Flotation

Example of Level Flotation Calculations

Step 3: Determine the flotation needed to support the persons capacity (Fc)

Formula:

Where:

Clev = C (maximum weight capacity) minus weight in column 6, Table 4 for the maximum horsepower rating of the boat, (See Appendix A)

B = Buoyancy of flotation material in pounds per cubic foot.

Discussion:
This may look confusing. The reason for the regulation requiring the manufacturer to support only part of the passenger load is that this weight (in testing) is added dry, and the assumption is that the actual passengers will be partially submerged thus enhancing buoyancy. The last entry [.25(Clev – persons capacity)] is the gear weight allowed or the difference between the values for maximum weight capacity and persons capacity exhibited on the boat’s capacity label.

NOTES:

1. If Clev is negative, use zero.
2. Use the persons capacity and maximum weight capacity that will be shown on the boat’s capacity plate.

In order to achieve a level attitude when conducting the flotation tests, it will be necessary to distribute the flotation material symmetrically on both sides and fore and aft of the passenger carrying area mid-point at the hull sides as close to the sheer line as possible. It should be located outside a vertical plane that is parallel to the keel, and within 6 inches of the hull sides at the widest point on the floor line. This will assure the necessary righting moments to pass the stability test. The flotation material must be as far out and as high in the gunwales as possible.

Step 4: Determine the total flotation material needed (F)

Formula:

F = Fb + Fp+ Fc

The total flotation material required is the sum of the results in steps 1, 2, and 3 above.

FIGURE 5.5 - Flotation Material Placement

FIGURE 5.6 - Flotation Material Placement

FIGURE 5.7 - Placement of Passenger Support Flotation Material

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