dinghy design questions

I've been reading this website and its led me to a few thoughts and questions

http://www.devboats.co.uk/plusplus/index.htm

If we take a single hander una rig.

If you were to make the boat purely for upwind performance and pointing (no compromise just purly upwind?) what would the hull shape be? Why?

Or for downwind? What would change on it to optimise it for this?

And I guess it has to be asked for reaching too?

Just curious.

Yep, as long and narrow on the waterline as you can make it, with the widest racks imaginable plus a trapeze, until only one man in the world is capable, with practice, of sailing it.

If you are allowing foils like an Int 14 or Nat 12, it can be shorter, but then why not go fully foiling and go quicker still?

And there's the rub. If you want a boat that is nice to sail, reasonably forgiving so that you can look around (e.g. for tactical fun), then you need to be prepared to make compromises on the absolute top speed. No big deal, given that the quickest sailboat you can make is slower than your car. How much and what sort of compromise is down to the individual, which helps explain the plethora of classes out there racing.

International canoe!

The question is, which is better, a shorter hullform that will plane upwind, or a longer one that doesn't, but is thin enough that the wave form doesn't affect top speed as it does in a fatter boat?

I have a feeling that the Contender is quicker upwind than the 600, and the IC faster than both, which might partly answer the question. But the weight of the 600 must have an effect.

Trouble is, we have only focused on the 1st part of the question. Once we bear away, do we still want the long, narrow hull? Again, catamarans seem to go fast enough on a reach, so it can't be all bad, but they don't plane. So, do we still want a very long boat, but compromise the shape from pure upwind work to allow the boat to plane? Or does the extra weight involved offset the advantages?
No point in suggesting a windsurfer, as like the catamarans they can only be used as a guide to what might happen, as the query was about dinghies, but from my understanding, a long board is much better upwind. What happens when you bear away - does the short board take over as the faster? I have no idea how long the boards used in the speed trenches are. I assume short, as once planing the extra size would be a waste or weight. Does this transfer to dinghies?
The FD was the fastest boat around in a straight line for many years, mainly because it was 2, 3 or even 4 feet longer than most of its rivals. Would a 20 foot 49er be quicker than the 16 foot version?

Originally posted by Medway Maniac Variable geometry, anyone?  It will come some day, for sure - just a question of working out the practicalities.