2022 Cruising Setup series – N02 – Sails
This month we explore the primary source of power on a sailboat, sails. What to expect out of them, what to look for if it’s time to replace them and the difference between a harbour set and one suitable for extended cruising.
You often hear the expression, “Came with the Boat” when cruisers talk about the gear they have on board but when it comes to your number one source of power on a sailboat, your sails, it’s a description that can lead to trouble. Don’t get me wrong, an old set of sails will get you there BUT one cruising season around the South Pacific, a circumnavigation of New Zealand or a trip up the east coast of NSW and Queensland is equal to ten years (or more) use for a Harbour cruiser as Lyn and I found out the hard way.
The sailmaker we got to do the repairs to our mainsail in Noumea, New Caledonia was most uncomplimentary about our sails. If he had been wearing a collar he would have been giving them the last rights.
We had left to return to New Zealand after a great season away, the wind was well forward of the beam and increasing in strength. We hadn’t even reached the Amedee light yet but I decided to put the last tuck in the main before heading out into open sea.
Now, our mainsail was a beaut piece of kit, “came with the boat”, fully battened and “carefully checked and repaired each season before going off again”, I told him. But there it was, last reef in place, bear away and pop. We now had a two piece mainsail, “B___er”.
The sailmaker, being a clever sort of guy, asked the obvious question. How long have you had the boat? Ten years. Hmmm. He fixed the rip anyway and off we went again. So there we were, back in NZ and looking into new sails.
So just when is a sail not a sail any more? According to Craig from Willis Sails in the Bay of Islands our’s should have been put to rest a long time ago. “For a cruising sail it’s not just about creating the right shape but also building a sail that will last the distance” he said.
Each time a sail is used, tacked, gets wet etc. the sail stretches ever so slightly. On a harbor or gulf cruiser this isn’t so much of a problem but on extended coastal or particularly an offshore cruiser where the sails are up for extended periods, the wear and tear is multiplied a hundred fold.
So why do sails loose their shape over time? A sail is basically an aerofoil so the deepest part of the shape should be about one third of the way back from the luff. This shape is generally achieved by stitching flat panels of cloth together with the shape created by giving the cloth a bias, or a curve along the sewn edge. The shape of the curve dictates the shape of the finished sail. On a large Dacron Genoa, like ours, with a foot measurement of 8.5 meters and panels of 1.0m the maximum bias is only about 2cm. It only takes a very small amount of stretch to start moving the shape aft and as you do so the efficiency of the sail reduces.
This may not be a problem if you only ever sail with the wind aft of the beam, great if you are sailing west in the trade belt, but sooner or later the wind will head you and whether you like it or not you are on the wind. Two things happen with a saggy baggy sail, the sail will produce less forward power and more sideways power. So instead of going forward the boat heals and increases it’s leeway. Because there is no power to drive you through the waves the boat will sit there and hobbyhorse leading us back to the reason cruisers don’t like going to windward.
So we have now decided our sails are not sails at all just great big pieces of fabric that catch the wind and by more good luck than management the boat still goes forward. What’s the next step? Yes I know it’s new sails but, how, where, what and how much?
Unlike racers we can’t afford to replace our sails every year, with the prospect of many miles with the sails up we want a set that will last but one that also provides power. There must be a compromise here and to find that we have to look at a number of things. Firstly what are we, or should we be, expecting out of our sails and what products are available?
Your average long range cruiser and that’s coastal as well as ocean is looking for a balance between, power, longevity, maintenance cost and purchase price. So let’s look at the options and discuss their various strengths and weaknesses.
Dacron:- On the Plus side:- Reasonable price, easy to fix and maintain, will last for about 8 to 10 years.
Down side:- Sail shape will degrade significantly over time, material is heavy, protected from UV by a resin that breaks down over time.
Mylar:- Dacron/ polyester mix, holds shape better than Dacron, sails can be specifically designed allowing for different weights in stress and non stress areas, can be radial cut, effective life 6 to 8 years. Lighter than Dacron. Less maintenance over time.
Approx. 25 to 30% more cost than dacron.
Exotic:- Moulded and Laminated sails. For example Doyle’s Stratis sails. The filter down effect from the Americas Cup. Constant shape over life of sail, significantly less weight aloft, lower maintenance costs again. With a cruising “Taffeta’ coating, good UV resistance. Effective life about 7 -8 years.
Downside:- Cost, approx. 35% on Mylar.
If you are totally budget driven then a new suit of Dacron sails is your answer but be careful with your specification, not all Dacron is equal. Weight, weave density, resin coating and the thread used all make a difference.
If we want a little more performance than Dacron can offer then next we need to look at where our power is coming from, Fore sail or main? What’s our configuration? If we are headsail driven then this is where most of our power is coming from so a little more spent here will make a big difference to performance. Each time you step up from one material to the next you will get an increase in power but the downside is longevity and cost.
Another factor for head sails is their ability to reef. If you have a roller furler on your Genoa, will it hold its shape with only half the sail out? In a brand new Dacron sail, probably in the short term, but even with a rope or foam insert in the luff to take out the shape as its furled, over time the sail will stretch and loose its shape this will be compounded in a furled sail.
We talked earlier about Mylar sails and radial cut. Take a look at your foresail when you are hard on the wind. Most of the loads are radiating out from the corners. With Mylar the shape can be cut to run with these lines of stress with the weight of the fabric matched to the load it will carry, as the loads reduce the further from the corners the weight of fabric can be reduced, saving weight and cost, giving a better shape and therefore more power. The downside with this is the stress points are always in the corners and as you furl your radial cut Genoa the original stress lines for tack and head disappear into the furled portion of the sail. With good sail design reefing points can be designed into a radial cut sail but sail shape will suffer and so will the sail if it is furled past these reefing points.
The same applies to a moulded or laminated sail. These sails are constructed by laying down filaments of different materials in a predetermined pattern to match the expected loads on a layer of mylar. This process is done by a huge plotter that runs back and forth across the sail laying down as many as 10 filaments at each pass. A second layer of mylar is placed on top of this the air is vacuumed out and the whole thing heat bonded together. On racing sails the two layers on either side of the filament is usually very light and clear and is really only there to stop the air from passing through the sail, the filaments do all the work. On a cruising sail the films are generally a little heavier and opaque called “Taffata’ and give a better life span to the sail with better UV resistance and less prone to damage from flogging and chafe.
Once the bonded sail has been cured for a week it is cut and stitched and the sail finishing work done.
So back to the question. On a headsail driven boat the first step up is Mylar genoa and Dacron main. The second is Mylar, mylar and the third is Laminated genoa and Mylar main.
For performance cruisers the top option is all laminated.
In a main sail driven boat the sails are more likely to be paired ie all the same material although a compromise may be laminated genoa and Mylar main.
There have been a number of well designed and built cruising boats launched recently and there is a trend towards two roller furlers on the bow, the inner with a 100% or smaller blade, good for upwind work and an outer furler with a larger, reaching genoa. The choice here would be laminated inner and Mylar outer.
So next step get the experts in, have the sails measured and priced, with all the options. Remember though, you get what you pay for and a sail constructed for extended cruising will have more detail and cost more than an equivalent harbor or gulf cruiser.
Specification for a cruising sail.
High Cut for visibility and catching waves.
Wide Seams with three rows of stitching.
Specify “Dabond’ or similar thread
Specify a dark coloured thread, its got better UV resistance and is easier to see damage.
Specify rope or braid corners, these can be led further into the sail for strength. Or webbing reinforced pressed metal compression rings.
Avoid heavy metal clues.
Add layers to chafe points
Double stitched leach protection
Provide velcro pockets for leach tension line.
Reinforcing strap around foil at foot of foil track on the genoa.
Built in foam or rope insert to help keep sail shape when reefing.
Full length battens for better sail shape.
Batten Pocket Reinforcement, make sure the batten is flush with the leach.
Roller cars for the slides at batten points.
Double slide headboard
Loose foot or fixed, ask your sail maker
Reef points. Make your first reef a deep one, then divide the next two equally to
leave you with a main with three reefs only 10 to 15 % bigger than your Trisail.
Double stitch at stress points
Fit all adjustment points in Pockets
Double up on reef point reinforcing
Triple stitch all seams
Reinforce the leach with a series of tapes not just one.
Perfect sail shape for upwind. Notice the aerofoil shape, the deepest draft of the sail is about 1/3rd back from the luff.
Cruising Main sail. Reinforced batten pocket, full length battens. End terminal fitting so the batten loads on the sail not the slide. Teflon strip for less resistance while hoisting and dropping.
Stitching.- note the dark colour UV resistant thread. Double stitched but each stitch Zig and Zag has three individual stitches.
Mainsail slide- Attached by webbing not a plastic shackle. Triple reinforced. Note the double luff tape.
Reinforced reef points with webbing and cloth reinforcing.
Reinforced leach. Note the triple leach tape and triangular panel reinforcing. The leach of a cruising main sail takes a beating and need proper protection.
A typical headboard, for a top cruising spec I would use a second slide. Particularly when deep reefed on the wind the halyard tends to whip which causes the slide webbing to chafe.
A good cruising genoa on a roller furler should have a strap around the foil to stop the sail from pulling out the foil track.