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Old 17-05-2010, 00:25   #31
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Aluminium Catamaran

We have had a 42 ft aluminium cruising catamaran for quite a few years , and have had no major problems with Aluminium , we do however take care with the electrical system and berth connections. In comparison to other craft we consider it to be low maintenance and rugged . We had the hull painted by a yard and no problems there and have insulated the hull above water line.
The only problem we saw was if wood which was slightly damp was touching the aluminium there were minor signs of corrosion , due to lack of oxygen .
If we buy another boat we will try and get aluminium .

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Old 18-05-2010, 08:37   #32
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hi all, i just bought a 44 feet aluminium sailing boat, built in 1980. it is painted and the paint getting old now but it still in good shape after nearly 30 years. they used international 2 K paint. i checked with severall owner here in germany and now i tried Seajet emperor antifouling from japan. it should easily hold 2 years, let see.

I like aluminium very much and it is a nice good safe feeling , rocksolid. last weekend we hit easily 8 knots with my 14 ton boat and we liked it. i have very little corrosion and it looks like they installed a very good electricical system . go for it it will last for ever if you keep some maintenance and it is easier to paint a little bit instead using gelcoat, filler and glassfiber etc after a you hit the dock next time as i will happen

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Old 23-05-2010, 01:48   #33
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we have Pilots boats made in alu more then 40 years old, and no problm.
i am getting a OVNI,
low maint is the key word.
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Old 23-05-2010, 07:17   #34
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USCG and other govt boats use Epaint antifouling. It is expensive and there are several different Epaint products out. I have been talking to them and am almost convinced...although I think a trip to a country where tin is still available might be a better alternative.

As pointed out, there is probably no stronger material for small (under 60 foot or so) boat building. Understanding that aluminum that is in contact with oxygen forms aluminum oxide, a very protective and hard coating can do much to help in basic things like paint sticking and getting good welds. For a good permanent paint base (under antifouling for instance), epoxy paint on freshly prepped material is key but for topsides and decks quite often a cheaper and more easily replaced alkyd paint will suffice and adhere so long as applied directly to a freshly (within hours) prepared surface. Aluminum oxide begins to form on bare aluminum imediately. Paint won't be able to hold if it is lifting it off. But it is also important to realize that paint (above the waterline) is optional as far as corrossion is concerned. (although white does help keep the bare feet from burning!) Aluminum oxide also begins to melt at temps where aluminum is in a liquid state. It is very important to remove the oxide just prior to welding. In my experience there is no nicer material to weld so long as it is clean, welds like butter! And therefore, as pointed out in a previous post, it is very adaptable! Biggest concern is electrolysis which can be mostly prevented with careful use of electricity and dissimilar metals so long as you aren't in close proximity to in a marina...where your hull material, being less noble than almost any other, will want to sacrifice it's electrons in the saltwater (electrolite) environment. Keeping materials like stainless off your boat is fairly easy (both mild steel and zinc-galvinized- are very close to aluminum on the galvanic scale and much better) but the bronze and stainless underwater fittings on a boat a few feet away in a marina can be a threat especially if there is stray current or any physical (green wire) connection to other more noble metals.
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Old 23-05-2010, 08:03   #35
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Copyed from owner off 435 OVNI.
In-Depth Discussion of Aluminum Boat Design & Selection, Part III|Offshore Sailboat Voyaging|Attainable Adventure Cruising

This was very useful when it came to wiring up the new electronics such as the autopilot and the radar, as after each item was fitted the leak test could be conducted to ensure that no fault existed as a result. All electronic units had to be isolated from the hull structure during installation, once again to avoid any chance of leaks to the boat's structure. We did, in fact, have a small problem during installation, which was traced back to a faulty AIS unit and rectified, so the leak meter is a vital component on this type of boat.
Another area which we approached with caution was the shore power circuit. Having heard of (and seen) the effects of galvanic corrosion on boats kept in some marinas, we were particularly aware that this was an area for concern for us. Not that we intend to base Pèlerin in a marina, but who knows where we may decide to overwinter her at times. We finally opted to fit an isolation transformer, a device that is virtually unknown in Britain, at least, but by all accounts is common in the USA, and should be fitted to all metal boats, not just aluminum. Of course, we may never know just how effective the transformer is—if it’s working then we should see no problems, and I don’t suppose we shall turn it off to find out otherwise! It is a heavy and costly item, though, so we hope that it will prove its worth.

In keeping with our aim of avoiding drilling holes (and so giving corrosion a place to start) in the deck, we are working out the best ways of attaching all mobile deck gear, such as spinnaker sheet and guy blocks, using simple Spectra (Dyneema) strops. So far we haven’t had to drill one additional hole in the deck, another step in keeping water out of the boat at all costs. All fittings in stainless steel (such as stanchions) are isolated in plastic sockets to avoid corrosion, and all bolts are isolated with nylon washers, and liberal use of Tef-Gel to avoid seizures between dissimilar metals is essential to allow future maintenance.
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Old 23-05-2010, 08:44   #36
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Originally Posted by David M View Post
I have been skippering an aluminum research vessel now for 17 years. MidLandOne is right on with his analysis of aluminum hulls. The only thing I might add is that since TBT paint was banned it has been impossible to find decent anti-fouling paint that is legal in the USA. The only option I have found is a non-copper, not TBT Interlux bottom paint which is not very good at all. I hear US government boats are allowed to use some sort of special paint which is not allowed on civilian boats. . . .
The actual treaty against TBT paint and the US Laws about it exempt any commercial boat over 25 meters or any aluminum boat from the ban on TBT. Of course military and other type vessels are and always will be exempt - and it is us "little guys" that have to "save the environment" milliliter at a time versus the big guys and their tons of pollution.
- - However, outside US waters TBT paints are still widely available and used on all sizes of vessels. Problem is they are horribly expensive due to the shrinking customer base. You can find very economical TBT paint made in China (they did not sign the treaty) that is used on big vessels. The local yard workers will siphon out 5 gallons for you (into your own can) for about $90/gal. Which is quite a bargain what with the marine stores selling it for $200-300 per gallon.
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Old 23-05-2010, 09:31   #37
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I never had any problem getting paint to stick to my Colvin schooner. Never. I never had any corrosion problems. Of course, I never installed a motor or electronics, either. I did have electricity aboard at a marina two years running in the winter. We put on the epoxy undercoat with rollers [a bit drunk, as I pointed out earlier]. It is very forgiving stuff, and when laid on thick as they instruct on the cans, it works forever. I used to ground my schooner out on gravelly beaches regularly to scrub the bottom. [A lot easier than diving to do it with brushes]. TBT paint, like all bottom paints, is nasty stuff. But it works better than any bottom paint I ever dealt with. If I could afford anything besides plywood, I would definitely use aluminum.
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Old 23-05-2010, 10:05   #38
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Aluminum is like steel, only better. It has its own set of maintenance demands, just like any other material does. I think it is number one material for boat building followed closely by advanced composites.


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