International Moth Class Sail

Hansen Sails is proud to announce the development and availability of a new, state-of-the-art International Moth Class sail.



The design philosophy behind the Hansen Moth sail is to apply the wide-sleeve (double luff) camber-induced technology developed for contemporary Formula racing windsurfing sails to the International Moth while enhancing specific attributes necessary for competitive Moth sailing. Due to the wide range of true and apparent wind speeds encountered in the foiling Moth it is important to reduce drag to a minimum while preserving the ability to actively control shape and twist using typical on-the-fly rig controls such as downhaul, outhaul and vang. Of prime importance is upwind angle and speed in light to medium conditions where the apparent wind moves forward rapidly after take-off into the foiling regime. A secondary but equally important feature is the ability to de-power as the forces build in stronger wind conditions by maintaining a draft forward, flatter and more twisted planform.

These goals are approached in the design as follows:

Wide, Double Luff Sleeve
Compared to existing Moth sails, The Hansen Sail has a noticeably larger luff sleeve with over 20% double surface which has proven to be superior in the high apparent wind regime experienced by Formula boards and now foiling Moths. The leading edge of the sail becomes more wing-like for higher lift and lower drag while also further supporting the sail body and mast keeping the draft forward even when the sail is tuned flat for high winds, high speed and pointing. The wider sleeve also distributes the downhaul tension over a larger area for improved camber rotation and a smoother entry.



Semi-Elliptic Lower Leech
In sails where the foot cannot be end-plated (closing the gap) an elliptical lower leech has been shown to be more efficient in terms of induced drag thus giving a higher lift to drag ratio and thus higher efficiency. Since the Moth sail's foot is quite high above the deck and the boat itself is high above the water, there is no chance for a proper end-plate. Thus a non-traditional elliptical lower outline is used to create a more effective sail. At the same time boat handling considerations are enhanced with a shorter boom by allowing more room for the sailor and hiking stick to transfer from side to side.

'Chop Top' Head
There are numerous aerodynamic and functional reasons for high performance sailing vehicles (especially the foiling Moth) to adopt the contemporary movement toward a more rectangular 'square-headed' planform. Due to the International Moth Class limits on square area and somewhat standard maximum allowable luff length, removing the area in the lower leech by shortening the foot allows both the desired lower leech elliptical planform and increased area in the head to create a more effective 'chop top' (square-headed) sail.

Construction
Several variants of proprietary Dimension-Polyant technical laminates are used in the sail body for light weight, low stretch and durability. The wide sleeve is constructed of several different fabrics according to function and position to provide a strong, durable, light and stable structure. Wide roller cams which allow increased batten angles and pre-preg carbon-epoxy rod/tube battens provide improved shape stability and save weight.

Availability
We are presently fine-tuning the batten flex profiles and stiffness as well as a small number of minor construction details. Tentative orders may be placed at this time with the understanding that a reasonable period of time may be required to finish the pre-production tuning phase to insure that the sail successfully performs at the highest levels of competition. Scheduled availability for immediate orders is mid-June. Subsequent orders can expect 3-4 weeks delivery from the time of order. These are estimates and subject to change.

Pricing and Ordering
Introductory pricing is US$1200 (not including shipping or applicable duty, taxes, etc.) The base price includes all battens, fittings and your class-legal country designation and boat/sail number. Adjustments for custom fabrics or details will be quoted separately in advance of your order and will be charged strictly on time and material considerations. Orders must be confirmed with a 50% deposit before production begins. Pricing is subject to change.

For further info and pics, go to:
< http://www.hansensails.com/Forum/forum_posts.asp?TID=115 >
< http://groups.yahoo.com/group/int-moth-usa/message/988 >
< http://www.int-moth.us/index.php?option=com_content&task=view&id=68&Itemid=9 >

To place an order, contact:
info@hansensails.com



Edited by Bill Hansen - 17 May 2008 at 8:45am

Cool stuff Bill! Neat to see windsurfing technology reach out and benefit other areas of sailing!

thanks, bry

I am the happy owner of the prototype in the picture,
It has been a lot of fun working with Bill, (although he did all the work!) and the sail has worked pretty much out of the bag - just some batten softening and cam spacers.

I will be racing with  it in UK in July, and in the first North Americans in the Gorge in August.

Incase anyone is interested,   Moths have had sleeved windsurfer style sails for several years, size is limited to 8SqM and racing is from 5-25Knots,
The boats lift up on foils in about 7k wind. (sail shape/crew weight dependent)

Bill's design is over 30cm shorter than most  other sails along the foot hense the currently over long boom - as soon as this sail is officially measured the hacksaw is coming out ! 
So far we have not had much 2 boat testing but GPS shows some real upwind improvement.

Regards,

Andy

WA:
The mast and boom do not need to rotate as a unit. However, if the mast is stayed, the twist profile will change somewhat as the sail is eased out since the side bend will be different than the fore-aft bend. Probably not a big deal on boats with high apparent wind speeds...
-Bill

Specifications:
Luff: 508cm
Foot: 179cm
Area: 8.0sq-m

Originally posted by wind_apparent I cant quite read the "luff,foot,area" data.   could you post it please? thanks.