Thursday, December 9, 2010

How to build a roller furler for under $40

Ellie's home-made sub-$40 roller furler

There are many different types of roller furling systems. This furler is a "wire luff" type which requires a jib that has a stainless steel wire sewn into the luff, or has a "jib set flying" (a jib that does not attach to a stay).  If your jib hanks onto a fixed forestay or needs to wind around a forestay this furler won't work for you. The furler you need would be more like this one, or perhaps this adaptation.

This furler, as illustrated below, is a small light duty unit sized for my 15' Welsford Navigator. It is somewhat similar to a Ronstan RF76 or a Harken 434, but not as strong.  It can be scaled up in size if desired, and can be made stronger by substituting a stronger eye-bolt, stronger u-boltupper swivel, and ball bearing thrust bearing.

Here is a test run of the furler


In issue #58 of Small Craft Advisor magazine, Kirk Gresham wrote an excellent article on how he designed and built two roller furlers for his 17' cutter Eider for a mere $40 each using bits of scrap and a few bits and pieces of hardware from a local hardware store. This saved Kirk a whopping $670 off the $750 price tag he was quoted for two furler units from a local Port Townsend chandlery. I knew from the moment I read Kirk's article that I wanted to build one of his furlers too. I love building things. I'd much rather build something than buy it, even if it ends up costing me more. But in this case building it saved me a bundle too. That's a two-fer for me!

I had some questions after reading the article, but I knew Kirk attends the Port Townsend Wooden Boat Festival every year, so I met Captain Kirk at the festival. He answered all of my questions and allowed me to take some close up photos of his furlers.

Being a mechanical designer by trade, naturally I couldn't resist making some improvements to the design.  I used bronze thrust washers in place of the steel radial bearings Kirk used, and I made the spool with a core of solid hardwood instead of using a section of PVC pipe.  These two changes significantly increase the strength of the furler, make it operate more smoothly and increase corrosion resistance. I also used an ABS end cap instead of the bent aluminum strap used to contain the furling line. It looks better and does a better job of containing the line.

So, here I present my improved version of Kirk's $40 roller furler.
Click to enlarge

Making the Drum Assembly

The drum is made from an inexpensive 3" ABS drain pipe end cap available at any home center that sells indoor plumbing supplies, like Home Depot, Lowes, Grainger, etc.  The cap I used is a Mueller 2979H.  You can use a 4" cap if you want a larger furler. You will also need a stainless steel eye-bolt. I used a 1/4" x 4" Stanley V2161, but welded eye bolts are a better choice as they are much stronger. To make the drum assembly, drill a 1/4" hole in the center of the end cap for the eye-bolt. Drill 7/8" diameter holes every 45 degrees around the outside for access to the furling line. Locate these holes so they are 1/4" below the open end of the cap.
I also drilled a series of small drain holes in the bottom of the drum.
Use locktite to secure the two nuts on the eyebolt.

Making the Spool Assembly

To make the spool assembly, first I cut two plywood disks from 1/4" plywood. The outer diameter of the disks should be just slightly less than the inner diameter of the ABS cap, which is 3-1/2" diameter. We don't want the furling line to slip through the gap and jam the furler. Sandwiched between the disks is a piece of oak (or any other hard wood) that is 2" in diameter and 7/8" thick. Glue these three pieces together taking care to align them accurately. Drill a 1/4" hole through the center for the eye-bolt. Drill two more holes to match the stainless steel U-bolt legs. The U-bolt I used is a 1/4" x 1-1/8" x 3-1/2" Stanley V2193. Drill one extra hole in the upper disk for the stop knot of the furling line. Paint the spool with several coats of enamel paint. Cut and file the legs of the U-bolt flush with the nuts. Use locktite to secure all four nuts.

Assembling the unit

To assemble the unit, place the spool onto the eyebolt of the drum assembly. Then add a 1/4" stainless steel washer, your thrust bearing, and a locknut. The thrust bearing is simply two or three 1/4" I.D. sintered bronze thrust washers. These strong, inexpensive corrosion resistant self-lubricating washers should be readily available at any good hardware store, or you can order them here. Once in a great while, apply a drop of motor oil to the thrust washers. It will soak into the porous metal and lubricate them for a long time.

A ball bearing can be used instead of the thrust washers if you prefer. They are more expensive but will operate more smoothly under high tension.  The exact size you need will depend on the diameter of your eyebolt and the space available inside your u-bolt. The style of bearing you would want is shown below, and a source for stainless steel thrust bearings in many sizes is here.

Tie a stop knot in the end of your furling line, feed it through the hole in the upper disk and out through one of the holes in the drum. Spin the spool to wind up the line.

Upper Swivel

A swivel is required between the end of your jib halyard and jib.  With a wire luff furler you want a swivel that spins easily. This anchor swivel available from Duckworks, is a good choice provided your luff tension is not too tight. It is extremely strong, inexpensive, and spins well under moderate tension but I've found that this swivel can stick if I over-tension my jib too much.

A ball bearing swivel is much better suited for larger boats with higher luff tensions, while a jumbo sized (size 10) ball bearing fishing swivel works very well for light duty applications like mine.  It is the largest ball bearing fishing swivel I've been able to find. It is rated at 810 lbs, which is adequate for my needs, and it works flawlessly for me.

A word about strength

Make sure you select components that are strong enough for your application. An easy and conservative way to do this is to look at the diameter of the stainless steel cable used to make your jib's luff wire.  My jib uses 1/8" cable, which has a Safe Working Load (SWL) of 352 lbs.  3/16" cable has a SWL of 740 lbs, and so on.  The SWL of each one of your components (eye-bolt, u-bolt, swivel, thrust bearing, shackles, etc) should be at least as high as that of your cable's.  You'll be able to find the SWLs on the product's packaging, at the manufacturer's website, or with a bit of Googling. That way you'll know your furler is stronger than your luff wire.

UK version
Click here to see Barry's UK version of this furler.


This furler works perfectly on my Navigator Ellie and I couldn't be more pleased with it.  If you have any feedback or if you build one of these furlers for yourself, I'd love to hear about it.  Please leave a comment below.



  1. Thanks a lot! I had thought a furler was out of my price range, but I'm glad to be wrong!

  2. Well done !
    It all looks very professional.
    An example of nice craftmanship and thought.

  3. This is great. Looks like you've upgraded your description and design since your earlier posting.

    You show thrust bearings on one side of the spool assembly. What about on both sides, i.e., adding thrust bearings on the eybolt shaft between the drum and spool? Duckworks readers might be interested in knowing of the updated description as a follow up to your letter several months ago.

  4. There is no need for a thrust bearing on the bottom side of the spool. The furler is under constant tension load from the forestay so a bearing down there would do nothing. The entire load is taken up by the upper thrust bearing. Be sure and use a very hard wood, such as oak or Ipe, for the center of the spool to minimize any abrasion caused by the eyebolt in the center hole - that will make the furler last for many many years.

  5. I'm planning on building a Passage Maker Sailing Dinghy this next winter. Doing the little things in preparation of the build. I've built the roller furling .... what size of a line would I use for the sailing dinghy? 3/16" would probably give me 8 or 10 wraps around the core.

  6. I use 3/16" line and I easily get 21 or 22 wraps around the core. I only need 12 wraps to furl my jib.

  7. I am in the early stages of building one of these. Mine will have to be a bit "beefier" as it is going on an Irwin 30. I have the drum made (I used a 4" cap) with drain caps as top/bottom discs. I am thinking of using a SS or bronze 1-1/4" nipple to run the forestay thru with ball bearings bonded in place for friction relief. Then attach a CPVC threaded adapter to the nipple's threads to begin running the pipe up the forestay. I have to say I'm nervous about cutting that forestay wire (my headsail goes almost all the way to the top of the mast)!

    1. Did you finish the one for the Irwin? Would like to see pictures if so.

    2. No, have not gotten any further. Ran into a couple of engine performance snags, but have almost gotten a hand on that. The $ needed to go there! Getting ready to get back to the furler soon. I'll let you know when it's done and post a few pics. Trying to figure out how to do this thing without cutting the forestay wire!


    3. How did it work on the Irwin 30? Any issues? I have an Irwin 37 and was thinking of taking on this project

  8. Please keep me in the loop!
    I would really like to see your Furler for your 30 footer.
    I have a 27 foot O'Day I would like to make one for mine.

    1. Kevin,
      I also have an Oday 27 and researching different homemade furlers. Have you built one yet or found any other helpful info?

  9. I made one using a pully system that was on a catalina 25. used 4 inch cap, worked the pully down to fit in the hood, then split the pully makeing a spool. looks like it's going to do the job. I am so glade to have found your furling info.
    Norm, Catalina 25
    Port: Mount Vernon Md

  10. Has anyone tried to make a roller for a larger sail?
    I need a furler for a 60 square meters Code 0 sail, but they cost 600 - 800 Pounds.
    Why not build one myself?
    My question: How do I make it work with an "endless" line, that is, how do I make the line get a firm grip around the roller?

    1. Making a furler for bigger sails requires sturdy material, larger furlingline etc. Much stress will be put to the unit so make sure it's solid

    2. I made one furler in 2012 for my sailing canoe. Good to all aspect, but I choose the wrong swivel. Will repeat experience with a ballbearing swivel next season. It's a 3 inch dia drum, from ABS sewer cap. I'm now building a 19 ft cruising sailboat and I want to another furler that will ha 4 inch dia. Will be design according to these specifications. No need to throw away hundreds of dollars. Make one like this properly and it will make you happy. Cheers.

  11. Hi,
    I've just found this site after searching for info on how to build a furler for my 16' Falmouth Bass Boat. I think the 3" black ABS one shown above is excellent and want to build one of these. The problem is I am in the UK and I can't get hold of black ABS, especially a cap with a relatively flat end to it (they're all slightly domed over here - and grey!). Lowes or Home Depot won't ship to UK so was wondering if anyone could offer me a suggestion how I might get a 3" black cap?



      Hi Barry,

      Check this out, maybe this will work for you.
      Works for my Hunter 19, you don't have to shorten your forestay.

      Good luck


    2. Thanks for the info Alex.

      Well, I finally got around to making my furler from a 3.5" cap. It has a furler drum made from 6mm ply discs and an oak centre drum. I had to make a bespoke mounting plate to ensure clearance of the drum and jib from the forestay but it all works fantastic. I would love to be able to include a couple of photos of the finished furler but am not sure if this is possible.

      I'd like to offer my sincere thanks to Joel, for sharing his knowledge on this web site, and to everyone else who collectively gave me the confidence and inspiration to give it a go.