“Aker Arctic Bronze Propellers for Ice-class Ships” –MarineLink

Image: Aker Arctic

Its nice when technology makes things better, but it really nice when tech makes things better and cheaper.

MarineLink is reporting Aker Arctic is claiming they have developed new parameters, “strength dimensioning criteria,” that will allow the use of bronze propellers on high ice class vessels, and that an ice class 1A vessel is now operating¬†with bronze propellers designed and supplied by Aker Arctic.

“While bronze is not as strong as stainless steel, it has a number of benefits in marine applications such as good resistance against corrosion and cavitation damage. The material is also easy to work with both during manufacturing as well as when carrying out maintenance and repairs. Compared to a similarly-sized stainless steel propeller, a bronze screw is also cheaper.”

10 thoughts on ““Aker Arctic Bronze Propellers for Ice-class Ships” –MarineLink

      • That was my point. Blade shape is about cavitation and cavitation is about, 1 noise and 2. propulsion efficiency, which as much as anything is about fuel burn.
        I was wondering if the structure required make bronze props strong enough for use in ice would also make them noisy and inefficient in terms of fuel burn..
        The thing about engineering is that you very rarely get something for nothing.

      • I was just saying that any prop designed to operate in ice is probably going to look a bit clunky, because it will have to be thicker, and will not have the swept back tapper to a point we se in modern destroyer and submarine props. No probably not as efficient but aside from the fact that the Bronze blades might have to be thicker (and that is not necessarily a disadvantage), I think the props are going to look similar.

      • The reasons for using bronze instead of stainless steel are quoted above. In this case, “high ice class” refers to Baltic ice classes 1A and 1A Super operating primarily in first-year ice. Stainless steel is obviously the only realistic alternative for icebreakers and other high Polar Class ships with extensive propeller-ice interaction in heavy ice conditions.

        As for the new “strength dimensioning criteria” mentioned in the article, it combines the company’s proprietary knowledge about the location and magnitude of the ice loads with the blade geometry and material properties. As a result, the propeller designer has a better understanding on where to add the extra strengthening and how much additional thickness etc. is required to make the blades strong enough for the intended use. While the hydrodynamic efficiency of the propeller will obviously be slightly lower than if it was designed only for open water operations, optimizing the design using the newly-developed method reduces the negative impact of the ice class.

        The propellers pictured in the article are installed on a tugboat so it’s of relatively simple design. However, the same approach is directly applicable to more complex blade geometries such as skewed blades.

      • While I’m not a specialist in ice class propellers, I’d probably recommend stainless steel for the Great Lakes icebreaker as I imagine the future vessel to be somewhat similar to USCGC Mackinaw with ice-rated azimuthing propulsion units used actively to break up the ice. However, smaller and/or lower ice class vessels such as buoy tenders could use bronze.

  1. December 21, 2018 award of contract to HII for the 10th and 11th National Security Cutters for $930M plus earlier awards of $94M and $97M for long lead materials, total $1,121M, understand Coast Guard will fund GFE under separate contracts.

    Understood the original Deepwater program was only for eight NSC ships, your thoughts on whether money spent wisely or are there other Coast Guard priorities, Congressional pork barrel politics in play?

    • Nick, this is off topic and would have probably been more appropriate for a post related to the Bertholf class NSCs, FYI,you can do a quick search by just entering NSC in one of the search boxes, but since you asked. We need to replace the older ships as quickly as possible. If we had started the OPC program earlier, say four years earlier, so that we would have had an OPC in commission in 2017, I don’t think they would have built more than eight or at most nine NSCs (nine was what the Fleet Mix Study said we needed). As it is, we will be seeing probably one NSC and one OPC completed in 2021, 2022, and 2023. If OPC construction continues as planned after that it will be two OPCs per year until 2034. Frankly I hope OPC construction will be increased to a higher rate after the first is completed and tested. Otherwise we are likely to see WMECs fail and be decommissioned before replacements are ready. Eleven NSCs and 25 OPCs will still leave us with a smaller number of large cutters than we have had. Abandonment of the multiple crewing “crew rotation concept” means they will not provide as many cutter days as planned, so we will probably need more than 25 OPCs anyway.

      We really need an updated Fleet Mix Study.

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