There seems to be a lot of us pig heads who insist on building smaller aluminum cruising cats (30'-36' range). So after searching existing threads I'm opening up a new one. Does anyone know where we can find such design plans ? Not custom drawn ?

Roger hill's 10m ply cat could be very quickly and easily turned into an aluminium design.

I have never fully come on board with aluminum and salt water. Unless it will be trailered. We work with ships' various hulls and decks. Things tend to go better if there are no engines or batteries. I have seen massive base metal waste due to improper use of anodes. It happens faster that rusting. It never sleeps. Use some stainless steel fasteners and reap the pleasure of bonding.

Then comes the joy of welding the stuff. The American Welding Society will tell you it is the easiest metal to weld. They have to be talking about melting temps only. It is the most prosity prone metal to weld... meaning lots of holes. We made money as consultants to the trawler industry to come in and troubleshoot their aluminum setups. They were having trouble getting it from being so brittle and manage to tensile strength too.

If you already know about these things, you are half way there.

Good luck.

The french are building Al yachts:
http://www.yapluka.fr/yacht-catamaran/yacht-catamaran.htm

One might ask why only a few builders are taking on the task. The US military built a few fast attack speedboats all aluminum, I understand they are now turning to carbon fiber.

Forming aluminum to compound curves is a task too. Depending on the grade of aluminum being used, there is very little flex before fracture. For example, we test steel by bending it over a 3/4 inch radius mandrel. To bend the average aluminum, five inch radius. There are just better metals for the sea. It is kind of like the practice of building boats out of concrete, it can be done.

Stainless steel could actually be cheaper in the long run. Prettier too. Much easier to weld.

Deepsees - A skilled aluminium boat builder knows the strengths and pitfalls of aluminium construction. We no longer provide plans of our designs to amateurs, because of the potential problems with weld quality, and insist on a professional boat builder to do atleast the structural welding. If done properly, aluminium boats are fine.

Well said... "skilled" is the focus. This is not about just forming limitations and corrosion, it is about electrolysis too. As stated before, we are marine welding and metal forming as a business. We have seen massive electrolysis damage happen much faster than normal metal corrosion simply because of interrupted anode failure.

Again I would pose the question, why are there so few skilled aluminum builders? Cost and service. I have seen skilled fitters cutting pie shaped slivers of aluminum to help make compound curvatures in areas where the base aluminum metals cannot be bent without breaking. This builds up multiple "notch" locations which service life affects resulting in weld cracking opportunities.

Non-engined designs will last longer because there is no bi-metal/battery issues... but repairing damage is the same hassle.

For me... small aluminum jon boats are fine because they trailer. Anything that is designed to sit in the sea 24/7, steel!!!! Beach cats by concept should be easily repairable in the drive way at the house. Metals complicate things.

Again... one might ask why there are not more skilled aluminum houses about. Guess one just has to see for one's self.

GR

Here's an aluminum cat that seems to be holding up.

How do you know what that vessel is doing? I have walked and climbed hundreds if not thousands of ships' tanks and voids with the American Bureau of Ships reps... there is all manner of issues with a vessel that size. Saying that is like judging a book by it's cover.

All I am doing is pointing out the pitfalls of using aluminum on salt water. A good many aluminum power boat makers will tell you that sea water usage will void portions of their warrantee. Trition is one that will not warrantee a boat in salt water. But hey... they only design and make the things.

Note too... the flat surfaces on this vessel... aluminum does not form well compared to other metals.

But if you are determined to do it... good luck.

Yea? but can they fly a hull?
Now that would be an interesting sight to see....

I am not sure Andrew... I saw a wrecked cat made out of concrete on Peanut Island in West Palm Beach. Never posed that question to myself... I was too busy being amazed that someone actually thought of concrete when the subject of hull materials came up. Even more... when someone else seconded the idea.

yes seems incredible...

There is a concrete battle ship aground of Galveston that has been there as long as I can remember and I will be 59 soon. Guess metal was at a premium during World War II? Good fishing spot when I was a kid with dad.

Doug

I am aware of all the pitfalls of building with aluminum. The arguments are not new. I have decided to build with aluminum period, thats why I started this thread. Scarecrow thank you for your input.

A couple of my father's customers own these boats (Pluckebaum's). All Al. They're not the slickest, rounded things but they are NICE and solid!

http://pluckebaum.com/pluckebaum/index.html