|
|
|
PREVIOUS | TABLE OF CONTENTS | NEXT SECTION 1A 3 SECTION 1: OPERATIONAL INFORMATION A 3.1 ARRANGEMENT OF TANKS AND BALLAST ^ Figure 4: Tank and Ballast Arrangement
Draughts are referred to an extension of the underside of keel All other vertical locations are referred to BASE All longitudinal locations are referred to MIDSHIPS Trim is defined as: Draught Aft - Draught Fwd Design trim = Rake of keel = 1.10 metres A 3.2 SAIL PLAN ^
Figure 5: Sail Plan Angles of Deck Edge Immersion and Downflooding ^
Critical downflooding is deemed to occur when the lower edges of openings having an aggregate area (in m2)greater than Thus immersion of the galley vent is not regarded as critical and it is the irnmersion of the forward skylight which defines the critical downflooding angle referred to in this booklet. The master should note that the presence of the vent and skylights significantly reduce the ability of this vessel to withstand downflooding and with these openings securely closed the safety of the vessel is enhanced considerably. A 3.4 Notes on Stability for the Guidance of the Master ^
A 3.5 Maximum Steady Heel Angle to Prevent Downflooding in Gusts. ^
Figure 6: Maximum Heel Angle, Gusts
Gusting Conditions When sailing in a steady wind the vessel heels to the angle at which the heeling arm curve intersects to GZ curve. When struck by a gust the heel angle will increase to the intersection of the gust heeling arm curve with the GZ curve. The heeling moment increases in proportion to the square of the apparent wind speed. Operation of the vessel at a mean heel angle not greater than 27 degrees ensures significant downflooding openings would not be immersed if it were to encounter the strongest gust in the prevailing turbulent airstream which could exert a heeling moment equal to twice that of the mean wind (i.e. mean apparent wind has increased in velocity by 1.4). A 3.6 Curves of Maximum Steady Heel Angle to Prevent Downflooding in Squalls ^ Figure 7: Maximum Steady Heel Ange, Squalls SQUALL CONDITIONS Curves of maximum steady heel angle indicate the range of mean or steady heel angles beyond which the vessel will suffer downflooding in the event of a squall. Operation of the vessel in cyclonic conditions particularly in the hours of darkness, where severe squalls are imminent requires the recommended maximum steady heel angle to be reduced depending on the mean apparent wind speed in accordance with the curves presented above. A 3.7 Examples Showing the use of the Maximum Steady Heel Angle Curves ^
Figure 8: Maxiumum Steady Heel Angle Curves ^ Example A The yacht is reaching, with a steady apparent wind speed of 16 knots. The mean heel angle is 15 degrees. Forecasts and visible cumulo-nimbus clouds suggest squalls may be imminent. By plotting the heel angle and wind speed (point A in Figure 8) the indication is that the vessel will be in danger of heeling to the downflooding angle in squalls in 30 knots. In order to increase safety from downflooding, say, to withstand squalls of up to 45 knots, sails should be handed or reefed to reduce the mean heel angle to 7 degrees (point A1 in Figure 3) or less. Example B The yacht is beating in gusty conditions with a mean apparent wind speed of 30 knots. The mean heel angle is 20 degrees. No squalls are expected. The heel angle is significantly less than 27 degrees, the maximum recommended steady heel angle, and there is therefore a good safety margin against downflooding in a strong gust. Plotting these values of wind speed and heel angle (point B in Figure 8) also indicates that the vessel would not be vulnerable to downflooding in a squall unless it resulted in a wind speed in excess of about 50 knots. There is thus no need to reduce sail area on the ground of stability. Note: Appropriate examples should be presented for the Master, to enable him to interpret the meaning of these curves and understand their use. |
|
Transport Canada |
Pacific Region |
Prairie & Northern Region |
Ontario Region |
Quebec Region |
Atlantic Region |
About us |
Our offices |
Organization and senior management |
Departmental publications |
Programs and services |
Acts |
Regulations |
[More...] |
Media room |
Advisories |
Contacts |
e-news |
News releases |
Photo gallery | Reference centre |
Speeches |
[More...] |
Emergencies |
Emergencies and crises |
Emergency preparedness |
Security |
Transport of dangerous goods |
[More...] |
Air |
Our offices |
Passengers |
Pilots |
Flight instructors |
Maintenance technicians |
Commercial airlines |
Security |
Transport of dangerous goods |
[More...] |
Marine |
Our offices |
Small commercial vessels |
Large commercial vessels |
Pleasure craft |
Marine security |
Marine infrastructure |
Transport of dangerous goods |
[More...] |
Rail |
Our offices |
Safety at railway crossings |
Rail infrastructure |
Transport of dangerous goods |
[More...] |