How do you calculate displacement from sail?
Traditionally, it is calculated by dividing the nominal sail area in square feet by the boat’s displacement in cubic feet to the two-thirds power. In this case, displacement is converted from pounds to cubic feet by dividing it by 64, the weight of a cubic foot of seawater.
How do you calculate the area of a sail?
The conventional way to find sail area is to calculate the area of the foretriangle (FT) between the mast, headstay, and deck; the area of the mainsail triangle (M) between the mast and the boom; and add them: SA = FT + M (= IJ/2 + PE/2).
What is I and J on a sail?
Here is how we define them at North Sails. I – Height of Foretriangle. Elevation of Forestay, measured down to elevation of main shrouds at sheer line. J – Base of Foretriangle. Horizontal distance measured from front face of mast at deck to position of headstay at sheer line.
What is ballast to displacement ratio?
The ballast/displacement ratio is simply the ballast weight divided by the boat’s total displacement. Since ballast is there to give the boat stability, it’s easy to jump to the conclusion that the higher the B/D, the stiffer the boat.
How is genoa sail measured?
First, take your headsail either laid out over a flat area, or raising the sail on the mast. Use a long tape measure and measure the (1) luff of the sail. This is the length of the front of the sail. Be sure you have the sail stretched out well to keep the measurement accurate.
What is LP on a sail?
LP is the shortest straight line distance from clew to luff. It’s expressed as a percentage of “J” (150% LP = 1.5 x J). It does no relate directly to area, but is a measure of overlap. For a given percentage of overlap, you get a much bigger sail on a boat with a long “J” dimension.
How are sailboats measured?
“I” is measured from the top of the jib halyard sheave to the deck (actually the sheer line). “J” is measured from the front side of the mast to the intersection of the deck and head stay. “P” is a measurement from the main halyard sheave box to the main tack fitting.
What is a displacement hull?
There are two basic types of boat hulls—displacement and planing. Boats with displacement hulls move through the water by pushing the water aside and are designed to cut through the water with very little propulsion. If you lower a boat into the water, some of the water moves out of the way to adjust for the boat.
How to calculate sail area?
The Formulae Sail Area in sq. ft. SA/D = ————————————- (Displacement / 64)^0.6666 (Sail Area in sq. ft.) ^ 0.5 BN = ————————————- (Displacement)^0.3333 * Displacement in pounds Sail area in sq. ft. Displacement in lbs. SA/D = Bruce no. = Caution & Warning…. Oh the ways we can deceive.
What is a sail area/displacement ratio?
Aboard sailboats, of course, the source of this power is the boat’s sail plan. The parameter designers normally use to evaluate a boat’s sail-power relative to its weight is called the sail-area/displacement ratio (SA/D ratio).
How do you calculate a boat’s Sa/d ratio?
To calculate a boat’s SA/D ratio you must first quantify its sail area in square feet. In that boats normally have an inventory of different-sized sails so their sail area can be varied, sometimes very significantly, to accommodate different wind conditions, it’s important to use a uniform standard when comparing different boats to one another.
How do you measure displacement of a boat?
As with the D/L ratio, the displacement figure used must reflect the real-world weight of the boat in the water. Where you’re most likely to be led astray is with the sail area figure. Total area has traditionally been considered to be the sum of the foretriangle, plus the triangular area of the main, roach not included.