Hi Grob

Wasn,t the volume calc and getting enough displacement in your 4 hull design the biggest problem ? -estimating a 4 ft hull dbl ended does not provide much ,-each hull need to support a crew if they stepped aboard at one end .

Looking at some of the C Class designs -they are L- 25 ft
BEAM 14 FT - SAIL AR 300 no min wgt.

here is a beauti from the Aussie C Class cat challenge
http://www.lacaustralia.com/images/hull_global_1.jpg

funny ,-the F-14s have a 300 sail area

Anyway , at this L , volume in hulls or sail carrying ability -stability is less a problem

Designers of these with their extremely fime L to hull beam ratio seem to concentrate on reducing wetted surface area to its theoretic min..
Hulls with the least w a are U shaped , which contains the largest volume with least surface area with proper volume calc per each section to support hull crew total boat weight and factoring in sail forces and heel with sailing modes from light wind to one hull up.

Hulls are generally divided up into 10 sections along its length ,-these are sometimes overlayed and deck lines added
here is an older {hand drawn } 18 sq meter provided by Dick Lemke -
http://www.catsailor.com/bb_files/28263-smnacra2.jpg

You can enlarge it --you will see sections --bow on right half -stern sections l half --side profiles and wl
and half deck plan - basic lines drawing-

Quite a difference between the 18 sq and the C Class -

The C s in section drawing would show U sections with much more rocker in side profile.
Check out the MM C Class freedom,s wing ,--it has a great amount of Rocker { for and aft curve to the hull profile } having high upturned bows and sterns as opposed to the more straight lined side profile of other types .
http://www.morrellimelvin.com/page31.html

If the designers goal is to reduce wetted surface area and thus frictional resistance to a min , then each of the 10 sections would be proportionally sized from the narrow bow in U SHAPE and progressive proportional depth ,--shallow entry bow to deeper U center to narrower shallower stern ,
thus the basic C Class hull shape -
check the UK C Class entry ,-it looks similar -
http://www.team-invictus.co.uk/invictus.htm

Some designers use a PC comparison number -which stands for prismatic coefficient ,-which is the area of underwater hull of greatest section expressed as a solid per L compared to actual hull . I,m not sure about this for multihulls or how effective this is .

A pc IN THE LOW .50s is very fine ended with little wetted surface , but will cause limits in form and wave making resistance earlier than the fuller bow and stern type hull designs with straighter profile and less rocker.

A direct comparison with another C Class cat -via cad as you suggest would be a much more effective prediction of speed potential .

I,m hoping to see some via cad .

Hope that may be a helpfull starting point to reference hull types , these C s are the deeper displ types ,-
They are faster in light wind as the main form of drag percentage wise is frictional resistance at lower speeds .

As speeds increase form drag becomes more predominant in limiting speed of displacement hulls .

The interesting trend in hull design per example of MM A Class cat or designs like the Marstrom 20 is flatter forward hull sections hoping to use hydrodynamic lift to reduce form drag by lifting it partially at speed along with canting the hulls .
speculation as to effectiveness,--

Think the C Class type hull of same L and sail ar wins in light winds and choppy seas ,-but the flatter type wins in higher winds and flatter water ,-varied with each .
If the C Class cats with higher total displ hull speed with longer L know the venue they will be racing in and time of year with average predicted wind speed ,they can optimize the design for those conditions -

Its quite a game at that level