The Offshore Voyaging Reference Site

S/V “Polaris”, Built For The Arctic

Those of you who have read some accounts of boats wintering over in the polar regions may have visions of dented hull plates, narrow escapes and three inches of frost on the INSIDE of the boat. That is not the Polaris way.

That is not to say that there are not hazards lurking in Michael and Martina’s project of wintering over on the west coast of Greenland, but the difference is that they spent years planning and having a boat built that could not only survive a winter frozen into the ice at 68N, but do it with a minimum of drama and adventure. (I think it was Amundsen, the incredible Norwegian explorer who was first through the Northwest Passage and first to the South Pole, both without losing a life, that said something like “adventure is the result of poor planning”.)

(See more pictures of Polaris here and here.)

To detail all of this boat’s features for an Arctic winter would take a book, but here are a few:

  • Hull scantlings: Although Polaris is not ice classed, the hull is still built super-strong from aluminum, with thicker plate over fewer ribs and stringers than a boat like our Morgan’s Cloud, which has comparatively thin plate over many ribs and stringers—a lighter technique but not as resistant to denting from ice pressure. Also, Polaris has a massive “U”-shaped beam welded to the inside of the hull right round the waterline to take ice stress and help stop the plate from denting.
  • Insulation: The hull is insulated with a special fire proof material that was, I believe, developed for the Space Station. The ports and hatches are the best available and double glazed.
  • Heating: The boat has not one, but THREE separate heating systems. More on that here.
  • Staying put: Polaris has the best and most complete system for putting in shorefasts I have ever seen.
  • Dry exhaust: The engine has a dry exhaust and is cooled by a heat exchanger inside the hull plating where it is safe from ice. As a result the engine will be in commission and ready to go all winter.
  • Huge fuel tanks: A total diesel capacity of 3000 Liters ensures that the crew will be warm and toasty even if they do not break out of the ice until mid-June.
  • Little details: The center board trunk has a valve that allows the crew to pump air into it, thereby displacing the water that would freeze and possibly damage the hull. The through-hull fittings are custom machined so that the outer diameter is slightly larger than the inner at the seacock. The result is that a plug of ice will automatically expel as it freezes, thereby relieving stress on the fitting.

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It’s a relief to see another exploration boat with dry exhaust and keel cooling. No system is perfect, but it just seems to make more sense to keep water out of a boat as much as possible. Less danger of galvanic corrosion via the cooling system too, and who hasn’t met someone who had an engine ruined when exhaust water got inside the combustion side of the engine (the reason for those inverted loops that can fail in following seas)? I once took a borescope and looked inside an engine that had ingested seawater. That’s enough to make anyone go for a dry exhaust. It did that for me. I don’t quite understand why dry exhaust isn’t more common on recreational boats.


Hmm. I don’t fully understand the concern about stack fires. This potential risk would of course apply to MILLIONS of boats (probably at least tens of millions globally) — not many fishing boats, including wooden ones, without a dry exhaust. And I think the same risk applies to wet exhaust — at least wet exhaust I have owned — because the exhaust coming from the engine is always dry, so you’ve got a length of hot (dry) pipe on the way to the wet side regardless. It’s hottest at the engine, so the “risk” drops the farther away from the engine the exhaust goes. If you use the same stuff to cover the entire pipe as you do at the engine, then by definition the “risk” drops dramatically. Of course a bad installation could be risky. That applies to wet exhaust, the other risk being flooding (see below).

As an aside, the fabric covering my exhaust is so effective that I can grab it an inch from the engine — often do unintentionally when climbing around in the engine room at sea.

As for the mess on deck, I don’t understand that one. I have a stack. The exhaust goes up to pollute the air, not onto the deck. I guess this problem would apply to an installation with no stack. But I have an unpainted aluminum boat, and one reason I like such a boat a boat is that I couldn’t care less about external cosmetics (bad experience in the past with caring for varnished teak). Again, I think it’s the installation that matters.

But there are problems with any choice on a boat; this website is good at looking at ups and downs. One downside of wet exhaust is that it’s noisier: it’s like a diesel truck instead of like, well, a diesel truck gargling. The real issue here, for this article, is which exhaust is best for a high-latitude exploration-type boat. To me, the ideal boat has NO HOLES in its underwater hull. There’s no ideal boat, but why not get closer by limiting the number of holes? One of those holes you don’t need is the one that sucks water into the boat — yes, actually sucks it in, in large volumes, which seems crazy for a boat — to cool and quieten the exhaust.

Oh, I forgot about a disadvantage of dry exhaust, at least on my boat: I need to put a cover over the top of the stack when putting the boat to bed to prevent rain from going down the stack (so I don’t have a wet exhaust!). AND I need to remember to take it off again before starting the engine. I swear that I have never forgotten to do that….


I absolutely love my dry exhaust for many years already. Mess on deck ? Not a bit of it.
Ok, the white transom gets a little greyish over time, no problem to clean it once or twice a season. Must look at Steve Dashews study though.


Sure thing John, I didn’t mean to imply that you implied anything like that. Just had to throw in my experience. The only disadvantage of dry exhaust that I’m aware of is the need for good insulation of exhaust tubes which takes up more space that way and it’s more expensive initially. One needs a compensator and stainless tubes and of course the keel pocket itself. And it has to be laid out correctly to work in all water temperatures.
But I will have a look at Steve Dashews piece to really be able to evaluate the dry exhaust system. As for me, it’s just perfect.