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Old 13-06-2014, 04:43   #16
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Re: Aluminium hulls

(Sorry - iPad has mind of its own)
Insoluble corrosion issues re the encapsulated lead keel and the toe rail which was bolted on with stainless steel !!! Could never get the paint around the sheer to stick. Had a sloppy electrician drop copper wiring into the bilge - wow that can really make an impact. A lifeline with a copper swage ate thru the deck in couple of months. Done right is good material though.


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Old 13-06-2014, 05:29   #17
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Re: Aluminium hulls

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Originally Posted by stillbuilding View Post
(Sorry - iPad has mind of its own)
Insoluble corrosion issues re the encapsulated lead keel and the toe rail which was bolted on with stainless steel !!! Could never get the paint around the sheer to stick. Had a sloppy electrician drop copper wiring into the bilge - wow that can really make an impact. A lifeline with a copper swage ate thru the deck in couple of months. Done right is good material though.


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There would be problems if the wrong aluminium was used.
was it AlMg4.5MnW28 or similar?
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Old 13-06-2014, 08:04   #18
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Re: Aluminium hulls

It was the maybe the first larger alloy yacht built in Melbourne, Australia so would have been stock standard plating and framing. Cannot recall now but think it was built around 1970 by Haulmaster Trailers so prob same as their bulk liquid freight trucks.


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Old 13-06-2014, 08:06   #19
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Re: Aluminium hulls

5083 from memory.



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Old 13-06-2014, 11:47   #20
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Re: Aluminium hulls

Yes, Deep, that is a perfect example: within a year or so, that hull will look like a workboat, a garbage scow barge. The lack of paint, and the inability to keep paint on marine Aluminium, leads to even the finest yacht looking like trash very quickly. Look at any pictures of Windhorse, for example.

Worse, as Still points out, the corrosion is not just on the outside -- ugly is far more than skin deep. Crawl around the bilges of any aluminum boat after a year or two. Or easier, just look at the stanchion bases or any other place where non-aluminum comes in contact with aluminum. Its not pretty. Its not strong. Its not clean.

And you can't do anything about it, any more than I can keep my hair from going grey, bones getting brittle. Its just a fact of life of the material.

The problems underwater, of course, are worse. Bottom paint, pitting near props, shafts, rudders. And consider how deep are those pits, and how thin is the plate. The boat is automatically perforating itself right where its worse: near the vibrations of the prop shaft strut for example.

Like too many things: great in theory, very bad in practice.
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Old 13-06-2014, 14:05   #21
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Re: Aluminium hulls

I would not want anyone to take a hard and fast set against alloy boats - that racer was a lovely yacht in most ways but the corrosion was significant. When I first put it up on the hard I found several inches of the plating adjacent to the keel just paper thin and indeed I ripped it open with a screwdriver. Easily replaced the plating of course but I know the issue is still there. The lead encapsulated keel was separated from the alloy plating of the keel by some sort of bituminous material which was plainly not effective and white corrosion by-product was always oozing out. I was always nervous as to the logical conclusion which may have meant replacing the keel entirely.

I agree with Ann's concern about the grunge in the bilges. There was always a lethal mix of salt and rubbish which I could never clean out and paint would never stick. On one haul-out I found a bolt holding an anode just threaded thru the plating and really just held in place by the corrosion. I do wonder what I missed. Alloy is certainly not forgiving of sloppy work. Was a nice sailing boat though.


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Old 13-06-2014, 14:47   #22
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Re: Aluminium hulls

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Yes, Deep, that is a perfect example: within a year or so, that hull will look like a workboat, a garbage scow barge. The lack of paint, and the inability to keep paint on marine Aluminium, leads to even the finest yacht looking like trash very quickly. Look at any pictures of Windhorse, for example.
Bull. Properly built and looked after there will be no problems with corrosion. Any builder that puts stainless in contact with aluminum is not doing a proper job. There should be no copper fittings on an aluminum boat. An electrician that scatters copper cuttings should be keel hauled. The owner should always vacuum the bilges after an unknown source has worked on the boat. All of these limitations are well known. There are many good looking aluminum boats that have been around 30 yrs or more. Now, you want ugly, take a look at a plywood cored deck that got wet because procedures that have been know for decades were not followed.
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Old 13-06-2014, 15:08   #23
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Re: Aluminium hulls

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Originally Posted by u4ea32 View Post
The problems underwater, of course, are worse. Bottom paint, pitting near props, shafts, rudders. And consider how deep are those pits, and how thin is the plate. The boat is automatically perforating itself right where its worse: near the vibrations of the prop shaft strut for example.

Like too many things: great in theory, very bad in practice.
Gee, that sounds a lot like what I hear from GRP boat owners saying about osmotic blistering!

And, FYI, I see 10 year old Garcia yachts that look damn good from a cosmetic standpoint. I don't know them well enough to comment on interior corrosion, but your comments about external cosmetics are simply wrong.

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Old 13-06-2014, 16:06   #24
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Re: Aluminium hulls

Well, I must apologize that yet again, my posting sounds like what I say is absolutely invariantly perfectly correct, and everyone else must agree or be wrong.

That's not my personality, but it sure seems to be my posting style! Wow. Sorry about that.

The point I am making, is that in my experience, which includes tens of thousands of offshore miles on uber quality aluminum offshore yachts, is that no matter what you do, you can't keep it looking in yacht shape, and the deterioration is pervasive even with very high levels of budget, man hours, and care.

For example, non-aluminum items are pervasive on boats. Wiring, fasteners, engines, sailing gear, food storage and preparation implements, and all sorts of other systems on board are not aluminum, and do cause issues with corrosion.

Bottom paint is a big problem. Ask anyone who owns or maintains an aluminum boat.

The electrical fields underwater caused by rotating props and shafts are an inescapable problem -- pitting always occurs, regardless of zincs, zinc under coats, epoxy, whatever. And the resulting pitting is very, very bad structurally: it causes extreme stress concentrations right where vibration happens. You can't prevent it.

All hard to reach places, especially in machinery spaces, are prime breeding grounds for corrosion. Sure, its not really a living cancer, but its a cancer nonetheless. As carbon dust from generators and alternators, steel dust from wearing bearings, copper sulfates from corroding wiring, etc etc collect in those hard to see, hard to find, hard to clean areas, virulent corrosion occurs.

Bubbling paint? Explore how deep that corrosion is, and you will look at the structural integrity of the vessel in a new light.

Unpainted topsides or interiors? Again, look at the pitting, and where it occurs: along welds, where the aluminum is already much weaker due to the welding process itself. Weakening the weakest parts -- self perforating.

Blown foam insulation? Hard to imagine a less suitable material for a boat. Consider just the fire risk. Then how mold forms. How do you inspect? A really, really bad idea.

Again, in my opinion, based on my experience. But its all real sailing experience, not armchair fantasy.
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Old 13-06-2014, 16:43   #25
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Re: Aluminium hulls

Here is a recent shot of Panope after her refit. She was first launched in 1982.



I did not need to strip the original paint. Very little corrosion was found. The original epoxy primer was completely sound.

I just sanded (36 grit) the decaying top coats, sandblasted the bare metal spots that I exposed and then applied a new layer of epoxy - followed by a brushed coat of polyurethane.

In this photo, next to my right arm, you can see an area of bare metal. This area probably did not get sandblasted properly during the original build in 1976. I am guessing there was a cradle support interfering. When I hauled Panope out of the water in the year 2000, there was no paint on this spot. The metal showed zero degradation.

At the waterline near the stem, a bobstay (galvanized chain) was formerly shackled to a welded chainplate with a SS shackle. This connection ended up being submerged for 20 years. The nearest zinc was 25 feet away. A small area of paint bubbling occurred with pitting of metal approximately 2% of the hull thickness (3/16").



This is by far the worst corrosion that I found anywhere on the boat. My father knew that bronze was a no-no on an aluminum boat so he attempted to isolate the bronze port holes and fasteners with plastic spacers and 5200. Corrosion pits are perhaps 25% of the thickness of the plate (3/16").



Here is a shot of the bilge. Note the ink marking from her original build (1976). Ballast is lead and cement. Some white paint is visible just above the cement. This was applied (haphazardly) by my father as an attempt to isolate the metal and cement. The frames that are visible are 6061 extrusions. 6061 does not posses great corrosion resistance. I have not found significant corrosion anywhere in the bilges.



Here is a shot of the bilge sump along with the new engine beds that I welded in place. I neglected the project for a few years and let some rainwater stand in the bilge - see stain (water entered through the gaping hole in the aft deck prior to pilothouse construction). This water was allowed to freeze. Now that I think of it, I let the water in the integral water tanks freeze also. No problems. Oh ya, I have had a look in the water tanks that had city water (chlorine - another no-no) in them for years. There are some tiny white corrosion bits floating around but the water is clear and tastes great after carbon filtering.



This is the typical condition of 38 year old foam. Foam was even blown in below the water line (yet another alleged no-no). I have looked under this foam in endless places throughout the boat and have found no problems.



For those that dislike the look of bare, oxidized aluminum, this is a nice compromise. The areas that will see abrasion are left bare. I would have left the hawse ports unpainted but they were previously painted. Note: The rusty washer in the far left of the photo is part of the road trailer.



Inspite of the numerous examples of "less than perfect" aluminum boat building practices, Panope has survived with all of her original plating intact. At the current rate of desegregation, I estimate that she will need some areas of re-plating in another 50 years. She will probably be beyond her service life in another couple hundred years.

Steve
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Old 13-06-2014, 18:32   #26
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Re: Aluminium hulls

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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.
LOL , I was a jobbing moulder , your cast boat would sink , to put a core into it, the shape of the inside of the boat , there would be so much pressure to blow the mould apart .the hull would not have enough displacement and sink
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Old 13-06-2014, 18:57   #27
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Re: Aluminium hulls

thanks everyone some very interesting views ,the boat I was looking at is 39 years old , so maybe tried , or maybe not . it sounds like if you now a lot about aluminium care , does and donts ,than it maybe allright . LOL just like steel
Thanks again

cheers

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Old 13-06-2014, 19:04   #28
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Re: Aluminium hulls

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thanks everyone some very interesting views ,the boat I was looking at is 39 years old , so maybe tried , or maybe not . it sounds like if you now a lot about aluminium care , does and donts ,than it maybe allright . LOL just like steel
Thanks again

cheers

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Old 13-06-2014, 19:15   #29
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Re: Aluminium hulls

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LOL , I was a jobbing moulder , your cast boat would sink , to put a core into it, the shape of the inside of the boat , there would be so much pressure to blow the mould apart .the hull would not have enough displacement and sink

Then I"ll turn it into a submarine. It was a joke and a cazy, absurd idea which made it a joke-could never collect enought alu pans
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Old 14-06-2014, 00:46   #30
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Re: Aluminium hulls

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Well, I must apologize that yet again, my posting sounds like what I say is absolutely invariantly perfectly correct, and everyone else must agree or be wrong.

That's not my personality, but it sure seems to be my posting style! Wow. Sorry about that.

The point I am making, is that in my experience, which includes tens of thousands of offshore miles on uber quality aluminum offshore yachts, is that no matter what you do, you can't keep it looking in yacht shape, and the deterioration is pervasive even with very high levels of budget, man hours, and care.

For example, non-aluminum items are pervasive on boats. Wiring, fasteners, engines, sailing gear, food storage and preparation implements, and all sorts of other systems on board are not aluminum, and do cause issues with corrosion.

Bottom paint is a big problem. Ask anyone who owns or maintains an aluminum boat.

The electrical fields underwater caused by rotating props and shafts are an inescapable problem -- pitting always occurs, regardless of zincs, zinc under coats, epoxy, whatever. And the resulting pitting is very, very bad structurally: it causes extreme stress concentrations right where vibration happens. You can't prevent it.

All hard to reach places, especially in machinery spaces, are prime breeding grounds for corrosion. Sure, its not really a living cancer, but its a cancer nonetheless. As carbon dust from generators and alternators, steel dust from wearing bearings, copper sulfates from corroding wiring, etc etc collect in those hard to see, hard to find, hard to clean areas, virulent corrosion occurs.

Bubbling paint? Explore how deep that corrosion is, and you will look at the structural integrity of the vessel in a new light.

Unpainted topsides or interiors? Again, look at the pitting, and where it occurs: along welds, where the aluminum is already much weaker due to the welding process itself. Weakening the weakest parts -- self perforating.

Blown foam insulation? Hard to imagine a less suitable material for a boat. Consider just the fire risk. Then how mold forms. How do you inspect? A really, really bad idea.

Again, in my opinion, based on my experience. But its all real sailing experience, not armchair fantasy.

U4ea32, one thing is clear from your posts. You have had all your experiences with boats that have not been built properly out of the right materials.

There is a simple one liner that sums up....
If aluminium boats were as bad as you write , then no one would use that material and they certainly would not use it twice.
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