Assuming you have sailed a fair amount and are reasonably practical with your hands, and have also made up your mind to build your own: STOP & THINK
First obtain the help from the best boat designer/Architect you can.
Over the years I have seen many boat start and listened to the builder's dreams. Some starting with their own designs. Unfortunately many of these broken dreams are to be found around most harbours and even in the country side.
I very nearly fell into this same trap:
At the time with very little financial backing, but an active building construction company, I acquired a couple off-the-shelf Ferro Cement designs, which praised this type of construction. My choice to accommodate our young family was a 40' Ferro Cement Monohull. Cost wise and with my knowledge of concrete and masonry it appeared easily affordable. To test some ideas I experimented with a Ferro cement scaffold plank 12' long 9" wide and 1 ¾" thick. This was made up of 5' x ³/₈" x 12' hi tensile rebar tied together ladder-like with more rebar and wrapped in several layers of galvanised chicken wire, then plastered with a strong water proof mortar. After curing it for 14 days, we tested it by supporting two heavy masons, while our concrete plank was supported at the ends. It easily passed its test, but no workman wanted to carry it.
Fortunately sailing friends and the plank's weight persuaded me to drop the idea, however the bug had bitten, and I still wanted to take the family cruising. Besides I got pleasure from creating, hence my contacting Angelo Lavranos, a well established and renowned marine architect.
This in 1988, was the start of St Francis Marine. Now with 27 years' of experience my ambition is still to build the finest cruising catamaran in the world. With modern developments and practical experience, I can truthfully say that my last boat is the best to date.
We have a building policy of "continuous product development", which every member of our staff is aware of. Any new idea or method of construction is discussed amongst our department heads. Should the idea have merit it is tried out before it is put into production. Then closely watched throughout testing and client feedback. There is always a little grey area, particularly when it comes to electronics and new equipment. We always choose what we believe to be the best brand for the job and enjoy displaying the very latest. Unfortunately many of the well known brands have changed hands or their suppliers who in this competitive market have cut corners. Their products are not up to the old standards. Fortunately because of our long dealing with most suppliers they have generally, with our urging stood by their warranty guarantees.
Boat Building has seen many advancements over the years, , but nothing like the pace of electronic equipment also by the time it has done 2 years of testing in race boats like Americas Cup and Volvo Ocean Races, etc. the price becomes more affordable and the standard integrity of the product known.
The basic strength analysis, in all parts that make up the hull, deck & bulkheads is designed and computed by the designer whose job is to keep us abreast of new developments and advise on any changes we make. In the early days of building, what was originally to be my boat, I proudly told Angelo Lavranos during one of his visits, how I had added polly- staal to beef up the main bulkhead, which takes most of the compression load of the mast and supports the two hulls. He quickly and rightly reprimanded me saying "that I pay him to do the structural design and leave that to him I was just adding weight."
Similarly as with Angelo's appointment, we largely rely on the spar makers for the mast and rigging and professional sail makers for the sails.
Our work largely comes to the fore in the manner in which we put the designer's instructions and materials together and in the construction of the furniture, our dove tail joints used in the drawers are manufactured today with the same principles as were used in Queen Victoria's day and they still run smoothly. That is without the aid of modern waterproof glue, which I believe to be superior to the old.
Structurally our boats are very sound, as demonstrated by the number that have completed their circumnavigation and safely sailed many hundreds of thousand miles. All this from a comparatively small base of 70 odd boats completed to date. Even our first boat now known as "Umineko" has done its circumnavigation and still does well in cruising races such as the Arc.
This Phenomenon is only accomplished by owners having faith in the structural integrity and comfort of the craft. Other than the best of the world's race boats we probably hold the record for the most sea miles covered by cruising owners in a production catamaran.
Building a comfortable boat requires good design that slips through the water rather than bashes its way. It is also a dry boat with minimal spray and very fuel efficient while motoring. The upside is that it is also fast under sail. Comfort comes from the above, but is enforced by keeping as much weight as possible amidships. Weight in the boat's ends builds up inertia as the boat pitches, which amplifies the movement.
Keeping weight out of the ends dampens the pitching movement… Some makes fit their engines as far back in the stern as possible, while the fuel tanks, etc. are placed well forward to keep the balance.
In the St Francis the positioning of heavy items are:
We will assume you have hit at speed a container floating just at the water surface. The collision creates a hole in the bow (unlikely as the bows, bottom, keels, engine & rudder positions are reinforced with a solid glass laminate. There to protect you against abrasion should you run aground.) However for illustration sake you have a hole, which floods the forward compartment. Depending upon your boat's design, you have about 2 metres from the bow to the shower or sitz bath bulkhead, which is a strong glass and foam laminate; 30mm thick bonded all around top bottom sides with an access hatch standing about 900cm above the water line. The loss of buoyancy here might depress the bow by 100cm leaving at least 800cm free board. To continue our imaginary catastrophe you now knock another hole about ¹/³ of the boats length from the bow. Here you have your fresh water tanks which once holed would act as a double bottom. You would exchange your fresh water for salt with very little change to the water line.
Progressing further you now damage the keel, which is your holding tank. Again little change to your water line. Next the container would make contact with your sail drive and or rudder. These are both in the engine compartment and aft in the boat, here like your forward bulkhead we have another bulkhead, which is sealed off from the hull. You may lose 200cm of buoyancy, but this still leaves 300cm free board. Should you go to the extreme and puncture every nook & cranny that may hold air there is sufficient foam in the laminate to render your St Francis unsinkable.
The ergonomics of the St Francis have been refined over the years. First to go were sharp corners to the furniture, also knobs on the locker doors. Sharp corners and knobs can leave nasty bruises in a seaway. Hand holds and railings have been strategically placed, giving you easy safe passage, whether below or on deck.
Galley – the original popular design was galley down. This has more space for cupboards and drawers, however with the new galley up you can safely stand in front of the hob fitted with pot guards in the worst conditions and prepare hot meals. Everything is close at hand; fridge hob, oven, microwave, double bowl sink, dish dryer, trash hole and cupboards containing cooking utensils. This is now the most popular design, as the cooks body cannot build up momentum while holding hot pots, etc. as the galley is only one stride wide, yet close to the cockpit, service hatch and saloon table without negotiating stairs. Cooking is now a social activity, with the chef right in the conversation, with good all round visibility.
Cabins – all queen & double bunks have been sized to take standard fitted sheets. The thick light weight foam mattresses have 2" of memory foam on top. This memory foam is a soft layer which holds you comfortably while the boat rocks. Bunks are designed so that when one party gets up you do not disturb your partner by climbing over. Access to the bunks is easy with steps and hand holds. There are also reading lights and night lights to the stairs and companion way.
Sailing – the St Francis 50 has an easy motion and is fast. All control lines come back to the sheltered cockpit, which can be opened up or closed as required. From the helm station there is good 360˚ visibility with clear view of all four corners, which simplifies docking. Instruments are easily readable and a hand amongst the usual chart plotter, radar, auto pilot, etc. are electric primary winches with control buttons to operate the opposite winch, anchor windlass. The VHF radio repeater with loud hailer and foghorn is also on hand.