AN ILLUMINATING TALE (This complete editorial can be found at: www.yachtingmatters.com Edition 31)
25 Years of Underwater Lights (Ltd.)
By Peter Urquhart
Does it benefit answering the telephone? Twenty five years ago it did as it was a request to design an underwater light that could be installed into the transom of a 50m yacht. The editor of this classy magazine Colin Squire wondered if I would write an article on the evolution of underwater water lights. He still has, and always reminds me, that he has one of those original lights hidden somewhere in his attic. I took it along to his home, we live close to each other and left it for him to ponder over prior to using his YachtFile to get my new brochure into the hands of Captains.
Well the year was 1991 when I started designing the underwater light, computers and drawing software were too expensive for me so pencils and drawing board were the tools to begin with. Fortunately my employment as a marine engineer and later as a surveyor for Lloyds Register of Shipping (LRS) gave me the knowledge of materials, naval architecture, thermo-dynamics and electrical/optical designs.
Luck was on my side as General Electric had started manufacturing single ended metal halide lamps which were far more efficient than the halogen lamps of the time and they had an output of around 12,000 lumens. Porcelain lamp holders and high temperature/voltage silicone cable were available. Everything you needed to make a light. After a few days the design was completed and an application was made to LRS to approve the lights for installation into the 50m yacht (M.Y. Lady Marina). Sometime later M.Y. Lady Marina switched on her four underwater lights whilst she was at anchor in the Bay of Palma and just about every yacht owner after that wanted underwater lights.
Our next order was for 32 lights on a 100m yacht being built in Germany. The lights would be installed around the yacht. This required the addition of two new inserts that are welded into the hull to compensate for the shell plate angle. The design and installation layout was approved by LRS. On reflection the 50m had her four lights on the stern and the next yacht had thirty two lights all the way round. There seemed no end to what one could do providing the system was safe and ‘Fit for Purpose’
The first underwater light was called the BULLEYT and used a 150 watt metal halide lamp. Minor changes were made to improve thermal and light output efficiency. In 2005 we started to test a 250 watt metal halide lamp in the BULLEYT and found that the extra power and lumen output (19,000) did not work and deteriorated the overall efficiency. Basically the diameter of the glass lens (62.5mm) was too small and too much heat was generated. We increased the lens diameter to 75mm. and the insert diameter from 100mm to 120mm. These increases in size had to be made to our screwed version which are installed in composite hulls. These lights were known as the UL Ti MATE range.
Having cracked how to use the metal halide lamp along came the LED with new underwater light companies entering the market. We started testing LEDs around 2004 and the first thing we noticed was the economic truth in the LED specifications.
1- LEDs do not generate heat/they run cool. ‘not true – more later’
2- LEDs have a 100,000 hr lamp life. ‘quite possible if you can keep the LED at 25C. But the life is seriously reduced with temperature.’
3- Light efficiency surpasses discharge (metal halide lamps) ‘at the time not true’
Our first observation was that when the LED was used with light focusing plastic collimators the heat distorted the collimator. To overcome this the drive current had to be reduced which reduces the lumen output. LED manufactures quote lumen outputs per watt which were around 100lm with a drive current of 350mA. They also quoted light levels at 700mA and 1000mA. Note the LED temperature was 25C. The increase in light levels at the higher current were around 20-40% and efficiency plummets resulting in a high LED running temperature. The LED efficiency and the running temperatures have increased. How we get the best thermal and optical efficiency from them is still ongoing.
There is no doubt that LEDs are the popular choice for all types of lighting. For interior low colour temperatures from 2,300k to 3000K with a high 90+ CRI are the best choice. For underwater lighting a cool white with a colour temperature of 6000-7000K and low 70 CRI
produces the best result. There are many LED colours to choose from and the popular colours are royal blue and RGB+W which requires a DMX type of control. Our latest development for fishing is using ultra violet LEDs (UV) and a blend of UV with white or royal blue LEDs which we will name CRISP WHITE and CRISP BLUE. This type of light enhances the visual aspect of the fish, fishing lures and the fishing line. All are supposed to increase the chances of catching a fish. However I would not advise wearing a florescent type of swimming costume with these lights in shark infested waters. Colourful you maybe but you become BAIT.
On a more joyfull note all the yachts that have our metal halide lights or similar can be retro fitted to LED. The original insert or screwed fitting and electrical cables can be used. It is very simple plug and play exercise.
What I have not mentioned are the rapid change of LED product. The positive part of this is that manufactures of COB type LEDs retain the basic dimensions but the lumen output per watt increases. No dimension change necessary for our LED heatsink. However LED drive current and voltage do change so driver specification and design alterations have to be electrically tested for statutory approval. We design and manufacture our own drivers which have all been tested and approved. All this allows us to easily exchange/supply new LED (when original LEDs are obsolete) parts with no modification to the light.
The above leads me to mention the Classification Societies and MCA. The detail required for class type approval has significantly increased. Structural drawings, electrical and mechanical test reports, workshop approval and installation information to name a few. Attending class surveyors always have the final say when it is a ‘Classed’ vessel. However there is always a flag of registration and their surveyors can have a say in all matters of construction and safety aspects and decide what is ‘Fit for Purpose’
The Underwater Light world is now on every body’s radar.
We have thousands of lights installed on sea going yachts and there are many more lights installed by our competitors. We have not had a ‘casualty’ but we know we have had lights installed 25 years ago that are still working.
Remember these are skin fittings installed below the water line, just like propeller shafts, suction and discharge valves/strainers and therefore as with all skin fittings require periodic inspection.