Aluminum Strongall Sailing Catamaran Plans?

[kimosadler]

I've been searching for plans for a strongall process aluminum sailing catamaran in the 40' to 50' range. The design of Antoine's "Banana Split" or Prometa catamaran comes to mind. I want to build a catamaran that is tough enough to bounce off of a coral head far from a boatyard, that needs little maintenance, and can take a person anywhere including the arctic.
I've researched this to death and have come up with only tin can catamarans.
Help!

[simon]

Have you checked out www.prometa.fr?
I think the french designers Joubert and Nivelt were responsible for the first generation of Strongall cats. I don't know about the newer ones.
www.joubert-nivelt.com/

Does it need to be Strongall or are you also looking at thinner aluminium construction?

[kimosadler]

Strongall type hull it must be. I like the hull profile of the Antares 44i' and will use the cabin top profile of the Lagoon with vertical windows. The hull will be constructed using 12mm flat bottom plating with 10mm sides and bridge deck. Cabin top and decks will be 3-4mm. Interior cabinetry and fitout will be a combination of TriCell Honeycomb and Duraflex composite panel. Insulation will be 'blown-in' polyurethane foam 20 to 60 mm finished with easy to clean vinyl like Manta Cats have.
Do you know of any architects with good aluminum catamaran experience?

[simon]

http://www.bloomfieldinnovation.com/
I worked with Stuart Bloomfield on a 50' aluminium catamaran with similar requirements than you have. But it has thinner plating than you wish. His design and the drawings are very good. I was very impressed about the detailing of his design and he has a lot of experience in catamarans.

http://www.devilliersyachtdesign.co.nz/home.htm has some thick plated monohull design and an aluminium catamaran mentioned on his website. I don't know anything about the quality of his designs.

http://www.ngyachtdesign.com/ has a 42' aluminium catamaran (Kat'alu 42) on their website.

http://www.adn-lelievre.com/ has a 41' aluminium catamaran (the Galileo 41).

[kimosadler]

Thanks! Excellent information.

[simon]

kimosadler,

please keep me updated on your progress. I am planning to build a aluminium catamaran soon.

Simon

[Guest62110524]

the cat Simon talks of is as strong as you would wish to go, the design is to strict Australin standards and has a great deal of shape strength with 6mm rounded bottom sections
I have seen very detailed dgws of the boat and as a builder with years of exp. was impressed

[Landlubber]

The hull will be constructed using 12mm flat bottom plating with 10mm sides and bridge deck.

Seriously strong here, you sure this is spec? she is only 40 -50 feet mate.....

[kimosadler]

I am in the researching stage and am relying on what I can gleam from the internet. I am seeking a more modern larger version of the Catamaran "Banana Split" which was launched by Prometa in 1989. Check out Antoine's web site of "Banana Split":

http://www.antoineweb.com/index.php?...e&idp=5&srid=7

The builder's web site is:

http://www.prometa.fr/FR/PAGE_Banana465.htm

Although I cannot speak French, I am hoping that they will allow me to build a design of theirs. They have not returned an email as of yet.

Antoine has been sailing Banana Split for 20 years now, and has no need for another design. That says alot for me. I seek a catamaran that I can spend 15 years on, and is large enough to meet my needs.

I have my shop built, have 25 years of welding/fitting experience and am ready to make it happen. Of course I will need all the help and advice that I can get, and would appreciate conferring with other builders.

[kimosadler]

Originally Posted by Landlubber

The hull will be constructed using 12mm flat bottom plating with 10mm sides and bridge deck.

Seriously strong here, you sure this is spec? she is only 40 -50 feet mate.....

From what I can tell from these sites the thickness is correct. And I agree that it is very thick. Bulletproof. Check out these sites and look for 10 m/m plate thickness for the Cat 41 (Banana Split).

http://www.prometa.fr/FR/PAGE_Cat41.htm
http://www.kamiros.de/media/kamiros/...nstruction.pdf
http://www.anchoryachts.com/strongyachts_strongall.php

As you read, the strongall boat does not use stringers, just several bulkheads and the thickness of the plates will provide the strength for the hull. The lack of stringers somewhat equals out the extra weight of the hull plating....somewhat. The other benefits are ease of welding at high heat and no plate distortion. Take a look at the undersides of Banana Split, she looks a little boxy out of the water, but there are no chines in this construction method. She looks just like a Fiberglass boat when in the water.

http://www.antoineweb.com/index.php?...e&idp=5&srid=7

What are your thoughts?

[Guest62110524]

Originally Posted by kimosadler

From what I can tell from these sites the thickness is correct. And I agree that it is very thick. Bulletproof. Check out these sites and look for 10 m/m plate thickness for the Cat 41 (Banana Split).

http://www.prometa.fr/FR/PAGE_Cat41.htm
http://www.kamiros.de/media/kamiros/...nstruction.pdf
http://www.anchoryachts.com/strongyachts_strongall.php

As you read, the strongall boat does not use stringers, just several bulkheads and the thickness of the plates will provide the strength for the hull. The lack of stringers somewhat equals out the extra weight of the hull plating....somewhat. The other benefits are ease of welding at high heat and no plate distortion. Take a look at the undersides of Banana Split, she looks a little boxy out of the water, but there are no chines in this construction method. She looks just like a Fiberglass boat when in the water.

http://www.antoineweb.com/index.php?...e&idp=5&srid=7

What are your thoughts?

my advice
do not, choose a pretty yacht she will be worth much more
there are no shortcuts in boatbuilding
Choose a designer with proven track record and dont be sucked into plans(made for easy to build) stuff
if you want you can mail me through my website, til saturday

[simon]

kimosadler,

the strongall constructions are hard chined. This is one argument for the strongall. They don't overstress the plates into compound curves.

I had my boat repaired at Prometa and met a young couple who had a 41' strongall cat built by them. It looked very boxy, but it is all about what you want. You will not be able to expect a lot of performance, but you will get a strong boat, if designed properly.

I think the advantage of strongall is that you have hull-skin that is very resistent to localized impacts. I am not sure about more global stresses, as the properly designed thin plate construction with stringers and frames may be overall stronger.

I read somewhere that the bottom needs to be length of the boat in m in mm. So a 12m boat will need a 12mm bottom. I still think that a naval architect should calculate the stresses to define the approapriate internal structure. I would guess that a combination of thin aluminium and thick aluminium could work out. Something like thick hull sheeting with lightened reinforced internal structure, instead of bulkheads of thick plating.
The deck could also be built of thin plates with stringers.

I took my thin plated aluminium monohull to Antartica and thought that it withstood quite well the ice. Of course there is always a limit and we did not encounter very thick iced surfaces and the iceblocks we had to dodge were maybe 1m big.

The problem with a catamaran will be the ice that blocks between the hulls and will create huge forces on the structure and not locally on the skin.

[Guest62110524]

I dunno how maný times I have to say, by putting compound into plates you do not stress the metal at all, you form it in Sure you do NOT form it in xou then have a plate under tension, after awhile this tension disappears, a querk of metaleurgy, or however you sp. that word

[kimosadler]

Curving aluminum plate is quite simple. Thickness up to about 1 inch can be done with little effort or cost. Without heat or the use of bending machinery. The plating will come out with the same radius every time facilitating the matching up along weld joints. So taking the box out of hull design without the need for huge plate bending machinery is a very simple thing to do.

[BlueWaterMarine]

Hi kimosadler,
I am new on this website & just discovered your interest in Al cats.
I have a 65 ft strongall-type monohull under construction. It is fast to build & ice-ready.....and....30-40% lighter than a steel hull.

You are most probably familar w/pros & cons of cats. One of the biggest problems is weight. Not a sure a strongall cat would make a seaworthy & good performing vessel. As my last project, we built a 53 ft al cat. The sister ship made it across the Great Barrier Reef---literaly---ran aground, no hole. We sailed ours around the world & had several instances where a foam sandwich cat would have gone down. The cat was built on bulkheads with T-bar stringers. Underwater she was built in the lobster tail system & had double floors for safety. This boat was also fast built.

What can I say, I am an AL convert after years of professionally building steel vessels! For cats, I would strongly consider the weight of the strongall system. For a 40fter would not go strongall.

Fairwinds