One of the reasons for working on the nav lights these last few days was to answer two questions.
Firstly, If a reflector was fitted inside the nav light would that affect the light cone emitted from the light and if so, by how much?
Secondly, how much brighter would a reflector make?
There was an additional question of whether the LED replacement bulbs affected the cone of light emitted as compared to the original incandescent bulb. This one was largely academic since I’m certainly going to use LED bulbs, but it will be interesting to see if there is a difference.
I asked on the Dinghy Cruising Association website for possible ways to add a reflector to an antique nav light and the two best options seemed to be scrunched up aluminium foil and an acrylic based mirror cut to shape.
Once darkness had fallen I went back out to Shoal Waters armed with a torch, a piece of scrunched up foil, a carefully cut mirror and a light meter.
I then spend half an hour or so taking a series of measurements of the light output of the starboard nav light. Firstly without any reflector, then the foil and finally the mirror. I placed a wooden block on the side deck and used that to ensure that the position of the light meter was the same for each measurement.
Not surprisingly, the readings for the light without the reflector was the lowest, as I expected, but the question was which of the reflectors was better. The foil didn’t reflect as much light as the mirror, but because of the scrunched up nature, the foil spread the reflections around a lot more than the mirror. Also, not surprisingly, the mirror reflected the most light but this was not as widely spread as the foil.
The foil was 8% brighter on average whilst the mirror was 25% brighter on average than the light without any reflector.
So which is better? It depends. The foil is 8% brighter across a broader spread but the mirror reflects a lot more light.
Take your pick.
Time for a cup of tea.