Coming Full Circle - The New LED Stern Light

By Tom Schultz - Belle River - PEI - Canada

Some time back I reviewed Duckworks’ Led navigation lights for the forward direction. Just recently, I saw what appeared to be an LED stern light (but was called a “transom light”) so I asked Chuck for details. Essentially, he had no information except the tiny bit Sea Dog supplied. He offered to exchange a light for an evaluation, with a comment (a pun I suspect, based on the manufacturer’s name) that he needed to know “if it was a dog” to determine whether to continue to stock it.

Examining the light: A couple of days ago the light arrived.

It looks somewhat odd in its bubble pack.

It is quite flat/shallow unlike traditional navigation lights. Opening the package, I found the light comes apart into three pieces—the metal cover, the plastic light assembly, and a flexible black (vinyl?) gasket that goes behind the assembly.

Three parts

The light assembly has a small rectangular part that sticks back behind the mounting surface.

Light assembly

The metal cover is 3” in diameter and the outer edge of the black gasket is 3¼” diameter. The front metal cover extends about ½” out from the mounting surface. Behind the mounting surface a 1 3/8” x 1 5/8” rectangular portion extends back about 5/16” with wires coming out from the center about 3/8” apart. The only deficiencies I noted were the use of non-tinned wires—presumably less resistant to corrosion if saltwater should get behind the insulation—and the apparent lack of a full seal where the wires go into the plastic assembly. The gasket behind seems to make a tight seal to the wires, so I don’t think water would easily get in. I think I would be tempted to seal things with liquid electrical tape and/or silicone when I installed it.

Stern light requirements: Colregs requirements for a stern light: 1) Visible for 2 NM (which is nautical miles rather than my initial reading of nano-meters!) 2) Light projecting around over exactly 135° (to fill up the circle started with the green and red forward lights. 3) Light intensity maintained for 20° above and below horizontal. The light is said to be compliant and a quick check supports that claim despite (or because of) the strange shape. At room temperature with a 13V battery it drew 114 mA (the spec says 100 mA @ 12V, but I don’t have a 12V supply to check that). There are 4 LEDs and they emit quite a bright white light—I was seeing 4 spots for quite some time after I first hooked them up and forgot to look away.

Close up of light

Getting out the protractor, I was surprised to find a sharp edge to the light at about 67° off the center axis, as required by the specifications. In addition, the band of light extended up and down with about constant brightness over about 40°. Above and below that it was still showing some light but the intensity began to fall off. That answered my initial question—this “transom” light does qualify as an official “stern” light.

Mounting Problems: Positioning the light may be a problem for anyone without a vertical transom wide enough to allow the light to shine past the outboard motor or (in my case) the rudder. I was shocked to discover that my existing stern light is blocked by the rudder and is not vertical, so navigation light requirements have not been met on my boat for the 5 years I have owned it and probably not for the 25 years of its existence!

My existing light position

The light mounts with two (provided) screws, but you have to either chisel a 1 ½” x 1 ¼” rectangular hollow or drill a 2” diameter hole to fit the back of the light. The hole must be at least 5/16” deep to fit the rear depth, or you can drill all the way through and count on the gasket to seal off the hole. The wires need to get out the back to the electrical connections.

I don’t know how you would mount to a fibreglass boat, but I think blocks of wood would be involved, both to accept the screws and to take care of any angle corrections for a sloping surface.

In any case a wedge could provide a vertical surface—a 3 ½” wide piece cut at an angle (in my case, 70 degrees) would do it. I would not rely on the 20° off-axis light spread to take care of a sloping transom since it would lose the effectiveness in waves.

If the light is to be visible around to 67½° on the both sides, on my boat I must change something else to get the light past the rudder. I see several choices. 1). From the picture of my trimaran, you can see that one choice might be to put the light on the stern of an outside hull. I think my outer hulls do not project back far enough for the side light to reach past the center hull and rudder, and getting wiring out there would be difficult. 2). I considered putting the light up on the top of the housing over the engine well (the white area with the orange handles on both sides in the picture), but the tiller would block the light even more than the rudder. 3). I don’t want to add a post sticking up because it would get in the way of the tiller swing and the stays. 4). My chosen solution is to mount the light to a thick block of wood that projects back about 4” from the stern. That would get it back far enough so the side light would clear the rudder. Mounted just below the deck, it would be below the rudder swing.

The lights lighted.

Pic top left: Lighted left

Pic top right: Lighted close up

Pic left: Lighted wider

The 4” projection would not put the light back further than the lower part of the stern, so backing into a wharf should not damage the light (the rudder projects back even further below the water line—it is in much more danger in collisions). I plan to add blocks as stops to keep the rudder from swinging past 45° when in reverse or in irons—the reverse flow can has jerked the tiller out of the helmsperson’s hands. I may incorporate a mounting place for the light as part of the blocks for the stops or at least do the epoxy job at the same time.

Conclusions: I think the light is a very good buy and, with the front lights described before, makes a wonderful low current, long-life solution to the navigation light requirement. The entire light system would draw less than ¼A compared to at least 3A with conventional lights—an improvement factor of 12. The mounting problems are not unique to this light—any properly located stern light requires a vertical surface with 67½° clearance to both sides. While I do my best not to be out at night, one occasion arose this last Summer and it is good to be prepared. Of course, that time I discovered I had put the dinghy blocking the starboard light, so another project is chocks to put it in a better place!

these LED stern lights are available from Duckworks


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