Any camber is part of a large circle.  For decks, a camber of 3% of the boats beam is normal.  For cabin tops, 5% of the width of the cabin top is the maximum recommended.   Cambers have reduced in recent years as modern methods, materials and higher freeboard makes it unnecessary to have the larger cambers that were fashionable in the past.   For power boats fitted with a flybridge, the cabin top camber should have a maximum of 2% .

DECK BEAMS

At this time you will need to decide if you are going to use transverse or longitudinal deck beams.   In the days of wooden boats, all deck beams had to be installed transversely because the deck planking ran fore and aft.   Now that we have plywood to use for decking you may find it easier to use longitudinal deck beams or a combination of both longitudinal and transverse beams.   At the same time as you are installing the beams, you should frame up for the cockpit coamings and hatch openings.  

   If you are planning a laid timber deck on top of the plywood sub-deck, then it would be better to use transverse deck beams so that you will able to through fasten the timber deck planks unless, the deck itself was thick enough to take these fastenings.   Even if you use longitudinal beams and later decide on a laid deck, you have the option of using the diagonal or herringbone design to pick up these beams.  

Before you can fit any deck beams or decking, if not already in place, you will need to install the deck shelf around the inside of the sheer.

   After the camber is cut, you may decide to attach a transverse beam to the top of each bulkhead and at the deck line before installing beams.  This applies regardless of whether your main deck framing is transverse or longitudinal.    Even with transverse beams you will need a few short longitudinal beams such as for the cabin top in way of the mast step and one in the fore deck, known as the king plank, in way of the positioning of the mooring bitts, anchor winch or fore deck cleat.   Fore and aft king planks can be wider and shallower and can be checked into the transverse beams.

   If you are installing transverse beams, these can either be sawn or laminated.   A typical beam would be 1 ¾” wide [45mm] by, say, 2 ¾” [70mm] deep.   This beam can be made up of laminations of 1 ¾” [45mm] wide by ½” [12mm] with one thicker layer to make up the odd amount.  The layers of timber can be set up in a purpose made jig or made over a master beam assembled on the widest bulkhead.   It is a good idea to make up the beams well in advance.   These beams can be laminated, daily or weekly and set aside until needed – when made, be careful to store them out of the sun and the longer you can leave the beams on the jig, the less spring back you can expect.

   Once you have fitted all the deck framing , check it over and dress off any unfair areas.   Make use of a batten laid diagonally across the surface of the deck framing to make sure you have no lumps or hollows which will give you problems when you start to fit the plywood decking.