3DL on your dinghy

Andy Nicholson investigates North's new Roto-Moulded small boat sails

With every single America’s Cup team using North 3DL sailmaking technology it was only going to a matter of time before they would turn up in your dinghy park. Turned up they have, in the form of 3DL RM, where the RM stands for Rotary Moulding. At the recent Sailboat show, North Sails One Design Loft, based in Gosport, had two new suits on display, one on an International 14 and the other on a B14. The Daily Sail caught up with North’s Dave Dobrijevic (left), who explained all.

The concept behind the sails, where yarns are laid to a specific computer controlled design, is the same in these smaller sails as America’s Cup mainsails, but they are made in a slightly different way on a different machine. Dave explains: "3DL for big boats is laid up over a mould, just as you would if you where making a boat, whereas this RM is a whole new ball game.” The RM process means that they can make small and deep dinghy sails, where the whole 3DL production technology is really designed for larger flatter yacht sails.

The big 3DL sails require a man in a handglider harness to lay the threads and apply the heat as the sail is built. In the RM sails the whole process is automated and so what would be a huge labour cost for something like a B14 jib is taken out. This is achieved by laying the sail up on a huge drum.


The RM machine is 4.5m long and 3m across and is driven by a computer. The skin on the outer drum is a flexible silicone rubber surface which is pushed into shape by around 1,000 little pneumatic actuators. The foot of the sail runs along the bottom edge of the drum and the luff length wraps around the outside circumference of the drum. The Mylar films are laid onto the surface of the mould and as the drum rotates the yarns are laid down from yarn heads running on tracks along the outside. After the second set of films are laid on then the whole sail goes through the heating process to complete the laminate. The ‘finished’ sail then comes off the drum and rolled up ready for dispatch, the local loft then finishes off the sail with luff tapes, batten pockets and the like.

Located in the Nevada factory the first RM machine has just started regular production following a two year test period on 505 sails. Early indications were positive with the new sails proving to be stronger than their ‘seamed’ counterparts.

Dave explains the anticipated benefits to the dinghy sailor: "The advantages of it are going to be the weight of the sail and the durability and it should maintain the racing shape for longer, that’s what we are really trying to do with it. You are also looking at a much smoother sail, you don’t have a stepped sail, like a panelled sail”

He adds: "With the first suit of 14 sails, the early indication is that we are running with too many threads in the Jib and so there is more optimisation and weight saving to come. We haven’t worked out exactly what the weight saving is but ballpark would be around 10%, as with the 14s we already use a very high spec and lightweight cloth anyway [in standard sails]”

The North One Design loft has targeted the International 14 class as the way to introduce 3DL RM sails to the broader dinghy market. Dave is a highly experienced sailor himself, having worked his way up through the dinghy classes as crew. He sailed last year in the 14 with Paul Vine and the pair won the Nationals and Europeans, Dave added the B14 National and European titles in a successful 2002. Dave explains the importance of the International 14 fleet to this new sail making technology:



"The 14 class is ideal for these new things to try, they work to a very high standard basically with their kit, everything has got to be the best available." He sees one of the main benefits with control-ability. "In anything like a 14 you are looking for the rig to be as automatic as possible, which I have been developing with the 14 quite a bit, because you don’t want to be playing around with the controls too much. For that you need a stable sail, you don’t need the shape to be shifting around all the time. And that will help the rig to do it’s work on it’s own."

He anticipates that once the sails become further refined and start proving themselves a new round of rig development in the 14 class will take place.

"As we go through the development we work out which designs are good and we try to work it out for all conditions, so you don’t just have one sail that is good in one condition and not another. We want it so you go out on the water and you will have one rig that will work throughout the range."

So impressed are North Sails with the new RM manufacturing process that they are now building another two RM machines. The first will replicate the existing machine while the second will be significantly bigger, with a drum length of 12.5m this will take the technology up to the Mumm 30 size bracket.

Dave sees the market for the sails growing all the time: "Anything that will allow a laminated sail in this way will benefit immensely from it. We already have a set on the B14, so that’s two classes already. The machine has only just come up into production so it’s early days, but classes like the 505 and Tornado."

Importantly the sails will be priced at a level close to North’s standard panelled sails. This is because North actually make their own Kevlar, so the cost of raw materials does not differ significantly between the two processes.

Looking at the flacid sails at the Sailboat show they didn’t look as impressive as you would anticipate. The cause of this is probably down to the role of luff curve on the 14 sails, combined with a static rig and not alot of breeze.

If you put aside the North Sails marketing machine for one moment and delve a little deeper into the manufacturing process a few interesting points can be noted. The mylar film is not a single moulded piece, but made up with three separate sheets which feed onto the drum in a vertical lay up. This allows the shape of the mould to be replicated in the beginnings of the sail with what must be some overlapping of the films, try to wrap a piece of newspaper around a beach ball and you will see what has to happen.

The main benefit of these type of sails (which arguably include UK Tapedrive and Sobstad Genesis) which rely on film laminated fibres, not cloth, is that loads in the sail, mainly at the corners, are taken up by a much higher concentration of fibres. This results in lighter sails that react better to the controls put on them, either by rig tune or sheet tension.

But for sailors everywhere it is the race course (fortunately) where sailmakers really earn their reputation, and North have chosen the highly competitive International 14 class as their main leader with this technology. This confidence in the product is matched with their investment in more hardware and you would be hard pushed to find someone who thinks that they are barking up the wrong tree.

Your Feedback: Will your class look to embrace these new sails?