From MITNA Wiki
This an outline of the training materials for using the catamaran at MIT.
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 serve 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.
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 shortie is usually enough for sailing on the Charles River.
- Check the hulls for water. Drain the hulls if there is any significant amount of water in them.
- Ensure that the drain plugs are in place. Do not over-tighten the drain plugs.
- Ensure that the rudder cams are up.
- 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.
- Lower the rudders. Ensure that rudder cams have locked the rudders down.
- Insert the daggerboards. The daggerboards do not slide directly up and down - they slide at a slight angle forward/aft.
- 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 then adjust to a tightness appropriate to the wind conditions.
- Secure the mast rotator.
- Check the jib traveler position.
- Ensure that the jib furling line is secured to the mast so that it will prevent the jib sheets from fouling on the mast.
- Ensure that the barber haulers are released.
- Check the trapeze lengths.
- 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.
- Furl the jib. Secure the furling line to the mast.
- De-rig the 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.
- Attach main halyard ring to outhaul. Tie traveler to loop at other end of main halyard, then pull main sheet to tighten everything up.
- Stow downhaul and other lines in storage bag on trampoline to keep them out of the sun.
- Remove daggerboards. Store daggerboards in orange protective sleeve, one opposite the other.
- Raise rudders.
- 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.
- Ensure that the rudders are resting on the dock.
- Drain the hulls of any water. Do not over-tighten the drain plugs.
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.
Leaving the Dock
Ensure 1/2 boat length of open dock space in front of the boat. Hold the shroud in one hand and the tiller extension in the other. Turn the rudders to direct the boat away from the dock, then take a few steps along the dock to get the boat moving. Push out and away and start sailing.
Returning to the Dock
Head directly toward the dock. When you are 3-4 boat lengths from the dock, reduce speed by sheeting out on the main, travelling out on the main, and sheeting out on the jib. When you are 1-2 boat lengths from the dock, furl the jib. Bring the boat into the wind, parallel to the dock, ensuring that the main sheet and main traveller are uncleated.
When tacking, roll the tack as much as possible. Minimize movement of skipper and crew to maximize boat inertia through the turn. If the boat does not point through the wind, back with jib if necessary. Ease main sheet through the tack, then tighten once the wind is on other side of the sails. The skipper must reach around aft of the main sheet for tiller. Do not move weight side to side too soon or the momentum of the tack will suffer, but do not move weight too late, or the boat will capsize!
Work on timing between skipper and crew. Some people prefer to have the skipper trap out first after a tack, others prefer to have the crew trap out first.
Gybes can be very fast on a catamaran. When the wind is up, be sure that your turn does not throw the crew off the boat! The skipper must reach around aft of the main sheet for tiller, then do the gybe. Be sure to have control of the tiller extension before the main sheet and traveller start to move. The skipper should help the main sheet and traveler across in order to minimize dynamic loading on the boom and blocks. Maintain control of main sheet and traveler lines throughout the turn.
Use the barber hauler to tune the shape of the jib. The mast rotator should be loose enough to cause an appropriate angle for the mast relative to the main sail. Pull up one or both daggerboards for more speed. Ease downhaul if appropriate. Shift skipper and crew weight foreward or aft depending on wind speed and hull angle. The ideal roll angle is flat, or the wild thing (leeward hull only) if there is sufficient wind. Beware that a beam reach can easily lead to capsize if you lose track of boat/wind direction. Let the main sail out, but keep the main sail off the spreaders.
Keep the mast rotator tight. Keep bows in water, but not too far. Do not over-tighten jib. Tighten downhaul if appropriate. The ideal roll angle is leeward hull only, windward hull just above the water surface (this will minimize wetted area). Keep weight forward to improve sail angle. De-power sails by pinching, but beware unintentional tack, especially when on the trapeze. Beware of de-powering by quickly releasing the main sheet or quickly heading up. Either of these maneuvers can generate more lift over the sail, resulting in a capsize.
Wing and wing is slow; it is almost always better to reach than run. When running, be sure to keep the main sail off of the spreaders.
Hiking and Trapping
Use hiking straps when there is not enough wind for trapeze. To go out on the the trapeze, pull the trapeze handle to you, secure it to harness, slide butt backwards off the boat until the trapeze takes your weight, get legs between you and the hull, then press out from the hull. Keep feet at least shoulder width apart. Balance fore-aft is just as important as inboard-outboard. Use the handle to come in from the trapeze, if necessary. Most of the time hands are not needed and should be dedicated to trimming sheets, not maneuvering on the trapeze. Ensure that trapeze length is appropriate for body geometry and wind conditions.
For most people, skipper goes out to the wire first, then crew. In variable winds, the crew moves more than the skipper. Skipper and crew should intertwine legs to reduce drag. Manage the tiller extension length to avoid skewering crew or self. Beware of line management, especially when at high roll angles. Beware of line management when crew and skipper are both trapped out; crew may have to help skipper sheet in or adjust traveler.
Be especially aware of weight management when soloing. Position fore-aft is just as important as inboard-outboard.
Capsizing and Righting
When capsizing, do not fall/jump onto the mainsail. Do not fall/jump onto the jib. Unhook from the trapeze, then jump into the wind (away from the sails).
The combined weight of skipper and crew must be at least 250 pounds in order to right the 'Miracle 20'. When righting the boat, do not stand on the daggerboards. Get the righting line over top of hull as soon as possible to avoid turtling. Ease the main sheet, but do not release the main sheet or the traveler. The jib sheet should be tight. Stand at one end of the hull or the other in order to rotate the boat so the mast is just about into the wind, with wind coming under mast. Hang on the righting light until the boat balance is in favor of righting. As boat rights, reach for and grab onto the dolphin striker.
When the skipper and/or crew weight is too far forward, the bows bury in the water, boat speed suddenly drops, and the boat pitch-poles. If the skipper and/or crew respond quickly and move their weight aft, recovery is possible. But at high speeds the pitch-polling happens quickly, and the crew and/or skipper are often thrown forward before they can react, burying the hulls even further.
It is possible to capsize by heading up too quickly. If you are sailing close hauled, but not pinched, heading up quickly will generate more lift, which tends to pull the boat over. Strong wind might require easing the main sheet and/or traveler as well as heading up.
It is possible to capsize by easing the main. When easing the main only by the main sheet (not by the traveler), the main sail curvature increases. With sufficient wind, the additional curvature causes more lift, which tends to pull the boat over. If the main sail is overpowered, spill some of the load by easing the traveler, not just the main sheet.
When flying a hull, beware of puffs. If the trampoline is 40 degrees or more relative to the water, it will act as a sail/barrier, and no amount of easing the main sheet, traveler, or jib sheet will unload enough to bring the boat back down.
At high roll angles, one can easily unhook from the trapeze, either to bail out for an impending capsize, or to move one's weight even further into the wind.
Parts of the Boat
- mast (aluminum base and carbon tip)
- main sail
- main sheet
- main traveler
- main battens
- mast rotator
- 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
- rudders (up, down)
- rudder cams
- rudder connecting rod
- extendable tiller
- drain plugs
- inspection portals
- storage pouch
There are three rating levels: basic, advanced, and instructor. To pass each level you must receive instruction on then illustrate proficiency at the items listed below.
The basic rating requires a helmsman rating.
The advanced rating requires the basic rating.
The instructor rating requires the advanced rating.
- rig/de-rig the boat:
- raise and lower the main sail
- set and release the rudder cams
- furl and unfurl the jib
- adjust the trapeze lengths
- raise/lower the daggerboards
- secure the boat to the dock for rigging/unrigging
- tie up halyard, sheets, and furler when boat is stored on the dock
- get the boat into and out of the water
- describe points of sail and sail trim, boat trim, crew positions for each
- close hauled
- beam reach
- broad reach
- describe weight management for catamaran (skipper/crew positions fore-aft and in-out)
- leave and return to the dock
- tack the boat
- gybe the boat
- get into irons, then get out of irons:
- using jib
- using main sail
- backing down on rudders
- heave to (stop the boat and point into the wind without unintentional tacking)
- illustrate use of hiking straps
- 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
- sail a specified course in light air (up to 10 mph)
- figure 8 around two bouys across the wind
- oval around two bouys across the wind
- triangle around 3 bouys
- demonstrate all of the basic skills
- put on a harness
- illustrate use of the trapeze
- drive boat while:
- crew on trampoline, crew on wire
- skipper on trampoline, skipper on wire
- capsize then right the boat without turtling
- leave and return to the dock in heavy air (over 15 mph)
- sail a specified course in heavy air (over 15 mph)
- figure 8 around two bouys across the wind
- oval around two bouys across the wind
- triangle around 3 bouys
- demonstrate all of the basic and advanced skills
- student-teach at least two catamaran classes
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
- video of sailing into the dock
- video of casting off from the dock
- video closeup of top of mast during raise/douse of main sail
- 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
- pictures of top of mast to show halyard ring and hook
- pictures of rudder cams in up and down positions
shoot the tacking and gybing videos from off the boat, also from on the boat? parts from on the boat?