>>>Anybody have a clue what this boat has for a Portsmouth number?

It provisional Texel number = 100 with spi and 104 without (I have not taken into account the oversized spi as that will drop the handicap number but it remains to be seen wether the craft is really faster with such a large spi)

This leads to some "conservative DPN" to be expected at 65 (spi) and 67,5 ( no spi) under PN.

I used 8 kg's for the weight of the mainsail, battens and jib together and added that to the 136 to give 144 kg's overall no spi = 318 lbs. My smaller Pentex sails together are this weight and so this should be a good comparison. Weight of spi package has NOT been included in this. With it the ready to sail weight of the spi version will be 144 + 5 kg = 149 kg's = 329 lbs. Pretty standard for a 5.18 mtr. = 17 ft long 2,59 = 8'6" wide platform with an 8,76 mast. Fully fitted Hobie FX-one and Inter-17 are on either side of it within a few kg's (lbs).

Its jib is quite normal in size 4,74 sq. mtr. = 51 sq. ft. The remainder of those 257 sq. ft. = shy 24 sq. mtr. is all to be found in the mainsail and mast. WOW ! just 3 sq.ft less than the US I-20 main.

measure of aspect ratio of the mainsail = luff^2 / area = estimate 8.5^2/19,1 = 3.78 (other definitions are used as well but this is a good approximation)

Compare this to some other types :

A-cat = 8,8^2 / 13,95 = 5,55
US I-20 = 9^2 / 19,4 = 4,18
F18 = 8,5^2 / 17 = 4,25
F16 = 8^2 / 15 = 4,27
Prindle 16 = 7.37^ / 13,82 = 3,93
Hobie 16 = 7,33^2 / 15,21 = 3,53
Nacra 5.0 = 7,65 / 13.50 = 4,335

Bill, how does aspect ratio impact on being overpowered exactly ? You have me at a loss here.

Spinnaker area 27 sq. mtr. I-20's is 25 sq. mtr. Boats of comparable length and mastheight have typically 17-20 sq. mtr.

Aspect ratio spi :

ARC 17 = draw^2/area = 8^2(max !)/27 = 2,37 (probable 7,6^2/27 = 2.14)
I-20 = 8,3^2 / 25 = 2.75
F18 = 8,25^2 / 21 = 3.24
F16 = 7,5^2 / 17,5 = 3.21
ISAF youth trail boats = about 7^2/ 15 : 7,2^2 / 17 = 3.26 - 3.05
NA NE Nacra 6.0 with 250 sq.ft. spi = 8,5^2/32.5 = 2.22
Mosquito 17 = 6,38^2/16,9 = 2,41
Mosquito 15 = 6,38^2/14.2 = 2,87


Mosquito 15 was found to be faster in most conditions than the Mosquito 17 both in Aus as in South Africa. We all know how the NA NE N6.0 spi performs with respect to that much smaller I-20 spi.

More than a few sailors have noticed that smaller spis of higher aspect ratio are quicker than larger spis with lower aspect rations; in most conditions except a small wind range between light and medium winds. When the winds are light than the large area spi limps before the smaller spi does so; therefor the smaller spi is more efficient again in light winds.

For this reason I did not hit the ARC 17 with the kind of several Texel penalty for oversized spis. Remember the Tybee 500 where the NA NE had to give the US I-20 time on Texel handicap but where they were found to be about of comparable speeds.

The jib is pretty normal is aspect ratio and comparable to those of the newer boats with spi kits.

With this I think the estimates of the PN given are dependable; the old sc17 was DPN = 73. Quite an improvement.

Wouter