Difference between 10m and 12m catamaran

What is the difference between a catamaran with LOA 10m and one with LOA 12M ? Assume the hull height and hull width remains the same.

 

Weight, speed, cost, sail area, righting moment, pitching (damping) ...

 

Hi Terhohalme,

I want to build a cat. I'm aware of the factors you mentioned. Some more weight, more speed, more expensive, can add sailing area, better righting moment, less pitching...

Will it be worth it ?

 

Hi Fanie. Are you allowed to tow 12m?

 

I'm with Bob Oram ... Length is good i.e. two boats that are comparable in most other respects the longer boat will be better to sail at sea and faster. I think there is a tendency to pack to much into a 10m boat ala Seawind 1000. JMO.

 

Yup, that'd be right.

 

Frosty, YER BACK !!!

With that answer of yours
Youve won first prize - one week in China
Second price is two weeks in China

As for the cat, max length towable is 22m includes everything

 

I'm not really after the speed.

How will a 12m cat behave better than a 10m cat ? Will it handle rough water better... ? If someone could explain how big a difference there is ?

 

Well ? Anybody have some kind of an idea maybe ?

 

Assuming that everything else is similar- ie, the 10 m and 12 m boats are of comparable displacement, hull shape, rigging, etc.- in general I would expect the 12 m version to have the following advantages:
- Slightly faster (due to longer waterline, possibly more righting moment, and less pitching)
- More comfortable at sea (longer waterline for similar displacement means finer ends and more resistance to pitching)
- More comfortable at anchor (again, less pitching, and the finer ends mean less jerky a motion when waves hit you)
- Reduced fuel consumption when under power (again, longer waterline)
This comes with a few disadvantages:
- Marina fees go up 20% compared to the smaller one
- Structure becomes slightly more difficult to engineer

For identical displacement, I don't think you'd see a significant cost difference between the two- for comparable construction style and outfitting, cost is effectively a function of displacement. The interior space would be comparable in both.

For the case described in the initial post, where depth and beam remain constant, the 12 m is now effectively a 1-D scaling of the 10 m boat- thus the displacement, and cost, will go up by about 20% compared to the smaller boat. However, the interior space and cargo capacity would be increased by a similar amount.

Given a target displacement and living space requirement, I would tend towards picking a longer hull whenever possible. The advantages, IMHO, significantly outweigh the additional engineering challenges and the dock fees (cats prefer to lie at anchor anyway!)

 

Dammit Mat ! I was hoping everyone would try to convince me to stick to 10m I don't have the space for a 10m cat (not really) and I'm seriously considering the 12m. I'll have to speak to the neighbours about some yard space next to mine

There may be other considerations too, ie the trailing of it so I'll have to do some math first.

Thanks for taking the time out.

 

12 metres are way,way too short. You'll need at least 20 metres, because? Well, just because, you'll need the space!

http://www.gunboat.com/gunboat_flash.html

Click quietly on Gunboat 66 layout. We don't want the other to hear!

Then sell the house and go to sea. Anchor with Rocnas and forget the marinas.

http://www.rocna.com/main.php?section=real&chapter=testing&page=0

You can tell I've thought this through.

Pericles

 

I'm not even going to look. You are very very nasty with me and I'm going to sit here and sulk for at least 10 to 15 seconds !

 

Fanie,

extra length is always good on a sailboat! Just remember that the volume increase goes up with the cube! So there's alot more volume to handle.
With no fitout of the extra length, the price won't increase much.

I thought you wanted something to fish from? Then even a 10m boat is a good size.

I think you are getting caught up in the design/looks of the boat - it's much easier to make a longer boat look good! There are few good looking 10m cats with standing headroom in the saloon, and good bridgedeck clearance. So either go longer, slam under the bridgedeck, or look bad. There are of course a few "tricks" to get the boat look elegant - have a look at some of the Australian boats, and maybe the FP Tobago. From what I understand you want, then have a look at the Maine cats - nice open boats for warm weather sailing.

Regards

Alan