|19ft Scow Proa|
This is an idea for a cruisng proa. It is a refinement of my first attempt at a Scow Proa. Compared to the first attempt I have reduced the sheer to reduce windage,and used a different mechanism to deal with grounding the rudderboards. Masts are simple unstayed solid wooden tapered masts, easily made and inexpensive. Construction is plywood and epoxy resin with fiberglass taped seams. I have a personal preferance for stringer frame building over stitch and glue.
Please note the rudderboards that pivot backwards in the event of grounding at speed. I have shown a breakable dowel as the mechanism that allows this, another alternative would be cord of low strength which keeps the board in place at most times, yet does not have the strength to hold the boards in place in event of heavy grounding.
In regards to the diagrams below they show endview comparisons of similar boats. Compared to the Mbuli proa waterline beam is a fraction wider indicating a slower hull, yet because of the hull flare overall cabin space is much greater, resulting in a much more comfortable boat. Cabin space is still a little less than the Trilobyte 16 scow. This proa should be much faster as it has a narrower hull, longer waterline, reduced hull windage, more streamlined hullshape and more sail area.
I have shown roughly to scale sail area of the Mbuli proa and Trilobyte 16 roughly to scale. Scow proa lies roughly miday between teh two. The lower sail area that Mbuli results in less speed, however it permits smaller, lighter and cheaper unstayed masts. The smaller rig should bring more sedate and hopefully safer sailing.
As to ideal rig the lug rig or junk rig is probably the ideal. The reason is that the Center of Effort changes much less on each shunt than on a conventional marconi sail. This in turn allows for smaller rudderboards to compensate for changes in the C of E position. The junk rig is best suited to a cruising boat and less so a high speed racing boat. This in turn fits in well with the beamier hullshape of this proa compared to the norm.
There is no doubt performance will be much less than the Mbuli proa. However when compared to the Trilobyte 16 boat things become very, very positive. It retains the advantages of simple lines and ease of construction, spacious all weather cabin, and hopefully ability to be built on a modest budget.