Open canoes come in a variety of sizes, with different lengths, widths and depths. Other aspects to consider are bow height, rocker, weight and price. Lengths range from around 14 to 18 feet, widths from around 30 to 40 inches and depths from around 12 to 16 inches.
Length and width
Boats that are intended for solo use will generally be shorter than tandem or family boats. If you plan to sail on your own all of the time then a canoe around 15 to 16 feet would be a good length. Generally longer canoes will paddle and sail faster than shorter ones, but extra length also adds extra weight and this is best kept down to be manageable for use alone. If you plan on going on extended camping trips in the canoe then the longer ones would be best.
If you plan to sail two up, a canoe of 16 to 17 feet would be a good choice. Again if you plan on carrying a lot of gear then go for the longer ones.
Solo paddling canoes might start with a width/beam of around 30 inches and go up to 35 inches. For sailing extra width is a good thing as it increases stability and the ability to hold up the sail. So usually it is a good idea to go for the widest canoe. A 36 inch beam canoe will be around twice as stable as a 30 inch beam one, so width is a good thing. Also as you try and sit out to counterbalance the sail when going upwind, a wider canoe gives you more room in which to move your weight to the upwind side. Canoes that are wider still, maybe 38 inch or more, will offer even more stability and are worth considering. Be aware that in a canoe shop the salesperson may not have any or much sailing experience so may steer you towards narrower hulls, as they can be more efficient to paddle.
Depth and freeboard
Depth of the canoe is another important consideration. The paddler might prefer a lower freeboard to cut down on windage when paddling into the wind, but the sailor has enough power to overcome the windage. A sailing canoe can travel at over 4 or 5 knots into the wind and the resulting waves. It is important that a sailing canoe has higher freeboard to minimise waves entering the boat. Also the sailing canoe can heel quite a lot under the power of the rig, so having extra freeboard can make for a drier boat. A few inches extra freeboard can make a lot of difference.
Bow height is another important consideration. As with freeboard (or depth), extra bow height can keep the canoe from burying into a big wave as you power upwind or sail fast downwind.
Rocker
Rocker, or the amount the bottom of the ends of the canoe are above the middle, is another factor that different canoes you look at will have. For flat water paddling, a minimally “rockered” canoe is favoured, as the canoe will be less twitchy and will track better. But under sail, once you have a large rig and therefore a rudder, tracking won’t be an issue. The ability to turn quickly as you go upwind can make it easier to keep up momentum as you go through the tack. Some rocker will make the sailing canoe more manoeuvrable and make it easier when doing multiple tacks as you sail upwind.