|Making the Tyvek Sail|
|By Bill Wallace|
As you travel around near where you live, keep your eyes open for a house being built. The odds are that, after the walls have been sheathed with plywood, but before it has been covered with the finishing surface of shingles or clapboard or brick or whatever, it will be covered with looks like white paper. On the paper, in big blue and red letters, are printed “TYVEK” and the DuPont logo.
Or you may have received things in the mail in a big white envelope that you discover you can't tear open, for it is too tough. And you may see workmen handling chemicals clad in white suits. These too are made of Tyvek.
You can make a good sail out of it, and very easily and cheaply.
In the first place, it is available in great width. What the house builder uses is typically ten feet wide. So there will be fewer seams, and in a small sail, no seams at all. In the second place, it doesn't need to be stitched. Wherever one piece of cloth goes over another, like at a seam or a corner reinforcement, it can be stuck together with tape.
Start by going by where such a house is being built, tell the boss you want to make a sail, and ask him to sell you some material. Odds are he'll be interested, and will give it to you.
You're going to get a sail that has blue and red advertising on it, but it is a conversation piece, and you'll have lots of fun talking about it to other sailors, and they will come away convinced of what a clever fellow you are.
You will need to go by the hardware store and buy the tape. What you want is found in the garden shop, and you will be asking for the tape, sticky on both sides, that is. used for holding down outdoor carpet. Get wide stuff- it can be had as much as two inches wide. And don't be afraid if the material looks like cheap paper, that might rot. It is mighty tough, designed as it is for the job it does...
While you are there pick up two grommeting kits, one for small grommets to attach slides or spar lashings, and another for larger grommets, for corners.
Now plan the sail. For this first sail, let's not have battens; they would complicate things a lot. Draw a picture of it, and figure out if you can make the sail without a seam. Remember, as you draw it, there will be curve to the luff, to. shape the sail. And also, at each edge the sail will be two inches wider, for the taped hem. If you do need a seam, plan to use the edge of the material at the leach, and run the seam parallel to the leach, as in the sketch. Located in this way the force across the seam, tending to pull it apart, is kept at a minimum.
Let's make the leach and foot absolutely straight, unless the foot is to be attached to a spar. But any edge attached to a spar needs to be curved in order to get shape into the sail. The deepest part of the curve, for a reasonably stiff mast, ought to be one third of the way up the luff from the tack, and its depth should be one inch for each five feet of luff (or foot). By the way, for now let's call that point “D” for now. More about it later.
Now you need a gym or a dance floor, or something like that. You can guarantee the owner that you will not harm it. And you and your helper, if you have one, will for sure need a set of knee pads, like volleyball players and flooring people use, or you will come away with sore knees.
Be sure the floor is really clean, and not dusty. Lay out the material, and cut it roughly to shape, leaving maybe a foot of excess along the luff and foot. Now lay it down again and use bits of masking tape to hold it stretched out. If your sail is to have a seam, stick down only the large panel. Do not, by the way, use a lot of force; you don't want to stretch the material. Now apply the tape to the edge where the seam is to be. This requires a lot of concentration, and is high precision work; take your time. The tape is really sticky; mistakes are hard to correct. Do not stretch the tape; if you do you will get a puckered seam.
Now get the next panel handy, peel the backing off the tape you have already laid on the other panel, and attach it. Also tricky.
Tape down what you have on the floor. Remember, minimum tension, just enough to hold it smooth.
I hope you were able to find a long, flexible batten, and also a long straightedge. With a little ingenuity and much cussing I was able to make do with an eight foot by one inch strip of aluminum that you can find in any hardware store, but maybe you do better than that. Draw straight lines for the foot and the leach, and also straight lines parallel to them and outside them by the width of the tape.
Locate Point D and mark it.
For bending the batten and holding it in place so that you can draw the curve of the luff, you can use. bricks, cans of paint, heavy books or lots of light ones. But be wary of this: the batten will tend to bend much more at Point D than elsewhere if you just pin it down at head, tack, and Point D, giving you a curve the is not fair. The batten wants to be bent outward just a little bit more, halfway between Point D and the corner. Do it.
To do a perhaps better job than you can do by eye, you might want to mark a couple of more points on the curve. Try this. Halfway from Point D to each corner, measure out from the straight line a distance equal to 3/4 of (or .75 times) the distance you measured out to find Point D. This will give us a really good approximation of an arc of a circle, in curves of the dimensions we are using.
Draw the curve. Draw also a line, like before, outside it a distance from it equal to the width of the tape.
Now you have the choice of attaching the tape to the edge and then cutting off the excess Tyvek, or cutting along the pencil line followed by taping. I say cut first. This can be done best with good, big, sharp scissors.
Tape the sail back down onto the floor. It now does look like a sail, doesn't it?
Apply tape to the edges. Getting it smoothly onto a curved edge will make you really appreciate the knee pads.
The next to the next step will be pulling the backing off the tape and folding it over. But this will produce an unsightly and hard to work with lump at each corner where the tapes overlap unless we prevent it.
Measure the angle at a corner. This is shown as angle C on the drawing. You want to cut off the tape so that the angle you are cutting is half this. These angled are shown on the sketch as angles A and B. Suppose the angle is seventy degrees: divide this number by two. Thirty-five degrees out from the corner, along the edges, is where you mark a line- shown on the sketch as a dotted line- and make your cut. The drawing may make this bit more clear.
By the way, do not cut tape with the scissors, if you can avoid it. The adhesive will gum up the blades. in no time. The right tool is an something like an Xacto knife.
Now do this slowly. You are going to peel the backing off the tape, and fold it over to make the hem. Once again be sure that there is no dust or dirt around. Do not peel all the backing off at once. Peel it back maybe three feet, fold and stick down, peel off more and stick down more....
You are going to be delighted, at this stage of the game, to find that the luff is really easy, in spite of the curve. And the corners are really neat, because of what you did in the previous step.
The corner reinforcements are no big deal, but they are a lot of nit picking work. Make them triangles- probably three at each corner will be enough- each one bigger than the next, and each one oversized along the edges of the sail. Cover them completely with tape, and stick on the small one, then the next one, then the largest. Then cut them to size with the knife, bang in the grommets and round the corners.
Reinforcements are in order at each point where you are going to put in a lashing or attach a slide. Two strips of tape, side by side on the material, will give you a strip three or four inches wide, and you can cut it into three or four inch squares. Cut the corners slightly round, or they will tend to come unstuck, and bend them around the edge of the sail, the diagonal along the luff, forming triangles. Cut your holes and bang in grommets through the three layers of material and three layers of tape.
If you want reefs or a headboard, use your imagination and experiment.
Now you have a sail, and it is stronger and will set better than you think, by a lot.
And now be sure that you haven't left anything sticky on the floor of the ballroom- you will want to use it again. Masking tape leaves little goo behind it, but be sure.
Take pictures of your boat sailing under your creation, and give one to the guy who gave you the material, and also one to the guy who runs the ballroom.
A Few Cautions
You will hate the sound of the sail luffing- it sorts of makes a rattling sound, it doesn't sound like a sail at all. But you will grow accustomed to it, especially as you check your bank balance.
Don't attempt to strengthen this sail by running the seams and edges through a sewing machine. The stickum on the tape will gum up the needle immediately. If you really want to sew the seams, make them a lot wider than the tape and sew through the Tyvek, but not through the tape. Any batten pockets you may want should probably be stitched.
The material is rather stretchy. It isn't as bad as the light nylon they use to make sails for boats like a Sunfish, but it is nowhere nearly as inelastic as Dacron. When it is blowing hard the sail will get slightly more full.
It turned out that the mast I made was a lot bendier than I had expected, and in any breeze at all the sail looks lousy- although it sure does drive the boat. On my next sail I am going to move Point D farther up the luff and make the curve deeper. Likely you will do something like that, too.
From making the first sail you will learn a lot about making the next sails better and faster and more easily. And you will probably want to start by calling up DuPont and asking for sample materials and prices. They make the material in a lot of different weights and textures, and different widths. But you'll have to buy a lot of it, probably a roll of at least a hundred. feet; it is still very cheap, however.
I have no idea how big a sail can be made in this way and still not blow apart. Bernie Wolfard writes of a 40+ foot schooner with Tyvek sails as big as 300+ square feet. Reinforcements could be bigger, seams could be made of two widths of tape, etc. And it is a truly minor disaster to have such a sail blow apart, most of the time. Have oars or a motor.... This is going to be cheap and fun and interesting. Set about it.
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