Brent H
Ultra Member
@Susquatch : the hubs and components are particularly large for the ice breaking requirements of the vessel and also the response time for the propeller - as you mentioned full ahead to full astern.
The props can rotate through the full say 60 degrees in roughly 12 seconds regardless of the loading or shaft speed. Given that the design of the ship is in the off shore tug category we are designed to push and pull oil rigs, set anchors and we even had a large foam induction fire fighting system that could drop 600 cubic meters a hour on an oil rig (this was removed in 2016 as it was not used and suffering maintenance issues)
With 4 engines running we do 14.7 knots ahead (27 KM/hr). In heavy ice 3 feet thick we are supposed to do at least 3 knots - however, depending on the ice density we usually clip along at 6 to 8 knots. We were busting up to 52 inches in Superior with only 3 engines a few years ago.
The blades are pretty much impervious to cavitation, we are still on the same set after close to 10 years service without the need to recondition. That means we haven't hit anything hard like dead heads, rocks, submerged buoys etc that would tear blade chunks out. Our last issue with that was sucking in a 4" hawser with a big shackle still attached some Laker dumped in the harbour. We chewed that up pretty good. The props are fitted with a Kort Nozzle - that is a mini tunnel to direct thrust that would be lost off the blade tips. The nozzle is fitted with an annular band of stainless welding that prevents cavitation damage of the nozzle steel.
You can see in the above picture the anti-cavitation band, some blade damage and the ground up shackle. Divers cut it out with an underwater lance - sort of the same principle as a gouging rod on land.
The props can rotate through the full say 60 degrees in roughly 12 seconds regardless of the loading or shaft speed. Given that the design of the ship is in the off shore tug category we are designed to push and pull oil rigs, set anchors and we even had a large foam induction fire fighting system that could drop 600 cubic meters a hour on an oil rig (this was removed in 2016 as it was not used and suffering maintenance issues)
With 4 engines running we do 14.7 knots ahead (27 KM/hr). In heavy ice 3 feet thick we are supposed to do at least 3 knots - however, depending on the ice density we usually clip along at 6 to 8 knots. We were busting up to 52 inches in Superior with only 3 engines a few years ago.
The blades are pretty much impervious to cavitation, we are still on the same set after close to 10 years service without the need to recondition. That means we haven't hit anything hard like dead heads, rocks, submerged buoys etc that would tear blade chunks out. Our last issue with that was sucking in a 4" hawser with a big shackle still attached some Laker dumped in the harbour. We chewed that up pretty good. The props are fitted with a Kort Nozzle - that is a mini tunnel to direct thrust that would be lost off the blade tips. The nozzle is fitted with an annular band of stainless welding that prevents cavitation damage of the nozzle steel.
You can see in the above picture the anti-cavitation band, some blade damage and the ground up shackle. Divers cut it out with an underwater lance - sort of the same principle as a gouging rod on land.
Was at Bent Horn for the longest time, then others. What were you doing up there?