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Old 11-06-2014, 17:01   #1
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Aluminium Hulls

I am looking at different boats , I see most are fiberglass , some steel , a few cement . now I see a 50 ft Aluminium mono hull . What are the pros and cons of aluminium . what is the maintenance like. what too look out for if looking to buy one . your feed back is most appreciated

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Old 12-06-2014, 04:55   #2
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Re: Aluminium hulls

That's a good question. From what i've seen aluminium corrodes in a wet envirement so what keeps aluminium boats from crumbling away and how long do they last.
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Old 12-06-2014, 05:59   #3
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Re: Aluminium hulls

Focusing on basic metal corrosion IE oxidation (or rusting in ferrous metals) and for now ignoring galvanic, stray current, etc aluminum is a very good choice.

Most metals oxidize which is they react with oxygen. In steel boats its called rust. Rust in steel once it starts can progress rapidly and eventually eat all the way through the metal. Aluminum is different. When aluminum "rusts" it forms aluminum oxide which is a very hard substance and actually forms a protective coating over the aluminum underneath. So aluminum oxidation is more or less self limiting making it a very good option for use in marine environments.

There are negatives. Most aluminum alloys bend easily so hull plating needs to be relatively thick to avoid denting in between frames, but this is mainly a cosmetic issue. Also, like any metal boat you have to be very careful with wiring to avoid shorts and stray currents that can very quickly eat a hole in your boat.

Also have to be careful about mixing other metals with aluminum. For example stainless steel fittings should be insulated from the hull to avoid galvanic corrosion.
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Old 12-06-2014, 06:14   #4
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Re: Aluminium hulls

My 35 year old aluminium hull is doing fine.

I have just replaced some plating under the engine that was pitted badly from 35 years of salt water and crap falling down under the engine, but aside from that it is in excellant condition.

The biggest downsides are electrolysis if you are not careful with anodes and wiring.

Expensive and ineffective antifouling (cant use copper based).

Also its hard to get paint to stick really well, with bubbling being common after a few years.

Check for corrosion (often seen as a white powder) and welds cracking in the internal framing, stringers, floors deckbeams and bulkheads.

Cheers Ben
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Old 12-06-2014, 06:18   #5
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Re: Aluminium hulls

Quote:
Originally Posted by HVYJimmy View Post
I am looking at different boats , I see most are fiberglass , some steel , a few cement . now I see a 50 ft Aluminium mono hull . What are the pros and cons of aluminium . what is the maintenance like. what too look out for if looking to buy one . your feed back is most appreciated

cheers


jimmy
If you buy an aluminium boat, then you will have to become an expert in aluminium boats.
There is no choice otherwise you will be at the mercy of all the wives tales.
And at the mercy of all the bad things that can potenially happen with an aluminium boat.

Wives tale examples... you need to hang a seperate anode over the side while in port.
Steel boats will corrode an aluminium boat if alongside.

But with everything, there are exceptions.

You need to really know electrics, both DC and AC.

You need to know how to have a floating electrical system and how to test that it remains floating.

If you don't want to have a floating electrical system, then you need to know how to do that as well.

And much more.
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Old 12-06-2014, 07:09   #6
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Re: Aluminium hulls

Once a year, at the harvest moon, you must sacrifice many hundreds of euros of trilux 33 to the gods of aluminium yacht hulls.

You must account for every lost nut, bolt, or washer, lest the alloy deity discovers one in your bilge and sinks your ship as punishment.

Your must endure the infinite pains of the electrical system which never seems to fully isolate

You must sacrifice propshaft anodes regularly to Neptune

You must swear to never look into the water tanks. Really, Dont!

However you are given sacred immunity to soggy decks and osmosis and corroding chainplates

You pick your poisons
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Old 12-06-2014, 07:11   #7
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Re: Aluminium hulls

oh, yeah, and the yellow goop! it gets everywhere!
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Old 12-06-2014, 07:31   #8
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Re: Aluminium hulls

Have a look at Boatbuilding with Aluminum by Stephen F. Pollard.
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Old 12-06-2014, 09:29   #9
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Re: Aluminium hulls

The "Cons" of aluminum have been covered fairly well above (although I do think people are generally a bit too paranoid, myself included ).

Here are some "Pros"

-The best thing about an aluminum hull is not the hull. It is the deck, house and the multitude of structures and hardware that (hopefully) are welded (not through bolted) in place. This makes for a boat that is easy to keep dry down below (I'm talking bone-dry even in heavy weather) with no repetitive re-bedding of hardware and no rotten/soggy deck cores. Deck structures like bollards and anchor rode attach points are often strong enough to support the weight of the entire boat. To me, aluminum as just the right combination of strength and lightness for decks and houses.

-Above waterline aluminum does not need to be painted at all. This utilitarian look is an "acquired taste" but a good compromise would be to paint only the non-skid areas and perhaps the hull topsides. Leave the edges of rails (paint easy to chip) and tangs that get hardware attached (most likely place for paint bubbling) bare.

-An aluminum hull can have standpipes instead of standard through hull fittings. Another no maintenance item.

-Aluminum boats typically have blown-in insulation on the inside everywhere. This makes for a very cozy and dry (no condensation) interior (let's not talk about the fire hazard of some blown-in insulation).

-Very strong and permanent modifications and repairs can be made fairly easily with normal wood working tools and a welding machine. Amateurs (like me) should probably stay away from large below waterline repairs.

-Aluminum (and steel) boats are free of the flexing at sea that other materials may have. No creaking cabinetry (internal hull framing provides endless places to attach interior). No doors that wont shut or stay closed.

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Old 12-06-2014, 21:43   #10
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Re: Aluminium hulls

And you dont have the horrendous problem of trying to get a magnetic compass swung properly. Aluminum has many advantages over steel if you follow all the rules about wiring, and dissimilar metals. If it wasnt for my limited pocket book, aluminum would be my first choice for a boat. ______Grant.
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Old 12-06-2014, 22:40   #11
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Re: Aluminium hulls

One time we were romancing an aluminum hulled Van De Stadt Samoa 47, and asked advice of some friends of ours with a round bilge home built aluminium (from Oz) boat.

What they told us to look for was mostly if the bilges had been kept clean (grunge traps salt and leads to pitting), and check welds for cracks. Once aboard, you can easily tell if the interior's pretty used up, but the structural ones require effort to check, lots of hard to reach corners. Mirrors and lights on flexible stalks time, for some of it.

That particular boat was pretty tired, and we kept looking.

Ann
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Old 12-06-2014, 22:54   #12
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Re: Aluminium hulls

Like most things related to boats, your question needs to be answered for you, personally.

I suggest you go look at some 10 to 40 year old aluminum boats, and fiberglass boats of similar vintage. And talk to owners of such boats that seem interesting to you.

But you asked, so I will respond.

Aluminum boats are ugly, horribly ugly. A boat should be beautiful, or it should not exist.
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Old 12-06-2014, 23:03   #13
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Re: Aluminium hulls

Yes, incredibly ugly...
https://www.flickr.com/photos/aventu...7644281026926/
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Old 13-06-2014, 00:40   #14
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Re: Aluminium hulls

Use to do aluminium castings. If I save all my old alu pots and pans, a sand casting wouldn't be hard. Just dig a hole in the sand the shape of a boat.
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Old 13-06-2014, 04:37   #15
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Re: Aluminium hulls

Al and steel share the requirement for good design and construction. I Han an older alloy racer which had insoluble corrosion i


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