Flotation

Level Flotation

The regulation is complex and difficult to read. The objective of this Guideline is to help the manufacturer calculate first how much foam will be needed to support each of the components (the boat, the machinery, and a portion of the passengers) and then indicate where that flotation material must be installed to pass the required tests. The methods were developed over many years, and the Guideline uses numbers and factors that result in flotation that meets or exceeds the requirements of the regulation. Following these steps carefully will result in successfully floating the boat in the manner prescribed. Some experimentation in testing may be necessary.

Boats requiring Level Flotation shall be fitted with buoyant materials or acceptable flotation systems in at least the minimum quantity as determined below. Void compartments or air chambers that are integral with the hull shall not be included as part of the flotation required.

Flotation material located at the sides, as far aft and as high as possible, will help make boats with machinery located aft float level when swamped. Some boats may require the keel area inside the boat to be void of flotation material so that the space can flood from either end to provide proper balance in the swamped condition.

Integral air chambers cannot be counted toward meeting the Level Flotation requirements. If non-integral air chambers are used for flotation, the Level Flotation requirements must be met excluding the two largest air chambers.

Basically, our method is to calculate the flotation material needed to support the following components when the boat is swamped:

a - the swamped boat;
b - the swamped outboard engine and submerged battery;
c - a portion of the persons capacity;

The total flotation material needed is the sum of a + b + c. The boat must float level and pass a stability test.

Calculations: To determine the total flotation material needed to support the boat and keep it level, we use the following formula:

F = Fb + Fp + Fc

Where:

F = Total flotation material
Fb = Flotation for the swamped boat
Fp = Flotation for the submerged propulsion machinery
Fc = Flotation for the passengers (a portion of)

The idea here is that the boat, without its propulsion equipment and passengers, will have to be swamped and supported with a certain amount of flotation material distributed symmetrically so as to keep it relatively level. When you add the propulsion systems, the boat will be disproportionately heavier aft and consequently the flotation material needed to support the engine and drive will have to be located far aft to counter this unbalance. Finally, through experience we know that the flotation material needed to support the portion of the passengers (persons capacity) must be located way out on the boat’s sides and as high as possible. This is so that the boat may pass the stability test’s maximum permitted heel angle.

Symmetrical location criteria for the flotation system are established for each of the three quantities above. For example, one cubic foot of flotation material three feet forward of the boat’s balance point (when out of the water) can be balanced by three cubic feet of flotation material one foot aft of the boat's balance point. The symmetry may, and should, be varied to account for equipment (such as batteries) if located off-center.

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