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    Furling service & maintenance made easy!

    By Dr. Harken

    In this article:

    • Tips for servicing your furler
    • Furler maintenance
    • Inspection checks
    • Troubleshooting guides
    • Replacing your furler
    • Benefits of modern furling systems

    How do I service my furler?

    Thankfully, modern furling systems are designed to minimise your service and maintenance requirements. Having said that, the need for performing these tasks hasn't been eliminated altogether (you didn't get that lucky!). Therefore, you'll need to do some housekeeping to keep your furler working nicely, and importantly, your warranty valid! The good news is Harken's website provides free online guides that walk you through the maintenance process.

    Click here for online furler maintenance guides.

    STEP 1: Identify your furler
    There's no universal rule for servicing furlers - replacement parts and maintenance requirements are specific for the type of furler you own. To start, you need to identify which furler you have.

    Click here to view the family identification table online (page 2)

    Harken Furler Family Table
    Harken furler family_750

    STEP 2: Identify the size of your furler
    It's worth noting that MKIV and cruising furlers have the unit size printed on the label and MKIV on the feeder. On older models you must measure the drum diameter (measure across the top of the drum), the clevis pin diameter and the torque tube length (see below image for reference). 

    Furler sizing chart_750

    STEP 3: Let maintenance begin!
    Clean regularly. It's important your furler remains clean and salt free. When giving your boat its regular wash down, it's a good idea to clean your furling drum with soap and fresh water while you're at it. In addition, it's a good idea to give it a more thorough cleaning twice a year.

    For more thorough inspections:

    • Remove the line (noting the direction on spool).
    • Flush the bearings with soap and fresh water.
    • Clean the foils with soap and fresh water.
    • Run a scrap of luff tape up foil groove to clean.

    Inspections are essential

    Remember all furling parts can loosen, wear, and corrode over time, so it is essential you periodically inspect the items that make up your furler. You don't want to discover there's a problem when you're at sea!

    Here's a list of some of the things you should check over.


    • Unit for any signs of chafe, wear, or damaged
    • Screws - loose or missing? These should be secured with Loctite® adhesive, so don't turn the screw as you will release the bond. Merely check to make sure they are secure.
    • Foils - make sure they haven't dropped into the drum assembly; check that the torque tube clamp is tight.
    • Wire - look for signs of wear, unravelling, or loosening.
    • Locknuts on leg kit -  see if they're still there and haven't come loose.
    • Lower toggles  - check for signs of wear, cracks, and corrosion.
    • Cotter pin at lower toggle - make sure it's securely splayed.

    My furler isn't working properly, how do I identify the problem?

    Okay, so you've done your regular furler service and maintenance checks, but it's still not operating as it should. If this is the case, then now's the time to do some problem solving!

    Below I've identified some common furling problems, their causes, and how you can deal with them. If you're having a problem with your furler try using this guide to establish how to overcome it. 

    Sail will not furl or unfurl
    Probable causeSolution
    Jib halyard is wrapping around the headstay because halyard swivel is too low.A wire pendant may be needed at head of sail to raise halyard swivel to proper height. Use a halyard deflector.
    Jib halyard is too tight.Ease jib halyard.
    Spare halyard is wrapping in sail as it furls.Secure spare halyards away from furling headstay by flipping them behind spreaders. Use a halyard deflector.
    Salt or dirt in bearings.Flush bearings with fresh water.
    Furling line tangled in drum.Overrides are best prevented by using a 7402 ratchet block as the last furling line lead to maintain proper drag on line while unfurling.
    Stop knot catching.Make sure knot is a single overhand and is pushed up inside spool.
    Sail full of wind.Luff completely before furling or reefing.
    Sail flogging too much.Release a short length of sheet, pull some furling line and repeat.
    Foil out of drum assembly.Reinstall foil in drum assembly and tighten adjuster clamp screws into holes.
    No wraps of furling line on spool.Remove sheets from furled sail. Rotate spool to wrap correct amount of line.
    Line led through ratchet block backwards.Rerun the line.
    Halyard swivel installed upside down.Remount swivel correctly.


    Sail will not furl completely
    Probable CauseSolution
    Insufficient furling line on drum.Remove sheets. Rotate stay, wrapping as much furling line on drum as possible.
    Too much line on drum.Adjust amount of line on drum or change position of forward lead block to allow line to roll evenly on drum.
    Spare halyard catching in sail as it furls.Move halyards away from furling headsail.


    Headstay rotates in jerks or elliptically
    Probable causeSolution
    Insufficient tension on headstay.Tighten headstay and/or backstay to eliminate sag in headstay.


    Sail does not stay furled
    Probable causeSolution
    Sail not furled tightly on stay.Maintain drag on sheets while furling.
    Furling line not secure.Secure furling line.


    Sail will not go up
    Probable causeSolution
    Luff tape will not go into groove.Check luff tape for fraying and check size is correct.
    Sail catching at feeder.Have someone guide sail into feeder. Purchase prefeeder part no. 947.
    Dirt in groove.Clean thoroughly.


    Sail will not raise completely or luff will not tension
    Probable causeSolution
    Halyard swivel is hitting end stop or trim cap screws.Luff of sail is too long and must be recut. Consult sailmaker.
    Angle between halyard and mast is too sharp and halyard is pulling too much to the rear.Luff of sail may be too long. Consult sailmaker.


    Sail will not come down
    Probable causeSolution
    Halyard is wrapping on headstay.Angle between headstay and halyard is too shallow and must be optimised.


    Sun cover rolls up inside of sail
    Probable causeSolution
    Furling line is wrapped on spool in wrong direction.Unfurl sail and lower it. Disconnect from furler. Note direction of line wrap on spool. Pull line from spool and rewind in opposite direction. Connect sail and hoist. See commissioning section of manual.


    Line is wearing on plastic drum assembly
    Probable causeSolution
    Line is not lead through guide posts.Lead line into drum between guide posts.

    Hopefully this handy guide will help you solve problems yourself, but if you're still stuck, or not quite sure, feel free to give me a call and we can work our way through it together!

    +44 (0) 1590 689 122

    Replacing your furler

    Which furler is right for me?
    Sometimes servicing isn't enough and it's simply time for a replacement! So you've decided it's time for a new furling system, but you're not sure where to begin? Before ordering, you must first consider your boat's size and the type of sailing you do. Harken have two main types: the MKIV for racers and performance cruises and the ESP for cruisers.

    Here are the main differences between MKIV and ESP furlers!

    FoilsAerodynamic foil profile. Double grooves for faster hoists, douses and sail changes.Round profile for easy rolling.
    Single groove
    Halyard & tack swivelsIndependent swivels for improved sail shapeFixed swivel
    DrumSplit drum removes for racingOne-piece drum, spool, and guard i.e. fixed drum

    What are the benefits of modern furlers?

    Good visibility
    Genoas are generally cut close to the deck which obscures visibility ahead and to leeward. As many of us sail within a few miles of a harbour, visibility is important for safety and peace of mind. Instead of increasing visibility by cutting your clew high, and permanently reducing your sail area, you can simply reef the genoa when near a harbour, whilst sailing at night or approaching an area with navigational hazards.

    Speed control
    Being able to reef the genoa enables you too quickly and easily depower the sail to meet variable shifts in weather.

    Full-power headsails
    If you don't have the ability to reef, you may be tempted to choose a smaller headsail as the primary genoa. With the ability to furl, you're able to maximise the size of your genoa and simply reef to the prevailing conditions.

    Sail more and motor less
    Furling systems can make it easier to take advantage of light wind conditions. On yachts where you need to run the genoa up every time you make a headsail change, it can become tiresome for the crew during a cruise. Furling systems enable the helm to set the sail with minimal crew input, making lighter work of sail planning and adjustments.

    Less crew needed
    Furlers allow you to reef or stow the genoa from the safety of the cockpit, removing the need to drag sails onto the foredeck. This makes it easier to sail shorthanded or use your normal crew to sail a larger boat.

    Got a question?
    For more information on furling systems, maintenance, troubleshooting, replacements, and/ or other hardware questions, feel free to contact me via the details below:

    01590 689 122

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    More articles by Dr Harken

    Choosing winches?
    Harken Radial Line winches, more than just a redesign
    Servicing winches for a longer, more efficient life
    Shackle vs rope block attachments…the facts revealed
    Block and traveller maintenance - what's the big deal?
    Fine-tune systems for mainsheets
    Accessorising your cleats for perfect trimming
    Ratchet blocks…they don't just go click!
    Towing genoa cars: proper sail trim from within the cockpit

    Loctite is a registered trademark of Henkel AG & Company KGaA.

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