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Inflatable Battens

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If you have spoken with me recently about sails, there is good chance that we spoke about inflatable battens and our recent success with this project on Sojana, Peter Harrison’s 115ft Bruce Farr Ketch. In St. Tropez we were one of three boats with adjustable inflatable battens on roached furling headsails supplied by North Sails. We all used the same supplier of battens, C Tech from New Zealand. Those involved in these projects in our group have all worked hard to innovate but actually have taken similar but fundamentally different routes with this technology which is still in its infancy.

C-Tech Ltd originated in 1997 building yacht masts, high performance dinghy rigs, carbon tube, rudders, centre-boards, etc.  When the America’s Cup came to NZ in 2000, C-Tech discovered there was a gap in the market for reliable full-length carbon mainsail battens.  The battens had to be strong, light, durable, and stiff enough for a Cup boat especially in pre-starts where the boats are doing low speed gybes. 

A design for such a product was put in place in 2001 and the prototypes were quickly snapped up by both TNZ and Alinghi.  C-Tech went exclusive with both teams for the 2003 America’s Cup but were also allowed to supply one other team in the Louis Vuitton, which in this case was Victory Challenge.  For the recent AC in Valencia, C-Tech supplied full-length carbon mainsail battens to every syndicate and developed an inflatable air-batten product which was supplied to four of the teams.

I asked Fraser Brown what his view was on the break through of inflatable battens in Valencia :

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FB: It’s definitely been a big talking point since the AC in Valencia and the use of inflatable battens has now gone into cruising and racing boats, mainly for the furling headsails.  A rule was created for the 2007 AC which allowed big overlapping headsails.  This posed many problems; supporting the roach and being able to tack and do dial ups in the pre-start without breaking battens in the big genoas being the obvious ones.  The air batten idea was developed as a way of having a structure supporting the roach/leech of the over lapping genoa that would be able to fold and crease as it bangs through the rig during a tack, hitting the shrouds and mast.  When the genoa is sheeted on again after the tack the battens pop back to shape.  A conventional batten wasn’t able to do this, as it would simply break or shatter the laminate.  Yes, this has been a big break through, which has already fed directly into racing and cruising boats.

On Sojana we fill and empty along the leech. The air supply is a dive bottle. With Geoff Meek, Andy Mitchel from North Sails CapeTown, and Marc Fitzgerald, the skipper of Sojana, we asked a simple question to Fraser Brown, “Is this going to work? Are the battens and air lines and their connections viable?” He replied ‘yes’ so we took him on his word.  We have one single air line running up parallel to the leech line feeding all four battens from the clew where there is a simple valve.

Once unfurled the air line is attached to the valve and the supply opened. Our direct feed requires under five litres of air at about four to six Bars despite using larger diameter tubes than the other boats to facilitate emptying. This process takes seconds. When it is time to furl we open the valve to release the air. Obviously as the sail furls, any residue air is forced out from the top batten downwards as the batten is wrapped around the furler.

I asked Fraser if he thought that this was just another passing fad:

FB: It’s definitely not a passing fad.  With the use of air battens in the leech of Super Yacht furling genoas they are now able to have a maximum size genoa, eliminating the big hollow leech you normally need to allow the sail to be furled.  With air battens in the sail and air lines running down to a connector you can inflate the battens once the sail is unfurled, then deflate the battens before the sail is furled away.  This means you can design a sail with maximum area so it can touch the spreaders.  This increases the roach of a sail which won’t be a passing fad, as Super Yacht racing is getting more and more competitive at every regatta.  Being able to increase sail area and power is a big step forward.

AD: And Inflatable battens for everybody?

FB: Within reason, boats with furling head-stays can have air battens with air lines so they can inflate and deflate battens, significantly increasing the area of their genoas.  Boats with hank/foil-hoist genoas can have air battens which are just pumped up and put in like a regular batten (as per air-battens in the 2007 AC).  Inflatable battens are already into the Open 60 fleet for the Barcelona World Race and the V70’s building up for the next Volvo race.

We are now working with Fraser on air battens on the future big roached 3DL main for Sojana. We think that this will enable the head to pass the backstay allowing us to build a bigger roached main than we had previously thought possible.

Nearly fifteen years ago I started working on a project with Claude Thelier (Trimaran Region Guadeloupe) on having an inflatable luff on a free flying code O to enable light but efficient furling on a mini transat, so I asked the final general question to Fraser:

AD : After battens what do we inflate next?

The list is growing everyday.  This is an interesting subject as inflation/deflation also doubles as a space saver, although this is still a little way off.

In my childhood I saved up my pocket money to buy  C.A. Marchaj  book “Sailing Theory and Practice” published by Adlard Coles Ltd in 1964. In the chapter on ‘Measurement of Aerodynamic Forces’ he discusses the aerodynamics of the new trend of ‘pumping’ in relation to rapidly changing the incidence of the sail to the wind to promote planning. In the controversy that followed with the I.Y.R.U. with respect to pumping and “means of propulsion” we have finished years later with rule 42.2 ‘Prohibited Actions’ a) “Pumping"— well, at least at present, the rule makers are not talking about “inflating.”

Fraser Brown :      fraser@sailbattens.com
Andrew Dove :      andrew@sales.northsails.com

Andrew Dove is Area Manager for North Sails Caraibes, based in Guadeloupe.

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