Safe Loading - Subpart C
Category Three: Boats Rated for Manual Propulsion and Boats Rated for Outboard Motors of 2 Horsepower or Less
Example of Calculations for Maximum Weight Capacity and Persones Capacity: Boats Rated for Manual Propulsion and Boats for 2 Horsepower or Less (Category Three)
For the purpose of this example we will assume a 14.5 ft. rowboat that has a transom capable of receiving an engine. The manufacturer has certified the boat for 2 HP.
In section 4.0, we discussed the methods to calculate maximum displacement. The assumed boat has a classic up-turned sheer and is sold as a rowing or low power outboard engine boat. The preferred methods to use in figuring displacement would be the immersion method or measuring a hull or mold and following Simpson’s Rule. We assume this has been done. Following are the specifications:
| Length overall: |
14.5 ft. |
| Calculation length: |
14 ft., 2 in. |
| Beam: |
5.75 ft. |
| Calculation beam: |
5.5 ft. |
| Boat weight: |
600 lb. |
| Outboard engine: |
2 HP |
| Engine weight: |
25 lb. |
| Fuel tank: |
built-in the engine |
We have established the static float plane as explained before. We have measured the hull either by the boat immersion method or by applying Simpson’s Rule, and have calculated a cubic capacity of 45 cubic ft. We now follow the steps to calculate maximum weight capacity according to 33 CFR 183.37.
Step 1: Compute maximum displacement
D = cubic capacity X 62.4 lb.
D = 45 X 62.4 = 2808 lb.
Step 2: Compute maximum weight capacity (W).
W = (maximum displacement (lb.) – boat weight) X 3/10
W = (2808 lb. – 600 lb.) 3/10
W = 662.4 rounded down to 662 lb.
This figure of 662 pounds is the maximum weight capacity that must be displayed in the capacity label. It can be less, but it cannot be any more.
Step 3: Compute the persons capacity in pounds (P lb.).
The boat may be used for rowing but it has a transom capable of carrying an outboard motor and the manufacturer has decided to rate the boat for 2 HP on the certification capacity label. Therefore the persons capacity numbers must be calculated following option 2 of the regulation 183.43 (a) (2) above.T
| P(lb.) |
= 90% W – 25 lb. |
| |
= (.90 X 662) – 25 |
| |
= 595.8 – 25 = 570.8 rounded up to 571 lb |
| |
|
Step 4: Compute the persons capacity in whole numbers (P no.).
|
=
|
32 + P(lb.) |
= 32 + 571 = 4.27 rounded down to 4 persons |
| |
141
|
|
The capacity label of the boat in this example may display a label such as:
U. S. COAST GUARD
MAXIMUM CAPACITIES
4 PERSONS OR 571 LB
662 LB PERSONS, MOTOR AND GEAR
2 HORSEPOWER, MOTOR
NOTE:
See 33 CFR 183.25.
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