Commercial Craft Rules

NOTE! Additional requirements may be given in Chapters 34-39 for special missions

To verify that the requirements presented in this chapter are met, the following documentation is required:

4.1. According to the design category, decking arrangement, and possible fitting of flotation material, craft will be assessed using one of the options given in Table 4.1a and 4.1b appropriate to the arrangement of the craft, following the international standard ISO 12217, and described below. The requirements shall be met in all relevant loading conditions

Table 4.1a. Requirements and tests vs. assessment option for decked and closed craft greater than 6 m.

TEST OR ASSESSMENT		OPTION NUMBER (4.2)	1		2		3A	3B
		Deck Arrangement (chapter 2)	Fully Decked				Closed	Closed
		DESIGN CATEGORY	A	B	C	D	B	C
RECESSES Chapter 5.		Recess type	Watertight or quick draining				Watertight	Watertight
RECESSES Chapter 5.		Recess size limitation	x	x			x	x
FREEBOARD TO DECK EDGE Monohulls only. 8.1.2		Minimum freeboard to deck edge, F_MIN = fraction of F_BASE:sta F_BASE= 0,7× /(1000 × L_WL × B_WL)	1,0× F_BASE	0,9× F_BASE	0,75× F_BASE	0,5× F_BASE
RESERVE BUOYANCY All multihull crafts, alternative method for monohulls instead of freeboard check. 8.1.1		Volume of weathertight spaces above waterline or up to downflooding opening, percentage of displacement	100	70	30	20	Closed space divided into at least to 5 compartments check 14	Closed space divided into at least to 5 compartments check 14
BOW VOLUME . 8.2		Forward trim restoring moment lever, h_TRIM, m	1,5	1,0	0,5	0,15	1,0	0,5
DOWNFLOODING HEIGHT 8.3		h_D [m] >	L_H/17 min 0,5	L_H/17 min 0,4	L_H/17 min 0,35	L_H/20 min 0,3	L_H/17 min 0,5	L_H/17 min 0,35
OFFSET LOAD TEST. 9		Max heel an _O(R) =	11.5 + (24 - L_H)³/ 520
OFFSET LOAD TEST. 9		Freeboard [m]	0,26×B_H	0,145×B_H	0,046×B_H	0,10	0,145×B_H	0,046×B_H
MAXIMUM RIGHTING MOMENT. 11		if _GZmax ³ 30^O, RM₃₀ [kNm] ³	25	7			7	-
		if _GZmax < 30^O, RM_max [kNm] ³	50/ _Gzmax	210/ _Gzmax	-	-	210/ _Gzmax	-
PROPERTIES OF GZ -CURVE. 12	Jos f_GZmax ³ 30^O	Area under GZ curve 0-30^o, [mrad] ¹⁾	0,055	0,055	-	-	0,055	-
		Area under GZ curve 0-40^o, [mrad]¹⁾	0,09	0,09	-	-	0,09	-
		Area under GZ curve between 30-40^{o 1)}	0,03	0,03	-	-	0,03	-
		GZ₃₀ [m] ³	0,20					-
	If _GZmax < 30^O	Area of GZ curve 0- _GZmax [mrad] ¹⁾	0,055+0,002 (30^o- _Gzmax)		-	-	0,055+ 0,002 (30^o- _Gzmax)	-
	If _GZmax < 30^O	GZ_max [m] ³	6/ _GZmax
	Always	GM ³ ¹⁾	0,35
	Always	Range of positive stability _v ³	90^O	60^O	-	-	60^O	-
WEATHER CRITERIA. 10		Calulation wind speed v_W (m/s)=	28	21	-	-	21	-
WEATHER CRITERIA. 10		Area A₂ ³ A₁ than _R=	25+20/	20+20/	-	-	20+20/	-
HEEL DUE TO BEAM WIND. 13		if A_LV > L_H ∙ B_H and v_W (m/s) =	-	-	17	13	-	17
HEEL DUE TO BEAM WIND. 13		Heel angle due to wind _W<	-	-	_O(R)/2	_O(R)/2	-	_O(R)/2
LEVEL FLOTATION. 14		Flotation and stability in swamped condition	-	-	-	-	Test weight 133% of max. load Material requirements	Test weight 133% of max. load Material requirements

Table 15. Requirements and tests vs. assessment option for open and partly decked boats greater than 6 m.

	OPTION NUMBER (4.2)	4		5		6
	DESIGN CATEGORY	C	D	C	D	C	D
DECK ARRANGEMENT. Chapter 2	Open	x	x			x	x
DECK ARRANGEMENT. Chapter 2	Partly decked			x	x
RECESSES		Recesses larger than L_H×B_H×F_M/40 either quick-draining or to be filled with water to 20% of their volume.
MAXIMUM DISPLACEMENT	Loaded displacement m_LDC, kg	(12∙ L_H∙ B_H)^1,5
BOW HEIGHT. 8.4	Bow height abowe wl, [m]	1,2×h_D
FREEBOARD. 8.3	h_D [m] >	0,4	0,35	0,6	0,5	0,7	0,5
FREEBOARD. 8.3	h_D [m] to be greater than	L_H/20	L_H/24	L_H/12	-	L_H/10	-
OFFSET LOAD TEST. 9	Max. heeling angle _O <	11.5 + (24 - L_H)³/ 520
OFFSET LOAD TEST. 9	Residuary freeboard [m] >	0,046×B_H	0,10	0,11Ö L_H	0,07Ö L_H	0,11Ö L_H	0,07Ö L_H
HEAL DUE TO BEAM WIND. 13	If A_LV> L_HB B_H and v_W (m/s) =	17	13	17	13	17	13
HEAL DUE TO BEAM WIND. 13	Heel due to beam wind _W <	_O(R)/2	_O(R)/2	_O(R)/2	_O(R)/2	_O(R)/2	_O(R)/2
LEVEL FLOTATION.14	Flotation and stability in swamped condition	x	x

5.2. Determination of light craft weight and centre of gravity
The light craft weight and centre of gravity used shall be determined by one of the following methods. Deviations in equipment compared to the definition of light craft weight (see 4.1) shall be taken into account when calculating the light craft weight and centre of gravity for stability calculations..

5.3. Maximum total load
The maximum load, m_MTL, is the load the craft is designed to carry in addition to the light craft condition comprising:

This definition corresponds with ISO 14946, except for the anchoring and mooring equipment and liferafts, see 4.4.1.

6.1. Decked boats (assessment option 1 and 2)
The stability of decked boats shall be assessed at least in the following loading conditions:

When relevant, other loading conditions shall be assessed as well. If relevant, the effect of icing shall be investigated according to 6.6.

6.2. Open and partially decked boats (assessment options 3, 4 and 5)
Open and partially decked boats are normally to be assessed only in the Fully loaded departure condition. and Offset load condition When relevant, other loading conditions shall be assessed as well.

6.3. Minimum operating condition
Craft equipped as for the light craft condition with the following added as appropriate:

a) mass to represent the crew, positioned at the highest main control position of:

6.4. Fully loaded condition, departure (= Loaded displacement condition ISO 12217)

Craft in the light craft condition with the maximum total load added so as to produce the design trim, the vertical distribution of crew mass being that used for the offset load test and described in 9. Cargo as described in chapter 34.

6.5. Fully Loaded condition, arrival
As the departure condition, but only 10% of maximum capacity of consumable stores on board. Free surface effects have to be considered.

6.6. Offset load condition
As Fully loaded condition, departure, all persons and possible cargo on deck are placed on one side of boat as described in 10.

6.7. Icing
When icing on hull and superstructures is taken into account, the weight and distribution of the ice shall be assumed as follows (always when boat has notation "Ice strenghtened" as described in chapter 40):

7.1. Light weight
The light weight used in the calculations shall be determined according to 5

7.2. Form stability
In defining the weathertight hull for calculation, all recesses, superstructures and underwater appendages affecting the buoyancy at the range of heel angles in question shall be correctly represented. Only structures that are sufficiently watertight (according to Chapter 3) and strong (according to Chapter 10, 14 or 18, depending on the construction material) may be included. Righting lever curves shall normally be calculated with recesses modelled, assuming that at each heel angle such recesses flood up to the exterior water level. However, up to the angle of heel at which recesses would otherwise fill (e.g., coaming submergence), righting moments may alternatively be calculated ignoring flooding of recesses through either:

8.1. Reserve buoyancy, freeboard and downflooding height (normally only for closed or fully decked crafts)

Figure 4.2. Typical downflooding openings and exceptions. Marking YES or NO indicates if the opening is regarded as a downflooding opening or not.

For open and partially decked craft, the required downflooding height within L_H/3 of the bow shall be increased, as shown in Figure 4.3 The bow height, F_BOW, shall be at least as given in table 4.1b.

For craft of design category A and B the bow height shall be measured to the uppermost watertight deck, in categories C and D also the watertight topsides of the craft may be included.

This test is to demonstrate sufficient stability for the craft at loaded displacement mass against offset loading by the crew and/or shifting of cargo. The test follows the method described in the international standard ISO 12217-1.

The offset load heel angle,

_O,is the heel angle resulting when persons and/or cargo onboard are moved transversally to one side of the craft. The offset load heel angle shall be determined for all types of craft and shall not exceed the requirement given in table 4.1a and 4.1b. For craft using option 4 or 5 (partly decked or open), the residuary freeboard (the least height from the waterline to the point at which water could first begin to enter the interior of the craft) shall be determined as well. The offset load heel angle

_O, and residual freeboard may be determined either by means of a physical test or calculation.

The offset load heeling and residuary freeboard are measured with same load as "Fully loaded conditon, arrival," see 6.5. Following exceptions to location of deck cargo and persons are made:

Persons, or equivalent weights, are placed as close to the outer limits of the Crew Area (definition see 9.4) as follows;

Complete description of offset load test procedures can be found from ISO ISO 12217-1.

The crew area A_C is the area available to the persons on board. It shall be taken as the area where people may stand, sit, walk or lie, and where any of the following activities may take place:

10. Rolling in beam wind and waves (weather criterion, decked craft Cat. A and B).

10.1. The purpose of this criterion is to ensure that the righting energy from an assumed steady heel angle caused by beam wind to the downflooding angle, the vanishing angle or 50 degree, whichever is less, is equal to or greater than the heeling energy caused by beam waves simulated by an assumed roll angle.

The wind heeling moment, M_W, is assumed to be constant at all angles of heel and shall be calculated as follows:

The righting moment curve and the wind heeling moment shall be plotted on the same graph, as shown in figure 3. Area A2 shall be greater than area A1, where A1 and A2 are the areas indicated in figure 4.4.

11.1. To screen out too small boats from design categories A and B, requirements are given for the maximum righting moment. The required minimum value of the maximum righting moment, which is given in table 1, is dependent on the design category and the heel angle at which the maximum GZ occurs.

12.1 The GZ-curve shall be determined for all relevant loading conditions (see 5), following the principles in 4.

If the heel angle at which the maximum GZ,

_GZmax, occurs is equal to or greater than 30°, the requirements for the area under the GZ-curve are given for 0 - 30°, 0 - 40° and 30 - 40°. The requirements for GZ at 30° heel are also given.0-30^o, 0-40^o

If the heel angle at which the maximum GZ,

_GZmax, occurs is less than 30°, the requirements are given for the area under the GZ-curve up to the heel angle of greatest GZ_max.

Regardless of the angle of maximum GZ, the requirements for GM and vanishing angle shall be met.

13.1. This criterion is to ensure that the righting moment is sufficient to withstand the heeling moment of a strong beam wind. Where the projected windage area A_LV < L_H × B_H, this requirement is omitted. Other craft shall be assessed as follows:

The wind heeling moment M_W shall be calculated as in 10 but using v_W = 17 m/s for design category C, and 13 m/s for design category D

The heel angle due to the wind heeling moment

_W shall be determined either by comparing the heeling moment with the curve of righting moments for the loading condition in question, or from the formula:

The angle

_W shall be less than half the maximum allowed offset heel angle according to table 1 and paragraph 9.

14.1.1. Level flotation means that the craft remains floating approximately level after having been swamped and possesses a minimum of stability. The level floatation test is to be carried out in accordance with ISO 12217 with the exception of RIB-boats under 8 m hull length, which shall be assessed according to ISO 6185. Level flotation test is made to crafts assessed with option number 4 , 3a and 3b.

14.2.1. Needed volume for flotation chambers can consist of air tanks, rib collars or pontoon foam.

Air tank is watertight and airtight space, which is restricted by walls of GRP, metal or similar stiff material. Tank must be equipped with mean of removing condensed water from tank. Air tank will be tested with 5 kPa initial overpressure. During one minute, acceptable loss of pressure is 1 kPa.

Pontoon is air tank made of thin, typically fabric reinforced polymer sheet. Pontoon is filled with overpressured air to keep its shape. Material of pontoon has to meet requirements in ISO 15372 "Ships and marine technology - Inflatable rescue boats - Coated fabrics for inflatable chambers." Pontoons are tested according to ISO 6185.

Pontoon foam consist of cellular foam. It needs to be in-built to structure or be coated with proper material to provide mechanical protection. Pontoon foam material has to fill requirements in IMO MSC 81(70).

14.3.1. Air tanks and pontoons has to be divided into several compartments if their portion of total required volume for flotation chambers is significant. Depending of the volume of air filled tanks and pontoons they have to be divided to separate compartments according to table 4.3.

Table 4.3

Proportion of air filled pontoons from needed flotation chamber volume	Number of compartments, at least
≤20%	1
≤40%	2
≤60%	3
≤80%	4
>80%	5

14.3.2. Volume of air filled tank can differ 30% from mean value of tanks. Volume of pontoon compartment can differ 20% from mean value of pontoons.

14.4.1. Level flotation test is made according to ISO 12217 with following alteration: Option number 3a and 3b (closed crafts) shall use additional weights according to table 4.1a.