Photo courtesy Tartan Yachts

MKIV Jib Reefing & Furling


Furling is easier than ever with Harken’s MKIV Furlers.


Harken Furlers don’t require professional installation.

Tech Tips:

Harken Link PlateLink plates raise the drum to clear the anchor, reduce sail chafe, and increase visibility for smooth sailing.

Lead Block Kit
The Jib Reefing and Furling lead block kit reroutes lines outside the stanchions for a cleaner deck. A ratchet block is included in the lead block kit to keep tension on the furling lines. This will prevent the line from overriding in the drum.

Harken Lead Block Kit

The 7402 Ratchet block offers total control over your furling line. The ratchet provides the extra holding power you need for reefing or furling the sail in heavy winds. The static sheave supplies the correct tension to help the line spool smoothly on the drum when unfurling, making it easier to furl the sail again.

MKIV Jib Reefing & Furling Q&A


Sails, Shape, Size & Design

How do I select the right furling system for my boat?

Clevis PinHeadstay

The Ordering Furling guide explains how to choose a furling unit and accessories for your boat. You will need to know the clevis pin diameter as well as your headstay length and diameter.

What are the differences between Harken's MKIV and ESP furlers?
Both are designed for longevity and ease of use, but the MKIV has additional features that make it more suitable for performance cruising and racing.

FoilsDouble-groove FoilAerodynamic foil profile. Double grooves for faster hoists, douses, and sail changes.Single-groove FoilRound profile for easy rolling. Single groove.

Pass headstay wire and marine eye through foils. Cut top foil to fit. Bottom foil adjusts to fine-tune unit length.
Halyard and Tack SwivelsIndependent SwivelsIndependent swivels for improved sail shape.Fixed SwivelFixed swivel.
DrumSplit drum removes for racing.One-piece drum, spool, and guard i.e. fixed drum.
Line Line is included. Line is not included

Are all Harken Jib Reefing & Furling systems capable of reefing a headsail?
Yes, as long as the furling system has aluminum extrusions covering the headstay.

Changing SailsCan I change sails with my Harken Jib Reefing & Furling system?
Yes, changing headsails is simple. Just attach the head and tack to their shackles, pass the luff tape through the prefeeder and feeder, and hoist. The feeders smooth out wrinkles and minor twists in the sail so you can easily raise sail while at the mast or in the cockpit. Choose the optional snap shackles if you plan to make a lot of sail changes.

How can I reduce heel and get better control with a reefed sail?
Harken's MKIV Jib Reefing & Furling units solve the inefficient shape of reefed sails with independent head and tack swivels. The independent swivels allow the middle to furl first, flattening the sail and reducing heel.

For the best results, use a sail designed specifically for reefing with your MKIV Furler. Reefing sails should be designed to have good shape from about 5 to 40 knots.

Genoa Trim AngleAdditional sail shape adjustments can be made by increasing or decreasing halyard tension and by changing genoa lead car positions. After reefing, simply move the car forward so the sheet between the car and the clew points to the middle of the luff.

Why do I need more than one jib if I can just reef?
Experienced sailors rarely sail without a heavy-air jib because even the best all-around reefing sails can fail. In a blow, you should change to a reefable heavy-air sail before leaving the harbor. A storm jib is vital for offshore passages because of the possibility of hurricane weather. In light air, having a large, lightweight genoa can make sailing a lot more fun.

What is the proper luff tape for my MKIV furler?
Units 0, 1, 2, 3, and 4 use #6 luff tape. #6 luff tape is 0.1875" in diameter (about 5 mm).

Sail Clews

Should my new sail be made with a high or low clew?
Most furling sails are designed with a high clew to give the lower part of the sail a better wrap around the foils, and to improve visibility under the sail. A sail with a moderately low clew has the greatest efficiency and will maintain good visibility because the tack of the sail is raised off the deck.

Do I need to alter my sails to fit the MKIV furler?
That depends if you are replacing another furler. Check your sails to see if they have #6 or 5 luff tape when you take your sails to your sailmaker. In addition to adding the luff tape, he will also add a cut-back above and below the sail to allow room for the halyard swivel and lower unit. The installation manual gives all required dimensions in the appendix.

Can I use my racing sails with a Harken furling system?
Removable Drum for RacingYes. Most racers don't use a #1 genoa on the furler because the luff is usually too long and the construction too light. A #2 or smaller genoa should be strong enough to handle reefing and short enough to use with your furling system. Harken MKIV Furlers feature an easily removable drum that allows you to secure the sail tack to the deck. The halyard swivel stores quickly below the feeder so you can use the dual groove extrusions as a twin-foil headstay-this means fast sail changes when you're racing. It also means you can use your full hoist #1 genoa while in race mode.

Can I use my cruising spinnaker with a Harken Jib Reefing & Furling system?
Yes. Most cruising spinnakers attach to the headstay with a snap shackle. Ask your sailmaker to replace the shackle with one that works with a furled sail-probably one with a padded strap or string of beads to hold the sail near the headstay.

Is it easer to install the furler on the mast when the mast is down or up?
If the mast is down for storage or for other work, the assembled furler can be attached and go up with the mast when it is stepped. Removing the stay and raising the assembled furler on a standing mast is best left to experts and professional riggers.

You offer a Harken Halyard Deflector as an option. What is a halyard deflector?
The Harken Halyard Deflector prevents the jib halyard and other halyards (such as a spinnaker or additional jib halyards) from wrapping around the foil.

What is the difference between the Harken Halyard Deflector and the Harken Halyard Restrainer?
The Harken Halyard Deflector installs on the stay above the foil system and prevents the jib halyard and other halyards from wrapping around the foil.

The Harken Halyard Restrainer installs on the mast near the top of the foils and keeps the line against the mast. This provides a better angle to the halyard swivel and prevents it from wrapping around the foil. Stainless steel brackets feature hardcoat-anodized aluminum sheaves that accommodate both wire and rope.

Questions for Your Sailmaker

What does it cost to add luff tape to my sail?
Costs vary, but most sailmakers base prices on luff and leech lengths.

What brand of sails should I buy?
Select a sailmaker who offers answers that show an understanding of reefing and furling systems.

What size genoa should I use as my primary reefing sail?
This depends on your boat and your normal sailing conditions. Most boats find a 135 percent genoa ideal. Light air 150 and heavier air 100 percent genoas are also common in certain regions. Discuss sail size with your sailmaker.

Can I use my old sails with my new Harken Jib Reefing & Furling system?
Yes. Ask your sailmaker to modify the sails you use regularly, including at least one genoa and one heavy-air sail. If you sail in an area that requires specialty sails like drifters, convert these as well. Sails should be in good condition.

How are sails modified for Harken Jib Reefing and Furling systems?
Your sailmaker will remove the hanks and add a luff tape so the sails slide into the foils. Larger sails may need to be shortened to make room for the halyard swivel. Adding a sun cover to the sails you store furled will protect them from ultraviolet damage.

What should I look for when I purchase a new sail?
Look for a sail designed for a range of wind conditions. The best sails to use with roller reefing and furling units are those built with shaping devices in the luff to improve sail efficiency. Adding a sun cover to the sails you store furled will protect them from ultraviolet damage.

Genoa Sail UV-Protection

What's the best way to protect my sail from the sun?
Prolonged exposure to ultraviolet rays deteriorates most sailcloth, so any sail left rolled on the headstay needs protection. Your sailmaker can add UV-resistant material to the foot and leech panels-this can usually be done without adding a lot of extra weight. Most sailmakers prefer to use material like Acrilan® fabric (the same material used for mainsail covers).

Alternatively, some sailors use a long sock-like bag to cover their furled sail. This design won't add weight to your genoa but you'll need a spare halyard to hoist it. Be aware these covers can flog in a breeze.

Acrilan® is a registered trademark of Solutia Inc. Corporation.

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