Most of the time the U.S. Coast Guard is not part of the military but rather a seagoing police and public safety organization. Only during wartime does the Coast Guard temporarily become part of the navy and that status ends when the war is over. Yet the largest seagoing Coast Guard patrol ships are those at least 20 meters long and called cutters. Some are the size of small warships like corvettes and frigates but most of them are smaller. While lightly armed in peacetime, the cutters are built to accommodate more weapons and sensors in wartime. The Coast Guard has always maintained a lot of cutters and every one or two decades they have to replace them. The cutters spend more time at sea than navy warships and often operate in bad weather navy ships avoid. The latest cutter design, the Sentinel class, had a difficult time during design and construction. Those problems appear to have been overcome, mainly by adopting a foreign coast guard ship design.
In mid-2021 The U.S. Coast Guard ordered another four of their Sentinel-class FRC (Fast Response Cutter) patrol ships. That makes 64 of these ships on order or in service. This is a rare success story in American naval ship design and construction. Most of the action in this area has been bad and getting worse for decades. What saved the coast guard was the politically unpopular decision fifteen years ago to abandon a failed local design and look for a foreign ship design that was already in service, successful and could meet American needs.
The current Fast Response Cutter is basically a slightly larger version of the Damen Stan 4207 patrol vessel. Damen is a Dutch company that creates basic ship designs that can be easily modified to meet customer needs. The Damen design was selected in 2008 because in 2007, the Coast Guard was finally forced to admit defeat in its effort to build an earlier design for FRCs. The ship builders (Lockheed Martin and Northrop Grumman) screwed up, big time. While the Coast Guard shares some of the blame, for coming up with new concepts that didn't work out, the shipbuilders are the primary culprits because they are, well, the shipbuilding professionals and signed off on the Coast Guard concepts. Under intense pressure from media, politicians, and the shame of it all, the Coast Guard promptly went looking for an existing (off-the-shelf) design and in a hurry. That had become urgent because of an earlier screw up.
By 2013, satisfied with its new modified Damen FRC (Fast Response Cutter) design, the U.S. Coast Guard began ordering more to be delivered in 2016. In 2012, the first of 58 FRC vessels was commissioned. These are 46.8 meter (154 feet) long, 353-ton vessels equipped with an eight-meter (25 foot) rigid hull boat launched and recovered internally from a ramp in the stern (rear) of the ship. Armament of this cutter (as seagoing coast guard ships are called) consists of a remotely controlled 25mm autocannon and four 12.7mm (.50 caliber) machine-guns, plus small arms. Top speed is 52 kilometers an hour and the crew of 22 has sleeping and eating facilities on board so the ship can be at sea 5 days at a time, FRCs each average about 2,500 hours (over 100 days) a year at sea.
In 2006 the Coast Guard discovered that an existing ship upgrade program made the modified ships structurally unsound and subject to breaking up in heavy seas. All eight of the modified 40-meter (123 feet) cutters were removed from service after cracks were found in the hull and decks. The 40-meter "Island Class" ships used to be 35.5-meters (110 feet) long and displace 154 tons. After four meters (13 feet) were added to the hull length, ship displacement went to 166 tons. Crew size (16) didn't change but top speed (53 kilometers an hour) was reduced five percent. The ships are armed with a 25mm cannon and two 12.7mm machine-guns. The original plan was to spend $100 million to modify all 49 of the 35.5-meter ships, so as to extend their useful life, normally 15 years, a bit until a new class of cutters was built. The modification also added a rear ramp for launching a small boarding party boat.
The modification program was already in trouble for being behind schedule and over budget. The program was first halted and then killed. This left the coast guard short of ships and in danger of being in even more trouble over the next decade. The coast guard has 250 cutters and the Island Class ships are 18 percent of that. With the failure of that first Fast Response Cutter program, the coasties had to really hustle to even get an off-the-shelf into service before many of their current ships are unfit for service.
Twelve of the new FRCs were ordered in 2008, and by the end of 2013 six were in service and performing well as the Dutch Damen class ships had already been doing since the late 1990s, and the U.S. Coast Guard will eventually account for about half of the Damen Stan 4100 type ships built. The success of this approach encouraged the U.S. Navy to use a similar approach to find a successful design for a new class of frigates to replace the failed LCS (Littoral Combat Ship) design. The French-Italian FREMM multipurpose frigate design is similar in concept to the Damen patrol ship concept. The first FREMM ship entered service in 2012. Not counting the twenty or more FREMM type ships the U.S. Navy plans to build, there are already 49 FREMM type ships on order or in service with five other navies.