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© 2014 -2018 by Kemp Sails.

MAINSAILS

At Kemp Sails, we take pride in building mainsails which perform exactly as they should. That means ensuring accurate measurements, selecting the most appropriate cloth and panel layout, and taking care of every detail of the design and construction.

 

We also need to know about your rig, to make sure we incorporate the right amount of luff curve to match the bend in your mast - a particularly important consideration with fractional rigs. 

 

The following features are either standard or available as an option, with most of our mainsails:

  • Tell-tails Indicate whether the wind is flowing cleanly off the leech.

  • Camber lines Make it easy to see the depth and shape of the sail.

  • Lens foot A lightweight panel of cloth along the foot, which substantially increases the sail’s fullness when the outhaul is slackened.

  • Leech line exits at reef points Let you eliminate any ‘leech flutter’ when the sail is reefed.

  • Luff cunningham Allows you to tension the luff in stronger winds, pulling the draft forward and opening the leech.

  • Leech flattener Lifts the boom and flattens the lower section of the sail in heavier conditions.

Cloth

We’ll recommend the cloth which best matches the panel layout. For example, a low aspect-ratio sail has very different stress patterns to one with a relatively longer luff. When the luff/foot ratio exceeds 3:1, we recommend the use of high-tenacity fabrics designed specifically for minimal stretch in sails with high leech loads. Other types of commonly-used cloth cost less, which may explain why some quotations are lower than ours. But for a stable, long-lasting shape, you won’t get away with cutting corners or using inferior fabrics. That’s why we always suggest comparing quotations on a like-for-like basis. And if there’s anything you don’t understand about ours, please ask. We’ll be happy to explain exactly why we’ve made a particular recommendation.

Panel Layout

The sail’s size and aspect-ratio, plus your budget and intended use, determine whether we suggest a cross-cut or radial layout. Radial designs are more expensive because they’re more complex to make, and need specialised types of cloth (see separate page on radial sails).

loose foot at clew

One of the most crucial elements in a neat reef is having the leech lines in the right place on the boom. Some older types of boom have attachment points on the bottom or side - but, if these aren’t accurately positioned in relation to the leech cringles, you’ll end up with an untidy, inefficient reef.

Our solution is to remove the bolt rope from the last few feet ahead of the clew slider, so you can pass the leech lines under the foot and secure them around the boom. This way, they’ll be able to slide to the best position automatically when the load comes on. Another example of simple, sensible solutions from Kemp.

reefing points

Unless you have cockpit-controlled reefing, we can offer ‘reef spectacles’ on the luff cringles for easier attachment to the tack horn. And at the outer end of the boom, we leave the last few feet of the sail loose-footed, so you can loop the reefing lines between the boom and sail. See opposite for more detail of both these features.

Battens

Two-ply batten pockets ensure no part of the batten is in direct contact with a load-bearing part of the sail. Tapered, glassfibre battens in Velcro-fastened pockets are standard on our Racing, Performance Cruising and Cruisemaster sails.

REEF Spectacles

The most difficult part of reefing can be forcing the luff cringle down over the tack horn - and then finding you’ve hooked it on upside-down. But there’s no struggling with a Kemp sail, thanks to our ‘reef spectacles’ - stainless steel rings on the end of a strong webbing strap which passes through the luff cringle. Hooking on is quick and easy, so you spend minimal time on deck.

bolt ropes or luff sliders

Up to the size where a bolt rope creates too much friction, you have a choice - a rope for optimum performance, or sliders for easy handling.

Velcro-fasten batten pockets

To hold the battens firmly in place with minimal weight and clutter at the leech, we use Velcro ‘hookand- loop’ flaps, whose hooks fasten to the loops on the insides of the pockets. The flaps are pushed in with a flat, glass fibre ‘prodder’, which also keeps the hooks and loops apart. Then, when the ‘prodder’ is withdrawn, the flaps attach themselves along their entire length, making it virtually impossible for the batten to escape by accident.

CRUISING SAILS

We try to offer a consistent level of quality - with varying degrees of features and upgrades thereafter, to suit your sailing aspirations and your budget.  If you want something different then please just ask us...

 

SUPER CRUISE

If you want no-nonsense, straightforward cruising sails without all the bells and whistles, our Super Cruise range is the perfect choice.

We incorporate all the features you're ever likely to need for coastal cruising - and, should you take part in the occasional club race, you'll be surprised at the difference a new suit of sails can make.

If you want no-nonsense, straightforward cruising sails without all the bells and whistles, our Super Cruise range is the perfect choice. 

We incorporate all the features you're ever likely to need for coastal cruising - and, should you take part in the occasional club race, you'll be surprised at the difference a new suit of sails can make. 

Although they don't have all the go-faster features and higher-tech fabrics of some of our more expensive sail ranges, the shape built in by our computer-aided-design will ensure first-rate performance. 

Combine that with our careful selection of cloth according to the load pattern in the sail -
plusourtopquality finishing - and you can be sure of efficient, easy-to-use and durable sails at a highly competitive price. 

Before your sails are started, of course, we need accurate measurements - because no matter how carefully a sail is cut, it's no good if it doesn't fit the boat. That's why we'll measure your boat when possible. If it isn't, and we're working from figures you've supplied, we'll cross-check them against a sail plan to try and eliminate any possibility of error. 

We also ask you to provide us with measurements from your boat, not your old sails. Other important factors include genoa track positions, so we can ensure the correct sheeting angle. In short, we take every care to ensure that your new sails fit, perform and last. Full details of your sails' specification will be shown on your quotation - and the features and extras for each of the sail ranges are as described on the relevant specification sheet.

 

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RACING SAILS

Kemp's radial cut laminate racing sails can be made in a variety of fabrics and fibre types, depending upon your sailing program, your yacht and your budget.

Laminates are like a 'sandwich' of Mylar film with the Scrim (that's the internal net or grid) giving the strength and being made of a choice of High Modulus fibres:

CLUB RACE

Polyester (PET) & Pentex (PEN) - 'Pentex' is a chemical hybrid, developed from PET by Honeywell and it has up to 40% higher modulus strength than regular Polyester PET.  Kemp Sails recommend the PX BLACK (PXB) Line fabric - for that 'Stealthy' appearance.

REGATTA RACE

 Aramid (Kevlar, Twaron & Technora ) - has become the predominant fiber for racing sails. It is stronger, has a higher strength to weight ratio than steel, and has a modulus that is five times greater than PET, and about twice as high as PEN.

Kevlar, along with other aramid fibers, have poor UV resistance (Kevlar loses strength roughly twice as quickly in sunlight as PET) and rapid loss of strength with flexing, folding and flogging. Minimal flogging and careful handling can greatly extend the life of a Kevlar sail.

Twaron has a slightly lower modulus strength than Kevlar 29 but a slightly higher resistance to flex fatigue. The fiber’s lower UV resistance is enhanced by dying the naturally gold fiber black.

 

FULLY BATTENED MAINSAILS

Over the past 10 years or so, fully battened mainsails have become ever more popular. In fact, many sailors now automatically assume they're the best choice - but are they?

 

The Pros...

Their popularity is not without good reason. Matched with lazy jacks and the right batten hardware, they can be easier to handle, stacking neatly on top of the boom instead of blowing all over the deck when you lower the halyard to put the sail away or tuck in a reef. Because the battens tend to hold the sail in shape, it flogs less, which makes for quieter and more relaxing sailing. The reduction in flogging also puts less strain on the rig and helps the cloth last longer. And what about performance? Fully-battened sails are often considered to be more efficient because of their use, among others, on racing dinghies, America's Cup yachts and high-speed multihulls. But none of these has a permanent backstay - and it's usually the backstay that limits the amount of roach you can build into the sail of a typical modern cruiser or cruiser/racer. So you probably won't gain much area with a fully-battened main. 

 

Nonetheless, it does tend to generate more lift - which, in turn, can lead to more speed and less heel upwind. In light airs, too, the shape built in by the battens gives these sails an edge when others are hanging limp. What's more, they're often closer winded by virtue of being cut slightly flatter. Combined with their flog-resistance, this makes them especially useful for motor-sailing: you can bring the traveller to windward, haul the boom into the middle, and the sail will continue to fill until you're almost head-to-wind. 

 

THE CONS

 

POWER MAIN​

Benefits

* Powerful sail shape 
* Easy to handle 
* Reduces flogging and improves durability 
* Sail trim advantages over fully battened sails 
* Fits all mast types 
* Fraction of the cost of fully battened sails 
* Can be retro-fitted to existing sails 

Features

* x 4 Power Main battens 
* Our unique velcro closure system on 
the leech 
* Double skinned 
Teflon re-inforced pockets, carrier extends to the luff of the sail 
* Luff cunningham fitted as standard

 

The popularity of Fully-Battened mainsails is well known and this subject has been extensively covered by the Yachting Press. However, these glowing reports tend to be biased towards more modern yachts with new mast designs, with no reference being made to the vast majority of sailors who own older style yachts.

As one of the market leaders in fully-battened mainsails, we at KEMP have a wealth of knowledge in batten technology. We often find a large number of owners are incorrectly advised towards fully-battened mainsails! A correctly fitting fully-battened mainsail is wonderful. It generates more power, reduces flogging and makes the boat closer winded so our design brief was to incorporate all these benefits into a sail which would fit the older style masts. The problem with fully battened sails on these masts is the cars which have to be used to transmit the compression from the full-length batten into the mast. Use full-length battens with normal sliders and you will find that the sail will not go up or come down easily. Use proper compression cars and they foul on the older style mast gates which are usually located high up from the gooseneck and stand proud of the mast. The answer was staring us in the face ..... use battens which do not go right to the luff. 

 

Our “POWER MAIN SYSTEM” produces all the benefits of full batten sails. They will fit any mast type, work superbly with “PACKAWAY” Mainsail Stacking Systems and above all are a fraction of the cost of fully-battened sails. The “POWER MAIN SYSTEM” can be specified with one of our new Mainsail ranges or, alternatively, can be retro-fitted to any good quality sail in reasonable condition. 

RADIAL CUT MAINS

Until the early ‘80s, sails were usually made to a cross-cut design - that is, with their panels running horizontally from leech to luff. Most are still made this way - and for good reason: it’s a simple, reliable and relatively economical method of construction which is best suited to the majority of readily-available fabrics.

A word of explanation...

Its weakness is in failing to align the threads in the cloth with the sail’s stress pattern - which, as shown in the diagram opposite, runs in curves from corner to corner. To understand the problem, imagine that you’re facing a roll of sail cloth, and pulling the end as you would a length of kitchen roll from its holder. 

The fill (or weft) threads are the ones running across the roll from left to right - in the weaving process, they’re pulled tight, straight across the loom. Being straight, they have the greatest resistance to stretch. Weaving between the fill threads at right angles,
along the length of the roll, are the warp threads - which, because of their natural tendency to straighten under load, are more prone to stretch. So most sail cloth tends to stretch more along the warp than along the fill - but, like any woven fabric, it’s most stretchy when pulled at 45 degrees to the threadine. And when a sail stretches too easily, its shape becomes difficult to control. What’s more, after a while it won’t return - so it’s time either for a re-cut or new sails. 

MORE

With radial sails, you can bring the panels into line with the stress pattern. This way, the loads run through each panel at a relatively constant angle, instead of crossing them at different angles as they do with a cross-cut sail. You can see from the diagrams on the other side that this works better with tri-radial designs (panels radiating from head, tack and clew) than with bi-radials (head and clew only). But there’s a potential problem: since the warp threads (along the length of the panel) tend to stretch more, is there really a net gain? 

 

IN-MAST FURLING MAINS

Ever since Ted Hood’s “Stoway” In-Mast Furling system brought Mainsail Furling to the mainstream, it has made great strides and earned a ‘refined and reliable’ rating throughout the industry. What are the options for sails?

Kemp Sails recognises that rolling up cloth that’s not designed to lay flat can create pinches of sail material that may jam during the furling or unfurling process. To avoid this, we shape our Furling Mainsails a little flatter and build them with a hollow roach. Kemp Sails only make In-Mast Furling Mainsails from stiffer Yarn-Tempered Polyester or a High-Modulus material, that resists stretch and wrinkling.

The Foot and Leech of Furling Mainsails can come under a great deal more stress than ordinary sails, which is why Kemp Sails also reinforce these edges with a specially created Kevlar Tape.

Adding Short Leech Battens to an In-Mast Furling Mainsail, allows us to support a straighter Leech profile.  This maintains more of the sail area which would otherwise have to be 'hollowed out' without the use of battens, therefore improving Light Airs Performance.  The use of battens also helps control the Leech and reduces the potential for vibration and flutter.

The Vertimax In-Mast Mainsail Reefing system accomplishes that simple function which many other battened In-Mast Reefing sails absolutely fail to achieve, 
and that is: Long-Lasting Furling Performance.  The reasons for this are simple – and two fold:

Firstly, Kemp Sails recognise that space is at a premium in most Mainsail Furling mast chambers and therefore the batten configuration is critical. Kemp Sails use 4 Full Length Vertical Leech battens to support the increased Roach Area, placed to be as accurately aligned as possible when furled.