# Difference between 10m and 12m catamaran

Discussion in 'Multihulls' started by Fanie, Feb 17, 2008.

1. Joined: Oct 2007
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### FanieFanie

I agree with you - the longer hull looks sooo much more attractive. There is also more space to accommodate things in that is a little crampy in the old ugly 10m hull design

The last few times we camped on the coast some of our stuff got stolen, and the time before that - something I'm really sick of and am scared I'll help someone passing from this life into the next. So I want the boat so you can stay on the water instead.

Sounds a bit funny if one says you give berth to the passengers

Anyway, I'll make a little 12V meat grinder to chum throughout the night to attract huge quantities of sharks and hope the thieves will attemp to swim to the boat. Use some PIR detectors and have the boat autmatic keep a 20m distance from the approaching thieves, now pyrates.

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### marshmatSenior Member

This is true (for both volume and approximate cost) if you scale length, beam and depth equally. Here, going longer means a much larger boat- scale a 10 m cat up to 12 m, with a uniform scale factor in all directions, and the resulting boat is 1.73 times larger by volume, weight and approximate cost.

In the case described in the original post, Fanie wanted to keep height and width equal in both cases- thus the scaling is only in the longitudinal axis, and the volume (and displacement, and cost) increase (approximately) linearly with length. By this method, the 12 m cat is 1.2 times the volume and cost of the 10 m cat.

In the first case I described in post #11, which I believe to be the most equitable and fair way of comparing similar craft of different dimensions, the displacement is held constant while the hull is stretched- thus the hull must get slimmer and/or shallower to maintain a constant displacement. Volume and cost remain roughly comparable in this scenario, provided you stay within the boundaries of common sense.

3. Joined: Nov 2007
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### multihullsailorJunior Member

Hi from Cape Town, Fanie!

What are your sailing plans for your cat, 1) day-sailing the sweet-water Gauteng dams or 2) seeing / cruising the salt-water world?

If 1) length is faster
If 2) 10m or 12m (if scaled up) make's a lot of difference to the interior space you require if you want to go cruising seriously.

Either way stay just under 12m OAL (including bowsprit) for marina berthing reasons.

Roger

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### FanieFanie

Eh Roger ! Gee whiz, this forum is riddled with SA guys eh !

You're so lucky to be close to the sea. Here I sit as dry as Canada Dry surrounded by green algea dams 600km from the blue ocean, not to mention all the fish in it, eh !

The marinas charge too much to look after my boat, and I just know they are going to give the job to Philamon and friends, so I'll rather park it here at home. At least I can go sit in it and make sailing noises...

I have drawed the 10m cat out on the paving again tonight. It fits in the yard front. The 12m does not fit, but I can see the extra space it would offer although it will seriously interfere with the wife's flowerbed here...

In my next life I want to be as rich as you guys and have enough space to fit my boats in

It's going to take me out on the sea and I plan to live on it for the duration of the holiday time, I just have to mention I may stay far enough offshore just so I cannot see any Philamons for the time I'm out. Be like a REAL holiday ! Sorry, I know it's different down there by you.

What boat do you have ?

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### masalaimasalai

6. Joined: Oct 2007
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### FanieFanie

Of course Masalai ! I do have my doubts if Brian can fish, I haven't seen a single fish picture on his web site. There's no mentioning of a scale, fridege or a grill mentioned either

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### masalaimasalai

Look at his links, the boat is fishing out of Tahiti. His website has scanned images of a magazine article.... It was after reading that when I thought of your fishing needs...

Bugger, I can't find the exact link... It's somewhere? rather poor B&W scanned pages, up to 3 per web-page set vertically...

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### FarmerColinJunior Member

One very minor thing - the higher the aspect ratio of the hulls the greater the wetted area per unit displacement so light wind performance may suffer somewhat with more slender hulls. I think it is going to be difficult to increase length by 20% (and thus increase surface area by anything between 20 and 40% depending on how other dimensions scale) without a significant weight increase (unless, of course, the 10m design is over engineered in the first place)

Of course there is a weight saving at 12m - the marinas will lighten your wallet more.

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### Nordic CatSenior Member

Is this the article?

http://www.alwoplast.cl/PastHighlights/BuildersoftheWorldsfirstSailGameFishingCatamarans.htm

Regards

Alan

#### Attached Files:

• ###### Taravan%20Multihull%201995.pdf
File size:
1.5 MB
Views:
337
1 person likes this.
10. Joined: Oct 2007
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### masalaimasalai

Colin, have a look at Bob Oram's designs - I particularly like the 44C, which is a very light "home build possible" which could make the "gun boat" look like a snail if that is your bent in sail powered vessels.

My limited experience leads me to believe, that weather conditions and lazy comfort, sees an average cruising velocity of 8 to 10 knots mostly, in a seaway much over 15 knots is not "leave the cup-of-coffee/glass-of-wine" on the table comfortable speed...

Do not look "to carry much stuff", for performance cruising. Weight is a performance killer in modern catamaran designs. PERIOD...

If you are one of those people who cannot resist adding this & that to your cruising vessel then DO NOT GET A CAT... - - - - - - A LARGE cement cruising mono-hull will be your home - And ferro cement can perform - even in the "Sydney/Hobart" some time ago, nicknamed the "flying footpath".

If you are "out there" you are not in a marina - entry for fuel-up is usually free... At 12m you should be able to be fairly independent of many permanent on-shore "umbilical" connections...

11. Joined: Oct 2007
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### masalaimasalai

Thanks Nordic, The yacht is featured in the first pdf file, but the one I read was underlined in parts by Brian Eiland, I guess... Points of praise duly posted to "your account".

Your attached pdf is on the boat in question, but not the series of pages...

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### Richard Atkinatn_atkin@hotmail.com

Fanie...you want reasonable sailing performance, AND standing headroom, and you don't intend to use marinas. The only problem you have is fitting the boat on your property. Sounds to me like you should buy a new property closer to the sea, and build a longer boat. Easy

13. Joined: Jul 2007
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### Richard Atkinatn_atkin@hotmail.com

Or move to somewhere like NZ. Less crime, and good fishing.

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### masalaimasalai

15. Joined: Jul 2007
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### Richard Atkinatn_atkin@hotmail.com

Masalai, Queensland is "somewhere like NZ". How close is Buderim to the sea? I think the Sunshine coast and parts of the Gold Coast (not Surfers Paradise) are heavenly places to live.
Mind you...i've seen post card pics of South Africa coastal areas.....wow....spectacular and beautiful.

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