Sailboard with slotted winglets

Abstract

A sailboard hull has at least one pair of winglets or foils beneath the top of the board. Each winglet or foil has above it a slot and allows dynamic lift from both the top and bottom surface of the winglet and reduction of drag when the board is traveling at a transition speed between displacement mode and planing mode. At high planing speed it does not normally have lift from the top surface of the winglet. There may be multiple pairs of winglets or foils. Back slots may be provided at the rear of the sailboard hull providing a higher ratio of winglet width to maximum hull width. A top slot may cover at least half the winglet area, and a winglet may have a camber/slope step on the planing surface.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is as follows: 
     
         1 . A board hull of a sailboard or watercraft less than or equal to 12 feet long, comprising:
 a top portion which has a top surface and a bottom surface;   at least one pair of winglets or foils at least a portion of which are beneath said bottom surface of said top portion; and   a slot above each winglet or foil of said at least one pair of winglets or foils, wherein at least a portion of said bottom surface of said top portion is a roof of said slot and at least a portion of an upper surface of said each winglet or foil is a floor of said slot,   wherein said slot has an opening in front of or above said each winglet or foil, and   wherein water passing through said slot reduces wave drag of said each winglet or foil.   
     
     
         2 . The board hull as recited in  claim 1 , wherein said slot has a height to width ratio which is less than one and a height to winglet chord ratio which is less than said height to width ratio. 
     
     
         3 . The board hull as recited in  claim 1 , wherein said roof of said slot has a slope in a transverse direction equal to or less than ±15° with respect to a horizontal. 
     
     
         4 . The board hull as recited in  claim 1 , further comprising:
 one or more front foot straps attached to said board top surface of said top portion, and   wherein said slot and said each winglet or foil are swept back at angles of 20° to 80° to allow shedding of weeds which enter said slot and/or to direct water passing over said each winglet or foil away from said one or more front foot straps attached to said board top surface of said top portion.   
     
     
         5 . The board hull as recited in  claim 1 , wherein said at least one pair of winglets or foils starts 90 to 160 cm from a back/rear of said board hull. 
     
     
         6 . The board hull as recited in  claim 1 , further comprising:
 a pair of back slots cut into a back/rear of said board hull which are above at least a portion of said at least one pair of winglets or foils, said pair of back slots being configured such that a ratio of slot width to maximum hull width at a point at said back/rear of said board hull is equal to or greater than said ratio at a point further from said back/rear of said board hull.   
     
     
         7 . The board hull as recited in  claim 6 , wherein each back slot of said pair of back slots has a support vane positioned therein. 
     
     
         8 . The board hull as recited in  claim 6 , wherein said slot extends to said back/rear of said board hull such that said back slots produce a streamline effect in displacement and transition modes while said top portion forming a roof of said back slots allows the back foot straps to be spread wider apart and still remain out of a water flow than without said back slots. 
     
     
         9 . The board hull as recited in  claim 6 , further comprising at least two back foot straps, wherein said pair of back slots are configured to allow said at least two back foot straps to be laterally spaced a distance equal to or less than a width of said board top surface of said top portion above said back slots. 
     
     
         10 . The board hull as recited in  claim 1 , wherein a bottom surface of said each winglet or foil has at least one camber/slope step having
 a camber with a depth of 0.2 to 2 cm and   a step with a height of 1 to 9 mm and a curvature of radius 0.3 to 4 cm.   
     
     
         11 . The board hull as recited in  claim 1 , further comprising:
 a back planing region near and in front of a fin at an underside of said board hull; and   a back planing surface to either side of said back planing region having a camber/slope step,   an intersection of said back planing region and said back planing surface, said intersection having a cusp,   wherein said camber/slope step allows said board hull to maintain an attack angle of 3° to 5° for transitional speeds to speeds greater than 20 mph, and   wherein said cusp keeps an outflow of water off said back planing region from said back planing surface in planing mode.   
     
     
         12 . The board hull as recited in  claim 11 , wherein said back planing surface has an additional camber with a cup angle of 7 degrees or less. 
     
     
         13 . The board hull as recited in  claim 1 , wherein said opening of said slot is 20 to 120 cm long in a longitudinal direction of said top portion. 
     
     
         14 . The board hull as recited in  claim 13 , further comprising a front planing or displacement surface at a front bottom of said top portion, wherein a roof of said opening of said slot comprises i) a first part which is approximately tangent said front planing or displacement surface, ii) a second part having a rocker, and iii) a third part having a camber toward and/or over a nose of said at least one pair of winglets or foils. 
     
     
         15 . The board hull as recited in  claim 1 , wherein said roof of said slot covers at least half of said upper surface of said each winglet or foil which is said floor of said slot. 
     
     
         16 . The board hull as recited in  claim 15 , wherein said each winglet or foil is straight or bent/curved in a transverse direction. 
     
     
         17 . A watercraft hull, comprising:
 a top portion which has a top surface and a bottom surface;   a winglet at least a portion of which is beneath said top portion;   and a slot above said winglet formed by said bottom surface of said top portion and a top surface of said winglet, wherein said slot has a height to width ratio which is less than one and a height to winglet chord ratio which is less than said height to width ratio.   
     
     
         18 . The watercraft hull as recited in  claim 17 , wherein said winglet is configured as a pair of winglets.