, type in Catamaran and you will find me.

As for the topic in question: there are 6 main things you need in a good Cat design and one of them is NOT low bridge-deck clearance. Most Cats have none of the 6 requirements, they either have Fat hulls, Skegs, reduced Sail area, bad Bridge-deck clearance, too heavy and wide open slot and they all sail like floating Homes.

I have 200 Cat listed on my database all with designer calculations saying which one is capable of sailing well, assuming 'well' is whats wanted.

I'm looking at 6 Cats I might buy in the 45-48' range, they must have at least 4 to 5 of the 6 design requirements listed above, if they don't I move on.

I have been told my requirement is very high and most Cats don't have what I want, that is true. I can find only 10 Cats that come into my top ten for sailing ability and the all have High Bridge-deck clearance.

I sail at 35deg to wind beating of Monohulls who try to get near me, to windward of course, I sail higher than them.

I don't want to give too much away in Loo of my Web site Launch. There is a small fee but it's worth it.

Regards

Barry Parkinson Ex Tornado helm and Catana 381 owner.
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Re: CATAMARAN DESIGN and BRIDEDECK CLEARANCE

Quote:

I can find only 10 Cats that come into my top ten for sailing ability and the all have High Bridge-deck clearance


Interested to see your top 10 sailling ability Cats and the hights of there respective bridge deck clearance.

I also notice from the Catana Web site there new design has reversed bows and they have increased there bridge deck clearance. Not to dis-similar from the design above hyperlinked. Interesting !!

Be interesting to see how yourwebsite goes-- Fee/ pay by credit card. I don't think so
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Re: CATAMARAN DESIGN and BRIDEDECK CLEARANCE

I am interested to see those 6 requirements as well.

The problem with catamarans is that in order to retain the excellent performance that multis are capable of, the catamaran has to have certain features such as narrow hulls, low windage (ie minimal bridgedeck), daggerboards, etc. These very features mean that to have comfortable accomodations the cat has to be very big. Otherwise something has to give. And once you get big, most boat owners get priced out. You need bucku bucks to buy a 50' catamaran, and even more to find a place to keep it. So, as with everything in life, compromise is required. Some compromise better than others, but since the charter market seems to drive catamaran sales, the accomodations are favored over the performance/safety in most commercial designs. I personally am a sailor, not a on the hook cruiser or live aboard, so even when cruising I can't tolerate a poorly sailing vessel and would never get a condo maran. But others, particularly those who charter, may have different priorities.

For this reason I think a trimaran is the way to go if sailing performance is what you want. Most trimarans are not built for anything but true sailing ability. Those who buy a tri generally want to go fast and have fun. The arms fold up so you can find a spot in a marina. The accomodations are more like a smaller loa monohull, and way less comfortable than a cat, but that is the kind of compromise I am willing to make personally.

If you want that standing headroom bridgedeck, the compromise is high windage and poor bridgedeck clearance, at least until you get to a really big cat IMHO.

BTW, "The Cruising Multihull", by Chris White, is an excellent book on this subject, and is available as a pdf download or else used on amazon for $10 when I bought it. It's a wonderful book and you should def read it before buying any multihull, it addresses all these issues and compromises from the standpoint of a designer and full time cruiser. Great read too, not overly technical and very enjoyable.
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Re: CATAMARAN DESIGN and BRIDEDECK CLEARANCE

Hi petercheck,

I have read your thread and I bet you are interested in my top ten Cats and the 6 requirements for quick Cat sailing, thats why I am launching My 'What Cat not to buy and why'

Lots of Cat buyers are sold up the river by Brokers who say 'have a nice day' but don't mean it. I got fed up listening to the garbage Brokers talk over the past 5 years, and that is the main reason for Launching my Website.

The other one is because a Great Cat in the West Palm Beach in the Cracker Boy Yard, has been butchered by the Loving owners, I wanted to but it until I put it through my Spreadsheet to get a 'Bruce number' (Power to weight ratio) and it sucked.

I asked the Architect what was in the original design and found they had cut the Dagger-boards in half and poss the rudders as well, loaded the weight up from 10 Ton to 12 Ton, reduced the sail area and generally messed up a very good Cat that cannot sail well anymore.

I wanted to expose people and Brokers like this to the budding Cat sailor who has a lot to learn about Cats and end up buying things that float, thats why it is called a boat, but it does not sail well because the production Cats do not have any of the 6 requirements I talk of.

I could talk for a week on Cat design but this is not the place to do it.

All I want to do is give potential Cat buyers somewhere they can go to ask questions about potential Cat purchases they might make, before they make a mistake, like so many Cat owners who are disappointed with what they bought, for one reason or another.

I know the answers, with 200 Cats on my database I should do, and soon I will be able to let the Cat buying public know what Catamaran/Multihull not to buy.

Give me 2 weeks and I should be Online with my Website but, there is a small fee, but you said you did not thinks so, I take it you don't thing buyers will pay $50 to find out what I know, we will see.

It's been great talking, no doubt we will do more. I am looking forward to helping cat buyers choose the correct boat before they buy.

Best regards

Barry Parkinson
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