The Handsewn Sprits'l




Demonstrates how I made a small Spritsail (around 40 sqft) out of natural materials.

I wanted a sail for my little scow
and while I do have a sewing machine I wanted to give it a try at hand sewing one. I've never made a sail before so I decided to go with a Spritsail because they're said to be the simplest to make and use.

After making this I'll deffinately use a machine whenever I've got one.

Some illustrations were borrowed from the book "The Sailmaker's Apprentice" whose illustrator was Christine Erikson.

Step 1: Materials

I gathered the necessairy instructions, dimensions, and other information from the book The Sailmakers Apprentice ($15-20 from amazon)

The materials for this project are:

Fabric - 4.25 to 6.1oz cotton with the tightest weave you can find ( I just used something called super muslin?) You could go with pre-treated cotton canvas from a marine supplier, but I don't of know any that do canvas.

Thread - I used a thick cotton thread, traditionally a reddish-brown was used for the seams and white (or roughly the same color as the fabric) was used for the patches. Also you could use synthetic thread (like polyester) on natural fabric, but you can't use natural thread on synthetic fabric.

Sailmakers needles - they usually come in a pack, just use the appropriate size for the thread you're using. Do not use the goofy shovel-shaped things you find in cheap packages of hand-sewing needles. Real sailmakers needles are very strong and have a triangular shape. I think I used a number 16 for all the seams and a number 9 for roping, I don't have any of them labeled.

Sailmakers palm (for really light work I use a little peice of leather around my middle finger)

Sailmakers hook - you can buy a real one, maybe they're better, but I just bent a large needle and threaded it with waxed twine then tied that to some cordage.

Rope - 25 ft of 1/4" manila and some cotton twine

Beeswax - I found some great stuff in Hobby Lobby, it comes in a one pound block.

some pins or nails to stick in the floor

enough floor space to lay out the whole sail, you could peice it together but for a beginner's project it's best to lay the whole thing out.

fabric pencil


batten - some thin material you can bend to trace off the foot curve, you could also use webbing.

straightedge - yardsticks work

carpenter's square - big metal square uaually around 18 inches on one side and 24 or so on the other. it helps when marking false seams.

To draw out your overall plan:

large peice of paper, 11x17 graph paper is usually easy to find

An architect's ruler, it's the funky 3-sided ruler with scales marked 16, 3, 1&1/2, 1, 1/2, 3/4, 3/8, 1/4, 1/8, 3/16, and 3/32.

compass, not the kind that points north.

Step 2: Make a Plan

The first thing to do is to figure out exactly what you want to make.
There's a lot of mathematics and physics involved in designing a sailing rig properly, so I'm just going to present what I've made and leave you to decide what's right for you. For my boat I designed a low-aspect, boomless, Spritsail. The dimensions-ratio formula is only for a low-aspect spritsail, other sail types will be different.

It's ok to make several drawings with each only presenting certain information, or just noting things without drawing them. Do whatever works for you, or get someone that enjoys drafting to help you make your plan.
To sketch out your sail you need to know some basic measurements. For example I knew I wanted the luff, the side next to the mast, to be 6 feet tall. So, based on a formula in my book, I can figure out the other measurements.

the formula, followed by my measurements.

luff - 1.0
leech - 1.365
foot - .944
head - .666
diagonal peak to tack - 1.555
diagonal throat to clew - 1.222

luff - 72 inches
leech - 98 1/8 inches
foot - 68 inches
head - 48 inches
diagonal peak to tack - 112 inches
diagonal throat to clew - 89 inches

knowing all these I used the 3/32 scale on my ruler and sketched my outline.
Start with the luff. then set the compass for the throat/clew diagonal and mark the arc. measure the distance from the tack to the clew and mark where it meets the arc. Set the compass for the head measurement and mark down that arc. Then measure from the clew to the head and mark where it meets the arc, then connect that point to the throat.
Next mark your foot curve. Again consulting my book I made a foot curve 2 inches, the deepest part of the curve being directly in the middle of the foot.

The next thing to decide is how you're actually going to sew it together.
For the edges I went with cut tablings(I'll explain it later), 1 1/2 inches on the foot, luff, and head and 5/8 of an inch on the leech. To draw these on measure in from the edges.

How wide will the cloth between seams be? Usually this is dictated by the width of your material, but on such a small sail there's room to tinker. Most commonly cotton cloth is 36 inches wide, mine however was 44. I decided to make seams every 12 inches, I had to sew some false seams which complicated things a bit. The seams were 1/2 an inch wide. Draw these on your plan.

Will you be adding reefing points? I know it's pretty excessive and unnecessairy for a sail this small. But if you do, generally you'll want these to reduce the sail about 30%. For mine they would start 21 1/2 inches up from the tack and follow the curve of the foot.

Next thing to do is to design your patches. After looking at some different types I decided on traditional looking curved patches. A basic guideline is that patches should be 1 inch long for every foot of sail edge it is applied to.

Then mark where any metal or other hardware will go. Along the luff I've got eyelets every foot. There would be eyelets in each reef point. There is a brail eyelet, 50 inches down from the peak in the leech.

Step 3: Lay It Out

Start by setting a line for the luff, just put a pin in the floor and stretch a line of string to another, 6 feet apart. In the same way you made the drawing you'll need to lay out the pattern for the sail. If you havn't got two tape measures just measure the string from the last point you laid down to the right length and then measure the diagonal with the tape to get the location of the pin. Measure 1 and 3/8 of an inch out from the leech and set another line, going just past the head and foot.
Once the sail outline has been set up on the floor, lay down your material. Start with the selvage edge against the outer leech string you laid out. Roll out the fabric until it goes beyond the head and foot at least 6 inches. Then cut the fabric and lay the rest along the edge of what you just laid down.
Mark the Leech with a fabric pencil.

Using a carpenters square measure into the sail from the leech and mark a line from head to foot at 11 and 1/2, 12, and 12 and 1/2 inches. Fold along the 12 inch mark so that the 11 and 1/2 and the 12 and 1/2 inch marks meet. Put pins in along the seam.
The other false seams will be measured, folded and pinned in the same manner.

Where the two peices of fabric come together make a 1/4 inch hem and overlap the two peices 1/2 an inch, pin them together.
Now that you have one big peice of fabric lay it over the outline and mark the other 3 sides.
For the bottom mark the straight line you laid down, then from the center measure down 2 inches. Use a batton or webbing to create a smooth curve.

Mark the space between the leech and the outer line at 1/4, 1/2, 1&1/4, and 1&3/8. Cut the material from the sail at the 1/4 inch mark. Then make a strip from the excess by cutting at the 1 and 3/8" mark. Fold the strip on the marks and you should have a 5/8 inch strip with two 1/4 inch hems. This will be the tabling for the leech. Use the fabric pencil and mark the sail and strip with the word leech.
In the same way measure out from the luff 1/4, 1/2, 2, and 2 and 1/4 inches and mark the lines. Cut the strip from the sail at the 1/4 inch mark and then at the 2 and 1/4 inch mark. Fold the strip on the lines and you should have a 1 and 1/2 inch strip with 1/4 inch hems. Label the strip and the sail Luff.

For the Head and Foot measure out 1/4 inch and cut off the excess. When you unfold the false seams the cut edge of the material will be jagged. Just move towards the center of the excess and draw a straight line, keeping the fabric weave going the same direction as on the sail. From this line make a strip 1 and 1/2 inches wide with an extra 1/4 inch on either side to fold under as a hem.

Step 4: The Flat Stich

In stitching I'm assuming you're right handed, for you southpaws just do everything in the opposite direction. Adapt and overcome.

The first thing you'll need to sew is the seams. To do this use a flat stitch.
Attach the sailhook to something at your right about the same height or slightly lower than your thigh. Sit facing slightly away from the sailhook anchor, just out of reach of the hook, don't want holes in your leg.
Take an end of your thread and draw it out about the distance from your work to where your hand is extended, double it. Cut off that peice of thread, thread your needle, then pass the thread over beeswax until it's well coated, the two peices should stick together.
You'll be stitching from right to left. Start just outside of the seam, insert the needle and bring it up through the inside of the seam. Leave an inch or two of the thread sticking out and sew over it as you progress. When you run out of thread, just leave an inch or two, rethread your needle, start about where you left off and twist your two ends together, then sew over them. repeat. When you get to the end of the seam pass the needle back through the stitches (about a needles length) and then cut off the thread.

Step 5: The Round Stitch

The next thing is to sew on the tablings.
I've found it easiest to pin everything in place and then take out a few at a time as I go. But do whatever you feel comfortable with.

The tabling will need to be staggered around the sail to prevent too many layers piling up on top of each other.
Start the luff tabling 1 and 1/2 inches from the bottom and go up to the throat. Butt the head tabling against that and continue around the sail. For the head and foot just make sure that the tabling doesn't end on top of a seam.
For a more traditional look you could even cut the head and foot tablings in 12 inche strips, with a 6 inch peice at each end.

To attach the tabling to the sail on the outer edge I sewed it on with a round stitch. Work from left to right, with the hook on the right. Just take your two peices and insert the needle up through them, repeat. The tension of the thread in this stitch is much less than with the flat stitch. Shoot for 10 to 12 stitches per needle length. Starting, ending, and connecting two peices of thread are the same as in the flat stitch.
When you get to the end of the peice of tabling you're sewing, just continue going around it and switch to a flat stitch.

Step 6: Patches

The main thing about patches, no matter what shape you make them, is to make sure the cloth direction is all the same, or perpendicular.

For this sail all patches have 3 layers, except the reef points which only have two. Each patch is an inch smaller on all sides than the next largest in it's group. The largest goes on top, the second largest goes on the bottom and the smallest in the middle. (my inner patches are kinda goofy in shape and size because the largest ones were so small.) I measured the straight edges of the patches and then free-handed the curves, as is probablly quite noticable.

All layers of a patch will need to be sewn at once, so you'll probablly want to mark the largest patch so you know where the inner patches are. Use a round stitch on the outside sail edges and a flat stitch on the inside edges. Once you go around the largest patch, flat stitch the remaing patch edges.

Step 7: Roping

Approximately 25 feet of 1/4" manila will be needed.

6 to 9 inches of each end on the sail will be pointed. This isn't entirely necessairy, but it improves the finished look.
To do this, create a whipping 6-9 inches from one end (see illustration). Then unlay the three strands down to the whipping. Take one of the strands and unlay the yarns. Use a sharp knife and scrape the blade along the yarn until it is full next to the whipping and tapers down to nothing. Rub this with beeswax and retwist it in the same direction it was. Do the same for the other yarn and then retwist the two yarns back into a strand. Repeat for the other two strands and then twist all three strands so you get a pointed rope end.

This end of the rope will go at the peak.
About an inch from the whipping make a loop for the sprit, mine's about 3/4inch diameter. To do this just double the rope so a loop forms and then wrap thread around the base of the loop. Finish it by wrapping vertically.

Now you'll need a bunch of small peices of thread. Start at the peak and tie the rope onto the corner. Stretch the rope and sail towards the head. The sail will stretch a lot more than the rope. Move about a foot at a time and tie the rope to the sail. Continue around the sail edge to the clew and then cut the rope with enough to make the same length pointed end.

Beginning with the first pointed end you made start sewing the rope onto the sail with a round stitch. For the pointed ends just sew over the whole thing until it's wide enough to only sew through about one strand. Continue around the sail and finish the other pointed end the same way you did the first end.

Step 8: Finish Work

Metal hardware could be used. I made most of mine with twine, thread and rope, except for the brail eyelet-I cheated and just punched a brass grommet on.

The clew, tack, and throat all have cringles. The luff and brail eyelets are small grommets sewn onto the sail. See the illustrations for making a penny-sized grommets out of twine, and for making cringles with one strand of your manila rope.

The becket, or loop, for the sprit can be reinforced by covering it with leather. Take a small strip just long enough to go around the inside of the loop and not quite wide ehough to wrap around the rope and cut two semicircles out of the middle, leaving about 1/4 inch in the middle. Then punch holes along the edges to ease sewing it on, a sewing awl helps here. Knot the thread and start sewing.



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    28 Discussions


    7 years ago on Step 7

    I'm not sure I fully understand the purpose of the pointing. Just to clarify, is the purpose of the pointing just to help tie in or hide the loose end of the rope?

    1 reply
    Dream Dragon

    8 years ago on Introduction

    Interesting work, nice instructable and Kudos to you for even ATTEMPTING to do it by hand.


    10 years ago on Introduction

    i sail optis and they have that exact same type of sprit sail, do you sail anything of the sort? the boat you made looks very similiar to a frosty with an opti sail, is your boat fast? ive made sailing rafts but ive never made a sail that cvomplicated b4, good job !

    7 replies

    Actually I'd never neard of optis or a frosty until now. I don't really know if it's fast, I've only been able to sail it in extremely light winds so far, and the only other boat I sail is a 16' hobie, so there's not much comparison.


    Hi notjustsomeone, DaniusGB is talking about the Optimist Class, a.k.a. Opti. This an international well known categoy, including championships. I think they take part of Olimpics as well. The boats have the same shape as yours, and the mast / sail is the same. May be you took the general desing from a boat you saw previously. Because the similarities (almost identical) cannot be something that just happened. Best regards, Raúl


    Well castro, it was something that just happened. I'd never seen an opti before, not even online or on tv. I took a plan from the 1870's and a plan from the 1930's used what I wanted to, and that's how my hull came into existance. Then I decided to make a sail for it, which came from the book I mentioned in the instructable and there ya go, a world-class boat from a guy without an ocean - go figure.


    I'm not sure where they are getting that your boat looks like the opti, the opti looks like a normal boat shape with a foot of so of the bow cut off so that the very bow is flat. However the sides taper in in a normal "boat" shape, your boat is a punt or scow shap, I have seen the plans you copied from many times on the net and they make a good little boat for simple boating.


    Reply 9 years ago on Introduction

    your boat is much more like the PDRacer a simple sailing box that has it's own website and fanatics.


    Reply 10 years ago on Introduction

    The sprit sail is a very old and widely used rig, that has been around a lot longer than the optimist class. It is hardly fair to claim all boats with a spritsail are 'opti clones'. Great instructible! Has given me some ideas to try out myself... I made a tiny sail for my canoe out of an animal food bag. Only about 1 square meter but works great on a little canoe. Nothing beats the look of days gone by though.


    Reply 10 years ago on Introduction

    well the sail can really be for any small boat i was just saying the boat itself looks like either an opti or a frosty.

    Yeah, I'm also interested in that, but it's hard to find the stuff they used to use. Have you read the Marlinspike Sailor or other books by Hervey Garrett Smith? I wanted to find the tarred marlin he's always talking about, but was never able to. I haven't done much with sailors' arts in a while, unfortunately. I have a great hunk of ebony to make into a fid that's been sitting around for years...

    no, I haven't read any of Smith's books. I learned some ropework in Boyscouts when I was little, and the rest I picked up from various online sources. I really didn't get interested in ropework until I started climbing a few years ago. I think I read somewhere that one or two people started making real sail-quality canvas again, but they're in europe somewhere. as for the marline, I know sells some.


    Reply 10 years ago on Introduction

    Sailrite is a good site. Jamestown Distributors has tarred marlin also. Good site to bookmark if you're involved in any kind of boatbuilding. Also the Woodenboat store has marlin & other odds & ends for boats.


    10 years ago on Step 8

    Holy crap thats impressive! It makes me appreciate how much work goes into a traditional sail. I never realized how involved it was for something as simple as a sprit sail. Thanks for sharing.