Phil Berman's book "the Hobie 18 Performance Manual" is a litany of detail (well worth the read for basic 18 theory). My comments are based on racing at or slightly above minimum crew weight (Paul and I weigh 305). The main message I get from Phil is the 18 main is flat and a flat sail means more RPM (speed) which is great for us at a light weight. Or, we don't need to build more power into the sail, which isn't designed primarily for power.

When not racing I, like everyone, am interested in two basic settings to cover everything for "real windy" and "wish there was a little more wind" (besides if we did everything Mr. Berman wanted us to do it would be dark before we got off the beach).

Spreaders are forward medium and heavy. Mast rake as far forward as possible for medium, one hole back for heavy with shrouds adjusted accordingly, tight(med) & tighter(heavy). The diamond wire set "just tight" on the leeward side when going to weather, which must be checked on the water. This is somewhere between the 24" and 36" marks on our mast (since we're light weight we go loose in light air also i.e. towards the 36" mark, heavy crews will go to 12" [tight]in light air). Diamond tension can be easily set by honking in your main and downhaul, while on the beach.

After that the only viable adjustment on the water is downhaul. 8:1 is class legal and cascading with pivoting cams for crew control is best.

Keep the main flat for speed.