MODEL TESTS OF A TUNNEL-BOTTOM 36-FOOT RIVER PATROL CRAFT,

Model tests of a new and somewhat unconventional boat, the 36-foot River Patrol Craft, were made by the Model Basin. The bottom of this craft has a single deep tunnel forward which gradually decreases convexly in depth to a flat bottom at 60 percent of the hull length. There it bisects into two shallow tunnels, which are symmetrical about their centerlines. The afterbody tunnels increase in depth to the transom. During the tests it was discovered that the single tunnel forward collected an appreciable quantity of air which then migrated aft past the propeller positions in the tunnels of the afterbody and from there astern into the wake. Test results for two design displacements, above water and underwater photographs at these displacements, and a discussion of the flow of air under the hull are presented. Author