Re: weigh/people capacity
Re: weigh/people capacity
Good source tincanman. The 185# rule applies to all passenger vessels but they have yet to update it for recreation vessels. It would make sense to use the newer, more accurate, number in North America but I think the scope of the change is so huge that they have decided not to worry much yet.
FWIW, we have some older 1860 boats that are rated for 7 persons, and some newer 1860 boats that are rated for 5 persons. Boats are pretty similar - think maybe mfrs are starting to migrate to more conservative standards.
The boats' actual capacities are much greater. I think they put max safe capacities at something like 30-35% of actual carrying capacity, to account for things such as bad weather, waves, idiots, etc.
If you want to know your boat's true capacity, multiply wetted length by wetted width in feet - turn that into 'cubic feet' and multiply by 61 for freshwater, 63 for saltwater as your STARTING point. As an easy example, let's use a flat-bottom 1860 boat that may have something like 15' x 5' feet wetted hull, so let's throw 75 cubic feet out there, multiply by 61 for freshwater - that gives us 4575 pounds floatation for submersing the boat twelve inches. If the hull, motor and rigging weigh a combined 1500 pounds, then that gives us 3075 pounds capacity at one-foot submersion. If your gunwales are 24 inches, you are at max. operating capacity if you use a lot of common sense, which most people seem to lack. Now, take 35% of that for a good safety margin and you come up with close to 1200lbs., which is more commonly what you see on boats of this size. Often, more conservative "rule of thumb" measurements/formulas are used to take into account other variables such as deadrise and gunwale flare. Always better for a mfr. to err on the conservative side. Most of this doesn't matter for most of you because you need to obey the mfr. capacity plate on the boat, but it is nice to know for true emergencies.
Some of the commercial boats/ships are a different story. They generally have multi-chambered hulls and self-draining decks with large scuppers - their carrying capacity is limited by the vessel's safe-handling characteristics and downflooding potential. And then you have boats like the small Texas scooters that are essentially a solid platform, maybe 8 feet by 4 feet by 6-8 inches thick, with a console mounted on top and an outboard on the back. Waves roll right over the platform/hull, but you keep on floating. Capacities there are again determined by safe-handling characteristics, but there is really no potential for downflooding. They are basically surfboards with motors.
