1

STABILITY Slides from ROM2 Only available direct from RYA training 2

Stability Righting lever Boats return to the upright because of an interaction between their weight and buoyancy centre of gravity centre of buoyancy As a boat heels, B moves away from G creating a righting lever called GZ A heavy boat takes more energy to heel because......energy = boat weight (force) x GZ (distance) = RM (righting moment) 3

AVS for a vessel without roller furling gear AVS for a vessel with roller furling gear 4

Lifeboat Curve 5

Testing underway 6

IMS 33 Racer 7

IMS 41 Racer 8

MALO 41 9

IMS 33 – Righting Arm (GZ) Curve 10

IMS 41 – Righting Arm (GZ) Curve 11

MALO41 – Righting Arm (GZ) Curve 12

IMS 33 – Righting Lever (kN) Curve 13

IMS 41 – Righting Lever (kN) Curve 14

MALO41 – Righting Lever (kN) Curve 15

Contessa 32 – Righting Lever (GZ) 16

Different Hull Designs 17

Water Ballast 18

Finding the Centre of Gravity 19

GZ 20

GZ (Righting arm) vs. kN (Righting moment) IMS 33 AVS 127⁰ Area above curve = energy required to capsize yacht

IMS 41 GZ (Righting arm) vs. kN (Righting moment) AVS 135⁰ Area above curve = energy required to capsize yacht

MALO 41 AVS 132⁰ Area above curve = energy required to capsize yacht GZ (Righting arm) vs. kN (Righting moment)

Different STIX… and different capacity to resist capsize IMS 33IMS 41MALO 41 ISO STIX 33.3ISO STIX 47.8 ISO STIX 55.4

???