The Project 5b was the final evolution step of the K-Verband developments for a small hydrofoil attack boat. The design was almost identical to the Hydrofoil Project, but two turbojets were added to increase the speed of the final attack and disengaging phase.

Although tests with a jet powered boat ("Tornado", 1944) showed several problems with this kind of propulsion - only usable at calm sea and serious control problems - the addition of turbojets was seen as a possible solution to increase the chance to survive an attack against allied ships.

None of these futuristic boats was ever build.