- #1
Colin Wilson
- 4
- 3
My question concerns what I call R.P.S. (Rotating Planing Surfaces). This version uses freely rotating disks to plane across the surface of the water somewhat similar to wheels on a car going down the road. Specifically what the lift / drag ratio might be and will it be higher than a typical planing hull at about a 5:1 ratio. My explanation of why I expect an improvement goes like this:
Since the disks rotate freely the skin friction is limited to the deflection of the boundary layer into a shallow arc from the front of the planing edge of the disk to the back of the planing edge of the disk. This results in an average differential in velocity between the planing surface of the disk and the water that is much lower than a non-rotating planing surface such as a planing hull or a lifting surface such as a hydrofoil would experience traveling at the same speed.
The following illustrations show the disks (attached hull not shown) with about 15% of the bottom surface area submerged. The attack angle of 5 degrees and the deadrise angle of 15 degrees being typical of a planing hull at speed.
Front view
Side view
Bottom view submerged area in orange
Since the disks rotate freely the skin friction is limited to the deflection of the boundary layer into a shallow arc from the front of the planing edge of the disk to the back of the planing edge of the disk. This results in an average differential in velocity between the planing surface of the disk and the water that is much lower than a non-rotating planing surface such as a planing hull or a lifting surface such as a hydrofoil would experience traveling at the same speed.
The following illustrations show the disks (attached hull not shown) with about 15% of the bottom surface area submerged. The attack angle of 5 degrees and the deadrise angle of 15 degrees being typical of a planing hull at speed.
Front view
Side view
Bottom view submerged area in orange