In both sets of sail area data the Genoa/Jib areas are the same yet the mainsail areas are given as 172 sq ft for the Parker 27 and 156 sq ft for the Superseal 26.

I have measured my fully battened mainsail fairly accurately and it comes out at 172 sq ft.

Does anyone have an original printed Superseal Brochure with the advertised sail areas and if so what is quoted. Does anyone know why the areas are different even though the E and P are the same on both boats. Is it just a difference in the roach?

The 156 sq.ft. is the nominal area of the straight line triangle on both the Seal and later Parker.The sail plan actually shows a 'curved' leach.

The 172 sq.ft. is the total area including the curved segment lying above the nominal straight line leach.The sail plan shows the same view.

I am assuming that your main has a curved leach.If it doesn't I'm not sure where that leaves us.

Peter

Many thanks for the explanation. This now makes sense of the published data.

My Main does indeed have a slightly curved leach between the full length battens and my measurement was constructed using the batten lengths and luff length between them, so my 172 sq. ft. may be a little shy.

Calculation shows that the main area, from brochure measurements, should be PxE/1.8 giving173 sq. ft. with P = 9.06m and E = 3.2m. However my sail in only 3.06m in the foot and 8.605m in the luff which

by the same formula gives 157.5 sq. ft. against my 172 sq ft measured as trapezoids between battens.