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Lennon 2017 Moth Sails

by Lennon Sails 23 Jan 2017 07:51 GMT 23 January 2017
Lennon A3m © Paul Goodison

Over the last 3 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 and A3m. The new sail is coded A4m.

Working closely with Paul Goodison and Dylan Fletcher we have moved the sail forward making a more progressive and easier sail to use design. A sail clearly needs to perform well in differing angles of sailing and wind strengths. Powerful from tip to foot in the light and down wind, plus flat with head washout in strong winds.

The new sail is fuller in the lower to mid sections and from there progressively flattens to the head. So to compare directly with the A3m - the A4m has more shape in the sail body from 50% down with a touch less in the head. The A3m had a tendency to hang on in the top once the bottom was flat. So the new design flattens more progressively with head flattening more quickly than the base. This gives a wider "groove" making the sail easier to use.

The head is wider with a change to the top battens angle to aid a more automatic twist for acceleration.


As standard the sail ships with Glass rod tapered battens - we introduced a new taper spec this year. This spec is softer in the font giving better downwind performance - however the extra flex does require carful 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.

Working with a new supplier have now introduce a new batten spec in 100% flat plate carbon - The pricing is also much improved!

The carbon battens are stiffer in the back half and lighter than the Glass battens. We have added glass in the tips to increase the robustness of the battens. The glass is at 45º so it doesn't increase stiffness in the tip.


We developed the long cam 2 years ago and introduced this last year as 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 So recently we have superseded them with a 3D printed version.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.


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

The A3m design has been used 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. But 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 as simply 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.

But as you can see 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 in mind, as well as the shape. 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. But 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.

Some branding and special printing is also available on request. Photo shows Chris Rast’s boat with S boom and A1m+. Also showing some art work we can to add to the sails.

General features standard specification list:

  • Teflon super slide front luff panel
  • Reinforced window panels ( Membrane designs )
  • Leech end batten vernier adjustment
  • Std short Roller cams on every batten ( 3D printed long / locking version upgrade available)
  • Vinylester tapered battens (Carbon upgrade available)
  • Fitted sail numbers
  • Rolled sail bag
  • Vernier adjuster key
  • Cam spacers
  • Door to door delivery included for sails only (EU only - other areas may incur a surcharge)

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