Sail Cloth Information

Sail Cloth Information


Many of our customers come to us
to talk about sails and can
quickly become confused when we start talking about different types of
Dacrons, laminates, taffetas, etc...



So we’ve put together this guide
to help educate you about the various components
of the cloth so the next time you talk to a sailmaker
you have a good working understanding of what the
various cloths do and why it matters to your sail.

In the sections below we'll be using terminology that may be new to you. That's ok. We've assembled a mini textile dictionary that you can open in a new tab and refer to. If it's still confusing feel free to contact us and we can explain it to you differently.

Why do I need a new sail?

When your sail was new the Sailmaker designed a shape that provided good power and control over a variety of conditions in a variety of sailing areas. Over time your cloth has deteriorated by elongating and losing it’s elastic recovery to point where the draft has likely deepened significantly and moved aft. This actually tends to power the boat up and make her harder to control often resulting in increased heel and a less comfortable experience. When trying to sail to weather you are also loosing pointing ability causing you extra tacks and a longer trip to your destination. Additionally as the fibers deteriorate they tear easier and the cloth becomes more brittle. Multiple repairs to the sail begin to increase the amount of problems you have with a sail since the patches are made out of new un-degraded cloth.

Why do I care what sailcloth I use, Dacron is Dacron right?

There are several different grades of Dacron cloth on the market ranging in quality of less than OEM to far superior cloth.   Generally cloth falls into one of 4 categories, sub OEM, OEM, Standard Cruising and Premium. With new sails you are going to see benefits such as less heeling, better pointing and easier boat handling. The better the quality of the cloth the longer it will hold the new shape that you’ve paid for plus some of the top cloths have built in UV resistance to help the sails last even longer to prolonged UV exposure before losing their strength. As a side note, untreated Dacron looses approximately 1/2 of it’s strength in 6 months of UV exposure. So usually for a fraction more you can get a sail that will outlast the cheaper one by a signifigant time frame.

What about using Laminted sails vs Woven? They're really just for racers right?

Actually no. Even with all the new finishing technologies and better stretch resistant yarns around to make better Dacron the basic process is still the same. The looms rock warp yarns up and down around fill yarns. Most wovens are made from polyester (Dacron is a trade name for DuPont’s version of Polyester) that was introduced back in the 50s to replace cotton. Over the last 60 years wovens have become a lot stronger and more durable resulting in extremely reliable sails. This makes them ideas for cruising sails. They became so good that the miter cut sail from the 50s & 60s which were designed to make up for poor bias stretch in Dacron cloth, have become completely obsolete.

Laminates are made by bonding together layers of different materials to form a sandwich. A simple laminate will consist of an open scrim of fibers with a layer of film bonded to each side. More complex laminates lay pieces of carbon fiber, Kevlar, twaron, spectra, etc. between two layers of scrim resulting in sails that resist elongation better than all other wovens with the possible exception of Hydra-Net (woven spectra).  Their main downfall is the durability and abrasion resistance of the scrim. Cruising laminates address this by placing layers of Dacron taffeta on one or both sides of the laminate. Additionally they are signifagantely lighter than wovens making it much easier for sail handling, folding, etc…

While laminates make great sails even for cruising boats they do carry some downsides. The biggest is their cost. They start at about the price of premium Dacron and go up from there. Additionally based on what sailing you’re going to do there are other issues that we can discuss with you to determine if a cruising laminate is the right choice for you.

What is Crimp?

When a cloth is woven the yarns ‘snake’ over each other to create the weave pattern. When the cloth is pulled (by having wind in the sail) these crimped sections will straighten out resulting in initial stretch. In modern sailcloth construction the manufacturer has machines that pull the cloth tight during the finishing process to get the initial stretch out of the cloth, this way there’s no longer a need for a loft to ‘pre-stretch’ the cloth before cutting it into panels.

Should my sail be Crosscut, Radial or Miter?

We’ll cover Miter cut sails at the end of this section.

For starters, a Crosscut sail is like most cruisers are used to. The sail has large broad seams running fore and aft where the panels are joined together, usually using zig zag stitching.In a higher quality sails the seams are taped together using special basting tape and then sewn with 1-3 rows of 3 step zig zag stitching to hold the panels even more securely together. The number of rows of zig zag is determined by the size of the boat & sail. You can count the number of panels used to construct the sail by starting at the top or bottom and counting them as you go up.

On the other hand a radial construction sail actually has the seams and the cloth oriented along the load paths of the sail which results in a triangular shaped design as the smaller and more numerous panels ‘radiate’ out from the 3 corners. Since the panels are flat and sails are not, the only place we can create the shape of the sail is at the seams. Therefore, a with its much more numerous seams, we can spread the shape of the sail over the many radial panels actually resulting in a smother shape to the airfoil generating better lift. However, this comes at a price, radial sails use 25 – 30% more cloth and require more work to sew the seams resulting in a more costly sail. This is why you generally will only see radial sails on very large cruising boats, race boats or the cruisers who have decided to make their sails out of Hydra-net (the longest lasting sail cloth we’ve found).


CrossCut Sail

Radial Sail

So, the choice of crosscut vs radial really depends on the cloth and how you want the sail constructed. In the weaving process of traditional Dacron cloth the warp fibers running along the cloth are bent around the fill fibers that run across the cloth. Therefore, fill fibers have less crimp so this cloth type stretches less across it’s width than is does down the roll of a same length of fabric. In most Dacron cloths the manufacturers take advantage of this by making the fill yarns as much as 400% larger than the warp yarns for even more increased elongation resistance.

Our suppliers also weave what’s called warp oriented cloth or radial Dacron. In this cloth, they use larger warp yarns and smaller fill yarns to ‘orient’ the strength of the cloth down the warp of the cloth. This is done in most cases to make radial Dacron sails.

So the net result? It depends. Our recommendation is generally for bay sailors and coastal cruisers to go with crosscut Dacron. For those going on extended cruising, well come in and talk to us and we’ll tell you what we think you should do after we hear about where you’re going and the type of sailing you are doing.

Earlier we mentioned Miter cut sails. Miter cut sails were a unique design. They divided the sail into two sections separated by a seam running from the tack to approx 1/2 up the leech. Each section then had multiple panels who’s seams ran from the foot to the miter seam (for the lower section) or from the luff to the miter seam (upper section). This was done to combat a problem that cloth manufactures had in the 50s & 60s where the bias stretch was so bad it would leave sails blown out in just a couple of seasons. Since then however there has been major advancements in the yarns, the strength and tightness of the looms, and the finishing chemicals and process that has so dramatically reduced bias stretch as to render this design as obsolete. There are still sailmakers out there making these sails and touting them as required for today’s cloths, but this is simply a marketing tool.

But, all the load can't exactly follow the yarns, can it?

No they can’t. As mentioned in the section above, loads radiate out of the corners and are concentrated at the edged. But with so many variables there is a fair percentage of stress that is ‘off threadline’. This is where the bias stretch resistance is important. To reduce the effects of bias stretch the manufacturers lock the warp and fill yarns together, so bias loads have a harder time moving the weave. This is achieved by making the weave as tight as possible by compacting and heat shrinking. Hold a handkerchief up to the windows and compare the weave to a 100x magnified piece of cloth. You’ll see the handkerchief has tiny pinpoint of light thru it where the sail cloth doesn’t, this is due to the tighter, heat shrunk weave.

To further stabilize the cloth and reduce bias stretch cloth manufacturers impregnate their cloth with a resin finish and other chemicals to bond the warp and fill together. On some lines of cloth the finishing process includes a UV inhibitor which helps the sail cloth retain its strength longer as the UV slowly degrades the cloth (think a sunscreen for sails).

For laminate sails, they place an X-ply yarn in the material. An X-Ply yarn is one that is laid across the bias direction of the cloth providing stretch resistance to the bonded material. Based on the materials being used, this yarn can be anything from polyester to carbon fiber.

What about Spinnakers?

Most spinnakers are made from woven nylon because it has good tear resistance. Nylons come in different families ranging from .4Oz to 2.2Oz. However you have to be careful as these numbers do not directly relate to the cloth weight. A few large boats and Code 0 sails (upwind spinnakers) are made out of polyester or a laminate material. If you’re interested in one of these contact us directly to discuss what options there are for you.

I get Nylons and Polyester, but where does Kevlar, Twaron and Carbon fit in the mix?

Polyester is still the best all around fiber for most woven and laminated cruising fabrics. It’s durable, strong and available at a reasonable price. However, since the introduction of Polyester many new fibers have become available such as Kevlar, Pentex, Spectra, Twaron and Carbon. In more demanding application, such as racing and long distance offshore cruising, the strength of these fibers can create a far superior fabric.

The chart below shows you the modulus of various fibers used in sail cloth. Remember, the higher the number the less stretchy. You can see that Pentex is 2.5x stronger than polyester, and Twaron, Spectra and Carbon are multiples bigger than that. The use of these fibers in laminated and woven sailcloth has led to progressively stronger and lighter sails. However the downside of this performance is a higher cost and in some cases a shorter sail life.

To Reduce this problem many high performance laminates and wovens use a mix of several of these types of fibers, each of which contributes its own attributes to the final fabric. Some cloths use Twaron warp and fill yarns for their stretch resistance and then blend in Spectra fill yards to provide better tear and flex strength. Other wovens use a polyester base with Ultra PE (spectra) blend to create a woven fabric with a softer hand than laminates but with many of their stretch resistant properties and the long life of a woven polyester (Hydra-Net).

So, sailcloth really does make a difference?

Absolutely, quality cloth is always a good investment in terms of performance and durability. It is usually worth buying the best quality cloth that’s within your budget. Contact us and we can have a discussion with you about what’s the best type of cloth and sail construction for you boat. One of the most common mistakes we see people make is to compare one of our quotes to a made in china sail using a lesser grade of fabric. After they’ve bought the sail they often come to us later buying the rest of their sails from us and wishing they could replace the one they purchased elsewhere.