Has anyone else put floats on a dinghy? I don't know but canoeists have been doing it for years. Floats have been put on kayaks to convert them to sail and there's a Wooden Boat article (issue 131) with construction diagrams for the floats and beam. But I'm thinking of open canoes (Canadian canoes to the ignorant). These are sailed to rules laid down by the American Canoe Association which limits the sail area to 44 sq ft and bans centreboards which means you can take a standard production canoe and fit a sailing rig without any modifications to the hull so it has a dual use for sailing and paddling.

Some canoe sailors strap on floats of some sort for additional stability. In some cases this has led to a genuine trimaran with little stability in the middle hull and not much resemblance to a canoe, while in others small floats on a single beam are favoured. I have also seen them with only one float which acts as a float to leeward and weight to weather. I have a feeling that the single float has gone out of fashion although it makes it easier to come alongside pontoons. Some souls go for proas but that's another story.

On my fourteen footer by 34 inch beam which I call a canoe - although it has a small transom - I have hung 5ft floats on an 8ft beam. The floats have about 60lbs maximum buoyancy. With about 15lbs weight on the upwind float there is a total righting moment of about 300 ft lbs. A 12 mph wind has a pressure of approx 1lb per sq ft so the outriggers should support about 50 sq ft of sail if the C of E were 6ft up. This is a very crude calculation but it seems more or less borne out by practice. I have a 70 sq ft balanced lug (a cut down Shearwater sail thanks to Ted Jones) but I sail mostly on rivers and even then I sometimes have to reef. No doubt the floats are a drag but it isn't noticeable; they enter the water very smoothly and it’s only when beating that they are hull down. They have removed the fear of capsizing but not, I suspect, the possibility. I don't know whether a capsize would be different from a dinghy but if the whole thing inverted you would have to sink one of the floats with your own weight which limits the float buoyancy and also the length of beam since you will have to tread the float down to the vertical and you need your head above water. At least getting back in ought to be easy. But fie on such thoughts. The floats are like a crew who can perfectly balance the boat and change sides in a split second and will take no end of cursing. Whether a single beam is adequate support in waves is something I have yet to discover. Sometimes the windward float will oscillate like a punch-bag.

The only thing I would add to what Paul Constantine has said is that I think the floats should be splayed outwards about 10 degrees so that when they hit the water they are upright. As regards design I think 4mm ply is a bit thin, though you could fill it with builder's foam which appears to be watertight - as long as you don't puncture the skin and some bulkheads - as Paul says. And do you really need the righting moment of two folk on trapezes? You could break the boat! A better shaped float could be designed and now that you can get free CAD software on the Internet (e.g. HYPERLINK "www.carlsondesign.com" www.carlsondesign.com), which will give you the dimensions of the cut up panels, you can go for more subtle shapes. But otherwise it is a workable idea as John Jermain has shown.