Flotation
Example of Modified Level Flotation Calculations
Example 1: Boat rated for 2 horsepower.
Assume a boat with the following specifications:
Wh
weight of hull (fiberglass)
|
80 lb. |
Wd weight of deck (fir plywood)
|
5 lb. |
Boat is rated for 2 HP
|
|
S (swamped weight of 2 HP engine)
|
20 lb. (See Appendix A, Table 4) |
C (Maximum weight capacity)
|
300 lb. |
| B (buoyancy of flotation material in lb./cu.ft.) |
60.3 lb. |
Step 1: Determine flotation needed to support
the swamped boat (Fb)
Formula: Fb = [(Wh
x K) + Wd ] ÷ B
Substituting in the formula above:
Fb = [(80 x 0.33)
+ 5] ÷ 60.3
Fb = [(26.4) +
5] ÷ 60.3
Step 2: Determine flotation needed to support
the propulsion equipment (Fp)
Formula: Fp = S
÷ B
Substituting in the formula above
Fp = 20 ÷
60.3
Step 3: Determine the flotation needed to support
the persons capacity (Fc)
Formula:
Fc = 0.25 (Cmod) ÷ B
Fc = 0. 25 (300 - 25) ÷ 60.3
NOTE:
The regulations call for 2/15 (0.133) of the persons capacity;
however, this Guideline’s calculations use .25, which
results in slightly more flotation for the boat.
Step 4: Determine the total flotation material
needed
Formula:
F = Fb + Fp + Fc
F = 0. 52 + 0.33 + 1.14
Example 2: Boat rated for manual propulsion
only.
Assume the same boat as in example 1 above,
but rated for manual propulsion only (no power).
Step 1. Determine flotation needed to support
the swamped boat (Fb)
Formula:
Fb = [(Wh x K) + Wd ] ÷ B
Substituting in the formula above:
Fb
= [(80 x 0.33) + 5] ÷ 60.3
Fb
= [(26.4) + 5] ÷ 60.3
Step 2. Flotation for engine: OMIT.
Step 3. Determine the flotation needed to support the persons
capacity (Fc)
Notice we omit the weight of the engine and
leave maximum weight capacity at 300 lb.
Formula:
Fc
= 0.25 (C) ÷ B
Fc
= 0. 25 (300) ÷ 60.3
Step 4. Determine the total flotation material
needed
Formula:
F = Fb + Fc
F = 0.52 + 1.24
Previous | Next
|
