Revision as of 08:52, 20 August 2009

This an outline of the training materials for using the catamaran at MIT. The intent is to develop the material here, then move it to the open courseware site for production.

General Principles

Catamarans have two hulls rather than a single hull. They tend to be faster and lighter than monohulls. Catamarans typically cannot point as close to the wind as a monohull. However, catamarans are typically much faster reaching or running. Although the basic sailing principles are the same for multi-hulls and monohulls, catamarans have their own quirks.

The twin hulls of a catamaran server a number of purposes. Weight is reduced by using two smaller, shallower hulls rather than a single, deep hull. The long, slender shape of the catamaran hull minimizes wetted surface area. And the hull shape minimizes cross-sectional area. Depending on the point of sail, the benefits of dual hulls are realized by balancing the boat on one of the two hulls, or by sailing so that weight is distributed evenly on both hulls.

Monohulls have a keel or centerboard, catamarans have daggerboards. On a keel boat, the weight of the keel counteracts the force of the wind on the sail, thus preventing the boat from capsizing. On a catamaran, the weight of the skipper and crew keep the boat from capsizing. As more pressure is applied to the sail, the skipper and crew move their weight further into the wind. Daggerboards provide area under water to slow the rolling of the boat as well as to reduce movement of the boat parallel to the wind.

Since the weight of the skipper and crew is fairly large relative to the weight of the boat, the position of the skipper and crew greatly affect performance. Skipper and crew must move not only side-to-side, but also front-to-back in order to properly balance the boat.

Clothing

You will probably get wet while sailing the catamaran, so wear a swimsuit or shirt and shorts that can get wet.

• gloves The main and jib sheets will quickly shred your hands, so invest in a pair of sailing gloves. Many people prefer gloves with no thumb or index finger tips - this makes it easier to deal with pins and ringdings without doffing the gloves.
• booties Ankle-height, tight-fitting booties work well.
• harness Use a harness that fits snugly without constricting. Back support is good. There are two types of attachment systems: ball or hook.
• life jacket A life jacket is mandatory.
• wetsuit A wetsuit is most useful in April or May when the water temperature is still fairly cold, or in September or October when the air temperature begins to drop. A 2- or 3-millimeter neoprene is usually enough for sailing on the Charles River.

Rigging

1. Check the hulls for water. Drain the hulls if there is any significant amount of water in them.
2. Ensure that the drain plugs are in place. Do not over-tighten the drain plugs.
3. Ensure that the rudder cams are up.
4. Get the dock very wet, then slide the boat into the water. Secure the boat to the dock by tying a short line around the bridle. If the wind is blowing into the dock, it might be better to tie the line around the crossbar instead of the bridle.
5. Lower the rudders. Ensure that rudder cams have locked the rudders down.
6. Insert the daggerboards. The daggerboards do not slide directly up and down - they slide at a slight angle forward/aft.
7. Raise the main sail. Attach halyard to top of sail, and be sure that the halyard is in the small notch with knot forward of the halyard ring. Pull the halyard in the plane of the mast so that you do not destroy the sheave at the bottom of the mast. With the sail up, attach the downhaul. With the mast rotator released, rotate the mast rotator to port then pull down lightly on the sail using the downhaul. If the halyard ring does not engage the halyard lock at the top of the mast, release the downhaul, raise the sail to the top, and try again. After the halyard ring is locked in place, stow the halyard in the storage bag on the trampoline. Attach the outhaul and adjust to a tightness appropriate to the wind conditions.
8. Secure the mast rotator.
9. Check the jib traveler position.
10. Ensure that the jib furling line is secured to the mast so that it will prevent the jib sheets from fouling on the mast.
11. Ensure that the barber haulers are released.
12. Check the trapeze lengths.

De-Rigging

1. Tie up to the dock using a short line around the bridle. If the wind is blowing into the dock, it might be better to tie the line around the crossbar instead of the bridle.
2. Furl the jib. Tie furling line to post in jam clean on front of mast.
3. De-rig main sail. Detach outhaul, leaving the shackle on the boom. Ease downhaul then remove downhaul from main sail, leaving the shackle on the downhaul tackle. Use halyard to raise main sail, rotate mast rotator to starboard, then pull down on the sail. Roll the sail from the bottom up.
4. Attach main halyard ring to outhaul. Tie traveler to loop at other end of main halyard, then pull main sheet to tighten everything up.
5. Stow downhaul and other lines in storage bag on trampoline to keep them out of the sun.
6. Remove daggerboards. Store daggerboards in orange protective sleeve, one opposite the other.
7. Raise rudders.
8. Pivot boat so that it is perpendicular to the dock. Pull the boat onto the dock so that there is enough space aft of the boat to place the rudders on the dock.
9. Ensure that the rudder cams are up.
10. Drain the hulls of any water. Do not over-tighten the drain plugs.

Sailing

Your position on the boat matters. When sailing the catamaran, you must not only move from the centerline of the boat outboard to counteract the force of the wind, but you must also move fore/aft to keep the hulls at a proper angle relative to the water.

The catamaran sails fastest with only one hull in the water. This is fairly easy to balance while beating, but it is a considerable challenge while reaching. If the boat rolls too much, it slows down drastically. The ideal roll angle has the windward hull just off the surface of the water.

In general, as the wind blows harder you should move toward the back of the boat, and as the wind eases off you should move toward the front of the boat. The top of the leeward hull should be nearly parallel to the surface of the water; the curve at the bottom of the front edge of the leeward hull should be a couple of inches under water. It is a common mistake for the skipper to sit too far aft, resulting in the bows of the hulls coming completely out of the water.

As the wind blows harder, the bow of the boat will tend to be pushed down. Only when this happens should the skipper and crew move aft.

Pitch-poling can happen if either of the bows is pushed completely under water. When the boat pitchpoles, boat speed drops immediately. Anyone on the trapeze will be thrown toward the front of the boat, digging the hull(s) in even deeper. In the worst case, skipper and crew will be thrown around the forestay of the boat, pulling the boat over on top of them.

Tacking

roll tack as much as possible. back with jib if necessary. ease main sheet through the tack, tighten once wind is on other side of sails. reach around main sheet for tiller. do not move weight side to side too soon (but not too late or capsize!)

Gybing

do not throw crew off the boat. reach around main sheet for tiller, then do the gybe. help main sheet and traveler across. maintain control of main sheet and traveler lines.

Reaching

use the barber hauler. mast rotator should be loose. pull daggerboards for more speed. ease downhaul if appropriate. fore-aft weight depending on wind speed and hull angle. ideal roll angle is flat or the wild thing (leeward hull only). beam reach can easily lead to capsize if you lose track of boat/wind direction. keep main sail off spreaders.

Beating

tight mast rotator. keep bows in water, but not too far. do not over-tighten jib. tighten downhaul if appropriate. ideal roll angle is leeward hull only, windward hull just above the water surface (minimize wetted area). keep weight forward to improve sail angle. de-power sails by pinching, but beware unintentional tack, especially when on the wire.

Running

wing and wing is slow. almost always better to reach. keep main sail off spreaders (which leads you to reach rather than run).

Hiking and Trapping

use hiking straps when not enough wind for trapeze. to go out on the wire, pull trap to you, slide back off the boat until trap takes your weight, get legs under you. keep legs shoulder width or more apart. balance fore-aft just as important as in-out. pull on handle to come in. ensure that trap length is appropriate for body geometry and wind conditions. skipper out to the wire first, then crew. crew moves more in variable air. skipper and crew intertwined to reduce drag. managing the tiller extension. line management when at high roll angles. line management when crew and skipper are both trapped out. weight management when soloing.

Capsizing and Righting

do not fall/jump onto the mainsail. do not fall/jump onto the jib. do not stand on daggerboards. get righting line over top of hull as soon as possible to avoid turtling. need 250 pounds or more to right the boat. ease main sheet but do not release sheet or traveler. jib sheet should be tight. rotate boat so mast just about into wind, with wind coming under mast. grab dolphin striker as boat rights. how to avoid pitchpoling. when easing the main still results in capsizing. heading up too fast results in capsize. puffs when already at 40 degrees or more. how to unhook from trapeze when high roll angle.

Parts of the Boat

these are the boat parts and what they are used for:

• mast (aluminum and carbon)
• spreaders
• boom
• trampoline
• hulls
• bridle
• forestay
• main sail
• main sheet
• main traveler
• main battens
• downhaul
• outhaul
• mast rotator
• jib
• jib sheet
• jib traveler
• jib furler
• jib halyard
• jib sheet preventers (blue bungie, use of furling line)
• barber hauler
• trapeze handles
• trapeze retractors - skipper
• trapeze retractors - crew
• righting line
• righting line retractor
• daggerboards
• rudders (up, down)
• rudder cams
• rudder connecting rod
• extendable tiller
• drain plugs
• inspection portals
• storage pouch

Sign-Off Skillz

There are two rating levels: basic and advanced. To pass the basic level you must receive instruction on the items listed below. To pass the advanced level you must receive instruction on basic and advanced items, and you must illustrate comprehension of and ability to execute all of the items.

Basic (crew)

• rig/de-rig the boat, especially
  • raise, lower, trim the main sail
  • rudder cams
  • use of the jib furler
  • adjust the trapeze lengths
  • tie up the boat in various wind directions
  • tie up halyard, sheets, and furler when boat is stored on the dock
  • get the boat into and out of the water
• raise/lower the daggerboards while underway
• furl/unfurl the jib
• put on a harness
• use of hiking straps
• go out on trapeze and come in from trapeze
• describe points of sail and sail trim, boat trim, crew positions for each
  • close hauled
  • beam reach
  • broad reach
• describe weight management for catamaran (fore-aft, in-out)
• describe procedure when capsizing/righting, especially
  • jump away from sails and boom
  • how to prevent turtling
  • boat orientation for righting - mast into wind, jib cleated, main loose but cleated

Advanced (skipper)

• drive boat while:
  • crew on trampoline, crew on wire
  • skipper on trampoline, skipper on wire
• get into irons, then get out of irons:
  • using jib
  • using main sail
• stop the boat and keep the boat in one place without unintentional tacking
• capsize then right the boat without turtling

Videos and Stills

this is a list of the videos and still images we need to illustrate the points above.

• still image or two for each of the boat parts
• video of tacking, no traps, illustrating the timing issues and rolling
• video of tacking, skipper and crew from trapeze to trapeze
• video of gybing, illustrating the timing issues
• video of crew during a tack (especially jib sheet management)
• video of a capsize, preferably from two viewing angles (windward and leeward)
• video of getting righting line ready for righting
• video of righting the boat
• video of putting rudders down
• video of putting sail up (closeup of top of mast and bottom of mast)
• video of trapping out/in - skipper
• video of trapping out/in - crew
• video of putting boat into water
• video of pulling boat from water
• pictures of mast rotator adjustment when beating and resulting sail shape
• pictures of mast rotator adjustment when reaching and resulting sail shape
• pictures of good/bad hull pitch angles
• pictures of good/bad hull roll angles
• pictures of good/bad skipper/crew positions (fore-aft/windward-leeward)
• pictures of good/bad sail shapes
• pictures of mainsail on shrouds (bad)
• pictures of good/bad jib trim

shoot the tacking and gybing videos from off the boat, also from on the boat? parts from on the boat?