Flotation - Definitions
Every definition contained herein shall be assumed to be preceded by the following statement: "For the purpose of this guideline, we will use the following definitions:"
NOTE:
In the event of a question of interpretation of these definitions, consult with the United States Coast Guard.
Mono-hull: Any vessel on which, when it is at rest and carries its maximum rated horsepower capacity and maximum weight capacity, the line of intersection of the water surface and the hull forms a single closed curve. For example: a catamaran, trimaran or pontoon boat is not a mono-hull boat. However, it is important to observe that some small catamarans, when loaded, do form a single water line and must be considered mono-hulls.
Race boat: Any vessel which is manufactured soley for use in sanctioned racing events, and is not intended for use as a recreational boat.
Sailboat: A boat designed or intended to use sails as the primary means of propulsion.
Basic Flotation: A flotation system which will keep a swamped boat from sinking when its passengers are in the water clinging to it, provided that the aggregate weight of the motor, passengers and equipment carried in or attached to the boat does not exceed the boat's maximum weight capacity. With Basic Flotation, the swamped boat may float at any attitude.
Level Flotation: A flotation system that will keep a swamped boat and a specified quantity of the weights of its motor, equipment and passengers floating in an approximately level attitude. Sufficient stability is provided to prevent the swamped craft from capsizing in calm water when one-half of the passengers are evenly distributed at one side of the passenger carrying area and as low as possible in the boat. Level Flotation does not provide a self-righting capability.
Modified Level Flotation: A flotation system that provides level flotation, as defined here, but with a reduction in the quantity of flotation required for passengers.
Dead Weight: For inboards, sterndrives and airboats, the maximum weight capacity marked on the boat, minus the persons capacity marked on the boat.
Horsepower Capacity: The maximum recommended horsepower capacity of a boat as stated on the boat's capacity plate.
Passenger Carrying Area: [see 183.205 & 183.305] Each area in a boat in which persons can sit in a normal sitting position or stand while the boat is in operation. Figures 2.1 to 2.5 explain the passenger carrying area for different boat configurations.
Subpart F – Flotation Requirements for Inboards, Sterndrives and Airboats
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FEDERAL LAW
183.110 - Definitions
For the purpose of this subpart:
- Bilge means the area in the boat, below a height of 4 inches measured from the lowest point in the boat where liquid can collect when the boat is in its static floating position, except engine rooms.
- Connected means allowing a flow of water in excess of one-quarter ounce per hour from the engine room bilge into any other compartment with a 12-inch head of water on the engine room side of the bulkhead.
- Engine room bilge means the area in the engine room or a connected compartment below a height of 12 inches measured from the lowest point where liquid can collect in these compartments when the boat is in its static floating position.
- Engine room means the compartment where a permanently installed gasoline or diesel engine is installed, including connected compartments.
- Open to atmosphere means a compartment that has at least 15 square inches of open area directly exposed to the atmosphere for each cubic foot of net compartment volume.
- Sealed compartment means an enclosure that can resist an exterior water level of 12 inches without seepage of more than one-quarter fluid ounce per hour.
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Subpart G – Flotation Requirements for Outboard Boats Rated for Engines of More Than 2 Horsepower
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FEDERAL LAW
183.205 - Passenger carrying area
(a) For the purpose of this section a boat is level when it is supported on its keel at the two points shown in Figure 2.
(b) As used in this subpart, the term "passenger carrying area" means each area in a boat in which persons can sit in a normal sitting position or stand while the boat is in operation. Passenger carrying areas are illustrated in Figures 3 through 8.
(c) The length of the passenger carrying area is the distance along the centerline of the boat between two vertical lines, one at the forward end and one at the aft end of the passenger carrying area when the boat is level as illustrated in Figures 3 and 4. For boats with a curved stem inside the passenger carrying area, the forward vertical line is where a line 45 degrees to the horizontal when the boat is level is tangent to the curve of the stem, as illustrated in Figure 5. For boats with cabins, the forward vertical line is where there is a minimum distance of two feet between the inside top of the cabin and the water line formed when the boat is swamped and loaded with weights under Sec. 183.220 as illustrated in Figure 6.
(d) The breadth of each passenger carrying area is the distance between two vertical lines at the mid-length, excluding consoles, of the passenger carrying area when the boat is level as illustrated in Figures 7 and 8. For boats with round chines inside the passenger carrying area, the vertical line is where a transverse line 45 degrees to the horizontal is tangent to the arc of the chine, as illustrated in Figure 8.
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NOTE: See Appendix B for 33 CFR Subpart H, figures 2 – 13.
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FEDERAL LAW
183.210 - Reference areas
(a) The forward reference area of a boat is the forward most 2 feet of the top surface of the hull or deck, as illustrated in Figure 9.
(b) The aft reference area of a boat is the aft most two feet of the top surface of the hull or deck, as illustrated in Figure 9.
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NOTE: See Appendix B for 33 CFR Subpart H, figures 2 –13.
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FEDERAL LAW
183.215 - Reference depth
Reference depth is the minimum distance between the uppermost surface of the submerged reference area of a boat and the surface of the water measured at the centerline of the boat, as illustrated in Figure 10. If there is no deck surface at the centerline of the boat from which a measurement can be made, the reference depth is the average of two depth measurements made on opposite sides of, and at an equal distance from, the centerline of the boat.
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NOTE: See Appendix B for 33 CFR Subpart H, figures 2 – 13.
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