Till Lincke — SPW Feathering Propeller in the Arctic
In January 2003, after an irreparable defect of our Maxprop feathering propeller in Gran Canaria, we have fitted our club-owned 18-metre sailing yacht “Passage” with the Variprop DF 112, a three-bladed feathering propeller by SPW. The “Passage”, a 18-metre Alusloop, was originally designed for the 1990s “Whitbread-around the World-Race” and has been in use for charter sailing trips and expeditions up north by our sailing club “Mare-Incognita” (www.mareincognita.ch) since 2010.
2013, before we tackled our first expedition into the ice-covered fields of the Arctic, pack-ice-experienced skippers recommended to replace the feathering propeller with a fixed pitch propeller. There would be a risk of damage to the mechanism of the propeller from chunks of ice. We ignored this warning, even though the seven-year-old SPW-propeller already had over 40,000 nautical miles on the clock. In spite of minimal service (yearly greasing during winter storage) the propeller still did its duty without complaint.
The switch into the sailing position by switching into the reverse gear always worked without any problems. When mooring lengthwise under offshore wind, a manoeuvre that we had to perform somewhat rapidly in stronger winds due to the lack of bow and stern thrusters, we particularly appreciated the very good braking effect when pushing backwards.
This is probably thanks to the possibility of setting the optimal pitch in forward and reverse separately.
Considering the warnings of Arctic experts, one can imagine how anxious we were while ploughing through a field of pack ice (frozen sea water, in contrast to glacier ice) for the first time. Usually, this is relatively unproblematic for the drive system because ice chunks are pushed aside by the ship’s bow or at times by the keel. But every now and then, one of the chunks scraping under the hull turns and if you are unlucky, one of its tentacles gets into the rotation of the propeller.
This may be fine with young ice with the consistency of rotten wood, but should be avoided with multiyear ice and glacial ice if possible, both of which are substantially harder.
This does not always work, especially if you are forced to free yourself from a dead end in reverse so that the propeller is not protected by the keel anymore.
We got into such a predicament during our circumnavigation of Cape Farewell, the southern cape of Greenland in July 2014, as we were locked in by a compression ridge (ice packs pushed on top of each other by the current). The blows that spread through the hull via the drive train due to the mistreatment of the propeller as an ice-mixer, gave us quite a fright. This, however, was relatively “soft” first-year ice.
During this year's inspection in the winter storage we found bearing clearance of the propeller axes, which – according to an examination by the SPW-specialists – can no longer be eliminated via revision. After 17 years and about 120,000 nautical miles of uncomplaining service under the toughest conditions our propeller will now go into a well-earned retirement.
We have ordered its successor at SPW, the Variprop DF 112, which is supposed to be even more efficient thanks to its four propeller blades. We are curious to see how it will prove itself this summer on its maiden voyage to East Greenland – see “Törns 2020” at www.mareincognita.ch