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Old 03-02-2009, 10:33   #1
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Pros and cons of an aluminum cat

OK, choose sides and start shooting! The general idea is a 40-something foot boat, cruising the Caribbean and the Med, a sixty-year old couple and occasional guests or extra hands, interested in speed and durability, with Watermaker, refrigeration, radar, heat and a sizeable, third-cruise dinghy. Daggerboards preferred.

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Old 03-02-2009, 11:48   #2
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It's got to be noisy at speed?

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Old 03-02-2009, 12:05   #3
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Sheesh!!.. one look at that Easton and you're hooked? (the dagger board requirement was the give away).

They're solid, abrasion resistant but sadly heavy.

I think if they're foamed, the noise levels are acceptable.
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Old 03-02-2009, 13:20   #4
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why alum? high maintanance hard and pricy to fix if you touch a dock not to mention electralisis....jt
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Old 03-02-2009, 15:09   #5
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you could build a one off cold molded foam/glass faster and cheaper
no headaches after the build been there done that
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Old 03-02-2009, 15:58   #6
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They crumple rather than smash if they hit things. Electrolysis can be a problem with any dissimilar metals. DON'T paint it, keep coins and sinkers away from contact.make sure there are no carbon black containing products adjacent the skin. They are heavier than equivalent composite but they don't get soggy cores or osmosis. Plenty of fishing boats have gone to aluminium for their toughness. They are dead easy to attch things if you have a TIG or a MIG welder handy.
I built a small aluminium tri almost thirty years ago and it was reasonably light and very tough. I could park it on rocks without punching a hole in it.
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Old 03-02-2009, 16:31   #7
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Here are a few pictures, and a video, of the nicest aluminum catamarans currently in production. A rather complex construction process, but yields a very strong hull that's certainly fire resistent. Gathering information from this company that's mastered the craft of aluminum builds is probably a good place to start... Yapluka Yachts.

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Old 03-02-2009, 16:31   #8
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Owen Easton and Peter Kerr in Australia have been building aluminium cats for years. My perosnal view is that they need to be at about 43/45 foot miniumum for the weight to start to even out. Peters boats are mostly done using dagger boards, and he has recently launched a 40 something foot power cat. Contact me if you want Peters details.
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Old 03-02-2009, 19:56   #9
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I agree with needing at least mid 40s in length before they are really useful, unless you want the ability to take punishment such as an aluminium runabout. I have seen lovely examples of both Easton and Kerr boats. They are reasonably quick and easy to build if you set yourself up well. Once a weld is made, it stays there, not like a resin filled strip of glass rovings that you are using to tape an overhead join. There is a bit of skill avoiding distortion and using shrinage to your advantage but I know Easton at least is extremely helpful and so I imagine would Kerr
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Old 05-02-2009, 04:27   #10
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Aluminum is cool

We lived aboard a 36' aluminum sloop for 7 years in the 90's. I would go back with an aluminum 40-44' cat in a heartbeat if I could afford it...There is the dive boat on Croatia is it??

Some really cool things.

Because of the strength you don't need anywhere near the material - 5/16" plate is plenty built on 18-24" center ribs. Lots more room. Our 36 footer had the interior of a 40.

You never paint it. (We never even washed the hull.) Let it oxidize and the thieves will go to the bright shiny waxed fiberglass beauty every time.

If you use TefGel on any SS fittings and attachments dissimilar metal corrosion is not a problem.

Aluminum is easy to work with (you can actually use some wood tools and a grinder) and welding it is very easy with a little practice.

When we hit the rocks at 4am off Little Vieques Puerto Rico - the rudder bent in half, and the bottom crumpled. We sailed to St John and I was able to haul and fill in the dents with glass. With glass of wood we would have sunk. No question.

Attachments like lifelines, cleats, anchor rollers, hatches do not leak as they are welded... And they are much stronger.

When you occasionally touch the bottom (hehe we called STK shine the keel) all you are doing is cleaning barnacles!

All tanks are integral and welded...


You must insulate for cold weather (aluminum sweats!)

They are more expensive.

Have to use special bottom paint. Copper is not a good thing with aluminum!

Don't know about more noise. Our boat wasn't loud to us...

Resell probably is no where near as good as they aren't accepted yet.

My 2cents anyway.

Soon as someone comes and buys this horse farm and business - I'll see what I can find!


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