aluminium catamaran

[Guest]

Hi,
I am considering buiding a catamaran for blue water cruising and am wondering about the the possibility of aluminium as a construction material. I am very near the beginning of this quest but there have not found any good information on the use of aluminium in catamaran construction.
If anybody has direct expereince or knows where I can get some advice I would be very grateful !!

John. (aka Baggywrinkle)

 

[extravert]

I don't know about an aluminum catamaran, I have never even seen one, but I do know about aluminum monohulls. I used to own an Extravert, a North East England boat made entirely of welded aluminum, similar to a Sonata.

The experience I had was that aluminum is an extremely durable and tough boat bulding material, as long as it is done properly and some care is taken during use.

Corrosion is generally perceived to be the biggest problem, but with proper design, construction and use it will be no problem at all. Dissimilar metals together in contact with salt water can cause corrosion, so the design of areas like keel attachment and prop shaft must be done properly. When using an aluminum hull a few precautions need to be taken, like no mercury (thermometers) on board, and pick up all the bits when wiring. Similarly make sure crew do not drop coins which can find their way into the bilges.

If these are followed, you'll have the most long lasting and maintenance free hull possible. The insurance company I used at the time said they had never heard of a structural failure of an aluminum hull, and the surveyor said the hull was as good at 20 years old as the day it left the factory.

So why aren't there more about? 3 reasons

1) Constructing aluminum hulls is very expensive. It is very time consuming and aluminum welders of the suitable quality cost a lot of money.

2) Like a steel hull, it is difficult (and even more expensive) to get smooth curves. Hulls will usually be mult-chined.

3) Painting can be a real problem. Marine aluminum alloy is fine without it (as the Extraverts are), but this is not very pretty, battleship grey. Getting paint to stick is tricky and involves nasty chemicals.

I had no end of comments when I owned an aluminum boat. They seem to appeal to engineers (strong, light, low maintenance, long lasting) but not to designers (hard to paint, boxy shape).

 

[snowleopard]

aluminium multis

the only one i've heard of was manureva, sailed by alain colas in various long-distance solo events. she was very quick but suffered from fatigue cracking of the cross-beams. If you want light weight (essential for cats if they are to go better than an equivalent mono) you'll get the best deal from grp foam sandwich.
take a look at www.kelsall.com for info about plans (i've now built 2 kelsall 40-footers)