OPC Derived Frigate? Designed for the Royal Navy, Proposed for USN

Earlier I suggested that a derivative of the Offshore Patrol Cutter might fill the role of a frigate.

It now appears that a ship with the OPC’s DNA has been proposed as a frigate for the Royal Navy and has been offered to the US Navy. The Babcock Arrowhead 120 is the latest of five candidates for the Royal Navy’s Type 31e (the other four are outlined here).

The common thread is Vard designs. The family tree looks like this.

  • Róisín-class patrol vessel, two ships, 1500 tons, 79 meters (259 ft) in length, 23 knots, built by Babcock, commissioned into the Irish Naval Service in 1999.
  • Protector-class offshore patrol vessel, two ships, 1900 tons, 85 meters (279 ft) in length, 22 knots, built by BAE Systems Williamstown, Australia, for the New Zealand Navy, the first commissioned in 2010.
  • Samuel Beckett-class offshore patrol vessel, three ships completed and a fourth under construction, 2256 tons, 90 meters (300 ft) in length, 23 knots, built by Babcock and commissioned into the Irish Navy Service in 2014.
  • USCG Offshore Patrol Cutter, 4,000 tons, 110 meters (360 ft), to be built by Eastern in the US with the first expected to be commissioned in 2021.

OPC “Placemat”

NavyRecognition has the most complete description of the ship I have seen so far, and also has three protos of a model of the proposed ship.

Arrowhead 120 has a length of 120 meters, a breadth of 19 meters for a displacement of 4000 tonnes. Its speed is 24+ knots and range is 6000 nautical miles at 15 knots. Crew complement is 80 (plus 40). The vessel was design with commercial standard with applied naval engineering standards.

Missions bays: Space for numerous containerized units within the optimally located mission bays. Facilities for launch & recovery of UXVs. Flexible, reconfigurable infrastructure.

Missile options: Deck space for up to 8 surface to surface guided weapons. Up to 16 cells VLS.

Small calibre guns: Design provision for SCGs up to 30mm with associated EO sensors and magazine arrangements. Weapons can be fitted at a number of upperdeck positions.

Medium calibre guns: Design provision for MCG up to 5 Inch (127mm) with associated infrastructure.

Aviation: Flight deck sized for AW-101 Merlin/MH-60 Seahawk. Hangar capable of accommodating a medium organic naval helicopter (e.g. Seahawk or NH90) or a lighter helicopter plus a VTOL UAV (e.g. AW-159 Wildcat & MQ-8C Firescout). Design can accommodate all envisaged customer naval aircraft.

Type 31e, outline of requirements (click on to enlarge)

Babcock is offering the design to meet the US Navy’s frigate requirement.

Among companies vying for the Type 31e design contract is Babcock International, which this week unveiled proposals for a 120-meter, 4,000-ton rapidly reconfigurable warship with multiple mission bays; deck space for eight surface-to-surface missiles, 16 vertical launch cells and a 5-inch gun; a flight deck large enough for a V-22 Osprey tilt-rotor aircraft and hanger for MH-60 Seahawk helicopter; and launch/recovery facilities for unmanned vehicles.

Babcock claims that its Arrowhead 120 design will reduce through-life costs by embedding real-time equipment health monitoring sensors during the build process, allowing information about key systems to be gathered during deployments to inform subsequent maintenance periods.
With transatlantic exports in mind, the company also points to its collaborative venture with Florida-based Eastern Shipbuilding to design a new offshore patrol cutter for the U.S. Coast Guard. (emphasis applied–Chuck)
Craig Lockhart, the managing director of Babcock’s Naval Marine business, said that an advisor for U.S. naval procurement had expressed interest in the Arrowhead design, and specifically its innovative ‘iFrigate’ platform monitoring system, at the DSEI event.

The length is up ten meters compared to the OPC, as I thought might be the case, but I am a bit surprised at the reported beam, 19 meters. Since the OPC is 4,000 tons full load and the Arrowhead proposal is both ten meters (33 ft) longer and 2.5 meters (8 ft) greater in beam, the full load displacement of the Arrowhead would likely be considerably greater. The 4,000 tons reported may be a light displacement, meaning this ship is actually larger than the FFG-7 class.

Given the relatively small stacks and the 24+ knot speed, this is obviously an all diesel ship. It will be economical to run and have a long range at relatively high cruising speeds. While I think 24+ knots may be enough, most of the ships to be escorted make 20 knots or less, a speed well below the 29 knots of the FFG-7 class will be a hard sell to the US Navy.

NavyRecognition also has news of another of the Type 31e competitors, the BMT Venator-110 also apparently being proposed to meet the US Navy requirement.

Meanwhile BAE is also offering the much larger and more expensive Type 26 to the USN as well, however with its size and cost (U.S. $4.9 billion for the first three British ships) approaching that of a Burke class DDG, I think that is a long shot.

By contrast the Type 31e is being designed to a price of 250M Pounds or about $340M. That much lower price may be the Type 31e’s best selling point.

Late addititon, Sept. 12, 2019


Babcock Arrowhead 140 chosen for the Royal Navy Type 31e project.

32 thoughts on “OPC Derived Frigate? Designed for the Royal Navy, Proposed for USN

  1. An interesting comment I’ve seen in a few Irish forums is that other than it’s length (10m shorter) it’s not too much different from the RFP that the INS put out back in ’06ish for Eithne’s replacement (in terms of speed, capability). I wonder given Babcock was working with the INS back then (as you mentioned the Roisin’s) if it started for the Irish EPV?

    • Just so every one understand the comment I interpret the acronyms as
      RFP Request for Proposal
      INS Irish Naval Service
      EPV Expeditionary Patrol Vessel

      To me Eithne (https://en.wikipedia.org/wiki/L%C3%89_Eithne_(P31)) always looked very much like a Coast Guard 270 foot WMEC (https://en.wikipedia.org/wiki/Medium_endurance_cutter#Famous-class_cutter). They were very much contemporaries with the first 270, Bear being commissioned early in 1983 and Eithne being commissioned in late 1984.

      • Yeah sorry for the Acronyms but you are right. As I said I’ve seen some questions as to whether Babcock might have been working on said design for a while.

        As to Eithne, from the designer of the ship, the Coast Guard were very impressed with her as a design. He was over in the States working with them in regards to the Daulphin’s. He claims that their view was Eithne was a quieter platform and a more survivable one than the WMEC’s were. It’s sad considering the effort they put into her that the project when wrong, there was meant to be 3 of them and to use Lynx’s instead of the Daulphins. The inter service feuding that went on are in no small part why the P50 and P60 classes didn’t have helicopter capabilities.

      • I see Eithne as an improved 270. Certainly moving the gun up a deck made it more survivable in heavy seas. The additional 8 feet of length would have also been welcomed. I was in CG Headquarters when the 270s were being designed and wrote the Resource Change Proposal justifying the training facility for the COMDAC (Command, Display, and Control system) that was installed on the ships.

        It was a Coast Guard designed ship and the Chief Engineer was determined to keep the cost down. Designers of the ship practically had to go down on their knees to add three extra feet to the ship, to give the bow a little sheer, otherwise it would have been a 267.

        –Penny wise, pound foolish

      • In terms of Eithne the only major regret that the designer had was not carrying the Flight deck all the way to the stern, other than that he was quite proud of her, they tried selling the design to the Indian’s as well, but sadly with the Cobh yard in liquidation nobody would buy into the project.

  2. A question of the OPC as a 4,000 t FLD ship as LOA 360 feet, beam 54 feet, draft 17 feet whereas the Dutch Karel Doormann class frigates with LOA of 122.3 m/ 401 feet, beam of 14.4 m / 47 feet , draft 6.1 m / 20 feet is quoted as only 3,320 t FLD.

    A murky area as length and beam not specified at waterline and draft not specified with or without HMS.

    The design house BMT (outcome of RN sell off of in house design) proposal for the RN Type 31e is the Venator 110 is LOA 117 m, LWL 107 m, draft 4.3 m, Max. beam 18 m, range: 6,0000 Nm at 15 knots. They have proposed the larger Venator 120 to USN for the FFG(X) which understand is 127 m. Also now collaborating with Babcock with their Arrowhead

    • There are so many different ways to figure displacement we have to be careful to ensure we are talking about the same measure. When they talk about 4000 tons is it empty, normal, standard, or full load? (not likely standard since that was an artifact of the Washington Naval Treaty and is not generally used now.)

      The OPC’s beam is 15% greater than the Doorman class, while the Doorman is 11% longer than the OPC so we would expect the OPC to be larger but the displacement difference is 20% greater for the OPC. That is explained by the fuller hull form of the OPC. The Doorman’s hull form is designed more for speed, and tapers over more of its length, while the OPCs hull is close to its full beam over much of its length.

      Since the Arrowhead 120 has such a large beam (19 meters) and is in the same design family as the OPC, I would expect its proportions to be more similar to the OPC than to Doorman class.

    • The Absalon, which shares the same base design with Iver Huitfeldt / T31 budget, per hull cost as much as the T31 budget (per hull) 15 years ago. That is 2 engines, built in cheap East European yards (and hand me down weapons) against 4 engines and built here in the UK. We aren’t getting 5 hulls on that basis. I would have preferred an extra T26 and some more budget for the rest of the class. If we need a patrol ship we could have bought 6 of Damen’s Holland class with change.

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