Stability continued: Unfortunately, you can't go down to your local outfitters and conclude the bottom of your canoe is flat, rounded, or "v" bottom as the hull may use two or all of the characteristics at various points on the boat. The best way to evaluate the stability is by trying out the canoe.
Again, you need to ask yourself what you will be doing with the canoe. If you plan to do flat water touring, the flat bottom will run fast through the water and be easier to paddle, but if the wind picks up you better be ready to head to shore. If you plan to fish, photograph, or paddle moving or whitewater, a rounded bottom may be better suited as you twist and turn to maneuver your canoe, cast, etc. When looking at a canoe, do not focus on the initial stability claims or statistics, focus on the secondary stability and if possible try out your canoe first, most quality stores will allow you to do this and even host demonstration days.
Capacity: The capacity of the canoe is typically rated in the number of pounds of weight it can carry. As you add weight to your canoe, it will sit deeper in the water. Most of the capacity of the canoe is borne at the center, as this is the widest part of the canoe, and has the most displacement in the water. A good capacity for a solo canoe is 400 to 500 lbs., while a good touring canoe should have at least 1,000 lbs. of capacity. This of course is also dictated by your size. If you are large framed and tall, you will need a higher capacity canoe if you plan to bring a friend along. There have been plenty of stories of two friends who want to canoe, but due to their height and build, are to heavy for a tandem canoe.
Another good rule of thumb is you should never load your canoe to capacity. The capacity rating assume ideal conditions, if you have 1,000 lbs. in your 1,080 lb. rated touring canoe, and get caught in a thunderstorm in open water, you may not have enough hull depth to keep from getting swamped. You should leave 20% of your capacity as a pad when loading your canoe.
Beam: The beam is the width of a canoe at it's widest point. The interesting thing about a canoe, is it's widest point may not be at the gunwales but lower on the canoe. A canoe has what is called tumblehome which is a curve of the hull. This curve is necessary to add strength to the hull, increase displacement, and increase secondary stability. Generally, the wider the beam the more stable the canoe will be. Shorter canoes can have very wide beams in relation to their length. You should avoid canoes that have a beam that is narrower then 32" unless you are very experienced. Likewise, if you plan to solo paddle you should avoid canoes with a beam in excess of 36" at the gunwales, as it can become very difficult to paddle.
Canoe manufacturers will typically provide three beam figures. The beam at the gunwales, the beam at it's widest point, and the beam at the 4" waterline. This last statistic is just as important as the other two because it will dictate the performance of your canoe. The narrower the beam at the waterline, the faster the canoe will perform as it has less resistance moving through the water. For whitewater and casual canoeing, a narrow beam below the water line is ideal. For backcountry trips a wider beam will provide for more stability.
Depth: The depth of the canoe is the measurement from the center of the canoe at the keel, straight up to the gunwales. Generally as a rule, the deeper the canoe, the drier things will be. A depth of around 13" is ideal. If you get higher than that, the canoe may be dry, but paddling can become a chore if you are smacking your hands on the high gunwales. Conversely, a shallow depth can make for better speed and better performance in the wind, but things will probably get wet, which if your touring is not the most ideal situation.
Stem: The stem on a canoe is how the bow, or front of the canoe is shaped. Stems can be squared, that is the most forward part of the keel, or the bottom of the canoe, is almost parallel to the upper part of the canoe. A rounded stem will come up in a curve to the bow of the canoe.
A square stem will help the track or straight line performance of a canoe. If you plan to do flat water or touring, this is an excellent quality in a canoe. Likewise a rounded stem helps out with steering and maneuverability. If you plan to do moving water then a rounded stem is a better choice.
Keel: A keel is a support that runs the length of the bottom of a canoe. The Coleman� canoe is a good example of a canoe with a keel. Keels are excellent at improving secondary stability, rigidity of the canoe, and straight line performance. Aluminum canoes are required to have a keel due to the way they are manufactured, and most natural material canoes also have a keel.
A keel can be mounted externally, that is under the canoe, or internally, that is inside the hull. Canoes with an added keel may have a keel on their to compensate for a design issue (this is not the case for aluminum). It may be a lack of rigidity, poor straight line performance, or poor secondary stability. A keel is also a major liability if you run whitewater. Where a canoe without a keel will slid over a rock, a canoe with a keel may hang on the rock and give you an unexpected swim. If you plan to do any moving water, you should stay away from an external keel. Canoes that do not have a keel, or only have an internal one in the case of aluminum canoes are typically of a higher quality.
Rocker: Rocker is how much the bow and stern of the canoe curves upward. This should not be confused with stem as a canoe can have a square stem, but still have a lot of rocker if the keel line extends all the way to the bow, or even further. Like stem, a canoe with a lot of rocker is easier to steer, but sacrifices straight line performance.
If you plan to do whitewater canoeing in extreme conditions, you will probably want a lot of rocker, more than three inches is not uncommon. If you are going to be doing a lot of touring with a load of people and equipment, you will want a moderate amount of rocker -- at least an inch. A canoe under load will sit deeper in the water, and if it lacks rocker, the bow of the canoe digging into the water will make it difficult to steer. If you plan to do some light cruising, then only a small amount of rocker is required. Unless you plan to do competition racing, you should never get a canoe without any rocker.
The way to determine rocker is to place the canoe on a flat surface. If it has rocker, it will literally rock at the beam (the center) of the canoe. You can use a tape measure to determine how much rocker there is, although most manufacturers provide this information.
Thwart: The thwart (or in some canoes thwarts) are supports that run across the width of the boat and are attached to the gunwales. Most good canoes that weight more than 40 lbs. will have a center thwart with a funny half moon cut out in it. This is where you would put the weight of the canoe on your back for portage. Two people carrying a canoe in portage is next to impossible if you plan to talk to each other during the trip. Unless you enjoy having your back muscles dug into, you should always opt for a padded thwart if you plan to do any portaging of your canoe. More and more portage trails are not allowing dollies or wheels to assist in moving your canoe as they cause a lot of damage to these trails. Any experienced paddler who has portaged a canoe without a padded thwart for more than 50 rods (about 800 feet) will probably tell you they will never do it again.
Solo whitewater canoe: shorter length, high secondary stability, rounded stem, extreme rocker, narrow beam, average depth, average capacity
Solo flat water canoe: shorter length, high secondary stability, square stem, minimal rocker, narrow to average beam, average depth, average capacity
Tandem whitewater canoe: average length, high secondary stability, rounded stem, extreme rocker, narrow beam, average depth, high capacity
Tandem flat water canoe: average length, high secondary stability, square stem, minimal rocker, average beam, average depth, average to high capacity
Touring canoe: long length, average secondary stability, square stem, medium rocker, wide beam, above-average depth, very high capacity