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Hall Spars to offer off the shelf carbon battens and extend range

by Richard Gladwell, 17 Nov 2018 23:13 NZDT
Hall Spars are making a generational change in carbon sail batten manufacture and supply © Richard Gladwell

Ahead of METS, the world’s biggest marine B2B equipment show, Hall Spars have announced a generational change in the way they supply and support the carbon batten market.

Recently the North Technology owned company announced a third carbon batten product rounding their range allowing Hall Spars to offer strong, lightweight sail battens suitable for yachts from small racing dinghies through to supermaxis and superyachts.

For two years Hall Spars have produced two styles of batten - the Compression and an UltraFlex batten products

Now an intermediate batten, the Flex batten, has been developed which is a hybrid of the two earlier models.

“The Flex batten is hollow at the outboard or leech end of the batten, tapering to a solid batten at the inner’” explains Hall Spars Sales and Marketing Manager Ben Gladwell.

The new batten is hexagon-shaped at its outboard end, and the laminate itself being tapered over the full length of the batten, instead just being ground to produce the required bend.

For larger sails, all three batten types can be deployed – with the stronger full-length Compression battens being used for support at the top end of the mainsail, and the intermediate Flex battens being used to support the rest of the leech.

Ultra Flex battens are used as flutter battens between the other two battens to provide leech support and avoid the need for leech hollowing or leech line tension to prevent fluttering.

Construction of the new batten is designed for strength, lightweight, and a high-quality finish.

“We lay full-length layers of carbon fibre down the outside of the Flex batten,” Gladwell explains. “That makes the batten much more resistant to fracture, and means there are no weak points which typically occur when the taper is ground into a plate batten.”

“The new Flex battens are made in a female mould, like the Compression battens. We lay down a flat piece of fibre that runs the full length of the batten. The mould is tapered from the outboard to the inboard end.”

“The battens are built from a stack of fibres, with the longest strip going into the bottom of the mould – and that becomes the outside of the batten. The shortest fibres are on the inside which makes the batten progressively stronger towards the outboard end.”

Developing the new batten products has required investment in specialist new plant by Hall Spars including a specially designed 8.5 metres long oven, manufacturing table as well as the plate moulds themselves.

On the production table, the battens are built side by side in multiple half moulds. After they have cured in a specially designed autoclave, the two halves are bonded together, and then water-cut to separate the individual battens.

Both the Compression and Flex battens are built in female moulds giving an external finish that is high gloss and smooth – producing an attractive looking batten that won't cause abrasion in the batten pocket.

The unique feature of the new Flex batten is a small flange on its edge which gives a half-hexagon shape at its hollow outer end, tapering away to a regular batten shape at the inboard end.

During the curing process, the halves of the Flex batten are compressed using a vacuum bag to ensure that layers of fibre bond correctly and consistently.

“The vacuum bag produces almost 1 BAR of pressure, and then we get another 6BAR in the autoclave,” Gladwell explains. “Effectively we are getting 7BAR of pressure on the batten during the curing process,” he adds.

The moulded battens are glued together using a special rubber toughened epoxy, to make a single plate, of five battens - which is then water cut to separate the individual battens.

“It’s a lot stronger than regular epoxy and more flexible,” Gladwell explains.

“The battens get their strength from the width of the hollow core, not so much from the thickness of the wall, giving strength where it is designed to be while retaining lightweight.”

While stronger Compression battens are intended for use on larger yachts the Flex and UltraFlex battens can be used on any size of yacht from a dinghy upwards.

“The Compression battens, at the top of the sail, support the camber on the leech,” explains Hayden Whitburn. “The others support the leech lower down.”

Whitburn has an extensive sailmaking background with North Sails and has stayed within the North Technology Group in his new role as a batten specialist with Hall Spars.

“We’ve used Compression battens on racing boats as small as a Class40,’ explains Whitburn. “At the top end, we have used them with yachts over 100ft in length, like the supermaxi CQS”.

“Flex battens are more common on TP52 teams – we’ve just done a set for a Hong Kong owner.”

For a yacht 70ft or longer all three types of battens – Compression, Flex and Ultra Flex would be used.

Small but perfectly formed

The stronger Compression battens are also made using a female moulding process using various sized aluminium moulds that are up to 10 metres in length.

The production secret lies in the way Hall Spars use an inflatable bladder inside each batten during its manufacture to force the carbon right to the edges of the mould – so internally while the batten is small, it is perfectly formed and lightweight.

The bladder itself is just thin-walled plastic tube and is inflated to 6BAR – that pressure increases further in the mould when the batten is heated, and the air inside the bladder expands.

The pre-preg carbon is laid into a two-piece female aluminium mould. The bladder is inserted for the length of the batten. Then the two laminated halves are brought together, with the top and bottom halves overlapping to form the edge of the batten. After the bladder is inflated, the pre-preg curing process is commenced in an autoclave at a pressure of 6BAR.

Once the manufacturing process is complete, the bladder is deflated and trimmed. It's left in the majority of its length as a safety measure - making recovery of broken battens a much more straightforward affair and minimises potential damage to the mainsail.

The female moulded battens have a polished external finish. As well as good looks that means the polished batten surface will slide more easily into a tight sail pocket.

Externally the smooth polished finish on the battens is to the same high standard as on any other part of a race-yacht.

The Compression battens come with a full range of end-fittings from lashed end fittings to rocket tensioners, screw in end fittings and the like which all the sailmakers are familiar, and are in what the sailmakers currently call their “Blue Book”.

Batten jointing is accomplished by connecting sections of batten using internal joiners typically 250-300mm long. The joined external surface is seamless, and the internal jointing process allows battens to be made of any length.

The internal joint means that the batten and pocket can be made for a perfectly snug fit. Other hollow battens typically have an external joint which means that the construction of the batten pocket has to be compromised. There is a chance of greater wear and tear on the sail with the batten flexing within an oversize pocket. The internal joint means that the batten is completely smooth and slides easily into the pocket.

The hollow Compression battens give crews the ability to carry spare batten sections aboard their race yacht meaning that battens can be jointed and repaired at sea if necessary.

"The weight of the extra batten is negligible. If you don’t have spares and break one during a race you may have to pull out and go home", says Whitburn. “That’s your race over and maybe series too – all for the sake of a sail batten which can now be easily repaired on the water.”

Off the shelf battens

Hall Spars are moving to a model where they manufacture and stock standard batten sizes and types which can be bought off the rack, and cut to length.

“We are now stocking standard batten lengths and laminates,” Whitburn explains.

“We will be carrying large stocks of battens so that we can satisfy an order immediately without having to quote the usual six week lead time. Next step is to establish a stock of ready-made battens in USA and Europe as well as New Zealand so that expensive air freight is no longer necessary and battens can be supplied within the same continent as the customer.”

For battens that are longer than a standard maximum length (5.8mtrs) Halls will supply a standard joining kit, with instructions, along with a list of suitable joining adhesives that can be purchased in a marine shop.

For overlength battens, there are a few options. The battens can be joined at Hall Spars and then pulled apart and shipped ready for the adhesive. Or the moulds can be joined together, and the battens made full length without any joints. The only limit on that is Hall Spar's main autoclave which could take a batten up to 40 metres long.

The shift to the "Ready to Go", fast-food style model, will result in substantially lower freight costs, and a reduction in batten prices.

“It will depend on the project. If it is a high-end project, we will still do custom battens," says Whitburn. "Generally, the sail designer will send through the bend numbers (bend is specified at four different points on the batten by the sail designer which translate into along with the wall thickness and width )

“We will have ready-made battens on the shelf that will enable us to supply as close to the design dimensions as we can, but for some projects, we will still have the ability to do custom builds.”

"It is going to be a lot easier and cheaper for owners if sail designers work to Hall Spars' standard batten product list. All we need to know is the length, and we trim a standard batten to be slightly over that dimension."

“Our lead times are excellent,” he adds.

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