Topside Flare in Dinghy Hull Design

Hollow and flare aren't the same thing. The N12 or Merlin technically don't have hollows as it is not allowed by the rules, apart from the sheer / gunwhale extending a certain amount within the overall beam measurement.
N12s and merlins are what, 6' and 8' wide, and are under 3' waterline beam.
Any development class will seek to maximise beam on deck, and minimise waterline beam within the rise of floor rule in the class.
N12s and Merlins would def have hollow if it were allowed - less penalty when heeled / rolling, at the expense of more reserve stability.

Most dinghies have a waterline beam between 0.9m and 1.2m, roughly speaking - less and its too tippy, more and its too slow. Many aren't that much wider on deck - 1.4 to 1.6ish -  (less of a faff for crew to get side to side), hence there isn't a lot of flare or hollow necessary.

Compound curves are trickier to make in anything apart from rotomould.
GP and Hornet are developable panel shapes so can't do hollow in any case
You can project the gunwhale off the side of the boat, but in a wooden craft this will require some support structure, or in grp it is just a bit more faff too - look under an RS400s gunwhales.

My memory of sailing old 505's in silly wind and rough water suggests that the flare can help lift the bow as waves hit it. It's not just a sitting-out shelf on the 505. Where a fireball will do a passable imitation of a submarine in Solent wind-over-tide, a 505 will seem to 'ride on its flares'.

Originally posted by Daniel Holman Hollow and flare aren't the same thing. The N12 or Merlin technically don't have hollows as it is not allowed by the rules, apart from the sheer / gunwhale extending a certain amount within the overall beam measurement. N12s and merlins are what, 6' and 8' wide, and are under 3' waterline beam. Any development class will seek to maximise beam on deck, and minimise waterline beam within the rise of floor rule in the class. N12s and Merlins would def have hollow if it were allowed - less penalty when heeled / rolling, at the expense of more reserve stability. Most dinghies have a waterline beam between 0.9m and 1.2m, roughly speaking - less and its too tippy, more and its too slow. Many aren't that much wider on deck - 1.4 to 1.6ish -  (less of a faff for crew to get side to side), hence there isn't a lot of flare or hollow necessary. Compound curves are trickier to make in anything apart from rotomould. GP and Hornet are developable panel shapes so can't do hollow in any case You can project the gunwhale off the side of the boat, but in a wooden craft this will require some support structure, or in grp it is just a bit more faff too - look under an RS400s gunwhales.

Hi Dan, can you clarify 'hollow' for me please? Does an RS300 have hollow topsides?