Hi Dan,
Thanks for the compliment. First I want to say that in my experience 'all beach cats are wave piercers'. I sail in the ocean so that is what I see. The foredeck of a boat can go underwater for two reasons. 1) A wave taller than the bows, two times as tall or more for example, can pass down the hull, bow to stern, and put the foredeck underwater for a short period of time. If there is enough bouyancy in the forward sections of the hull, the bow will lift and the wave action will actually push aft on the hull for a moment. When the bow is being lifted higher than the transom as the wave passes, the transient bouyant force actually has an aft component to it relative to the forward velocity of the CG of the boat. There is some recovery of lost boat speed as the transom goes higher than the bow as the wave passes but the loss, bow up, is greater than the recovery, stern up. Also the sail/rig is made to pitch, changes relative velocity rapidly, as the boat goes over and through the waves and this reduces sail thrust.
We can reduce the hull pitching up action due to waves by reducing the volume in the front end of the hull. If we reduce the width of the hull, we upset the displacement distribution of the hull. So how else can we reduce the hull front end volume? Reduce the height of the hull at the bow! Doing this will reduce the response of the hull to wave action; it will reduce hull windage while sailing to windward; it will reduce hull surface area which will reduce hull weight. These are the plusses, +++. There is one big minus, ---.
2)There is one very important situation which occurrs while sailing downwind where hull volume in the front end is very valuable. This situation is "verge of pitchpole". The max forward sail force, maximum pitching moment, that a hull can support occurrs when the waterline is at the top of the bow. As the forward sail force increases, the bow is pushed downward which causes the transient center of bouyancy to migrate forward in the hull. This increases the distance between the hull instantenous center of bouyancy and the boat plus sailor center of gravity. This is the "restoring moment" which opposes the "pitching moment". The taller the bows are the deeper they can be driven into the water and the further forward the transient center of bouyancy can be made to migrate so the larger the restoring moment and the larger the sail force can be and the faster the boat can be driven downwind in windy conditions. So there's the trade off, reduced response to wave action vs reduced restoring moment to prevent pitchpole. A noteworthy point relative to A cats is that 18ft is a 'long hull' for a 'one man boat'. With that in mind it may be possible to reduce bow height some without too much loss in restoring moment. Note that Marstrom has not lowered the bow on his A cats and his are amoung the best and fastest.
One other comment: If we take an 18ft hull and put two people on it and double the sail thrust which doubles the pitchpole tendency, we probably should not consider the downward sloping foredeck and reduced bow height trade off on this size boat. A downward sloping foredeck is still draggy when forced underwater if it is flat on top. A high crown foredeck is much less draggy when forced underwater and it is inherently stronger and stiffer.
Good Sailing,
Bill