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Old 09-09-2015, 19:54   #1
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Aluminium yacht quesstions..

We're looking at a couple of aluminium yachts at present, both of which require flights to view so we're yet to look through them.
A couple of things that have occurred to me that someone will likely have an answer for...
1. Unpainted aluminium oxidises and is low maintenance, I get this and like the concept... but does the oxidation leave blackening on hands and feet when contacted? I had an aluminium bar attached to a shingle rake at home and when I used it my hands ended up black from the oxide...

2. Is the noise from aluminium hull significantly greater in passage or at anchor than fibreglass boats?
3. Does the lighter construction necessarily create a less sea-kindly motion in passage or are there ways to overcome-compensate this?

4. I've read varying reports on the heat generated from unpainted decks in the Pacific climate, does anyone have a frame on this that comes from experience (is it too hot to walk on all day... or how is this overcome without painting?)

5. Are there any health impacts from sustained contact with aluminium oxide?

These may be stupid questions... but all the serious thinking is complete now and I only have stupid left, sorry.
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Old 09-09-2015, 20:19   #2
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Re: Aluminium yacht quesstions..

Quote:
Originally Posted by nzmal View Post
We're looking at a couple of aluminium yachts at present, both of which require flights to view so we're yet to look through them.
A couple of things that have occurred to me that someone will likely have an answer for...
1. Unpainted aluminium oxidises and is low maintenance, I get this and like the concept... but does the oxidation leave blackening on hands and feet when contacted? I had an aluminium bar attached to a shingle rake at home and when I used it my hands ended up black from the oxide...

>>No

2. Is the noise from aluminium hull significantly greater in passage or at anchor than fibreglass boats?

>> it is if uninsulated, but most aluminum boats are insulated and in fact generally quieter than fiberglass boats

3. Does the lighter construction necessarily create a less sea-kindly motion in passage or are there ways to overcome-compensate this?

>> no issue

4. I've read varying reports on the heat generated from unpainted decks in the Pacific climate, does anyone have a frame on this that comes from experience (is it too hot to walk on all day... or how is this overcome without painting?)

>> you sure it has unpainted decks? Most aluminum boats with unpainted topsides in fact have non-skid painted decks. But yes a few have unpainted decks and yes they get hot in the tropics. Friends of ours with such decks wear shoes.

5. Are there any health impacts from sustained contact with aluminium oxide?

>>no . . . . . Yea sure if you were to eat several kg's a day for years there would be . . . But practically speaking no. You do want the insides of the water tanks to be coated with a food grade approved coating.

These may be stupid questions... but all the serious thinking is complete now and I only have stupid left, sorry.
.......
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Old 09-09-2015, 20:46   #3
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Re: Aluminium yacht quesstions..

Thanks estar,
the topsides are unpainted on one yacht but have some type of rubberised tread pads fixed at appropriate intervals.
The other has a painted deck.
I guess I'm looking for the best solution bearing in mind longevity of paint on aluminium vs potential discomfort of hot decks. We have kids travelling with us (11 and 13) who will undoubtedly spend a lot of time messing about on deck while at anchor. We're thinking about how an unpainted yacht (and specifically the deck) will impact on them.
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Old 09-09-2015, 20:50   #4
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Re: Aluminium yacht quesstions..

You might be interested in Michael Kasten's web site and his articles on boat building.

Articles by Michael Kasten - Kasten Marine Design, Inc.
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Old 10-09-2015, 07:51   #5
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Re: Aluminium yacht quesstions..

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Originally Posted by nzmal View Post
I guess I'm looking for the best solution bearing in mind longevity of paint on aluminium vs potential discomfort of hot decks. We have kids travelling with us (11 and 13) who will undoubtedly spend a lot of time messing about on deck while at anchor. We're thinking about how an unpainted yacht (and specifically the deck) will impact on them.
The rubber pads nonskid (tread master and the like) are good and comfortable. They do tend to peel up over time and need to be redone.

Nonskid paint (with grit) is probably the easiest solution. the thing with it is that, unlike gloss topside paint, it is very little work to maintain. Repairs and touch up do not show (like they do in gloss paint) and you can just go around once a year and touch up any little bad spots.
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Old 10-09-2015, 12:48   #6
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Re: Aluminium yacht quesstions..

Quote:
Originally Posted by nzmal View Post
We're looking at a couple of aluminium yachts at present, both of which require flights to view so we're yet to look through them.
A couple of things that have occurred to me that someone will likely have an answer for...
1. Unpainted aluminium oxidises and is low maintenance, I get this and like the concept... but does the oxidation leave blackening on hands and feet when contacted? I had an aluminium bar attached to a shingle rake at home and when I used it my hands ended up black from the oxide...

2. Is the noise from aluminium hull significantly greater in passage or at anchor than fibreglass boats?
3. Does the lighter construction necessarily create a less sea-kindly motion in passage or are there ways to overcome-compensate this?

4. I've read varying reports on the heat generated from unpainted decks in the Pacific climate, does anyone have a frame on this that comes from experience (is it too hot to walk on all day... or how is this overcome without painting?)

.
Two aluminum yachts I've worked on extensively and sailed/made passages on are a custom Palmer-Johnson 52' sloop and a custom 54' cockpit MY. The PJ was finished like a yacht: Awlgrip'd and varnished trim; the MY was finished like a nicer work boat, but mostly unpainted outside. The PJ had extensive corrosion issues, integral aluminum holding tank, for one. The MY had none. As to your questions:

1--Bare aluminum oxidizes as it is exposed to weather. Examples of this oxidation are everywhere for us to see, street light and sign poles being just an example. The surface oxidation can rub off on your hand or clothing, if you rub hard enough. But on a yacht, regular washing controls this to a great degree.

2--Generally, aluminum boats are very definitely noisier than wood boats; glass boats fall somewhere between them. Compare the sound made by your wooden chop sticks, against the lacquered wood bowl, with the sound of stainless flatware against an army stainless tray. But there are many ways to partially compensate for this through thoughtful design and the use of damping and sound deadening materials.

3--In a well designed cruising boat the relatively small weight savings of aluminum construction (over composite construction) should not significantly affect its motion.

4--Metal is most unforgiving on bare feet. And decks require some type of non-skid. The crew of one famous yacht discovered they needed mountaineering boots to cope with an oh so slippery, bare aluminum diamond-plate deck. A teak overlay can be exquisite, but it's costly and requires extra care. Sand in paint is pretty tough on exposed skin; Griptex is better. Treadmaster type coverings provide insulation and can be more comfortable on bare feet, but stain easier and must be carefully glued down using epoxy glue. Imitation teak decks look, well, imitation...ugh!

As far as hot metal, aluminum makes a most excellent heat sink.
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