Section 5 Impact loads

5.1.1 The impact pressure, P _dh, for mono-hull and multi-hull craft is to be taken as specified in Pt 5, Ch 2, 5.1 Impact pressure for displacement mode 5.1.2 and Pt 5, Ch 2, 5.1 Impact pressure for displacement mode 5.1.3 as applicable.

5.1.2 The bottom shell impact pressure due to bottom slamming, is given by the following expression:

• P _dh ≥ P _m

Intermediate values to be determined by linear interpolation. T _x is taken to be the draught T, as defined in Pt 3, Ch 1, 6 Definitions, but need not be taken greater than 0,08L _WL.

P _dh at 0,9L _WL and 0,8L _WL from aft end of L _WL need not be taken greater than P _f at L _WL from aft end of L _WL as defined in Pt 5, Ch 2, 5.4 Forebody impact pressure for displacement mode 5.4.1.

5.1.3 The side shell impact pressure shall be taken as P _dh at the operating waterline, reducing to 0,4P _dh at the weather deck. Intermediate values between the weather deck at side and operating waterline, are to be determined by linear interpolation.

5.2.1 The impact pressure, P _dI, for mono-hull and multi-hull craft is to be taken as specified in Pt 5, Ch 2, 5.2 Impact pressure for non-displacement mode 5.2.2 and Pt 5, Ch 2, 5.2 Impact pressure for non-displacement mode 5.2.3 as applicable.

5.2.2 The bottom impact pressure due to slamming, P _dlb is given by the following expression:

Intermediate values to be determined by linear interpolation.

Otherwise, Φ = 1,0

5.2.3 The side shell impact pressure due to slamming is to be taken as:

but is not to be taken as greater than P _dlb

(40 – θ_B) is not to be taken as less than 10°

(θ_S – 40) is not to be taken as less than 10°

P _dIs is to be taken as constant from the chine or operating waterline to a point half G _o from the chine, or the weather deck if this is reached first. Multiple chines will be subject to special consideration based on the above principle. See Figure 2.5.1 Angles used in determination of side shell pressure for planing craft, P _dIs .

5.3.1 The impact pressure, P _fb, for craft supported by hydrodynamic lift provided by foils or other lifting devices is to be taken as specified in Pt 5, Ch 2, 5.3 Impact pressure for craft with foils and lifting devices 5.3.2 and Pt 5, Ch 2, 5.3 Impact pressure for craft with foils and lifting devices 5.3.3 as applicable.

5.3.2 The bottom impact pressure, is given by the greater of P _fba or P _fbb, where:

P _fbb is not taken as less than zero.

V _R is the relative vertical speed of the craft at impact, in knots. If this value is unknown, then the following equation is to be used:

5.3.3 The side shell impact pressure shall be taken as P _fb at the chine or at the operating waterline for round bilge hullforms as appropriate reducing to 0,3P _fb at the weather deck. Intermediate values between the weather deck at side and the chine or operating waterline, as appropriate, to be determined by linear interpolation.

5.4.1 Forebody and bow slamming pressure, P _f, at the load waterline due to relative motion is to be taken as:

Intermediate values to be determined by linear interpolation.

5.4.2 The side shell impact pressure shall be taken as P _f at the chine or at the operating waterline for round bilge hullforms as appropriate reducing to 0,4P _f at the weather deck. Intermediate values between the weather deck at side and the chine or operating waterline, as appropriate, are to be determined by linear interpolation.

Intermediate values to be determined by linear interpolation.

5.5.2 The side shell impact pressure shall be taken as P _f at the chine or at the operating waterline for round bilge hullforms as appropriate reducing to 0,3P _f at the weather deck. Intermediate values between the weather deck at side and the chine or operating waterline, as appropriate, are to be determined by linear interpretation.