Through-Hulls In Polar Regions

[bigman1]

iv' thought about this one for some time,google cant answer it,the question is this,boats that sail in the polar regions,do they ever suffer from frozen thru-hulls,if not why not,if they could the consequences could be disastrous,i hope someone can answer this.thanks.Ronnie.

[cburger]

By through hulls I am assuming you mean seacocks discharging below the water line, (Do to the word disastrous in your post). The answer is that usually the water is acting as an insulative barrier to the through hull if it is discharging far enough below the water line of the boat. If the water is so cold that it is freezing a foot or two below the water line there are other issues more pressing than freezing through hulls. Most skippers that are operating in frigid conditions for any lenght of time know the general areas of their boats that need some extra attention, I.E. insulation, heated spaces etc.

[barnakiel]

I believe if the water outside is not freezing, the water in the thru-hulls, generally, is not freezing either.

For more extreme cases the intake and discharge may be arranged via wells and such wells can be either warmed artificial circulation may be enforced to avoid ice build-up.

b.

[estarzinger]

Originally Posted by bigman1

iv' thought about this one for some time,google cant answer it,the question is this,boats that sail in the polar regions,do they ever suffer from frozen thru-hulls,if not why not,if they could the consequences could be disastrous,i hope someone can answer this.thanks.Ronnie.

For summer navigation in the polar regions this is not a problem because the ice is melting, and not freezing.

However, it is a more interesting situation for those few who choose to winter over in the ice. In the NW passage, for instance it can get to -50C and the freezing point of the water is about -2C, so the water surface freezes an average of 1.8m deep (about 6') over the winter. What happens then depends on how much and well the boat is heated and how often a thru hull is used.

For polar designed boats with a lot of power (full time gensets) there is no problem just heating everything and keeping water circulating to stop it freezing solid. But on a more normal cruising boat the situation is more 'interesting'.

In a poorly heated compartment, with a rarely used thru hull, the conventional technique is to pour some sort of antifreeze solution down the pipe into the thru hull and then quickly close the thru hull. If you close the thru hull with the straight salt water in it, the water might freeze and expand and crack the thru hull.

Of the three cruisers we know well who have wintered over, two were able to use their head thru-hulls all winter (I presume because they heated their boat well and pumped the head several times a day) and one has his freeze (he ran very short of heating fuel and let the boat get very cold) and had to go to a bucket. But that frozen pipe caused no damage.

All three boats had a different problem with the thick ice. It froze around their props early in the winter. Then more snow fell and the ice thickened and the sterns of the boats were dragged down (while the bows stayed floating on top of the ice). All three came to such an angle that there was serious danger and all three had to cut the ice around the transoms to let the sterns pop up. Fortunately a chain saw turns out to cut ice pretty easily.