{(Length - Beam) X Beam X 1/2 Beam} / 94 = Tonnage
This rule penalised Beam and did not take into account, among other things, sail area. The rating led to the production of very long but narrow yachts with huge sails. The rule was modified by various yachting organisations in many countries and attributes such as Water-line Length, Sail Area and Girth were included in the many different ratings to be tried. Eventually in 1970 one rule applicable to yacht racing world-wide came into being - the International Offshore Rule. This rule with its various modifications governs all offshore racing. There are a lot of measurements to be made and applied to the basic formula.
EPF is the Engine & Propeller Factor CGF is the Stability Factor MAF is the Movable Keel Surfaces Factor
When someone is deprived of sleep, the physiological response is sleepiness, which is the brain's signal to prompt an individual to obtain sleep. Eventually, when sufficiently deprived of sleep, the human brain can spontaneously shift from wakefulness to sleep in order to meet its physiological need. The sleepier the person, the more rapid and frequent the intrusions of sleep into wakefulness - these spontaneous sleep episodes can be very short (microsleeps) or last for extended periods of time. Fatigue has frequently been found to be a major contributing factor in aviation, marine, rail and road accidents with catastrophic consequences.
Sleep inertia and microsleep are two just
areas of research that have recently gained able prominence after decades
of study of fatigue and levels of alertness. Sleep inertia is a recognised
state of transition from sleep to wakefulness. New research into sleep inertia
has revealed a range of effects, including:
o Impairment of
performance and reaction time on tasks ranging from arithmetic, to simple
motor tasks such as
grip strength.
o Reduction in
memory ability.
o Impairment of
the ability to make decisions.
Decision making is a cognitively complex process
that involves recognition of the need to make a decision, generation of decision
alternatives and selection of a decision alternative. Within the first three
minutes of waking, decision-making performance can be as low as 51 percent
of the person's best decision making ability before sleep. Decision making
performance may still be 20 per cent below optimum performance 30 minutes
after waking. When woken, most people experience some degree of sleep inertia.
The degree of impairment that sleep inertia has on performance is influenced
by a number of variables, including:
o The
abruptness of awakening. When awakening from sleep normally, the effects
of sleep inertia are
believed to last for less than five minutes; however, if you are
awoken suddenly, these effects can last up
to 30 minutes or more,
o The stage
of sleep that has been interrupted. If you are woken from deep or slow wave
sleep, the effects of sleep
inertia are more pronounced. Slow wave sleep is more likely to occur during
the early stages of sleep.
o In a well
rested person, slow wave sleep usually occurs within 45-60 minutes,
o Sleep
deprivation, which will increase the effect of sleep inertia.
o The type
of task - the effects of sleep inertia vary among different types of tasks.
For example, performance
accuracy is more impaired by sleep inertia than reaction time.
o The time
between awakening and time of performance - sleep inertia will cause less
impairment as the time between
awakening and task performance increases.
Some variables have been shown not
to have an impact upon the effects of sleep inertia on task performance.
These include:
o The time
of day - the effects of sleep inertia arc most apparent when the individual
is abruptly waken from sleep,
regardless of whether the sleep occurs as a daytime nap or occurs during the
night. The exception to this
is naps that end during the low point in the alertness cycle. Sleep inertia
will generally last longer following
naps ending between 0300 and 0700 hours. If you are awaken suddenly, the effects
of sleep inertia
can last up to 30 minutes or more.
. o Sleepiness - no evidence
of any relationship between sleepiness and sleep inertia has been found. If
you have
sleep inertia, you might demonstrate all the outward physical signs of being
awake, but are not cognitively
awake. It can occur regardless of the duration of sleep - disorientation is
experienced after a few seconds
of sleep (microsleeps), a nap or a long episode of sleep
Stage 1 sleep Is a transitional phase between wakefulness and sleep. Brain waves become smaller and slower. In this stage, a person is still easily awakened and might even deny having slept.
Stage 2 sleep is a deeper, intermediate stage of sleep and occupies about 50 per cent of an adult's sleep pattern. In this stage, blood pressure, metabolism and cardiac activity decrease. Brain waves are larger with occasional bursts of activity. A person will not see anything even if the eyes are opened, however, can easily be awakened by Sound.
Stage 3 sleep is the beginning of deep sleep and is characterised
by delta waves -
slow brain waves which are about five times the size of brain wave patterns
in
stage 2 sleep. A person will be far more difficult to awaken during this stage.
Stage 4 sleep is when the deepest sleep occurs and is characterised by large delta brain waves. If the person is a sleepwalker or a bed wetter, these activities will begin in this phase. Waking someone from Stages 3 and 4 sleep is quite difficult. A person awakened from these deep sleep stages will probably be groggy, disoriented and confused and experience sleep inertia.
These factors should be taken into account when designing the watchkeeping roster - especially in allowing enough time during a watch handover for the new watchkeeper to become sufficiently alert to perform the duties properly.
TOO TRICKY !
General Considerations
By far the majority of navigable entrances have a
bar - usually across the whole entrance nearly parallel to the extended shoreline
across the mouth. A BARRED ENTRANCE CAN
BE VERY DANGEROUS. Whenever a bar is to
be crossed extra precautions need to be taken to minimise the risk to boat
and crew.
Regardless of the vessel type the conditions at the
bar must be carefully examined before committing the craft to either entry
or exit. The combined effects of tide, swell and wind need to be assessed.
A run out tide against either wind and / or swell can produce waves so big
that an entry or exit is a foolish proposition - even during the cycles of
smaller waves. Waves not running perpendicular to the required course can
also make the situation worse. A narrow entry / exit channel gives less room
to manoeuvre and therefore smaller margins for errors in judgment. Unfamiliarity
by the skipper and crew also makes for higher risks. Sometimes familiarity
can be detrimental to making good decisions - because of overconfidence and
an attitude that the "home bar" has no fears. There will usually
be a strong desire among the crew to either "get home" or "get
out" which could easily be detrimental to making wise decisions in marginal
conditions. IF IN DOUBT DON'T ATTEMPT TO CROSS.
Irrespective of the type of craft some precautions
should be taken when crossing a bar whenever conditions are likely to be anything
but very flat.
Standard Precautions
- All Boats
Check appropriate weather
forecasts
Arrange a radio safety coverage in marginal
conditions.
Secure all loose items.
All crew don life jackets
Close and secure all hatches.
Brief all crew on emergency drills.
Determine the wave pattern before
committing the boat.
Don't cross a bar with another
boat.
Avoid white water - the prudent
skipper will not cross unless it can.
Spend as little time as possible
on or near a bar.
Cross about 1-2 hours before high
tide.
There are two basic scenarios - the entry and the exit; and there are quite marked differences in the techniques that should be used for a safe bar crossing. An important technique common to all craft is to keep the boat perpendicular to the wave fronts - especially when the waves are either large or steep.
For an Exit the main decision is whether the boat can be adequately controlled as it travels against and through the waves - especially as it falls off the top into the trough. Two conflicting requirements arise - the need to have the boat go over each crest slowly against the need to minimise the time spent on the bar. Judgment and experience are required. A further consideration becomes necessary in marginal conditions - for the return will the bar allow a safe crossing and, if not, what are the alternatives? Can the boat be positioned safely close enough to the bar to properly observe the wave pattern on and just outside the bar? Is the navigable channel wide enough to allow the boat to travel at right angles to the wave fronts?
For an Entry the technique depends primarily on the type of craft and whether it has the capability to travel at or above the speed of the waves. This can usually be achieved in runabouts - and in most other powered craft capable of 15Kts or better. Such craft should be held on the back of the wave once committed - exercising extreme caution to stop the boat getting on the forward face of the wave. A sailing vessel with a fixed deep keel will normally not be able to keep pace with a wave. These craft should use most or all available power to minimise the time spent in the danger zone and reduce the risk of broaching. When on the face of the wave the rudder use becomes critical to keep the boat as straight as possible and perpendicular to the wave. This problem for slower boats usually makes an entry much more hazardous than an exit. All skippers should only commit the boat at the end of the large waves of a set - in marginal conditions this will involve considerable time holding the boat in a safe position from where the wave pattern can be best seen.
Acrylic Sealants & Fillers
Bathroom & Kitchen Sealers
Brick & Concrete Sealers
Ceramic Tile Adhesives
Construction Adhesives
Contact Adhesives
Floor Adhesives
General Sealers
One & Two Part Fillers
PVA Wood Glues
Roof, Gutter & Metal Sealers
Shower & Laundry Sealers
Silicone Sealants
Window & Glass Sealers
Water Proofing Membranes
Spanners - Ring,
Open-ended, Adjustable
Spanners - Specialised eg Crescent
Sockets - Variety of Drives
Screwdrivers - Blade, Phillips & Posidrive
Pliers - General, Multi-Grip, Needle nose
Wirecutters, Strippers & Crimpers
Hammers - Claw, Soft Face
Saws - Wood, Hacksaw, Sabre, Keyhole
Chisels - Several sizes
Knives - General, Rigging, Stanley
Files - Flat & Round
Scrapers - Various Lengths & Widths
Clamps - Several Sizes
Brushes - Wire, Fibre
Drills & Bits - Hand, Battery
Taps & Dies - Metric & SAE
Wood Plane & Wood Rasp
Bolt / Cable Cutter
Swaging Tool - Assorted swages
Tape Measure & Calipers
Magnets - Attachment Rod
Soldering Kit - Battery powered
Hydrometer
Multimeter
Torches -Several types
Fasteners - Screws,
Nuts & Bolts, Washers etc
Gloves - Light Wt & Heavy Duty
Tape - Adhesive & Stretch
Adhesives & Sealants - Good Range
Glues - One & Two Part
Lubricants & Oils - Engine & General
Purpose
Grease - Winch & General Heavy Duty
Gasket Materials
Paints & Varnishes
Penetrating Fluids
Cleaning Fluids, Agents & Cloths
Corrosion Inhibitors - Sprays, Fluids, Pastes
Wooden Plugs - Various sizes
Filters - Fuel & Water
Belts - Engine Drives
Electrical Spares - Fuses, Bulbs, Wire, etc.
Anodes - Shaft, Cooling Systems
Winch Spares
Abrasives - Steel & Bronze Wool, Sandpaper
Plastic & Rubber Hose
Sewing Kit - Needles, Palm and Thread
Sailcloth
Thick Hard Wooden Block - Hammer Cushion
Extension Mirror
Fibreglass Repair Kit
The marine environment is particularly harsh on metal tools - especially mild steel things. To protect all metal tools, including drill bits, coat them lightly in grease or vaseline after use. Other methods include the use of water repellant sprays or other corrosion inhibiting sprays and fluids - such as two stroke fuel with added kerosene or bike chain oil. Items not in frequent use can be protected further from corrosion by wrapping them in plastic as well and sealing with tape - old shopping bags are very useful for such a purpose. Steel wool is useful in removing corrosion residue if used in the early stages.
