Once again you given very interesting information Tuomas, well I wonder though, why did "Sibir" not have that, if (which sounds like that from your post) other earlier ships had already? I mean earlier ships like "Arktika" and "Lenin".

Yeah, the stainless steel ice belt is pretty nice and maintenance-free. When designing the new Finnish icebreaker, me and my friend were toying with the idea of covering the whole hull with the explosion-welded compound plate.

Anyway, even Inerta 160, which is today the "standard" for icegoing ships, is pretty okay. Sibir didn't have even that, to the hull roughness was quite high (they gave the value somewhere else in that book). That considerably increases the ice resistance.

Tuomas, this is very interesting information, I have never heard of such, and could not imagine, such might happen.. now I know why the newer icebreakers have this special stainless-steel coated part of hull to reduce friction! Very impressive to see last summer on "Kontio" as well "Otso".

Marchenko: Russian Arctic Seas, page 250:

There was no information about the nuclear icebreaker Sibir, which was the same type of icebreaker as the Arktika (the Leonid Brezhnev), in the press. The Sibir did not have Inerta-160 [low-friction hull coating] and had no heel system. The ice resistance was substantially less due to a lack of coverage. The Sibir spent 58 hours being nipped, which was 31% of the transit time. It needed to be chipped from ice repeatedly. Sometimes the operation to extricate the Sibir from ice captivity was carried out by the [SA-15 class] ship Okha, which navigated independently. The powerful nuclear icebreaker could not work effectively because of its corroded hull.

Sibir, the infamous nuclear-powered icebreaker that got stuck in ice and had to be freed by a cargo ship...