Simplifying the Sail Buying Process - Part 2 - Panelled Sails

By far the majority of sails sold across all manufacturers on a global basis are panelled sails. That is to say, sails that comprise individually engineered sections (panels) which are sewn, glued or bonded together to form a complex curved shape, precisely according to the sailmaker's design programme.

Most Sailmakers have their own brand name for the different construction methods they use. This can make things pretty confusing for the buyer who is trying to draw comparisons between the products on offer from different sailmaking businesses in order to be able to make informed decisions regarding a purchase.

Here, we're not trying to compare the various advantages or disadvantages of any one sailmaking brand, but rather to explain the design thinking involved in the construction of panelled sails and to familiarise you with some of the brand names of the materials used in their construction.

Panelled sails can be constructed from a variety of different materials and in a number of different ways. The most frequently used panel shapes for upwind sails are "cross cut" and "tri radial". Almost all downwind sails are built using "tri radial" panel layouts. Cross cut panelled sails are mostly manufactured using woven polyester which is often referred to by the trade name: "Dacron".  Tri radial sails are most commonly made using a laminate of mylar film and polyester. This is sometimes sandwiched between layers of very lightweight woven polyester (taffeta) for added durability.  Spinnakers, cruising chutes and other downwind sails such as Code Zeros are almost always panelled and the material used is most commonly (but not exclusively) some form of woven nylon or polyester laminate.

The sailcloth manufacturers that you are likely to come across when talking to your sailmaker include (alphabetically) Bainbridge, Challenge, Contender  and Dimension Polyant. Their ranges all have various styles of woven polyester, Nylon and mylar laminates. Common brand names include: TNF, AP, Fibremax, Marblehead, Durasail, Touring, Nordac, Airex, Superkote, Superlite, Dynakote, CZ and ZL. 

Cross Cut Upwind Sails pros and cons:

The cross cut sail gives the sailmaker the ability to make an inexpensive sail out of good quality materials. Most woven polyester is made stronger across the roll than along it so Cross Cut makes the most of this material's characteristics.

The downside is that the loads from the corners tend to run across the bias of the cloth in certain areas of the sail. The bias is stretchier so the sail does not hold its shape well unless the material is extremely high quality. It's so important to talk to your sailmaker about the quality of the materials he has selected for your sail and the reasons behind his decision making process because not all woven polyester is the same. The type and weight of polyester used, "tightness" of weave and the amount of resin used in finishing all affect the stretch characteristics and durability of the material. In general a tight weave with low resin finishing content is best for durable cruising sails. High resin content helps to reduce stretch on the bias so is good for higher performance sails but when the resin breaks down the material become stretchy and less durable.    

At Ultimate Sails, in our Cross Cut sails, we have developed a method of 'rocking' the panels around the 'catenary curve', which is the curve between the head and clew of the sail, along which the loads run. This reduces the amount of load on the bias of the cloth and so the sail holds its shape for longer, thus increasing its lifespan.

Tri Radial Upwind Sails pros and cons:

Generally speaking, one would not often expect to see a Tri Radial sail made from woven polyester, because of the characteristics of this sort of material, as detailed in the section above. That said, in the interests of cost efficiency for owners, the rules of some one-design classes do encourage the use of Tri-Radial polyester sails.

Tri Radial layouts in mainsails and headsails are more usually used in conjunction with laminate materials which are stronger along the roll rather than across it. Laying the panels in a radial layout reduces to a minimum the loads on the bias.  Also the sail can be specially designed with with different weights of material in the high load / low load areas. The result is greatly improved performance through better shapeholding and lower weight aloft. 

It is a commonly held misconception to assume that panelled sails do not meet the needs of the Grand Prix race market. In fact, many 'moulded' sails are produced using a complex panel design and engineering process.

Downwind Panelled Sails

The downwind sail design pictured here uses a 'Tri Radial' panel layout. Bonded seams radiate out from the corners of the sail to spread the load across the sail. The precise layout of the panels, the dimensions of the load patches at the corners on each sail, the cloth weight and tape weight will vary subject to the purpose of the sail and the sail designer's specification.

Many Grand-Prix race-boats will have several designs in various cloth weights and sizes in their sail inventories but unless you have an unlimited budget your sailmaker will advise on which design and cloth weight will best suit your purpose.

We’ll be looking at the various materials used in membrane sails in the next instalment, but please do not hesitate to pick up the phone if you have any questions in the meantime.