Thanks to WhyMe kind permission:
The Ch-4 design was an evolution of the Ch-3 one. Nine ships were built and commissioned between 1937 an 1939. They were 56,2m long, 5,6m abeam and drafted 2,1m. displacement was 291T standard, top speed 20knots and endurance 2.000nm at 14knots. They were armed with a twin 40mm machine gun and 36 depth charges. Crew was 59 men.
Six (or Seven, as sources differs on Ch-12 fate) were sunk during WWII.
Units surviving late in the war were fitted with 25mm machine guns and a Type13 air-search radar.
Ch-8 as of 1938:
![[ img ]](http://i.imgur.com/IpKNY0U.png)
Ch-4 as of 1944:
![[ img ]](http://i.imgur.com/UKbiU3J.png)