Fiberglass vs. aluminum?

[GordMay]

Copper-Nickel [Cu-Ni] Boat Hulls:


In 1938, a 45 ft [13.72m] motor cruiser 'Miss Revere' was built, in USA, using 70-30 copper-nickel [Cu-Ni], welded over 70-30 framing, and fitted with aluminum bulkheads. Between 1938 and 1965, many US Coast Guard motor whale boats were sheathed, at the waterline, Cu-Ni.
In 1968, the pleasure yacht 'Asperida' [1] was built, using 70-30 Cu-Ni hull plating, over framing of the same material; this boat is still in service today.

The first of several copper-nickel commercial-fishing boats was built in 1971. The hull of the 67 ft / 20 42 M 'Copper Mariner' was constructed from 1/4" [6 mm] 90-10 welded copper-nickel plate, installed over steel framing. More recently several other trawlers and general-purpose fishing boats have been built using copper- nickel alloys.

One interesting example is the 18 year old sailboat ‘Pretty Penny’. This all copper-nickel boat, had not been slipped for 16 years, and required only a wooden scraper, to remove the layer of grass from the hull.

Some interesting articles about Copper-Nickel alloy [Cu-Ni] Boats:

[1] “The Asperida: A Copper-Nickel Sailboat after More than Thirty Years in Seawater” ~ by Harold T. Michels and Kenneth P. Geremia
➥ https://www.copper.org/applications/...boat_hull.html

“Copper-Nickel Boat Hulls: Performance and Corrosion” ~ by Carol Powell
➥ https://www.copper.org/applications/...corrosion.html

“Copper-nickel sheathing and its use for ship hulls and offshore structures” ~ by Carol A. Powell
➥ https://www.sciencedirect.com/scienc...64830594900914

Michael Kasten’s excellent “METAL BOATS For Blue Water” webpage includes a review of Cu-Ni for boats.
➥ Metal Boats For Blue Water - Kasten Marine Design

[s/v Jedi]

Monel was created in the early 1900’s but cupronickel has been used since the beginning of time by the Chinese. Monel is not a cupronickel because it has less copper and more nickel than cupronickel.

There are many alloys but cost is the big problem with these. We all have Monel and cupronickel parts aboard, from strainer baskets to heat exchangers and sometimes even prop shafts, but to build a hull out of these materials is very expensive.

For shipbuilding there are some interesting trends, like aluminum superstructure on steel hulls. I believe they even invented steel plates with aluminum coatings.

An modern aluminum sailboat is at the top of the line and has no corrosion problems. Dutch and French builders are famous for their quality sailboats.

[glenn.225]

[QUOTE=s/v Jedi; I believe they even invented steel plates with aluminum coatings.

[/QUOTE]

That would be aluminized steel. Widely used in automotive and industry. More corrosion resistance than steel but has many of the properties of steel.
I'm not sure of its marine use.



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[glenn.225]

There is also an aluminum/steel bar made, one side steel, the other aluminum, so you can weld to each. Useful for joining aluminum to steel, such as an aluminum superstructure on a steel hull.

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[Cheechako]

Fiberglass all the way. Many issues with maintenenace on aluminum boats. I've managed construction of aluminum smaller craft to 30 ft. Two transoms were replaced at less than two years due to small discrepancies in the alloy. Various other issues. Welding can be an issue as the weld bead is soft compared with the alloy and cracks readily as the boat flexes. Aluminum is about 2.5 times more "flexy" than steel. But I suppose it compares with fiberglass well enough in that regard.
It's a fun material and does have some advantages, but interaction with other metals, or with seawater, is not one of them. Your boat becomes the sacrificial zinc.

I buddy sailed with friends who had their custom 48 ft aluminum cutter for about 10 years. They painted that boat 3 times in 10 years. The first time it was done by a high end yacht yard in Florida. The second time 2-3 years they did it in Trinidad. The third time it was painted in Columbia. It may have been painted again in the states to sell it a fourth time, I'm not sure.
Leave it bare, but watch for corrosion anyway.

[Cheechako]

Originally Posted by glenn.225

There is also an aluminum/steel bar made, one side steel, the other aluminum, so you can weld to each. Useful for joining aluminum to steel, such as an aluminum superstructure on a steel hull.

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It has been done by explosive bonding the two mateials. Some fittings on Aircraft Carrier decks were made this way. I knew a guy whose company did it. We used to call him "Crazy Al".
There may be more modern ways now?. The "unbondable" materials supposedly dont have time during an explosion to "realize they are not compatible" and bond like welding....

https://www.youtube.com/watch?v=u9_bqafUJfA

[s/v Jedi]

Originally Posted by glenn.225

That would be aluminized steel. Widely used in automotive and industry. More corrosion resistance than steel but has many of the properties of steel.
I'm not sure of its marine use.

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They build river barges in Europe from it.

[Hendrik fiji]

I have a 14m alloy boat for about 2 years . The boat is 30 years old. I have not found any pitting inside or out and I think the bilge has always had water in it because of the keel mounted mast. There are also no anodes on the hull. can see where they where cut off. It has a stainless steel keel that lifts with hydraulic and it is bonded to hull. the keel has anodes. Also the SS rudder shaft is bonded to the hull. I dont have shore power connected but the boats next to me do.

[dlj]

Originally Posted by CarlF

Steve Dashew built his legendary offshore boats - both sail and power - in aluminum. He is especially a fan of unpainted aluminum for low maintenance.

Managing the corrosion risk isn’t difficult as long as you follow some basic rules.

Yes but Dashew is doing high latitude sailing. His boats are aimed at an extreme end of sailing. The two preferred hull materials for high latitude sailing are aluminum and steel.

A heavy FRP hull will likely have much higher impact resistance than previous posts suggest. The best material for that is steel.

It is much easier to find knowledgeable workers dealing with FRP than Al hulled boats so if you are planning to spend a lot of time in more remote locations, but not high latitude, then FRP would be preferred. Or, you need to be an expert in everything from welding aluminum to any kind of electrical installation. Plus you need to have the equipment to do all that work.

dj