What hull material is best for cold water ocean boating?

Good question ...

I would pick the hull which is best suited to withstand running over and into ICE !! That would reduce your choices down to steel. Though if you don't have a concern for that, I would think that Fiberglass is the easiest material to deal with. Fiberglass can easily have issues such as cracking or decay from say trapped water but the hull itself can't rot from galvanic corrosion per se. Though the anodes are needed to protect other parts of the boat.

If you are serious about stray current or galvanic corrosion, a fiberglass boat with a bonding system, properly maintained electrical system, and perhaps one of the devices; either galvanic isolator or Isolation transformer being installed is the best solution in my opinion. Also be careful not to put parts in the wrong places made of materials which will cause the boat to decay before it. And NEVER use brass.

COMMENTS:

Fiberglass is relatively cheap, holds up well, and is the most commonly used consumer boat material. Of course anodes are still required.

Aluminum, is light and even more durable than fiberglass. Since it's lighter it may be more ideal for planning boats opposed to displacement or semi-displacement hulls. Maybe good for sailboats ? Also, salt water will pit aluminum over time, I'm sure it requires a lot of attention and sacrificial anodes to ensure protection.

Steel, is the comerical grade stuff. Though steel is constantly trying to return to it's original state (red dust). When steel starts to rust badly, it costs a lot of money to repair. Steel is best suited for serious sea travel in my opinion.

All three can be classed for ice conditions. There are Canadian fishing trawlers that fish above the ice pack with fiberglass hulls... of course, they're 6 inches thick at the bow! I'm not a fan of aluminum hulls. There are too many opportunities for surprises with the wide variability in stock quality, and even the best builder can't see what's happening on a microscopic level.

You need to consider whether or not you're planning on transits above the ice pack... most people don't, and transiting an area where you encounter 'growlers' (loose ice) is far different from transiting an area above the ice pack.

I'm a fan of steel. Good paint is more than enough to keep electrolysis from getting out of hand. Zincs do need replacement, of course, and steel hulls have more zincs than do fiberglass hulls, but all things considered, steel has more friendly properties in dealing with ice strikes than does fiberglass. It's all about trade-off's.

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