Hello to Dan Ward & Carl-Sail6000,

Thank you indeed for your enthusiast and curiosity...

About hulls that are being sucked down at high speed...well, it's rather complex...the speed-pressure Bernouilli's law coupled fields that build up around slender hulls are divided into 2 main domains ( with a physical continuity between them of course ):

1st domain : the neighborhood of free surface that is Froude Number dependant, Froude = Vboat / sqrt( gravity x LWL ) and from where most of the waves and spray generating phenomena originate.

2st domain : The "more constantly" deeper immersed part of the hull where the pressure-field remains more stable ( not completely, it would be too simple and stupid...)

So, if you take a look at a standard Tornado or NACRA 5.5 hull, the 2nd domain is the keel line and the middle sections, buttocks and waterlines that all show a certain degree of curvature...it's like the bumped upper side of a NACA cambered profile running upside down...

When the hull, an "upside down cambered slender body" is running into water, low pressures establish themselves just at the locations of higher curvatures and especially back them. This leads to a "negative lift", i.e. a suction that could reach beyond 20 kts, 15 to 20 % of total displacment..its value increases at a rate of speed squared ( what is called dynamic pressure )

The boat's total apparent weight becomes 875 lbs ( or more )instead of 725, and it dives even more.

About the huge amount of SPRAY, the previous reply is also quite true...all the water that is thrown up in the air contributes to a ( few percentage however ) more diving attitude...and the final "coup de grâce" is given by the propulsive force moment from the rig that buries even more the fine entries of bows and increase the whole vicious circle...that STOPS ACCELERATION !

I have read with enthusiasm what Carl-Sail6000 tried 17 year ago but some explanations about his concept seem not very clear. Noticeably, what's the interest of extreme canard bow rudder foils and high canted bottoms ?

Could Carl post some pics of his marvel boat ?


FRIENDLY YOURS,
Frenchie