SAIL Flashcards
Sailing Theory
Sail: forces
- II. Newton Axiom: Kinetic Energy (force = mass * accelaration) => max pressure close to mast => keep sail profile in shape
- Bernoulli: pressure differential due to air slowing on luff and speeding up in lee (wind in lee reaches leech earlier than the wind in luff!) => lift
=> air envelopping wing profile: Coanda Effect
Lift with
Upwash and Downwash
Airflow: angle of attack
goal: laminar flow; little disturbance => airflow ‘sticks’
angle too small: luff will flutter
angle too big: airflow will tear off => no Coanda Effect
Sail Power: vectors
SP (Sail Power = Lift) perpendicular to sail and centred in CoG (Centre of Gravity)
PF := Propulsive Force <=> WF (drag)
TF := Transversal Force => leeway
Running: II. Newton
Beam Reach: small TF, large PF
Close Haul: big TF, small PF
Sails working together
upwash and downwash
Forces to windward
- torque from TF (SP) ./. LP
- windward torque
Leehelm ./. Weatherhelm
relative longitudinal position of transverse force (TF) of Sail Power = Lift (SP)
vs
Lateral Point (CoG of underwater area)
=> most important for upwind
=> balance LP and SP
Windward torque
most important for downwind
Propulsion Force (FP) of Sail Power = Lift (SP) is outside of centreline, whereas drag is in centreline
- dynamic: increases with drag with ship’s speed and heeling (wetted area in lee increases and SP moves further outside centreline)
- design compensation: place SP in front of LP
- use big foresails on broad courses to counter weather helm
impact: either on forces or on arm
Windward torque: influences
- heeling
- LP vs SP
- speed of ship
- windspeed
- factors intensifying drag:
* shallow/narrow waters (UKC)
* hull resistance (fouling)
=> adjust the sailpoint to counter
Determining Sailpoint
- CoG of all sails close hauled
- split in triangles
AREAS: - triangle = 1/2 x base x height
- (otward) curved leech = 2/3 x base x height
Combining Triangles/Sails: - weighed leger lines corresponding with relative areas
- total: 1. foresails; 2. + Mizzen; 3. + Main
Twist
- higher up: Apparent Wind more astern
- traveller midships: sail pulled down => less twist
Trimming
- very, very little wind => flat
- little wind => very deep
- lotsa wind => Main flatter (less pressure, less heeling, better balance)
- trim staysail with halyard (tight => draft moves forward) => too tight => vertical fold behind luff => tighter backstay => straighter forestay => flatter sail => pointing higher
Deep Sail: much power, good accelaration, points less high
Flat Sail: less power, points higher
Increasing wind: flatten sail to decrease pressure
Bearing away: use deeper sails
Waves: deep sails for accelaration <=> calm sea => flat sail
(Counter) Measures on a weatherly ship
1. move SP forward
* extra or larger foresail
* reef mizzen
* trim mast forward
* trim Main flat
* slack off Main / Mizzen sheets
2. move LP aft
* raise leeboards a little (or move the aft)
* move weight/ballast aft
bland ship: opposite measures
Staysail: description
Yank: staysail upside-down between masts (with wishbone) like on Chronos
Schooner Sails: names
Schooner w Fisherman
3M schooners
Schooner: standing rigging
Rudder
- rudder needs water flow
- rudder force = Lift : perpendicular to rudder profile
- drag (BF = Ra) will slow down vessel
3 principles why you sail
- Newton (F=m * a)
- Bernoulli
- Coanda
Angle of attack
(flat vs deep sail)
Trimming
rules of thumb
Trim
= react to changes
Staysail trim
(halyard)
Names of a gaff sail
Gaff: running rigging
Cutter Rigg
Mast/shrouds/spreader
Mast band
= hounds band
halyards/stays not to cross each other
lowest mast band: hommer
Masts
Rake
Gooseneck
sheet attachment to boom
on a ring to avoid twisting (torsion) of boom
Gaff
details/names
Blocks
MBL: minimum break load
WLL: working load limit
WLL = 1/5 - 1/6 MBL
SWL : old
Blocks: parts
a) cheek
b) breech
c) cheek = face
d) nail
e) pin
Blocks:
inside/outside binding
the whole thing is held togehter by a metal binding or strap, which can be inside or outside
Forces in tackles
Force= 1 / Number of running parts
Friction: 5-10%/sheave
Shackles: parts
Shackles: basics
Shackles: adjusted WLL due to side load angle
Working Load Limit (WLL) is the maximum working load
designed by the manufacturer. (used to be SWL)
MBL is Minimum Break Load
WLL= MBL / 5 or WLL= MBL/ 6
winch maintenance
- grease
- replace broken/wornout parts
- train crew on handling
- ensure lines/cables in good shape (twists)
Sail handling
principles
- responsibility is the foundation of good seamanship
- sail choice depends on weather, sailing area, seas, course => maintain balance while hoisting, lowering, reefing
gaff sail foot / luff
attached foot is preferred to prevent bending stresses in boom and overloading of clew in strong seas
between mast and luff: 1/2 mast diameter space (hoops; bead lines)
Jigger
Hoisting a gaffsail
- Topping lift up
- Sailbands loose, on the windward side
- Peekhalyard slightly up
- Peek and claw up together
- Sheet a bit out, sail loose but boom steady
- High enough: fasten claw halyard
- Adjust the peek halyard
- Lower the topping lift
- Adjust the sheet
- Adjust the tack
Dousing
Lower the sails
- Staysails are easy to douse, especially broad reach
- Gaffsails won’t come down on broad courses, or very difficult
- Sails attached to a rail at the mast will only come down with head in the wind
reefing
- slack sheet slightly
- topping lift
- lower sail enough to connect reef tack
- tighten reefing line
- set reef tackle
- haul halyard
- slacken topping lift
- adjust sheet
- pack away lower part of reefed sail
Tacking
preparation
- maintain good speed before manoevre
- prepare and man sheets; running (back) stays
- notify crew and guests
- haul in mizzen; possibly keep foresail(s) backed
- move running backstays
- don’t overtrim foresails on new tack
- big waves: stopping forward movement - dead in irons
Gybing
for square riggers: called wearing
danger of booms wearing involuntarily
essential: you control when the boom(s) move over
loss of sea room towards lee shore
foreward sails in wind shadow, don’t need much crew - aft sheet require the manpower
heaving up anchor under sail
not a difficult manoevre - falling away on the desired tack is the challenge
Orgainization of ship’s routines
Safety
Administration
Operation (nav/eng)
Upkeep (maintenance)
- Maintenance engineroom
- Corrections in maps
- Maintenance safety equipment
- Maintenance rigging and sails
- Check certificates
- Drills
– MOB
– Fire
– Evacuation
ISM for sailing vessels
- organizing safety
- system to structure tasks on board
- inventory of tasks
- structure of command
- tool to coordinate all activities on board
- MOB
- Fire
- Collision
- Checklist: leaving port
- Maneuvers
- Watch order
Instruction
guests
welcome + basic briefing + repeat next day
tell & show
- House rules
- Calamities
- Alarm signal
- Musterplace
- Escaperoutes
- Use lifejackets
- Boat drill
Instruction
crew
- House rules
- Function description
- Structure of organisation
- Work instruction
- Practice routines:
– Boat drill
– Fire
– Mob
– Colllision or grounding
watch instructions
watch orders: standing orders; night orders
“Standing Watch” orders
applicable all the time; boundaries of responsibilities between Master and OOW under normal circumstances
Night orders
specific for the actual situation, e.g.:
Keep these sails until…
Call me when we are …mile from …
Tasks for different officer
preparing for Heavy Weather
- good preparation is essential
- checked and deploying safety gear; plotting position; stowing all things
- focuss on safe navigation
- seasickness
waves
3 categories
Dangerous, where big waves enter shallow waters => speed down; steeper waves; shorter intervals
- Seaway
Waves created by the
current wind - Swell
Created by Seaway further
away or wind from some
time before now - Land Wash
Waves when Seaway or
swell arrives in shallower
waters
wind and current:
influencing each other
wind against current: short, steep waves
Stragegies in heavy wind
- in irons head into wind: w engine or sea anchor (if not much room to lee)
- heaving to (comfortable; minimum speed); stormsail+trysail
- running: riding the storm: going long distances to leeward (sufficient sea room?) => scud under bare poles; long ropes or sea anchor from stern
Heavy weather
dangers
SAIL
- Damage to the rigging or the hull
- Danger of lee shore
- Less stability on top of the wave ,rolling
- Less rudder on top of wave
- Broaching
- Crew and guests seasick
Reasons for hull shape
- water depth
- locks/sizes
- still water <=> waves
- speed requirements (clipper; pilot cutter)
- cargo
- taxes
Keel types
- Finn
- Bulb
- Long
- Twin
- Leeboards
Klink ./. Kravell
Klink doesn’t need caulking; overlap of planking creates lots of strength; water resistance
Cravell allowed construction of bigger, wider, stronger hulls with smoother surface; caulking
Cordage
kravell vs clinker
kravell: planks laid edge to edge; smooth surface; greater strength due to more robust framing; larger constructions possible
clinker: overlapping planks; lighter due to less framing
