[Alberg30] Re. Sail area.

[Maggie Ross]

Michael, #220 wrote:
Also, I don't think luff X foot/2=sail area will work for genoas. I think that formula requires a right angle, and there aren't any on Genoas.

The right angle is LP (load perpendicular) from the luff to the clew of the Genoa. No need to use calculus as the missed area from the triangle below the LP makes up for the extra area from the clew to the head.

The right angle from the luff is usually a few feet above the tack - or, using a tape measure held at the outer edge of the clew ring, find the shortest distance to the luff. This is the way we measure genoas when reducing them from their original size, 150% etc., to 135% etc. The length of the foot is not the governing factor.

If you have a specific point at which you wish the clew to be located, first check to see if the sheeting angle will be suitable for the current location of your winches, then use the tape measure from the point where you wish the clew to be located and find the shortest distance to the forestay (the right angle), mark that point on the forestay and  note the measurement, then measure from the point at which the sail will be attached at the tack to that mark on the forestay. A total distance for the maximum desired length of the luff will also help your sailmaker design the perfect sail for your individual needs. The three measurements, total length of LP, LP intersection at forestay to tack of sail and maximum length from tack of sail to head of the Genoa, should be all that is needed as computers do wonders with the rest. In each case, the two sides of the two triangles you've given the sailmaker also gives him the length of the two hypotenuses (leech and foot).

Here are the measurements we have on file for the A30:

I=36.00'        J=10.5'        P=31.00'        E=14.30'

Standard Mainsail    =    240 sq. ft.
No. 1, 150% Genoa =    290 sq. ft.
No. 2, 135% Genoa =    243 sq. ft.
No. 3,   98% Genoa =    166 sq. ft.
Storm Jib =                     65 sq. ft.
Storm Trysail =                78 sq. ft.

Just a thought - I notice the Alberg regulations specify a specific width of material, perhaps these should be reviewed as most fabrics are now available is widths of 54 inches, thus reducing the number of seams, time and labour. Today's fabrics are superior in strength from even a few years ago and don't need the narrower panels which were regulated by the production of narrower material.

Maggie.
Strathgowan, #400
P.S. I hope I haven't stepped on any toes or opened a can of worms, but if I see room for improvement I'll usually say something, as a few of you already know. ;-)

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