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INFLATABLE BOATS

Safety standards for inflatable boats including RHIBs.

The U S Coast Guard defines an inflatable as any boat that depends primarily on inflation for it's buoyancy.  There are basically two types of inflatables,  those that have only fabric or rubberized material divided into compartments that can be inflated with air, and those that have a small rigid hull that is surrounded by inflated cylinders.  The latter are usually referred to as RHIBs, Rigid Hull inflatable Boats.

ABYC defines Inflatable Boats as:

"A boat that achieves all or part of its intended structure shape and buoyancy through the medium of inflation."

and a RHIB as:

"Rigid Inflatable Boat - RIB. also know as a Rigid Hull Inflatable Boat, (RHIB): An inflatable boat with a portion of its hull constructed as a rigid unit and another portion that achieves all or part of its intended structure shape and buoyancy through the medium of inflation."

The U. S. Coast Guard does not directly regulate construction of recreational inflatable boats. They are required to have a Hull Identification Number (HIN). Other than that there are no US Coast Guard standards for Horsepower, Capacity, or Flotation.  There are standards for all of these published by the American Boat and Yacht Council (ABYC), the International Standards Organization (ISO) and Canada (see below). All inflatable boat manufacturers follow one of these standards and they are all nearly identical. The ABYC Standard is H-28

However, should the boat have an inboard gasoline engine, then the boats must comply with the U S Coast Guard fuel systems, electrical systems and ventilation systems standards.  The engine may have to have a flame arrestor.  Several manufacturers of inflatables have boats with inboard gas engines, similar to those used in Personal Watercraft (PWC).  Use of PWC engines may require a Grant Of Exemption from the US Coast Guard. Also some manufacturers have had difficulty complying with the fuel systems standard. there is a portion which says that fuel cannot be spilled into the boat.  Inflatables that have a permanently installed fuel tank have problems with this.  There have been some unique solutions such as catch basins that have a drain that goes overboard. If you are installing an inboard engine in an inflatable boat consult with the US Coast Guard Office of Boating Safety first to find out what requirements they have for you.

If you look at an inflatable boat, most will have a capacity label listing maximum weight capacity, persons capacity and horsepower if rated for an outboard engine. The below image is a European capacity label for an inflatable boat. It is in both metric and english units.

You can put a capacity label on an inflatable. However, it cannot say US Coast Guard at the top of the label. If you are installing navigation lights or an inboard gasoline engine then it must have a Certification Label. Otherwise do not put the certification statement on the capacity label.

The Canadian Rules for Inflatables are in TP1332 Section 4.6 and are as follows:

4.6 Recommended Maximum Safety Limits for Inflatable and Rigid Hull Inflatable
Vessels

4.6.1 Calculation Criteria (Intact Condition)

4.6.1.1 The criteria for developing the recommended maximum safe limits to be marked on a capacity label for an inflatable or rigid hull inflatable vessel is based on the buoyancy provided by the inflated tubes, and in addition, where applicable, the volume of the hull below the cockpit sole.

4.6.2 Recommended Maximum Gross Load Calculation

4.6.2.1 The recommended maximum gross load in kilograms marked on a capacity label for an inflatable or rigid hull inflatable vessel is determined in relation to the total volume of inflatable tubes (V) and the weight of the vessel as follows:

 GL = (Vt × b × 0.75) − Wv

Where:
GL = recommended maximum gross load in kilograms
Vt = the total volume of the inflated tubes in cubic metres, and where present, the volume of the rigid or inflated hull below the cockpit sole
b = constant buoyancy factor = 1000 kg/m3
Wv = the weight of the vessel in kilograms, including deck, railings, console, seats, and any other permanent structures and fittings. For outboard powered vessels, the outboard engine and related equipment weight from Table 4-2 is excluded. For vessels fitted with permanent fuel tanks the fuel weight must be included.

4.6.2.2 The following load reduction dependent on design features is applied to the recommended maximum gross load, calculated in accordance with 4.6.2.1.

4.6.2.3 The load reduction based on the minimum number of chambers in the collar is as follows:
(a) 1 air chamber = 50% load reduction;
(b) 2 air chambers = 33% load reduction;
(c) 3 air chambers = 25% load reduction;
(d) 4 air chambers = No load reduction.

4.6.3 Recommended Maximum Number of Persons Calculation

4.6.3.1 The recommended maximum number of persons marked on a capacity label for an inflatable or rigid hull inflatable vessel is determined in relation to maximum gross load and engine weight in kilograms as follows:
(a) For inboard or stern-drive powered vessels:

Number of Persons =  GL/75

(b) For outboard powered vessels:

Number of Persons = (GL-We)/75

Where:
GL = recommended maximum gross load in kilograms
We = engine and related equipment total weight in kilograms, as determined from Table 4-2
75 = assumed weight of one adult person in kilograms

4.6.3.2 The maximum number of persons shall be rounded off to the nearest whole number. If the fraction is less than 0.5, round down to the next whole integer and if the fraction is equal to or greater than 0.5, round up to the next higher whole integer.

4.6.4 The Recommended Maximum Power Calculation

4.6.4.1 The recommended maximum power for outboard powered inflatable vessels is determined by:

(a) The formula given in 4.6.4.2 for vessels of all sizes; or
(b) The test given in 4.6.4.3 for vessels fitted with a motor of more than 15 kW.

4.6.4.2 The recommended maximum power for outboard powered inflatable vessels is determined in relation to total vessel length, its beam, the total internal volume of the inflatable tubes and a design factor, as follows:

Maximum Power kW = (Lh × V × fx) = B

Where:
Lh = vessel length of the vessel in metres as per Figure 0-1
V = total internal volume of the inflatable tubes in cubic metres
B = beam of the vessel in metres
fx = a constant factor determined by transom type as follows:
(i) Factor (f1) for stern tube type = 2.5
(ii) Factor (f2) for stern transom type, vessel length not exceeding 3.0 m = 6.5
(iii) Factor (f3) for stern transom type, vessel length greater than 3.0 m but not    exceeding 5.0m = 7.5
(iv) Factor (f4) for stern transom type, vessel length greater than 5.0 m = 9.0

4.6.4.2.1 For vessels of more than 3 metres in length that are fitted with a remote steering, the factors f3 and f4 may be multiplied by 1.25 when the steering position is located more than 25% of the length (L/4)forward of the transom.

4.6.4.3 The maximum recommended power may be determined by the Manoeuvring Test Procedure specified in the standard ISO 11592 Small craft less than 8 m length of hull – Determination of maximum propulsion power rating or the Avoidance Line Test specified in section 26.8.3.2 of the ABYC standard H-26 Powering of Boats.

4.6.4.3.1 For vessels not fitted with a remote steering, the maximum recommended power determined by the test specified in 4.6.4.3 shall not exceed the value determined by the following formula:

Maximum Power (kW) = 10× Lh × B − 33
Where:
Lh = vessel length of the vessel in metres as per Figure 0-1
B = beam of the vessel in metres

4.6.4.4 When the calculated power is not more than 10 kW (15 hp) the power may be rounded up to the next increment of 1.5 kW (2 hp). When the calculated power is more than 10 kW (15 hp), the power may be rounded up to the next increment 3.75 kW (5 hp)

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