brigid mary

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STABILITY : 

STABILITY

FIRST PRINCIPLES : 

FIRST PRINCIPLES BUOYANCY CENTRE OF GRAVITY RIGHTING FORCE FACTORS WHICH CAN CAUSE CAPSIZE

CBCentre Of Buoyancy : 

CBCentre Of Buoyancy Force generated by boat displacing water CB is point of concentration of this force Changes with HEEL ANGLE, TRIM and LOADING CB

CG Centre of Gravity : 

CG Centre of Gravity Determined by structure and weight distribution of boat Best when it is low down

GZ The Righting Lever : 

GZ The Righting Lever Force that combination of CG and CB make, to return boat to the upright. CG CB GZ

RM Righting Moment : 

RM Righting Moment Mass (Weight and volume) of boat affects stability When multiplied with GZ it gives RM CB GZ X mass = RM

ANGLE of HEEL : 

ANGLE of HEEL As boat heels more, RM becomes greater RM

POINT OF VANISHING STABILITY : 

POINT OF VANISHING STABILITY RM is ZERO BOAT INVERTS CB

RIGHTING MOMENT CURVE(Flat Water) : 

RIGHTING MOMENT CURVE(Flat Water)

DIFFERENT TYPES OF CURVE : 

DIFFERENT TYPES OF CURVE

DESIGN CATEGORIES : 

DESIGN CATEGORIES CATEGORY TYPE WIND FORCE WAVE HEIGHT A OCEAN >F8 >4M B OFFSHORE F8 4M C INSHORE F6 2M D SHELTERED WATERS F4 0.5M

CATEGORIES : 

CATEGORIES

RE-RIGHTING : 

RE-RIGHTING A = Re-righting factor B If it is large then re-righting is good

RE-RIGHTING FACTORS : 

RE-RIGHTING FACTORS Type A will be harder to re-right than type B A’s re-righting factor is lower than B’s

FACTORS THAT CAN CAUSE CAPSIZE : 

FACTORS THAT CAN CAUSE CAPSIZE SWAMPING OR FLOODING FREE- SURFACE EFFECT LARGE BREAKING WAVES CG MOVED UPWARDS RESONANT ROLLING BROACHING

FACTORS WHICH CAN IMPROVE STABILITY (1) : 

FACTORS WHICH CAN IMPROVE STABILITY (1) INCREASED LENGTH HEAVY DISPLACEMENT FOR SIZE HIGH PROPORTION OF OVERALL WEIGHT AS BALLAST HIGH ANGLE OF VANISHING STABILITY HIGH RE-RIGHTING FACTOR GOOD RM AT 90° OF HEEL MODEST BEAM IN RELATION TO LENGTH

FACTORS WHICH CAN IMPROVE STABILITY (2) : 

FACTORS WHICH CAN IMPROVE STABILITY (2) GOOD BUT NOT EXCESSIVE FREEBOARD MINIMAL TOPSIDE FLARE ABSENCE OF LARGE NEARLY FLAT AREAS OF DECK LARGE ANGLE OF HEEL BEFORE FLOODING CAN OCCUR INCREASED KEEL PROFILE AREA ABSENCE OF BULWARKS

IN ROUGH WEATHERDO : 

IN ROUGH WEATHERDO CLOSE HATCHES, WASH BOARDS ETC. PUMP OUT BILGE REGULARLY WATCH OUT FOR GUSTY CONDITIONS AVOID BEING CAUGHT BEAM ON TO LARGE, BREAKING WAVES BE AWARE OF CATEGORY AND CAPABILITY OF YOUR BOAT

IN ROUGH WEATHER DO NOT : 

IN ROUGH WEATHER DO NOT SAIL IN CONDITIONS THAT ARE OUTSIDE THE CAPABILITY AND CATEGORY FOR WHICH YOUR BOAT WAS DESIGNED DELIBERATELY SAIL THROUGH KNOWN TIDAL RIPS, RACES, OVERFALLS OR WHERE THE BOTTOM SHOALS RAPIDLY