Hello Carl,
I would have responded sooner but my computer has had the 'worm blaster' lately. Just got it fixed today.
You are not aware but the hull you have described in your 'ideal cat' is the ARC21 with one foot removed from the transom. The tooling was designed so that this could be done in production. This puts the rear beam on the transom and the main beam 9ft forward of the transom. This places the weight of the rig further aft than any other 20ft boat. Also the hull is clean for trapezing all the way to the transom; no rear beam in the way. Both of these features maximize pitchpole resistance. The original SC product line was designed and developed on the SE coast of Florida. This is why these boats have the tallest hulls with the highest beams and the highest crown foredecks of any beach cat available. They were designed and developed to sail clean in the ocean in 3ft to 4ft chop.
Let's look at this wing comment for a minute: Everybody likes the way the Tornado sails in a strong breeze. The reason it excells here is that it has a high righting moment to sail area ratio. The sails can be driven hard on the Tornado when the narrow boats have to depower. Well let's put wings on the narrow boat and make it at least equal to the Tornado. The Tornado Sport has 24.3 ftlbs of righting moment per square foot of sail area. Now let's put about 300sqft of sail on our new narrow boat to power it up a little. We will let it weigh 400 pounds including everything. So the basic platform generates 400 pounds times 8.5ft/2 = 1700ftlbs of righting moment and that turns into 1700/300 = 5.67 ftlbs of righting moment per sqft of sail area. Now the 320 pound crew has to make up the remaining 18.63 ftlbs of righting moment per sqft of sail area to equal the Tornado Sport. What lever arm must the crew have to generate the required remaining righting moment? Ans: (Crew lever arm = 18.63 x 300/320 = 17.46 ft.) WOW, a 35 ft wide wing boat that is only 20 ft long. What do you think of that answer?
As for sailing in the surf: The ARC rudder head is the only modern beach cat rudder head that adequately supports the rudder blade when the blade is sailed through the surf in the partially down position. All of these new rudder head designs that have no framework aft of the pivot bolt cannot support the rudder in the partially down position because there is no support structure. 'You can't support something with nothing'. These are deep water start rudder head designs.
You mentioned you wanted a carbon mast. Marstrom makes a fine one for about $5,000.00 and you can rig it and paint it yourself.
As far as planing: You want a 20ft hull to plane while supporting 400 lbs plus 320 lbs = 720 lbs total. That is a hull loading of 36 lbs per ft of hull length. You also mentioned the A cat. The A cat hull is 18ft long and supports a 165 lb boat and 160 lb crew. This leads to a hull loading of 18 lbs per ft of hull length. If a hull loading of 18 can plane sometimes under very special conditions, then a hull loading of 36 just can't get there from here, can it? How about a 36ft long two person boat?
Spin pole lengths: The ARC product line has the longest spinnaker poles of any beach cat on the market.
You mentioned lee helm with the spinnaker up: Read about 'shared lift' on the Aquarius-Sail web site and note the forward centerboard position on these boats.
The ARC product line has got you covered on all aspects, Carl. Be sure and take a long hard look.
Good Sailing,
Bill
