Embedded Files
“To reach a port we need to set sail - sail, not tie at anchor; sail, not drift.”
“To reach a port we need to set sail - sail, not tie at anchor; sail, not drift.”
Franklin D. Roosevelt
Franklin D. Roosevelt
1. Classification of Sailboat
1. Classification of Sailboat
(a) Hull based-classification:
(a) Hull based-classification:
Mono-hull:
Most classic design for boat hull. It derives its stability from ballast (weight) at the bottom rather than from the beam (width of the boat).
Catamaran:
Double hull sailboat which derive its stability from wide-beam rather than ballast, making it potentially faster. Catamaran usually has more space than mono-hull. Modern catamarans are inspired by ancient Oceania and South East Asian boats.
Multi-hull:
Such as a trimaran (double outrigger) has good side-ways stability. Capsize is mainly pitch-pole type; when turtled, multi-hull sailboats are more difficult to upright.
(b) Sail/Mast Configuration (Sail-Plan)
(b) Sail/Mast Configuration (Sail-Plan)
Dinghy:
Single main foremast with single sail (usually Bermudan rigged). Used for small training sailboat.
Catboat:
Similar to dinghy but with gaff rig to increase sail size, hence speed.
Sloop:
Like dinghy but with an additional headsail in front of the mainsail.
Cutter:
2 Headsails in front of mainsail; this configuration can be applied to other sail plans (e.g. Ketch, Yawl, Schooner) as well.
Ketch:
Sailboats with one tall main mast and a shorter mizzen mast positioned fore of the rudder post.
Cutter rigged Ketch:
Ketch with 2 headsails.
Yawl:
Similar to Ketch but the mizzen mast is positioned aft of the rudderpost.
Schooner:
Typically larger sailboat with mizzen mast taller than main mast, allowing more sails to be rigged.
(c) Sail Rigs
(c) Sail Rigs
Gaff:
Configuration where a 4-cornered sail is rigged to the mast via the head of the sail to the gaff spar. This provides larger sail area compared to the Bermudan rigged sail (up to 25% larger).
Gunter:
Configuration where the lower half of the luff (front) of the sail is attached to the mast, and the upper half is fastened to a spar which is almost vertical and reaches above the top of the mast.
Lugger:
Evolving from square rig, lug rig uses 4-cornered sail. When raised, the sail area overlaps the mast. For standing lug, the sail remain on the same side of mast while for dipping lug, the sail changes side during tacks.
Square rig:
Usually used on larger sailing ships, it carries driving sails that are on horizontal spars perpendicular to keel and mast of vessels. Square rigs are good for running wind.
Lateen:
Long triangular sails set at an angle to the mast running in the fore-aft direction. The fore of the lateen spar is usually tied to the bow of the boat.
(d) Keels classifications
(d) Keels classifications
Full Keel or ballast keel is an extension of the hull downward, running from fore to aft. It is usually ballasted to add stability. Steering takes more time due to lateral resistance.
Fin Keel is a narrow plate fixed midships to the keel of a shallow boat projecting downward to provide lateral resistance. It is intended both to steady the boat and to make it handy to steer.
Bilge Keel comprises one of a pair of longitudinal plates that, like fins, project from the sides of a ship or boat and run parallel to the centre keel. It prevents side way roll of the sailboat.
Skeg is is an aft extension of the keel intended to keep the boat moving straight and to protect the propeller and/or rudder from underwater obstruction.
Bulb Keel is a keel that ends with a teardrop shape ballasted bulb at the bottom. This lowers the centre of gravity and greatly improves stability. These are used mainly for deep water sailing.
Wing Keel have small winglets on the keel to reduce draft and roll without longer keel. It is useful for cruising in shallower water.
Drop Keel is a retractable keel midship that may be lowered to increase lateral resistance and prevent side slip. Examples include daggerboard keel (slide up and down) and centreboard keel. (rotate up and down via a pivot)
Centreboard
Daggerboard
2. Physics of Sailing
2. Physics of Sailing
(a) Density and Buoyancy
(a) Density and Buoyancy
How a boat floats can be explained either by density or buoyancy.
Density: The overall density (mass per unit volume) of a boat is less than that of water; hence boat floats on water.
Buoyancy: The boat is positively buoyant because the buoyant force (difference in pressure between the top and bottom surface multiplied by the surface area) pushing it up is greater or equal to the gravitational force (weight) pushing it down.
(b) Stability
(b) Stability
A boat is able to right itself despite choppy water as long as the force-weight of the boat (acting at the centre of gravity) act downwards within the effective base area of the boat to provide the counteracting moment.
Hence a boat with larger base and lower CG will be more balanced.
(c) Bernoulli Principle and how a boat moves upwind
(c) Bernoulli Principle and how a boat moves upwind
Sailing upwind is similar to how airplane flies using Bernoulli principle. When air travels over a curve surface (of the sail) it is faster relative to the side below the curve. This faster speed creates a lower pressure on the curved side and causes a resultant force "sucking" the curved sail forward.
As the boat is propelled towards the curve of the sail, there is a reaction force acting on the keel / centreboard hence creating a net forward motion.
While sailboard cannot sail directly into the wind, this can be accomplished by a series of "tacks".
See video for in depth explanation.
(d) Balance of Forces
(d) Balance of Forces
Sailing is essentially an art of balancing forces and turning moments.
Sail trims are set to optimise the greatest net forces to maximise speed [see (c)].
When the wind force pushing on the sail is too great, there is a need for sailors to hike out to use body weight to counter the overturning moment.
Boat (fore-aft) trim is performed to keep the boat level, hence reducing the resistant force acting on the boat as it propels forward.
Hiking out to balance forces from wind
Good boat trim reduces resistance on boat
(e) Relative motion
(e) Relative motion
Besides its own means of propulsion, a boat is also affected by wind and tide. The forward velocity of the boat and the velocity of tide/wind will produce a relative velocity and direction of motion.
Due to the relative motion, the wind seems to blow from the direction of motion. This result in the Apparent Wind which is different from the True Wind.
(f) Bow Waves
(f) Bow Waves
Bow (and slightly smaller stern waves) are created as a boat moves through water. The larger the boat's profile and higher its speed, the bigger the bow wave. Larger bow wave will create larger drag on the boat making it less efficient and also create water disturbance for other vessels around it.
3. History of Sailing
3. History of Sailing
~ 3500 BCE: Sailboat represented on Eqyptian vase.
~ 400 BCE: Viking Longships used in the Scandinavia.
~ 1000 BCE: Sailboat (such as the Filipino Paraw) and canoes used by Astonesians in their Pacific expansion.
~ 100 BCE: Junk /Jong sails used in China and Malay Archipelago.
~ 1400s: Cheng Ho led 7 trade and diplomatic expeditions to South and South-East Asia.
1492: Columbus reached America in the Santa Maria. The vikings were found to have reached America centuries earlier.
1760s: James Cook sailed the Endeavour to become the first European to reach Australia.
1819: Raffles landed in Singapore in a tall ship, the Indiana . Such ships are common to European countries in the colonial era.
1896: Sailing (also known as yachting) has been part of the modern Olympics since the first game. However, there were no race in 1896 due to combination of bad weather and insufficient boats.
Resources:Classification of Sailboat: ImproveSailing.com, MarineInsight.com, NationalHistoricShips.org.uk
Physics of Sailing: University of New South Wales; Physics Today; NASA
Physics of Sailing: University of New South Wales; Physics Today; NASA
History of some nautical terms
History of some nautical terms
'Weigh Anchor'
'Weigh Anchor'
UNRAVELING THE THREADS OF NAUTICAL LINGUISTICS
Every phrase we use has a history, often etched deeply into the annals of human civilization. The term 'weigh anchor' is no different. To unlock its meaning, we must first unfurl the sails of understanding. The word 'weigh' is derived from the Old Norse term 'vega,' meaning to raise or lift. And an anchor, as we know, is a heavy object attached to a ship that is thrown into the water to hold the vessel in place.
Merge the two together, and voilà - 'weigh anchor' - in essence, an instruction to lift the anchor. Now we not only know what it means but also why it's phrased the way it is. Language and its etymology, dear reader, are as exciting as uncovering hidden treasure.
THE SIGNIFICANCE OF WEIGHING THE ANCHOR
The term 'weigh anchor,' however, extends beyond its literal meaning. When a captain gives the command to 'weigh anchor,' it's more than just lifting a heavy object from the water. It's the initiation of a journey, beginning a new chapter, setting off towards the unknown – a symbol of transition and transformation.
Think about the first time you heard someone say "weigh anchor." Didn't it set your heart aflutter with the possibility of adventures? That's because it's a phrase imbued with change and motion – the very essence of life! As Amelia would often quote, "Life is a series of natural and spontaneous changes. Don't resist them - that only creates sorrow."
O Captain! My Captain! by Walt Whitman
O Captain! My Captain! by Walt Whitman
O Captain! my Captain! our fearful trip is done,
The ship has weather’d every rack, the prize we sought is won,
The port is near, the bells I hear, the people all exulting,
While follow eyes the steady keel, the vessel grim and daring;
But O heart! heart! heart!
O the bleeding drops of red,
Where on the deck my Captain lies,
Fallen cold and dead.
O Captain! my Captain! rise up and hear the bells;
Rise up—for you the flag is flung—for you the bugle trills,
For you bouquets and ribbon’d wreaths—for you the shores a-crowding,
For you they call, the swaying mass, their eager faces turning;
Here Captain! dear father!
This arm beneath your head!
It is some dream that on the deck,
You’ve fallen cold and dead.
My Captain does not answer, his lips are pale and still,
My father does not feel my arm, he has no pulse nor will,
The ship is anchor’d safe and sound, its voyage closed and done,
From fearful trip the victor ship comes in with object won;
Exult O shores, and ring O bells!
But I with mournful tread,
Walk the deck my Captain lies,
Fallen cold and dead.
“The pessimist complains about the wind; the optimist expects it to change; the realist adjusts the sails.”
“The pessimist complains about the wind; the optimist expects it to change; the realist adjusts the sails.”
William Arthur Ward
William Arthur Ward
Page updated
Google Sites
Report abuse