Norm Rumsey — Sector Navigation Lights

Difficult harbour entrances around the world have claimed the lives and livelihoods of many seafaring folk in the past but thanks to Norm Rumsey's clever and simple invention, Sector Navigation Lights, the danger has been greatly reduced. The invention was a new kind of sector navigation light using a slide projector to guide shipping into harbours.

It all began at Paremata harbour near Wellington when committee members of the local boating club sat down one evening in 1961 to try and find a solution to the lack of navigation lights on the harbour. Paremata harbour is unsuitable for traditional navigation lights and was badly in need of some way of guiding boats in, especially at night.

It has a treacherous reef halfway across the entrance, a sharp rock just below the surface off the end of the reef and a sandbar further inside the harbour. There is one narrow channel which boats can follow safely in, but without navigation lights it is difficult and dangerous to find.

One of the members of the committee was Bob Barnes, who was also in charge of the optical workshop of the Physics and Engineering Laboratory of the DSIR, that is the Department of Scientific and Industrial Research, in Lower Hutt. Mr Barnes came to work the next day and asked his colleague Norm Rumsey, an optical physicist and an expert in designing high quality lenses, if he could think of a way of putting navigation lights in the harbour. Mr Rumsey quickly thought of using a simplified slide projector to project white light down the safe channel, red light to one side of it and green light to the other. This turned out to give much more sharply defined boundaries between the different colours than the old fashioned sector lights which consisted of a central lamp with panes of different coloured glass placed around it.

The slide at Paremata had a broad up and down stripe of red colour on one side, a narrow white strip near the middle and a green stripe on the other side. What comes out of the projector are three clearly separate areas of colour, an area of red, an area of white and an area of green with no gaps between them. The idea was to place the projector of land in line with the channel so incoming ships would see either red or white or green depending on what part of the harbour they were in.

Mr Rumsey thought the red colour could cover the area of the reef to the north of the channel, the green the shallow water to the south and a thin white strip would show the path of the channel.If they saw red they knew they had to go right, if they saw green they had to go left and if they saw white they knew they were on the right path to follow the narrow channel safely into the harbour.

Hearing Mr Rumsey's idea Mr Barnes set about building a model of it with a three coloured slide. By lunchtime he had it finished and took it up a nearby hill and shone it down to where Mr Rumsey stood. Mr Rumsey said he could stand with the dividing line between the red and white colours running down his nose, so when he closed his right eye he saw one red, when he closed the other eye he saw white. He knew then the idea was a good one and would work.

The reason why traditional navigation lights wouldn't work in Paremata Harbour, and many other harbours in New Zealand and around the world, was due to its shape, with a large cliff across the inland end of the channel. Usually navigation lights consist of two lights in a row, one slightly above and considerably further back than the other. An incoming boat lines the two lights up, one above the other and heads in on a straight and safe line. At Paremata the cliff goes up so close to the sea that even if the rear lead light was placed on the cliff face, the forward led light would have to be on a structure in the sea to achieve a sufficient horizontal distance between the two to give an acceptable performance.

It was only a few months after Mr Rumsey suggested the slide projector type of sector of navigation lights that they were up and running at Paremata. Fortunately for the boating club another one of its members was a railway engineer and they were able to take electricity for the projectors from the railway signaling system. Mr Rumsey patented his design for sector navigation lights and the DSIR offered the license to make them to a local company.

The first company to take up the license gave it up when they decided lasers would replace existing types of navigation lights. This has not happened, when this company gave up the license Vega Industries took over in 1972. Vega Industries is now managed by John Rochfort and is based in Porirua, Wellington. Vega has exported their sector navigation lights to nearly every country in the world and there are over 50 places in New Zealand which use them. Vega has made a lot of refinements to the initial model, including designing a sector light which works during the day and night, changing its brightness accordingly. They have also gone on to become world leaders in supplying all kinds of navigation equipment, including making the best lenses in the world for lighthouses.

Mr Rochfort said the slide sector lights were worth about $1 million dollars a year to Vega Industries. They also supply a version of the sector light to all of New Zealand's international airports. The airport lights have two colours, white and red, the red is on the bottom and the white above. Four of the lights are placed in a row either on one side or on both sides of the runway and an incoming pilot can use the lights to follow the right angle of descent for a safe landing.

When the plane is coming down on the right angle the pilot will see two white lights and two red lights, if the plane is too high the pilot will see three or even four white lights and will know to go down. If they are too low they will see three or four red lights and will know to go up.

Norm Rumsey's career in designing lenses began after the second world war when he was asked to learn how to design high quality lenses to assist in making accurate maps from aerial photographs. He accepted the job and was sent to the University of Tasmania in Hobart where he learnt the skills to do the difficult work of getting the final details of a lens perfect. It was this knowledge that enabled Mr Rumsey to see the solution to the harbour lights so quickly. He knew that a projector with a good lens in it will give a very clearly defined line between areas of colour even at a distance of several hundred metres. And its lucky he did, his invention has saved both boats and crew as well as becoming the basis for a highly successful New Zealand company.

Classroom activity - Flashing Lights