So, what can go wrong with aluminum?

[Wckoek]

Originally Posted by DeepFrz

That was discovered on a 20 yr. old boat. Know any 20 yr. old fiberglass boats that don't need significant repairs or have gone through a very arduous and expensive refit?

There are a lot of 20 year old GRP boat that doesn't need significant repairs, more so for the hull alone, it had to depend on how the hull is constructed.

Speaking of problems does anyone have any issues or stories about condensation under insulating materials or problems with insulating materials in aluminum boats?

[Hasbeen]

I ran a couple of alloy tourists boats in the Great Barrier Reef trade. One 24 metre & one 29 metre, both catamarans, with large diesels, cruising at about 30 knots. The 24 m boat was fairly good, but the 29M boat had some problems.

The plating of the keel panted, causing cracks adjacent to the main welds. We chased these cracks for about 9 months, putting the thing on the hard & welding them up about every 3 weeks. She finally went into dry dock & the framing was increased & new plates welded in. Not even the designers could decide if it was wave action or engine vibration causing the problem.

At 3 months the main sea chests in each engine room, [1/2" plate] pin holed with electrolysis as the builders had made no provision to replace the cathodic protection with the boat in the water. The use of bronze gate valves was a real no no. With this replaces with stainless, & provision to fit anodes every 2 months this gave no further trouble.

Both boats developed cracks where the hull to wing deck met, but these were easily contained.

The boats were still working after 18 years, but I believe the maintenance bills were approaching the prohibitive level.

[Wckoek]

Originally Posted by Hasbeen

I ran a couple of alloy tourists boats in the Great Barrier Reef trade. One 24 metre & one 29 metre, both catamarans, with large diesels, cruising at about 30 knots. The 24 m boat was fairly good, but the 29M boat had some problems.

The plating of the keel panted, causing cracks adjacent to the main welds. We chased these cracks for about 9 months, putting the thing on the hard & welding them up about every 3 weeks. She finally went into dry dock & the framing was increased & new plates welded in. Not even the designers could decide if it was wave action or engine vibration causing the problem.

At 3 months the main sea chests in each engine room, [1/2" plate] pin holed with electrolysis as the builders had made no provision to replace the cathodic protection with the boat in the water. The use of bronze gate valves was a real no no. With this replaces with stainless, & provision to fit anodes every 2 months this gave no further trouble.

Both boats developed cracks where the hull to wing deck met, but these were easily contained.

The boats were still working after 18 years, but I believe the maintenance bills were approaching the prohibitive level.

Maybe for tourist or commercial boats it is wiser to build in steel, yes it requires more regular rust busting and maintainence, but it's routine in a commercial run boat, and if anything went wrong it can be fix faster and much cheaper.
Yeah, for leisure boats that get used once in a while, alum is the only way to go.

[Jim Cate]

Originally Posted by Wckoek

Maybe for tourist or commercial boats it is wiser to build in steel, yes it requires more regular rust busting and maintainence, but it's routine in a commercial run boat, and if anything went wrong it can be fix faster and much cheaper.
Yeah, for leisure boats that get used once in a while, alum is the only way to go.

Perhaps, but my observation is that around the world, the majority of work boats are aluminium, not steel. If steel is better, why do all t hese folks not use it?

Jim

[Zven]

Originally Posted by Wckoek

Yeah, for leisure boats that get used once in a while, alum is the only way to go.

I used to have a canal boat in England ...
It was built from steel.
What is more, I believe virtually all canal boats in England are steel boats.
Never saw a single aluminium boat around there.
I would not know the reason ... Perhaps because performance is not an issue?
There is a 5 kn speed limit on those canals.
Also, the water is not salty. :-)

[Stumble]

Originally Posted by Zven

I used to have a canal boat in England ...
It was built from steel.
What is more, I believe virtually all canal boats in England are steel boats.
Never saw a single aluminium boat around there.
I would not know the reason ... Perhaps because performance is not an issue?
There is a 5 kn speed limit on those canals.
Also, the water is not salty. :-)

Also because canal boats need to be heavy in order to get enough head room. using steel allows the boat to sink deeper without adding ballast, which allows a lower floorboard (relative to the water).

[El Pinguino]

Originally Posted by Stumble

Also because canal boats need to be heavy in order to get enough head room. using steel allows the boat to sink deeper without adding ballast, which allows a lower floorboard (relative to the water).

probably a lot more to do with tradition....

An alloy canal boat would be a bit like a reed boat on Lake Titicaca made out of plastic...

[markpierce]

Aluminum works great for airplanes.

[David M]

Originally Posted by Wckoek

There are a lot of 20 year old GRP boat that doesn't need significant repairs, more so for the hull alone, it had to depend on how the hull is constructed.

Speaking of problems does anyone have any issues or stories about condensation under insulating materials or problems with insulating materials in aluminum boats?

My aluminum boat has spray on foam on the inside of the hull making it impossible for water to reach the aluminum....except in the bilge areas, where it is possible to keep track of any corrosion because nothing is covered in those areas.

[David M]

Originally Posted by Wckoek

Maybe for tourist or commercial boats it is wiser to build in steel, yes it requires more regular rust busting and maintainence, but it's routine in a commercial run boat, and if anything went wrong it can be fix faster and much cheaper.
Yeah, for leisure boats that get used once in a while, alum is the only way to go.

There are many many many commercial aluminum boats in the world today. Aluminum does not rust nor does it need to be painted. In fact it is best not to paint an aluminum boat. You cannot say that about a steel hull.

Aluminum also has a higher strength to weight ratio which saves fuel. The fuel savings alone eventually pays for the price difference between steel and aluminum. You also have to consider the cost of labor of constantly chasing down rust.

[Wckoek]

Originally Posted by Jim Cate

Perhaps, but my observation is that around the world, the majority of work boats are aluminium, not steel. If steel is better, why do all t hese folks not use it?

Jim

The majority work boat that are build of aluminum are punts, sport fisher, runabouts, the lighter boats. Trawlers, tugs even recreational ones build of aluminum are rare.
Maybe the majority workboat build of aluminum is the lighter types but not when you look at the heavier types, maybe the lighter types can make use of the more corrosion resistant alloy like 5083 instead of the stronger but prone to electrolysis type.

What David M mention is right too, it's hard to say which is better by material or individual boat alone.
I see benefit in steel taking on paint, for antifouling purpose, and on displacement boats maybe weight isn't as much an issue as planing or semi planing types.

[double u]

btw: avoid treadmaster-type of non-skid mats: they are somewhat waterpermeable & there is corrosion going on under them. much worse of course teakdecks - to be avoided at all costs on an aluminiumboat

[Wckoek]

Originally Posted by double u

btw: avoid treadmaster-type of non-skid mats: they are somewhat waterpermeable & there is corrosion going on under them. much worse of course teakdecks - to be avoided at all costs on an aluminiumboat

How about those faux teak or cork type?
I know not all products are created equal.

[double u]

water can get under any of those, corrosion with trapped water (differential "oxygenation") is inevitable. friends had the alloy of the cockpitsole eaten through under the teak...
nonskid paint is the only thing we'd have
(but due to the near-inavailability of second hand aluminium boats-apart from Ovnis - TNB is going to be GRP)

[Wckoek]

Originally Posted by double u

water can get under any of those, corrosion with trapped water (differential "oxygenation") is inevitable. friends had the alloy of the cockpitsole eaten through under the teak...
nonskid paint is the only thing we'd have
(but due to the near-inavailability of second hand aluminium boats-apart from Ovnis - TNB is going to be GRP)

I guess the reason for going for aluminum even given the reduced GRP boat price now is for one off builds, most probably make sense for boats above 60 feet on the market as they are still competitive to build under the price.
The choice would be rather limited for decks, anyway I read that there are now vinyl wraps that could work well for aluminum hull, antifouling also. No experience with its use and longevity.