J/121 Speed Guide

  • Last Updated: April 15, 2019
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North Sails experts Kimo Worthington and Chuck Allen answer questions in this speed guide for the J/121 class.

Who sails a J/121?

There are several distinct types of people who sail a J/121, and most are experienced sailors. Some race the boat one design, some race shorthanded or fully crewed offshore, and some head south and cruise the Caribbean. Many are individualists who have been changing keels and adding sails. In the 2018 Newport Bermuda Race, four J/121s raced in three different configurations. The point is, the J/121 is a versatile boat that’s ready to sail offshore, and the sailors who do buy one all seem to agree that they’d rather do something other than race windward-leeward course configurations.

J/121 sailing upwind
The J/121 is a versatile boat that’s ready to sail shorthanded and/or offshore.

What’s the ideal J/121 crew size?

That’s a trick question for this boat. The most crew you’ll ever need is five or six, total, for an event like Block Island Race Week, but the boat was designed for sailing doublehanded. It sails well without water ballast, but it really shines when you fill the windward tank with 850 pounds of water; that’s like having four or five extra people on the rail. Testing in a strong breeze, we have found the performance is spectacular with a reefed main and inner jib.

J121 reaching into sun
The most crew you’ll ever need on a J/121 is five or six, and the boat is designed for doublehanding.

How do you move a J/121 around between races?

The boat is 40 feet long and weighs 11,900 pounds with 4,800 pounds of ballast, so you’re going to move this boat on its own bottom or with a professional trucker. It’s equipped with a 30hp Yanmar diesel and saildrive, so it moves along well under power. And remember, even with only a couple of delivery crew you can add water ballast and power right up.

What sails are recommended?

The boat is billed as a five-sail boat. There’s one mainsail and two jibs, one that roller-furls on the headstay and the other that roller-furls on the inner headstay. The boat has an extendable sprit that can fly a Code Zero/gennaker on a roller-furler, or you can use an all-purpose asymmetric spinnaker. For a closer look at all these sails, view the North Sails product page, but it’s worth talking to a North class expert to make sure you match your sails to sailing style and location. Other speciality sails include smaller and flatter spinnakers and spinnaker staysails.

J/121 Tuning

What are the keys to rig set-up?

The J/121 has wide spreaders with chainplates outboard at the rail. We recommend easing your headstay length enough to rake the mast, inducing prebend to help keep it stable and secure. Use a rod-rigging tension gauge (e.g. Loos RT-11) and the numbers in the table below as a starting point.


J121 tension gauge in use
The rig is set up for heavy air with 52 on the uppers.


Any tricks to tuning a boat with multiple headstays?

The inner jib is a big upgrade for most people. Now, instead of wrestling to set and douse a heavy air jib, you can raise and furl it anytime on the inner headstay, which has a halyard lock-off. The lower end of the inner headstay has a 3:1 purchase, and before deploying the heavy air jib we grind the daylights out of it—enough to make the forward headstay just start going slack.

What’s involved in setting up and hoisting the mainsail?

The mainsail has luff slides that live on the mast track. Before bending them on for the first time, tension and secure the battens and check that the main halyard purchase has no twists. Be sure the headboard is on the track and that the battens aren’t too tight. Check that the pressure is evenly distributed between the bottom car and the tack point, which is adjustable. You should be able to hoist the sail by hand; don’t use a winch, because you might over-hoist the sail.

J121 Mainsail slides
With track cars and batten tension set correctly and no twists in the two-part halyard, you should be able to hoist the sail by hand.

What’s involved in adjusting the bobstay tension?

The bobstay on a J/121 counters the upward pressure on the pole from the Code Zero or spinnaker, and your goal is to keep the pole projecting forward in alignment with the sheer line of the hull. The adjustment is in the center of the bobstay and can be set at the beginning of the season. Be sure that the pole is all the way out and that you have a mark on the pole control line before adjusting the bobstay tension.

J121 pole detail inside boat
When the pole is extended all the way, there should be a ½ inch between bulkhead and turning block.

J/121 Upwind Sailing

What sail combinations do you use upwind on a J/121?

One of the exciting things about this boat is that you can use different combinations depending on the situation. Standard upwind configuration is a full main and J1 (the bigger jib). As the wind builds, you might reef the main and keep the big jib going; offshore, you might not reef and use the inner jib instead. In enough wind, of course, you’ll use the inner jib with a reefed main.

J121 inner jib deployed
The inner jib sets up on the inner forestay. Note the furling line, which should be rigged along the windward side.

Upwind, where does the crew sit?

The goal is to keep your “bow knuckle” in contact with the water. So if you have a full crew of five or six, in light air most should be sitting well forward. At 10 knots, you’ll still have two crew sitting in front of the shrouds. At 14 knots, one crew is forward; at 18 knots, everyone will move back to normal hiking position.

J121 bow knuckle with weight placement correct
If your weight placement is correct fore and aft, the knuckle will just kiss the water.
J121 bow knuckle with weight too far aft
If your weight is too far aft, the bow knuckle will always be out of the water.

Upwind on the J/121, when do you add water ballast?

As soon as you’re heeling 18 to 20 degrees, start adding water to the tanks to maintain a constant angle of heel. With a full crew, that’s likely to be around 15 knots true wind. Doublehanded, it might be at 12 knots. Don’t forget to add water when you’re cruising or doing a delivery, too. Not only will it reduce heel and improve speed, it can also settle the motion of the boat.

J121 with too much heel
The boat is heeled too much; it’s time to add water ballast (or depower).

How do you trim the main and jib upwind?

In light to medium air, center the boom by raising the traveler, and then sheet as hard as you dare to get some rudder angle and heel the boat over 12 to 15 degrees. Don’t head up and slow down; let the foils work and the boat will gain height. Look for the top telltale to be stalling about 25 percent of the time in light air, 50 percent in medium air. When the breeze comes up, keep the traveler high; ease the sheet to add twist when you have trouble reaching the target numbers.

J121 traveler up to windward
In medium air, the traveler should be raised well to windward to keep the boom on centerline.

For the jib, add three marks on the spreader that line up with the leech for eased, normal, and tight trim. We also recommend marking the deck for the inhauler to set the lead angle between 7 and 12 degrees. Set the angle tightest in flat water and moderate breeze.

J121 jib inhauler numbers on deck
The inhauler is set at 8 degrees.

How do you trim the heavy-air jib on the inner headstay?

As mentioned, you need to crank on the inner headstay until it is carrying about three-quarters of the rig load and the forward headstay loosens just a little. The jib sheets lead to the same floating lead as the J1 and you will still trim to the same spreader marks, as well as watching to keep the leech telltales flowing.  

What are the key gear changes for sailing upwind?

We’ve developed a playbook for five wind speeds. It goes like this:

  • Zone 1 (0-8 knots):You’re looking for power; move weight forward, and keep backstay and headstay loose and outhaul eased. Try to get some heel; pull in the mainsheet.
  • Zone 2 (9-12 knots): Start moving weight to the rail. Pull on backstay, jib halyard, and outhaul. Sail shape should still be deep. Trim the mainsheet hard.
  • Zone 3 (13-18 knots): Max outhaul, backstay, cunningham, and jib halyard. Find “magic heel angle” (12 to 15 degrees). Crew weight starts moving aft, sail shape becomes flatter. Consider moving jib leads back.
  • Zone 4 (18-22 knots): Now you need less power. Consider a single reef. All controls should be maxed. Find the “magic heel angle” (12-15 degrees). Sail shape should be really flat. Trim sails so the boat is easy to steer and fast; ease main (if it flogs, open the slot by easing the jib or moving the jib lead back).
  • Zone 5 (23+ knots): Smaller jib on inner headstay and/or reefed main. Strive for “magic heel angle” (12-15 degrees). Make the boat easy to sail and keep it going fast through the water.
J121 magic heel angle
The Magic Heel angle for the J/121 is 12-15 degrees.

J/121 Reaching and Downwind Sailing

What are the best J/121 sail combinations when reaching?

When close reaching in lighter winds, an eased J1 is very efficient because it has leech battens. As you bear off, switch to the Code Zero well before you think it’s time—about 70 to 80 degrees true wind. By easing the tension on the front of the Code Zero and letting it scallop you can sail even higher, but don’t overdo it. Crew should remain forward, in upwind position.

Not all Code Zeros are the same. North’s are a little smaller and not as deep as some other sailmakers. They also have a shorter foot and lower clew with less girth at the top, for a wider range; you can sail them from 70 to 120 degrees apparent before setting the A2 spinnaker.

J121 sail selection depends on angles downwind
Learning the crossover from spinnaker to Code Zero is a key to best reaching speeds on the J/121.

What are the crossovers between downwind sails?

Learn your sail crossover chart (see below) to determine the correct angles for the two jibs, Code Zero, and A3 and A2 spinnakers—and keep the leech of your main and headsail well-matched.

Matching leeches between main and code zero
The main and Code Zero leeches are well-matched, a fast combination.

At  the top end of Zone 3 (18 knots) from 90 to 125 degrees true wind angle, sail with a double-slotted Code Zero and inner jib. In winds over 18 knots, you may be able to carry the combination to 135 degrees. If you have one, you can use a spinnaker staysail at 135 degrees and deeper. When it’s really windy, an A4 (small spinnaker) and inner jib can be a very effective double-slot reaching combination.  

This team should be switching over to the Code Zero
This team should be switching over to the Code Zero.

sail crossover chart for J/121

Where does the J/121 crew sit when sailing downwind?

Under spinnaker in light air, crew weight should be forward and on the leeward rail, similar to upwind sailing. As the breeze comes up to 8 to 10 knots, you’ll sail with three in front of the shrouds to windward. For wind in the low to mid teens, those crew come aft of the shrouds. When power reaching, they will move halfway back to companionway, or even right back to the skipper.

light wind crew position is well forward
Both upwind and downwind, light air crew position is well forward to keep the bow knuckle touching the water.

Video of power reaching:

J/121 Maneuvers

How do you set and drop the Code Zero?

Always hoist a Code Zero on the weather side of the headstay. Raise it until the tack is 1 meter above the pole and tie off the halyard, then tension the luff via the 2:1 tack line. The Code Zero should run through a twing and then aft to the primary block. Unfurl when ready.

To drop a Code Zero: Furl the sail and bear away, tensioning the windward sheet to pull the sail to weather of the headstay as you ease halyard. Accordion it onto the foredeck. When dropping the sail while going upwind, you may have to luff up to get the furled sail to weather of the headstay.

How do you furl the Code Zero?

The key to furling this big sail when it’s windy is to ease the sheet far enough to take the pressure off the sail—but not so far that the sail completely luffs. Maintain a little tension to ensure a tight furl.

How do you reef the main?

Mainsail reefing is straightforward on the J/121. Ease the halyard and take up the tack line until the new tackpoint is snug. Next, trim the reefing line until the clew is snug against the boom and put a sail tie around the loose sail aft. Then raise the halyard enough for proper luff tension.

How do you change from J1 to inner jib?

Hoist the furled inner jib to its halyard lock with the tack eased off one meter. Then tighten the tack until the luff rope is quite tight—with significantly more load than the headstay. Keep the tack line on a winch for further adjustment and deploy the inner jib, then furl the J1. Your furling lines should run along the weather side of the boat.

How do you set the J/121 spinnaker?

The key jobs when setting the J/121 spinnaker with a crew are as follows: The sail starts in the bag, typically zipped up and tied off to the foredeck. Bear off to hoist, and raise the sail at least halfway before pulling out the tack and pole. The driver should call for the set when the boat is sailing at the right angle—if windy, bear off so it’s well hoisted before it fills. Also, don’t furl the jib(s) until the kite is up and flying, or you may mistakenly furl a lazy sheet or other part of the spinnaker. For shorthanded sailing, use a snuffer system or spinnaker zipper system.

How do you jibe the J/121 spinnaker?

We recommend an outside jibe, so the clew travels forward around the luff before sheeting in on the new leeward side. The new sheet must be in the “gybulator” or “sheet catcher” before the jibe begins so it doesn’t accidentally drop below the sprit pole. (The gybulator is mounted about six inches above the tack on the luff of the sail.)

J121 gybulator
The “gybulator” is located about six inches above the tack and the sheet must be in it for jibing.


Any tips on the starting line?

Be careful not to sail too slowly when approaching the starting line. If your speed falls below 2.5 knots, it can take a long time to get back up to speed and you’ll make a lot of leeway until the water starts flowing effectively over the foils again.

How do you tack a J/121?

In light air, roll tacking the J/121 is important; use all the crew weight you have. When using water ballast, plan ahead and start shifting the water from one side to the other a minute or two ahead of time. The goal is to come onto the new tack with the water ballast already transferred.

How long does it take to fill, move, and empty the J/121’s water ballast?

It takes five minutes to fill the windward tank, one minute to transfer it to leeward before a tack, and two minutes to empty the tank.

J/121 water ballast controls
The water ballast tanks are filled and drained with three control lines.

What are the keys to sailing a J/121 well?

  • Keep your crew weight out of the aft end of the boat.
  • Plan ahead for tacks so you have time to shift the water ballast.
  • In most breezes, max out the backstay to improve headstay tension.

What is the coolest thing about sailing J/121s?

We think what’s best about the boat is all the different types of sailors it attracts. J/Boats listened to its clients and introduced a boat that people can sail fast with their families or a few friends, either near shore and for long-distance adventuring.

Class Experts

Tim Dawson

Portsmouth, Rhode Island

Jack Orr

Milford, Connecticut

Tim Healy

Portsmouth, Rhode Island