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Moth Sails 2019

Over the last 5 years Lennon sails have been working with leading sailors in the class, and we are now able to release the successor to the highly successful A1m, A2m, A3m and the all conquering A4m. The new sail is coded A5m.

Working closely with Paul Goodison we have moved the sail forward making a more progressive and easier sail to use.

In March 2017 the Class changed its rules in the way the luff is measured. Rather than it having to always fit between the masthead and “white band” painted on the mast 5185mm from the head, now the sail simply can’t be bigger than 5185 mm at original measurement. Prior to this change the sails were designed around 80mm short - so a luff length of 5105mm, to ensure on max downhaul the sail never went beyond 5185mm long.

Paul asked to try a sail to 5185mm and we took the area off the foot and leech making the sail longer luffed but shorter in the leech and foot - this combination was also set on a lower mast height. So sail span got longer whilst the mast height and centre of pitching moment came down thus reducing drag and heeling force.

The sail shape has remained very similar with some small tweaks to luff curve distribution and seam shape, but certainly no revolution to this aspect of the design.

A few days before the 2017 Worlds we also made some big changes to the batten spec - so the combination of the new sizing and sail tweaks combined with the new batten spec makes the A5m behave differently from the A4m. The new battens give more power down wind in the upper sail widening the groove. The lower battens are significantly stiffer at the back end improving the performance upwind allowing a slightly deeper sail to be used generally.


As standard the sail now ships with the new carbon batten spec - we introduced a new taper last year. This spec is softer in the front giving better downwind performance - however the extra flex does require careful set up with cam spacers. Locking the cams on the the battens to restrict rotation coupled with the softer spec has also improved tacking rotation without giving up entry angle.

We introduced a new carbon option in early 2017 and have now significantly changed the spec for 2018. The new spec, whilst having a different flex profile in the top and bottom of the sail, is also much more robust with the introduction of Eglass into the layup. This means the batten will flex into a very extreme curve before snapping. The 2018 battens will be far more robust.


We developed the long cam 3 years ago and introduced this in 2016 as an option. The lower 4 cams are double the length of the old style standard cams. The reason for this is easier rotation when under load. The upper two cams are less prone to locking and remain the shorter “traditional” length.

Originally we introduced carbon long cams, but we have struggled to maintain the right consistency on this hand made product. So recently we have superseded them with a 3D printed version. These are very similar in weight but far more accurate and less aggressive on the mast/sail and easier to handle. This version is now available for all the cams - long and short - and come with integral locking bulkhead.

The locking bulkhead has been developed with the new batten spec to allow a blunt entry but enable the cam to properly rotate and not lock on one tack. For 2018 the cams will be “Lennon Sails blue” and be made from a new material which is stiffer, stronger and has a higher melt point. The 2018 cams, like the battens, will be much stronger.

Lennon Sails Moth Cams

Cam colour may vary !

Available sail range for 2019

A5m (Winner 2017 Worlds & 2017/2018 Europeans). See design notes above. Also we still offer the A5m with differing sizing to fit other Moth designs.

Lennon Sails Moth A5m

H1m (3rd / 6th 2017 Worlds (part inventory) The H1m is our first design specifically for strong winds. This sail is derived from the Worlds / European and numerous National titles winning A3m from 2016. This is a flat sail and H1m is flatter in the head compared to A3m. Compared to the A5m its flatter all over.

Lennon Sails Moth H1m

A3.5m (UK Nationals winner 2017/2018 Foiling Week Winner) This design is a bit of an outlier and we didn’t offer it in 2017. Dylan Fletcher developed the sail in the back end of 2016. It has some unusual features and countered the direction of travel on the A4m / A5m. After several requests, we have included this option for 2018. It sits between the A3m and A5m in terms of shape. It is flatter in the base compared to the A5m but from the middle up it is more like the A5 than the A3. Its unusual in that its very short in the luff and needs to be set on short mast. It also has a very wide luff pocket which is made from “yarn tempered racing cloth” (165 HTP SQ). Its a tricky sail to pigeon hole due to needing a specific mast length - it could be used with a standard mast but it would sit very high above the boom. It is still a good all round sail as Dylan has proven but would suit lighter sailors being flatter and on a lower set mast reducing the heeling force.

Lennon Sails Moth A3.5m


We work closely with both CST and Ctech who both have several very good mast designs available for the Moth.

The A5m design will work successfully on most of the current popular masts. The standard luff curve works on the CST 21 and 22 and the Ctech 03 and 03b. Mach 2 medium masts also work on this design.

The above mast designs have quite a large difference of total max bend - using the IMCS system they vary from 52 to 67 so having the right mast for your weight is important when looking at this number. However, just as important is the “flex curve”. This is the differential between the bend offset at 25% and 75%. It is this number the luff curve must match.

If the difference is 2% between the upper and lower points then the flex curve is expressed simply as 2.

This only informs part of the story however. The bend at 50% is expressed as 100% , then the bend at 25% and 75% will be less (normally). Typically the bend at 25% will be around 67% to 70% of the mid bend and the top bend (75%) will be 72% to 76% of the mid number.

As you can see though, a 69% / 73% giving a “flex curve “ of 4 won’t be the same as mast with a curve of 80% / 84% also having a “flex curve” of 4.

However, having said all that, most of the current popular designs are pretty close to 4 having 69 / 73 curve.

Why String?

Membrane sails, sometimes called string sails and are often given all kinds of wonderful names by other lofts, are designed with the structure and shape in mind. The amount of fibre (string) used in the sail is varied by the designer and this variation can be used to get different characteristics from the sail.

All sails stretch but the degree of stretch can be controlled to a much higher degree compared to more conventional sails.

Low stretch is not always the end goal and having a progressive feel through the controls is also important - often this is achieved by allowing more stretch. So some stretch here and less stretch there will also lend itself to achieving the desired shape and handling characteristic.

Our string sails for the Moth are 100% Technora fibre with 1.5 mil of film.
Our relative high DPI in the loaded areas of the sail is giving great life as a welcome by-product of achieving the desired stretch characteristic.


As we work with some great sailors who are committed to being the best they possibly can be - we want to produce sails to help them - and so we can offer the best product to market. To get to that position we do produce a reasonable number of sails. These sails are often sold on into the general market. This can paint a confusing picture as to the number of designs we offer. We do not release new designs until the testing has reached its goal and the sail has produced the result intended. The new design will then be given a production code like A2m ( All purpose design 2 - membrane cloth). Sails designed for specific conditions like light winds will carry an L pre fix and H for heavy winds. Second hand development sails are exactly that and should not be confused with our standard designs. Ex-development sails will not have a production code.

Non standard - standard sails

Although much of the development for our designs has been done on low stump rigs, we also offer those same designs to fit high stump boats. This change will result in a different looking sail as leech roach is removed when making the leech length longer. However, the luff curve and mould section remain exactly the same. We also offer all our designs with 2 sleeve cut outs or 3 for the upper beak if required.

S/Z Boom / Ultra Low rig “Decksweeper” Options

Lennon Sails has been working on lowered rigs since Chris Rast brought his “S Boom” sail to the 2015 Worlds in Australia. Chris got his best result in a Moth Worlds finishing 7th overall. Since then we have made others along the same lines.

In early 2017 Lennon Sails started to experiment with lowered sails for the Thinnair Moth project and produced a double skin sail meant for use at the 2017 Worlds, but due to delays in project this concept was put in hold to concentrate on perfecting the A5m for Paul Goodison’s stunning victory at the Garda Worlds of that year. It became clear to Paul during that event that there might be some milage in pursuing the lowered rig and so over the winter we made several double skin “decksweepers” based on the A5m for Paul.

Lennon Sails Moth Sails and Accessories

Dylan Fletcher has also wanted to pursue this concept for some time and we also produced a version of the A3.5m in “decksweeper” format.

The concept is fairly straight forward. Most of the benefit comes from simply lowering the rig. The mast head typically comes down 200mm for the “normal“ rig height while maintaining max luff length. A small amount of area is borrowed from the back of the sail to make the part that “sweeps” the deck. To actually get this to happen you need a deck fairing but not having one has little or no effect on getting the benefits.

Lennonn Sails Moth sails and Accesspories

Benoit Marie using an A4m “S Boom” design

Managing this extra section of sail is tricky as the boom distorts the area. So it can look untidy but the benefits can be felt as soon as you sheet in for the first time!

To make a decksweeper work you need the distance from the top of the foredeck to the mast tip to be around 5200mm. Ideally the boom will be fitted to a mast gooseneck fitting with the bolt countersunk or very close to flush.

The opening for the hounds and spreader are usually placed in the same position relative to the top of the foredeck so, for example, if the mast is 200mm shorter the mast fitting are 200 closer to the mast tip.

To work out what mast length you need simply measure the height of your king post and deduct it from 5200mm.

Lennonn Sails Moth sails and Accesspories

Brad funk using the AH1mDS

When to go sweeping or conventional?
So far it seems as soon as you are solidly on the foils the decksweeper sails are faster. But in marginal foiling conditions conventional sails are earlier up. The combination of the mast tip been higher (in less ground effected air),

and having more to lean against in the black art of coaxing the boat in to the air, does offer earlier foiling opportunities.

There are also questions around how aero efficient the bit of cloth under the boom is compared to having it on the back of sail.

Paul Goodison using the A5mDS

Paul Goodison using the A5mDS

Decksweeper designs available

A5mDS - Derived from Garda Worlds winning design. This shape is the allround shape. This is also the 2018 Worlds winning sail!

AH1mDS - Flatter version of the A5m. We supplied several of these for the 2018 Worlds getting 4th and 5th overall.

A3.5mDS - Derived from the 2017 UK Nationals winning design developed in conjunction with Dylan Fletcher.

2018 Moth worlds results

1st Paul Goodison A5mDS / A5m
3rd Rome Kirby A5m
4th Brad Funk AH1mDS / A4m
5th Victor Diaz de Leon AH1mDS / A3.5m
7th Benoit Marie A4m “S Boom”

General features standard spec list

Teflon super slide front luff panel
Reinforced window panels.
Leech end batten vernier adjustment
3D printed long/locking version
Carbon special tapered battens (glass battens alternative available)
Fitted sail numbers
Rolled sail bag
Vernier adjuster key
Cam spacers
Door to door delivery included for EU only (other areas will incur a shipping charge)


Standard type Membrane Moth sails
Complete sail as listed above: £1840.00

Decksweeper type Membrane Moth sails (DS).
Complete sail as listed above: £1980.00

For sails supplied with no battens and or no cams please contact us for pricing. For glass battens take off £149.00

Cams and battens sets when sold separately.
Long or short 3D cams with integral bulkhead.
Set £215.40 Individual £39.00 each.

Full carbon battens.
Set £381.62 Individual #1 £36.83, #2 £36.83, #3 £45.20, #4 £55.25, #5 £63.62, #6 £70.32, #7 £73.66

All prices exclude local tax and VAT.

Lennon Moth sails have won a major championship in every year since the company started, in 2014, and are current Moth World, European and UK National champions.

Lennon sails are the current I14 world and European champions.



Products - To discuss any Moth Sails or Accessories call Mike on +44 (0) 7764 933890 or email Here

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Lennon Performance Products Ltd
Registered Office : 55 Crown Street, Brentwood, Essex, UK. CM14 4BD
Company Number : 7641784.

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