The mainsheet trimmer works in the cockpit aft of the grinders, and has the responsibility of controlling and trimming the mainsail.
Additionally, the mainsheet trimmer keeps the running backstays (runners) out of the way of the driver and the boom, grinds the spinnaker
sheets if the grinders need assistance, and helps with other shared cockpit tasks, such as keeping the cockpit clear of lines that are not
in use.
If you're not familiar with some of the terms or concepts on this page, look them up in the Glossary and
review the Sailing Basics page.
Figure 1: Mainsheet Trimmer Working in the Cockpit
At the Dock
Double-check the rigging for the mainsail:
Lubricate all moving mainsheet hardware (blocks, traveller, etc.), being careful not to get any lubricant on the lines or the deck.
Check all the mainsheet tackle, making sure that no parts are missing or damaged, and that all parts are lubricated and run cleanly and
smoothly.
Check the the boom, mainsail, and mast, making sure there is no damage and that the rigging is correct.
Untie the coiled mainsheet and lay it down on the cockpit floor so that it will uncoil neatly.
Check the boom lift and make sure it is clear of the backstay and running backstays.
Double-check the rigging for the backstay and the running backstays (runners):
Check the backstay for damage and make sure that the backstay blocks and adjusting lines run clean.
Check the runners and make sure that the blocks and runners run clean.
Check the “twanger,” if it is rigged, and make sure it works properly to keep the runner blocks and the runner
out of the way of the driver.
Coordinate with the crew:
Talk to the boom pusher about when to push out the boom, and run through the commands that you will be giving.
Talk to the boom vang crew about when to put on and take off the boom vang.
Talk to the outhaul flattener crew about when to put on and take off the outhaul flattener.
Talk to the grinders about when to put on and take off the cunningham, and about who will put slip knots in the spinnaker sheets.
Talk with the skipper about any other responsibilities or instructions (e.g. looking for other boats, tactics, sail trim, etc.).
After leaving the dock:
Just after leaving the dock, center the traveller.
Make sure that the runners are not cleated and that they are loose enough to push out clear of the mainsail as it is raised.
Ask one of the grinders to take control of the mainsheet.
Get in position to push one of the runners (usually the port runner) out clear of the main, and to take the boom lift off the boom.
Make sure you stand aft of the boom, so that when it is live it can't swing and hit any part of your body.
As the deck crew raises the mainsail, push the runner out (away from the boat) so that it doesn't get caught on the mainsail battens.
When the mainsail is hoisted all the way and the main halyard is cleated, remove the boom lift from the boom and attach it to its
bungee cord at the stern. Make sure the boom lift runs clean and doesn't foul the tackle, stays, or lines at the stern.
Pull in the twanger so that it has about 1.5' of slack, and secure it in the jam cleat. Ask the grinders to tension the runners so that
the blocks stay out of the driver's way.
Get back to the cockpit and take control of the mainsheet.
At the Start of the Race
Before the race we typically sail on a reach, parallel to the start line. Tacks are from reach to reach.
When we begin our final approach to the start line (within a minute or two of the start signal), trim the mainsail for maximum speed
(see trimming the mainsail below).
Make sure that the crew has adjusted the control lines for a close haul:
boom vang: off
outhaul flattener: on
windward runner: on
cunningham: tensioned just enough to get rid of the wrinkles in the luff
leech line: tensioned just enough to stop the leech from fluttering
As we approach the start line, we may need to slow down to kill some time. Listen for these commands:
slow speed: ease out the mainsail so that our speed goes down to about 50%
kill speed: let out the mainsheet completely, but be prepared to bring it back in quickly
As we cross the start line, the driver will turn the boat up to a close haul. Trim the mainsail for a close haul.
Sailing to Weather
Trimming the Mainsail
Adjust the traveller and the mainsheet:
On a close-haul:
Move the traveller up (“travel up”) just past the wood rail on the windward side of the boat.
Bring in the mainsheet tightly.
After you've adjusted the traveller and the mainsheet, the boom should be positioned along the centerline of the boat.
On a reach:
Let out the mainsheet until the luff of the mainsail starts to break.
Make slight adjustments with the mainsheet and the traveller to get the telltales on the mainsail streaming back smoothly.
Check the other control lines for the mainsail. Ask the crew to adjust the lines as necessary:
boom vang: off
outhaul flattener: on
windward runner: on if sailing close hauled
The runner adjusts the backstay, which pulls the top of the mast aft and de-powers the top part of the mainsail.
cunningham: tensioned just enough to get rid of the wrinkles in the luff
After the mainsail is in the close haul position and fully adjusted (e.g., the outhaul flattener is on), check the luff on the
mainsail. Put on the cunningham just enough to get rid of the wrinkles in the luff. The cunningham moves the draft of the mainsail
forward.
leech line: tensioned just enough to stop the leech from fluttering
If the mainsail is trimmed correctly but the leech is fluttering, tighten the leech line JUST to the point the leech stops
fluttering. Do not over-tension the leech line as that will cause the mainsail to have an inefficient shape.
Tips for trimming the mainsail:
Listen to commands from the skipper and adjust the lines accordingly:
Travel Up or Travel Down means to move the traveller windward or leeward
(respectively).
Sheet In or Sheet Out means to bring the mainsheet in or let it out
(respectively).
On a reach, watch what the grinders do and adjust the mainsail accordingly:
If the grinders let out the jib, let out the mainsail.
If the grinders bring in the jib, bring in the mainsail.
In high winds, set the traveller in the middle. Don't set the traveller lower, as this limits our ability to point high.
If you have trouble uncleating the mainsheet when you want to sheet out, stand near the cleat and pull the mainsheet up (toward the sky).
The line comes out of the cleat much more easily in this position.
Listen to calls from the deck crew about wind puffs or gusts.
When the crew calls out wind gusts, prepare to travel down, but don't travel down early. React to the wind, not the “gust”
calls. Travel down (move the traveller toward the leeward rail) when the gust hits us or when you feel the wind getting too strong.
After the gust, travel back up to center the boom.
Travelling down lets air spill out of the main and enables us to maintain our course. If you don't travel down, a strong gust may
cause us to get “rounded up:” The boat will heel over drastically, point into the wind, and practically come to a stop.
Round-ups really hurt us because it takes a long time for an 8,000-lb. boat to get back up to speed.
If you're not strong enough to bring in the mainsheet, pull the fine tune line (see Figure 1 above). The fine tune line is attached to
one end of the mainsheet and runs through a number of its own blocks, which multiplies the mechanical advantage provided by the mainsheet
blocks. In other words, the fine tune line is easy to pull, but you need to pull a lot of it to bring in the boom.
Pay attention to how much effort it takes the driver to maintain our course. If the mainsail and the jib are trimmed properly and
balanced, the tiller should be mostly centered and should not require a lot of effort to maintain the course.
When we bear away to miss a boat or a mark, let out the mainsheet – this affects the driver's
ability to steer around the obstacle. Bring the mainsheet back in as we head up.
Tacking
When the boat tacks, you must move the traveller so that it's lined up with the wood rail on the new windward side of the boat. You do not
need to adjust the mainsheet. Here is the tacking procedure:
Listen for the skipper to give the following sequence of commands:
Grinders Get Ready (pause)
Ready About (pause)
5-4-3-2-1, Hard-a-Lee
When the skipper says “Ready About,” uncleat the traveller.
When you uncleat the traveller, the wind will push the boom to the leeward side, and the traveller should end up close to where it
needs to be – aligned with the wood rail on the other side of the boat.
Cross the boat and sit on the other side.
Keep the mainsheet in your hand when you cross the boat. Always keep the mainsheet in your hand in case you
need to depower the boat immediately.
Move the traveller up until it's aligned with the wood rail on the new windward side of the boat, and cleat the traveller.
Be quick – move the traveller up and cleat it off before the wind pushes the traveller down to the new leeward side.
In strong wind it may be hard to move the traveller up. Pull the line up (toward the sky) directly above the cleat. Ask one of
the grinders to help you if you still have trouble.
In light wind, wait until the boat starts to flatten out before moving the traveller. In normal wind, you can usually wait until Rod
gets to “1” or “hard-a-lee” before you move the traveller, but in light wind, that's too soon – you want to
wait until the boat starts to flatten out, because that's when the mainsail is no longer effective. You should only use this modified
procedure when the wind is light enough that you can easily move the traveller up to the windward side while the mainsail is under
power.
Tips for tacking:
As you get comfortable with the tacking procedure, you can wait until the skipper gets further along in the sequence of commands –
e.g., move across the boat when the skipper gets to “3” or “2” in the countdown. The longer you can stay on the
windward rail, the longer we maintain our boat speed.
Below is a video of the tacking procedure. The video illustrates tacking from both starboard to port and port to starboard.
Each tack is replayed in slow motion.
Rounding the Weather Mark
Prior to the Mark
Help the grinders prepare the windward spinnaker sheet: Take the coiled sheet from the top of the lazarette at the stern, and put it on
the cockpit bench.
At the Mark
Uncleat the mainsheet and let it run out as we go around the mark.
Climb down into the cockpit and stand in front of the traveller.
After the Mark (Spinnaker Hoist)
If we're doing a jibe set, grab the mainsheet above the blocks on the traveller (use both hands), and pull
the boom over to the other side of the boat as we jibe.
See the jibing procedure below for a description of how to grab the mainsheet and move your body
during the jibe.
Yell “Watch your head!” when the boom crosses the boat.
Make sure the mainsheet runs all the way out – the stopper knot at the end of the line should
be at the cleat. Ask the boom pusher to push out the boom, and walk out the line if you need to (pull the mainsheet through the pulleys).
Move the traveller as far down to the leeward side as it goes.
Make sure the crew adjusts the control lines as follows:
boom vang: on
outhaul flattener: off
runners: off
cunningham: off
Below is a video of rounding the weather mark. The video illustrates a tack around the mark, followed by a bear-away spinnaker set.
Sailing to Lee
Trimming the Mainsail
Adjust the mainsheet and the traveller:
Let the mainsheet run all the way out. Ask the boom pusher to push out the boom until the stopper knot at the end of the mainsheet is at
the cleat.
Move the traveller as far down to the leeward side as it goes.
Check the other control lines for the mainsail. Ask the crew to adjust the lines as necessary:
boom vang: on
outhaul flattener: off
runners: off
cunningham: off
Ask the grinders to release the cunningham completely. After they do so, check the luff of the mainsail – if you see wrinkles,
as the grinders to put a little cunningham back on.
Tips for leeward legs:
The grinders may need help bringing in the spinnaker sheet. Pay attention to the grinders and be prepared
to grind the spinnaker sheet a few turns if they ask you for help.
Clean up the lines in the cockpit – this really reduces the likelihood of the lines getting fouled during spinnaker jibes or douses.
Put the runners through the portholes near the cockpit floor.
Wrap each spinnaker sheet twice around its secondary winch (always wrap lines CLOCKWISE around a winch), coil the lines neatly, and
put the coiled line on top of the cockpit bench.
Jibing
To jibe, you pull the boom toward the centerline of the boat, and then let the wind push out the mainsail on the new leeward side of
the boat. Here is the jibing procedure:
Skipper commands: Prepare to Jibe
Stand forward of the traveller and a little bit to leeward (toward the boom).
Move the traveller to the center.
Centering the traveller keeps the mainsheet from cutting across the cockpit too far forward after the boom crosses the boat.
Skipper commands: Trip the Pole
Yell “Watch your head!”
Look to make sure that all crew members near the boom are clear of its crossing path.
The boom comes across the boat hard and everyone must be aware when this happens.
Grab the mainsheet as close to the boom as you can, and pull the mainsheet toward you arm-over-arm.
The mainsheet runs through two lower blocks (just above the traveller) and two upper blocks (just under the boom). When you grab
the mainsheet, use one hand to grab all 4 sections of the mainsheet between the upper and lower blocks. Pull your hand toward you,
reach forward with your other hand, and grab all 4 sections of the mainsheet using your other hand. Continue to pull the boom toward
you with arm-over-arm grabs.
If the wind is light, the boom will come toward you with a few easy arm-over-arm grabs.
If the wind is heavy, it can be much harder to pull the boom toward you. Use your legs for leverage: Push off the leeward bench
in the cockpit, and lean toward the windward side of the boat.
As the boom begins to cross the boat, move and turn your body so that the mainsheet passes around you toward the stern. As it
passes between you and the stern sit on the new windward bench (the side the boom came from), while still holding onto the bundle of sheets.
Then let the boom out to the new leeward side in a controlled way so that it doesn't add unnecessary stress to the boat's hardware.
You must move your body out of the way of the crossing mainsheet, or it will trap you and hit you hard as it cuts across
the cockpit.
Move the traveller to the new leeward side as far down as it goes.
Below is a video of the jibing procedure. The video illustrates the spinnaker jibe from both starboard to port and port to starboard.
Each jibe is replayed in slow motion.
Modifications to the jibing procedure for light or heavy wind:
In light wind, pull the boom toward you and hold the boom just past the
centerline of the boat. Let the boom swing out to the new leeward side at the end of the jibe.
In light wind, the spinnaker tends to collapse when the mainsail blankets the spinnaker (i.e., when the mainsail and the spinnaker
are on the same side of the boat). By stopping the boom halfway through the jibe, you keep the mainsail from crossing the boat until
the foredeck crew makes the pole and the grinders start bringing the spinnaker over to the new windward side. This makes the spinnaker
much less likely to collapse.
In heavy wind, you may not be strong enough to pull the mainsheet by grabbing it between the block. In this
case you must do a power jibe:
Sit on the windward side of the boat and pull the mainsheet through the cleat (i.e., do a normal trim, but do it fast –
there's a lot of line to bring in).
As the boat turns, the boom will cross to the new leeward side.
After the boom crosses the boat, uncleat the mainsheet and let it run all the way out.
Rounding the Leeward Mark
Before the Mark
Skipper announces: Floater Douse, Mexican Douse, or
Stretch-Foot Douse
For a floater douse or Mexican douse:
Coil the spinnaker sheets and put the coils neatly on the cockpit bench.
Preparing the spinnaker sheets is very important: The sheets must run cleanly once the grinders blow them off the winch, or
the entire douse may be screwed up.
For a stretch-foot douse:
If the grinders ask for help, grind the working spinnaker sheet until the foot of the spinnaker is stretched out along the side
of the boat.
Just Prior to the Mark (Spinnaker Douse)
For a floater douse or stretch-foot douse, move th
traveller just past the wood rail on the windward side of the boat.
For a Mexican douse, leave the traveller on the leeward side (we jibe around the mark, and
that will be the new windward side after the jibe).
Bring in the mainsheet for a close haul. There's a lot of line to bring in, so start early:
In light wind, start just before the bow gets to the mark.
In heavy wind, start when the bow is about one boat length away from the mark.
Sit high up against the rail and use full, arm-length pulls to bring the mainsheet in quickly, but look up at the mainsail to make
sure you don't over-trim:
Start by bringing the mainsail quickly to about 45° (beam reach).
Time the rest of the trim with the boat's turn, so that we maintain power throughout the turn.
If we're doing a Mexican douse, jibe the mainsail.
The boat turns quickly around the mark and the boom crosses the boat on its own. All you need to do is cross to the other side of
the boat, sit up on the rail, and continue to bring in the mainsheet for a close haul.
TODO: experiment with Mexican douse procedure: sit on the leeward side to start trimming, sit on the windward
side to start trimming, or just wait for the main to jibe and then sit on the windward side?
After the Mark
Check that the crew has adjusted the control lines for a close haul:
boom vang: off
outhaul flattener: on
windward runner: on
cunningham: tensioned just enough to get rid of the wrinkles in the luff
leech line: tensioned just enough to stop the leech from fluttering
Below is a video of the procedure for a floater douse (rounding to port). The video illustrates the douse with annotations and with some
slow motion.
Below is a video of the procedure for a Mexican douse (rounding to port). The video illustrates the douse with annotations and with some
slow motion.
After the Finish
Center the traveller.
Put on the boom lift.
Release the twanger.
Make sure the crew releases or loosens all the control lines for the mainsail:
boom vang
outhaul flattener
runners
cunningham
leech line
Make sure the spinnaker sheets and the afterguys are secured before Rod turns on the engine.
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