How to Put Reef Points in a Sail

(This article was published in an abridged version in the September, 2012 issue of Blue Water Sailing. )

BEFORE setting off on a 9-day trip in October in the Chesapeake, Philip and I thought it might be a good idea to be able to reef the sail. A reef allows you to reduce the surface area of sail catching the wind, which is useful in heavy winds to keep the boat from tipping over and all. (It’s also useful in moderate winds to keep Philip and Heather from getting a wee bit too nervous when the boat goes all tilty. (Yes, that’s a technical term. Tilty. Look it up.) (OK, it’s not. You caught me.) It’s a good thing we did put in the reef, as we used it quite a bit on that trip – see me looking all sporty at right?

I worked in part from instructions in The Sailmaker’s Apprentice: A Guide for the Self-Reliant Sailor by Emiliano Marino. Reef points are covered in about 10 places in the book, and the instructions are very brief and actually quite hard to understand if you aren’t 100% up on the technical jargon. So here’s my version.


  • 1 used sail
  • Spur die kit 5/8 inch – this is the thingamajiggie that allows you to set grommets
  • 5/8 inch grommets, one for each reef point
  • Self-adhesive sail cloth (I suppose you could use regular sail cloth, but it’s so much easier to sew on something that’s already stuck to the sail.)
  • Sail thread
  • Measuring tape and yardstick
  • Something to mark on the sail with (I’m a fan of the disappearing ink pens that quilters use)
  • Scissors
  • Paper to make patterns
  • Sewing machine – my grandmother’s 1950s Kenmore stood up to the test, with the advice of the folks at Sailrite on using a home machine for sail work
  • About 2-3 feet of line for each interior reef point (I forget just how long I made mine)

I hope you’re good at math…

Before starting, the first thing I needed to do was figure out where the reef points needed to be put in. I figured out that the first reef in a sail should reduce the sail volume by 20-25%. Accordingly, I laid out the sail and measured the length of the foot and the luff in inches (114″x360″), and from that calculated the volume of the full sail (pretending that a sail is a perfect triangle, which it isn’t, but it’s close enough):

(114×360)/2 = 20,520

Then, figured out what a quarter of that volume was:

20,520/4 = 5,130

Since we’re dealing with approximates here, I figured that I would just compute the height of a rectangle with the same width as the foot of the sail. While this won’t be exactly 25%, it does fall within the 20-25% range. Accordingly,

5,130 (volume of theoretical rectangle) = 114 (length of foot) x X

X = 5,130/114

X = 45″ = 3’9″

Therefore, the reefs should be 3’9″ above the foot.

Now, this seemed a bit much to me, so I called Jeff Frank at SailRite HQ, and after he confirmed that my math was correct, he gave me a lot more useful advice on the project. In fact, I was very impressed that he spent over a half-hour on the phone with me, walking me through the project. I love SailRite!

Find a big space and lay out your sail

Easier said than done. My dining room floor sufficed. You don’t need the top bit, but do need a space large enough to lay out the sail from the foot (bottom) up to the reef points.

Now, mark the sail

First, I marked off the spaces for the reef clew ring and the reef luff ring (the two outside rings, on the leech and luff of the sail), measuring 3’9″? vertically from the foot of the sail. Then, I drew a straight line two inches below these two points for the rest of the reef points – you want the middle reef points to be below the points on the luff and leach so that they don’t bear any of the load of the sail – all of the load of the sail should be on the two outer points, with the inner ones just holding the rest of the sail from flopping about.

I honestly can’t remember how I figured out how many reef points total there should be. It has something to do with – again – sail volume, but they ended 18 inches apart. They shouldn’t be more than 2 feet apart.

Make patches

You need to reinforce the reef point locations so that they are strong enough to stand the strain. The inside reef points can – theoretically – be reinforced with patches in almost any shape – but I went with the traditional square/diamond shape as it is way easier to sew, particularly on a home machine. They four inches on a side and placed with the corners on the axis, like diamonds. I created paper patterns for the inside and outside reef point reinforcements. For the reef clew and tack, you want to create a pattern that mimics the shape of the sail’s corner patches.

You want to try to keep the patch fabric direction the same as the sail direction so that it all pulls in the same direction; I found this quite difficult, but got it right most of the time by actually drawing Xs on the sail and on the adhesive sail fabric I was using for the patches in the weft and warp directions of the fabric then matching it up before cutting the patch.
For each of the reef points, cut two reinforcing patches, one for each side of the sail. Remember to flip the patterns for the clew and tack points so you get two sticky sides together. Now, you can just stick on the inside ones, but the outer ones – the clew and tack points – are trickier. You need to unpick the sail at the leach and luff reinforcements so you can stick the patches under the reinforcing fabric and directly on the sail.

Now, you’re ready to sew

Each one of the patches should be sewn around the edges. This is actually quite a project on a home machine, as you are trying to force yards of very heavy fabric through a very small space in the machine. (In fact, it convinced me that I really should buy a sewing machine meant for I actually ended up leaving one of the edges on two inner patches unsewn, as I just couldn’t get to them.

What you should do is sew the same side of each patch in order with the widest zig-zag setting, rolling the sail as you go. So, for example, sew the top right edge of each patch, rolling the sail tightly as you go. Again, this part was a byatch of a job. The edge patches are easier, though – just make sure to remember to re-stitch the reinforcements for the luff and leach.

VERY LOUD NOISES NEXT – don’t do this part at night

Now, I love making noise. I also love hitting things (things, not people!). So the installation of the grommets was the FUN part of the job.

First, you want to cut a hole through the sail and patches. While you can make an X, I wanted it to be neater so I cut little holes out with an X-acto knife. I bet this job is much easier with a sharp X-acto, and even easier with a hot knife, but I managed with only a little swearing to make my pretty little holes. You want the holes (or X) just large enough to force the barrel (male part) of the grommet through.

To put the grommets in, follow the instructions on the box or read about it on the Sailrite site. (Dude, I heart Sailrite. They are TEH BOMB.) You should definitely use a heavy rubber, plastic or wood hammer to tap down the barrel with the pointy tool – you can hurt the die kit with a metal one, and it’s WAYYYY unpleasant anyway. Also, don’t forget to rotate the grommet a quarter turn about every other tap (which, when dealing with a big sail, means turning yourself).

Last steps…

Cut your line to the length you want your reef lines to be – I think mine were about 3 feet each, but it has been several months, I’m not at the boat, and so this is pretty much just a guess. Use a lighter or other fire source to seal the ends. Pull each through the center reef points until even on each side, and put a simple knot on either side of the grommet to keep the line from falling out, and, VOILA! You have made reef points in your sail!