Boat-builder Kenneth Gibbs designed the Junior in 1954 and the Senior in 1955 for the Yachting Monthly series of sponsored designs. He is known to have built these, as well as a few Eventides, at his boatyard on the Upper Thames at Twickenham. In the years leading up to his death he became something of a recluse and withdrew completely from the boating scene.
Unfortunately not a lot is known about Kenneth Gibbs and we would be extremely grateful if anyone can add any further information about him.
Instructions for building both the YM Junior and YM Senior can be found in the book "Building Chine Boats" by Michael Verney and available exclusively from the EOA.