How to build a roller furler for under $40

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

Introduction:

There are many different types of roller furling systems. This furler is a "Wykeham Martin" or "wire luff" type.  This popular design has been in continuous use worldwide for well over 100 years.  It 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.

This furler, as illustrated below, is sized for my 15' Welsford Navigator, or any similar sized small sailboat. It is comparable to a Ronstan RF76 or a Harken 434 dinghy furler.  It can be scaled up in size and strength for larger boats by substituting a stronger eye-bolt, stronger u-bolt, upper swivel, and ball bearing thrust bearing.

Here is a test run of the furler

Origin

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 much 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.  (Note: a 3" cap is actually 4" in diameter.  It caps a 3" inside diameter drain pipe).  Caps are available in a variety of sizes if you want a larger or smaller furler. You will also need a stainless steel eye-bolt. I used a 1/4" x 4" Stanley V2161 from Lowes, but this metric SD-080708 welded eye bolt from Duckworks is a better choice as it is 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. 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 securely locked nut. It is crucial that this nut be secured so that it cannot turn in either direction, or worse yet, come off in service causing the furler to come apart.  A locknut alone is insufficient - it will eventually loosen.  There are many ways to safely secure this nut.  Using locktite is adequate. Using two ordinary nuts tightened against each other, either with or without locktite, is excellent.  Or, if you want the ability to disassemble the furler  easily, you could use a castle nut, drill a tiny hole through the eyebolt and secure it with a cotter pin or split ring.

 

The thrust bearing is simply one or two 1/4" I.D. sintered bronze thrust washers. These strong, inexpensive, corrosion resistant self-lubricating washers should be 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 may 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.  I've tested both the thrust washers and the ball bearings on my boat and there was no noticeable difference.

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 at the head of your jib to allow the wire luff to spin and roll up the jib.  With this type of furler you want a swivel that spins easily. I have tested three different swivels on my boat that have worked well for me.

This anchor swivel, is a good choice provided your luff tension is not too tight.  If your jib uses a jib halyard, this swivel will work for you. It is extremely strong, very inexpensive, and spins well under moderate tension.  However, since it's not a ball bearing swivel, it can stick when tensioned too much.

Ball bearing swivels are a better choice.  The Ronstan RF75 swivel is considerably more expensive, but is an excellent choice for larger sailboats with higher luff tensions.  Amazon has a number of swivels that look promising, but I haven't tested them.  And this jumbo sized (size 10) fishing swivel is an excellent choice for smaller sailboats and sailing dinghys.  It is the largest ball bearing fishing swivel I've been able to find and works very well on my Navigator. It is rated to support up to 810 lbs.  Do not rely on this fishing swivel to hold up a mast on anything larger than a sailing dinghy.

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.

Conclusion

This furler has performed flawlessly on my Navigator Ellie for over 12 years now, 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.

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Seats

This weekend I worked on the seats.

Saturday I cut out and glued on all the seat side supports.

I also epoxy coated the inside of the seats/flotation compartments. No need to paint inside there.  Inspection and repairs are easier without paint getting in the way.

I also added a doubler underneath the port side seat. This is to reinforce where the boomkin mounts.

Sunday I glued in the seat tops.

The seat tops will eventually be covered with laid decking.

A little more work on the transom

Tonight I cut two more holes in the transom. A 1" drain hole, and a square hole for the boomkin.
That makes a grand total of 17 perforations through my transom. Six for the Duckworks motor mount, eight holes for the gudgeons, and three more for the tiller, boomkin and drain!  I hope the boat will still float despite all these holes!

Another challenge was how to trim all the planks flush with the transom. I thought about using a saw but was afraid of scratching the surface of the transom and chipping the planks. Then I thought I'd carefully whittle away at them with a sharp chisel. That would have taken forever.  I ended up using the Gain Machine


I set the Gain Machine so that the router bit was flush with the bottom of the base, like this:

Then, holding the base firmly against the transom, I used the Gain Machine to route the protruding planks flush with the transom.

The planks were perfectly flush a few minutes later.

Planking Complete!

We passed another major milestone this weekend - installation of the final plank - the sheer strake.
WoooHooo!

I decided to minimize the number of splices in this strake, because I am hoping it will look good enough to varnish. Since the Navigator is a 15' boat, I was just barely able to make the sheer strakes using one scarf joint in the middle. I figure one splice looks better than two.

I tried to do the best job I could with the scarf joints.  They look nice and clean but I won't know for sure until after they're faired and a coat of epoxy is applied. If it doesn't look good, I can always paint it or apply a vaneer.

But for now, time for a beer!

Planking away

Work has slowed a bit as we move into the rainy season here in the Pacific Northwest. Not only are the days getting shorter, colder and wetter, but I'm back to working overtime. *sigh*

Nevertheless, I'm glad to say that I am making some progress.

I've got most of the third row of planking on.

I've fitted the anchor well floor, the front seat, and started fitting the rear side seats. It's a good idea to cut these to size before installing the third row of planking. It's much easier to fit them in place over sized and scribe the outer hull position using a batten then to try and fit them later.

I have learned two valuable lessons this time around:

Lesson #1. Carefully inspect your plywood, no matter how good it's supposed to be. After installing part of my starboard plank, I noticed that something looked odd at one of the edges. Closer inspection revealed this:

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Yikes! About a half inch of the edge of this sheet of plywood didn't get bonded properly. I'm using Aquatek BS-6566 marine plywood and I've built two boats using this stuff, and this is the first time I've run across a flaw like this.  I had to trim a half inch from the forward edge of one of my planks, which was already installed, to get rid of the bad edge.  I'm inspecting every piece from now on.

Lesson#2: When installing the planks, it's easy to clamp them along the top edge, but the bottom edge has to be fastened with screws, which are removed after the epoxy cures.  This leaves a line of ugly screw holes that has to be plugged and sanded. I started doing it this way but then I found a better way. Now I use my PowerShot staple & nail gun loaded with 1/2" nails.

This stapler has just enough power to drive these tiny little nails most of the way through a 1/4" sheet of plywood and into the underlying stringer.  To install the plank, I goop the stringers up with "peanut butter", clamp the plank in place along the top, then press firmly along the bottom and drive in a nail every few inches or so.

 The little nails are easily pulled later on with a pair of pliers, leaving just a little pinhole.  The only downside is that the stapler has a tendency to jam but it still beats using screws by a long shot IMHO.

The Gain Machine

Before the next set of panels can be installed, there is some prep work to do. First, I had to mark where the bottom of the next panel will go so that I could cut the bevel in the lower panel. The panels overlap by 20mm which is the same width as the stringers. I made this simple jig with a pointer that rides along the top of the stringer and it holds a pencil 20mm away that draws the line on the lower panel.

The bevel has to go from this line the stringer above it.

I cut this bevel by aligning the two stringers and the plane by sight. Plane off some material and frequently check the progress.

Keep planing away material until the bevel reaches the line and it looks like this:

Making the remaining planks is similar to the way we made the garboard plank. First we measure the greatest width between the stringers and add about 50mm. Measure the desired length and add about 50mm. Cut a rectangular piece of plywood to that size. Clamp it to the boat. Trace the upper edges of both stringers onto the panel. Remove the panel.  Offset the lower curve by an additional 20mm so that the lower edge of the panel will align with the lower edge of the bevel.  Cut the panel to the profile. Fair the lower edge of the panel nice and smooth.  Epoxy the panel to the boat.

Cutting Gains

At the bow, the overlap between the two panels blend together with a tapered half-lap joint called a "gain". Gains can be cut many different ways. Often they are cut by hand using a saw followed by a chisel and finished off with a rabbet plane. I decided to cut the gains using a router, and I cut them in the panels before installing them on the boat. I didn't have much confidence in my ability to cut them by hand and I knew a router would be much faster and more accurate.

To use a router to cut the gains, I first had to come up with a jig. This is the jig, which I call "The Gain Machine".

The jig is made from two scraps of wood. The lower piece is made from 3/4" (20mm) stock and it has one pointed end cut at 45 degree angles, which I'll refer to as "the pointer".  The pointer rides along the edge of the panel to control the width of the gain.

The other piece is made of a scrap of 1/4" (6mm) plywood. The base for the router is attached to one end.  It has two slotted holes for screws and washers that attach it to the lower piece and allow the position of the pointer to be adjusted. The router is a trim router that I got from Harbor Freight Tools on sale for $20.

After assembling the two pieces, put a 3/4" (20mm) diameter straight router bit into the router. If you don't have a 3/4" bit, a smaller bit could be used but you would need to cut the gain in multiple passes. Adjust the pointer so the distance from the tip of the pointer to the far side of the bit is equal to the desired width of the gain.  In my case, the bit and gain are both 3/4" so the pointer just contacts the bit.

Set the depth of the bit so that the bottom of the bit is raised up by an amount equal to the thickness of the plywood panel (1/4" or 6mm in my case).

Now the jig is ready to cut gains.  Here is a video of the Gain Machine in action.
I don't see how cutting gains could be any quicker or easier than this!

Chapter 9: A tale of 2 planks

It was the best of planks, it was the worst of planks...

Sorry Charles.

The garboard plank on the Navigator is in many ways the easiest plank, and also the hardest to install. The aft half of the plank is quite flat. It is spliced together with nice friendly butt blocks - no scarfing is necessary. The plank is quite uniform in width. The entire lower edge of the plank is attached to the lower panel using the ever popular stitch-and-glue technique.

The forward half of the plank is a another story. It makes a near 90 degree twist while curving around the bow and increasing in width, culminating with an attachment to a contoured stem with a rolling bevel.

Let's start with the easy part.

Here is a section of the garboard plank from the transom through bulkhead 7. To make the plank, first we measure the greatest width between the bottom panel and the stringer and add about 50mm. Measure the length and add about 50mm. Cut a rectangular piece of plywood to that size. Clamp it to the boat. Trace the profile of the lower plank and stringer onto the panel. Cut the panel to the profile. Epoxy the panel to the boat. The joint between the lower panel and the plank gets stitch-and-glued, which means it is temporarily stitched to the lower panel with wire ties or bailing wire, dabs of epoxy are applied between the stitches. When the epoxy dabs cure, the stitches are removed, a fillet of epoxy/wood flour is applied over the joint, which is then covered with fiberglass tape and epoxy. There are two splices in the panel. Both splices are hidden under the seats, so there is no need to bother with scarfing the plywood joints. Simple "butt blocks" are glued over the top of the joint, held in place with temporary screws until the epoxy sets.


At the bow, the panel has to twist from near horizontal to vertical

It's hard to believe that plywood can actually do this, but it can.

The drill starts out much the same as before. Cut out an oversized panel and clamp it to the boat, slowly and carefully bending it into position so it can be traced to actual size and then be installed.

So first we clamp it in place at the aft end, making sure we overlap the lower panel, stringer, and the aft panel.

Then we work our way forward, applying more clamps and carefully and evenly apply pressure to the panel.

At this point I noticed that the panel was riding quite hard on the front, lower edge of the stem. I forgot to take a photo, but you can see what I'm talking about in this diagram. I had to remove the panel and plane off some additional material in this area until the panel fit properly.

Keep working your way forward. Avoid using clamps between the panel and the stringer. Quite a bit of force is required to bend the panel. The stringers will deform under that much force. I mostly used spreader clamps between the building jig and the panel to press it into place. Once the panel was in place, I added clamps to the stringers to pull the panel in the final fraction of an inch.

Another shot of the spreader clamps.

Finally the panel is in position.  Now trace around the lower panel, the stem, and the stringer onto the garboard panel.

Remove the panel and cut it to the traced profile.

Re-install the panel and re-clamp it to its final position. Stitch the garboard panel to the lower panel. Bailing wire or copper wire stitches work better than plastic ties in this area.

Glue the panel in place and repeat for the other side.

All I have left to do is finish the stitch and glue fillets and tape, and add the butt straps.