(4) How you get cruising boats to sail better in light air and swell - and I mean the non-obvious ways like a taller stick and a cleaner bottom. There is a ton more light air than breaking waves, and in swell there can actually be quite a bit of fatigue damage done to a boat that can not sail and just rolls.
- Low drag running gear. A feathering, or better yet a folding prop. A retractable system would be best of all.
- In small boats, getting the boat to heel to leeward helps a lot by getting some shape into the sails. That's hard to scale up to a 35 or 40 footer, though. Water ballast or other forms of moveable ballast might help here, as well as help the boat stand-up to a larger rig when the breeze is up. Does anyone know what the various classes with moveable ballast do in the really light stuff?
- In flat conditions upwind, a very low area, high aspect ratio keel is probably ideal. In a swell or left-over chop, the keel will invariably get stalled occasionally. A keel with more area might be more effective at preventing leeway.
- high aspect ratio rig to get as much of the sail area up high as possible.
- A large crew: keeping a boat moving well in light air takes more attention and care than in a moderate breeze.
These are mostly 2nd order effects, though. A big rig and minimal skin friction dominate the picture. It's not so hard to build a light air monster, the problem is making that boat workable when the breeze is up.
A large sailplan is great in the light stuff, but to make it workable it needs to be able to "change gears" effectively. So ironically, I think well thought out reefing systems and sail inventories matter a lot for making the "light air rig" workable the rest of the time. The growth in popularity of Code 0's and similar sails seems to have helped a lot with this.