Actually it does matter, because the all up weight of a Laser is very very low. So a 20 lb difference will be alot. On a keelboat, it is fixed, but on a laser it effects everything. The all up weight will change the ratios of sail area to displacement. As will something like hearing hiking pants (9 lbs) dry or not.

Sailor*Total Displacement*Sail Area*SA/D

215 397 72 20.91

210 392 72 21.08

205 387 72 21.26

200 382 72 21.45

195 377 72 21.64

190 372 72 21.83

185 367 72 22.03

180 362 72 22.23

175 357 72 22.44

170 352 72 22.65

165 347 72 22.87

160 342 72 23.09

155 337 72 23.32

150 332 72 23.55

145 327 72 23.79

140 322 72 24.03

135 317 72 24.29

I calculated the Sail Area / Displacement Ratio for various weights.

To get total displacement(defined as the all up weight of the boat in the water with the sailor dressed) I used 15 lbs for the spars, 15 lbs for the blades, and 10 lbs for the rigging. My guess would be that hiking pants weigh 8 lbs, the rest of it 4-5 lbs, 12 total. So take your weight in your boxers. 183lbs + 12 for your clothing that is your all up weight.

195

Compare that to a 175 all up and you get a difference in SA/D of 22.44-21.64= 0.8

.8 as a percentage of 22.44 is 3.56%

a 175lb sailor has a 3.56 percent advantage downwind and in light wind over someone who is 195lbs based on SA/D, (which is a generally a oft used and good predictor of light air and downwind performance, (not so much upwind)(not a measure of fitness).

On a 1 km leg that is 35.6 meters, about 8 Laser Boat-lengths (assuming equal skill) (assuming SA/D is 100% relevant and significant)

If you double the difference in weight from 195 to 155 you get 23.31-21.64 = 7.16%

On a 1 km leg that is 71.6 meters, about 16 Laser Boat-lengths (assuming equal skill) (assuming SA/D is 100% relevant and significant)

Click on the blog below to get the background info....