Update April 2015 - this is a yuck design - I stuffed up
This TO-19 design is bad. It is too wide, too slow and has too much windage. Better to have a narrow hull at the waterline, then come up vertically 10 inches or so and have a wide platform and put the cabin on that. Cabin should be kept short, say 7ft or so, to keep windage to a minimum. So TO-19 is a bad design and I admit it. Its yuck and only serves as an example of not what to do.
These are some early sketches of the newer and better version of TO19. This page put up about April 29 2010. More information to follow shortly. Notes on the older superseded version can be seen here
The mainmast is stayed, the mizzen is unstayed. The mainmast is on a tabernacle so as to allow for a fast launching time. 19ft was chosen as length as that is long enough to give moderate performance whilst still remaining compact enough for easy backyard storage and for easy trailering. Cabin height is 4ft 2" which is just high enough for comfortable sitting headroom, this may have to be increased by a couple of inches later for more margin
By adding an outrigger to a non-ballasted cabin day-boat, cabin height can be increased, waterline beam reduced and sail area increased without having to worry about stability issues. The split rig allows for occupants to raise themselves out of the very large sliding hatch without fear of being hit by the boom. The large sliding hatch allows for sun and fresh air in good conditions. The boat could be sailed from inside the cabin if desired by using a yoke and tiller arrangement.
The outrigger would employ a generous volume of water ballast, maybe 80kg or so, in order to give good righting moment for when on the 'proa' tack. Outrigger is of approx 600L volume.
Overall performance is aimed for the moderate range, midway between that of a small cabin day boat and that of a trimaran. If more sponson area was desired, a telescopic sponson could easily be developed where the sponson was extended towards the outrigger. Crew on the sponson may be exposed to the elements, thus a clear plastic dodge could conceivably be placed on the front of the sponson for protection against spray, though at some penalty in extra boat windage.
Crossbeam bury whilst outrigger is extended is generous. Thus there is much freedom to move in terms of increasing beam overall if desired. This may be useful in increasing performance. Crossbeams are located at position of major bulkheads, thus maximising intrinsic hull strength.
In coming weeks I will develop a series of sections to give more detail than the above diagrams, also I will do some freehand 3D drawings in isometric view (I think I can still remember how to do this)