North Korea media took pictures of leader Kim Jong Un visiting a shipyard and engine manufacturing plant on the east coast during July. What was actually going on took a while longer to leak out as reports from people in the area reached China and South Korea. Kim had ordered the engine plant to switch from making replacement engines for the 200 largely worn 30-40 year old Russian designed torpedo boats and gear up to produce ten engines a month for what have been called VSV (Very Slender Vessels) because they depend on a “surface effect” design to achieve high speed (90 kilometers an hour). The eight or so VSV that have been built since 2011 have been spotted largely via satellite photos and details obtained from tourist photos and North Korean TV reports. There are at least five variations on the basic design, the differences being mainly in length (10-32 meters or 32-100 feet). Only one ten meter VSV has been spotted and Kim Jong Un was seen touring one of 32 meter models which, like the others, is armed with two (light or heavy) torpedoes, two pedestal mounted short-range anti-aircraft missiles and three small 24 tube launchers for what appear to be chaff (which would momentarily blind enemy radar). Now comes for the wait to see if North Korea can actually get the engine and VSV hull production going. The shipyard complex shown in the video also has plants for producing torpedo components and sheet metal for small ships. It North Korea can actually muster the resources to start large-scale production they will be able to replace more of the 200 obsolete and largely inoperative PT (Patrol Torpedo) boats.
The North Korean leader communicates with his people largely through videos of his visits to factories, farms and other facilities and written or verbal reports of what he said. His visits to military bases or factories that make military equipment are of often revealing. Along with commercial satellite photos and tourist cell phone camera pictures if ships (often taken by accident because that sort of thing is illegal and has led to tourists being arrested or killed) provide a lot of information on otherwise obscure aspects of the North Korean military. These sources have provided a steady flow of information about the sparse, but steady, North Korean effort to build new warships since their economic collapse in the 1990s.
In addition to the VSV, there are some larger new patrol boats referred to as the Nongo class. In late 2015 North Korea was seen moving at least six of their new high-speed patrol vessels south and basing them near the South Korea sea border. This was meant to be some kind of threat, but mainly it gave South Korean naval intelligence an opportunity to get a better look at these new designs. There are about ten of these new patrol boats, whose development began after 2000 and first appeared at sea in the last few years. These boats vary in size (35-40 meters/112-130 feet long) none appear larger than 500 tons. These boats are characterized by stealthy design, high speed (up to 100 kilometers an hour or more) and light armament (autocannon, maybe a 76mm or 57mm gun or 30mm autocannon plus a few torpedoes or anti-ship missiles.) It was later discovered that there were two of these catamaran designs; one with a stealthy superstructure (sloping sides to reduce the effectiveness of radar) and standard (non-stealthy) superstructure. The eight anti-ship missiles were copies of the Russian Kh-35 anti-ship missile and the 76mm gun was a copy of the Iranian copy of a widely used Italian 76mm design. There were also two 30mm autocannons, two heavy torpedoes and a launcher with eight short-range anti-aircraft missiles. There is also fire control and navigation radar. These are complex and expensive ships to build and operate. The VSV are cheaper and based on a design widely used in the West for some time.
Another useful source of information is that obtained from North Korean fishermen who have escaped to South Korea (some using their fishing boats). The North Korean fishermen report encountering fewer patrol boats since 2000 and sometimes seeing one of these PT boats dead in the water waiting for a tow back to port. Most of the late model (and reliable) patrol boats are stationed near the DMZ and the nautical border that extends out to sea. A second priority is the Russian and Chinese nautical borders. But for the waters in between you generally see only decrepit and ill-equipped North Korea fishing boats trying to make a living.