The $45 radar reflector

Sue Watt and husband Peter decide to make a simple octahedral radar reflector themselves after pricing commercially available ones.

We have spent the past four months preparing our 12m gaff-rigged schooner Argos for our circumnavigation of Australia and to sail her back to British Columbia where she was originally built. We didn’t have a radar reflector on board but thought one would be an essential item.

Passive device

A radar reflector is a passive device that improves the radar image of the yacht it is mounted on. It works by reflecting incoming radar pulses and bouncing them back, providing a strong indication of your presence to other shipping.

On a yacht, where the hull and any naturally occurring reflective surfaces are close to the waterline, you are almost invisible. We learned that
with a passive reflector your visibility increases significantly.

Radar transmissions follow the line of sight, so naturally the higher your reflector, the further away you’ll be seen, so it is important to mount a radar reflector on the vessel’s masts at the highest position possible for maximum efficacy in a permanent position where it is can do no damage to the running rigging or sails.

Obviously the more visible you are, the safer you are.

Types

There are different types and styles of reflectors. A corner reflector (for example the Plastimo octahedral reflector or the Davis Echomaster) is a retro-reflector consisting of metal vanes set at right angles to one another — usually three perpendicular, intersecting flat surfaces which reflect waves back directly towards the source, with little loss of strength. These usually consist of three conducting metallic surfaces or screens perpendicular to one another. There are also cylindrical reflectors, most of which fall into the type containing a stack of aluminium corner arrays (like the Echomax 230 or the Firdell Blipper 210-7) although some have concentric layers of plastic that focus radar impulses and return the beam. Also available are lens reflectors (like the Viking Tri-Lens, also marketed as Rozendal) that look like a ball or a cluster of balls encased in a plastic case.

There are also active radar reflectors (for example the Sea-me Radar Target Enhancer — RTE), which appear to work more effectively but have the disadvantage of requiring power to operate, a significant downfall where power usage is a key factor.

Commercial range

You can purchase passive radar reflectors for your yacht from any major yachting suppliers and the range is extensive. Prices start from under $100 for fairly flimsy collapsible cardboard-covered-foil models through lightweight metal styles that cost a little more but are also more sturdy up to $1000 or more for you-beaut fancy ones. None claims 100-percent efficiency and the simpler reflectors seem to work as well as the fancier and more costly varieties.

There are studies available which rate the various types. We also consulted with other sailors and gleaned a lot of information before deciding that without a couple of spare thousand dollars to spend on the optimal models, we’d go with a corner reflector. In looking at the types available and being pretty handy, we ended up making a simple octahedral radar reflector ourselves.

Materials required

• Aluminium — very thin sheets – 2 sheets — 600mm x 900mm

• 4 pieces 900mm x 20mm aluminium angle

• 1 packet aluminium blind rivets

• Fix-Seal Plus (MSP190) marine-grade silicon adhesive

Pattern

Each square was cut to 400mm, the third piece divided into two triangles and then the grooves cut.

The aluminium angle was cut into two lengths of 400mm and eight lengths of 200mm.

You could increase the number of pieces cut to double the amount of supports holding the reflector together. However, we chose to use as few as possible to keep weight to an absolute minimum.

We started by cutting the aluminium with tip snips but found this resulted in a jagged edge. Ordinary kitchen scissors produced a much more smooth result. However, we did cut the angle with tin snips.

Construction

The pieces were joined with aluminium angle and pot-riveted together — we used approximately nine rivets for each section. The first two joins were completed with the 400mm lengths of angle, then the other sections added using the 200mm lengths of angle. After joining all the pieces together we then used the silicon on all the external corners to prevent chaffing to lines and rigging (not to mention ourselves!).

Installation

A U-bolt was added to top and bottom and then we tied a halyard line to the top and the bottom and pulled it up like a pennant. Our halyard allows us to take the reflector to the top of the mast — it is recommended that the reflector be hung at the highest possible point.

Time and money

All up the radar reflector cost us $45 and took less than a day to make and install.

You don’t want to wait until you are hit by a ship to discover that your reflector isn’t sufficient — the easiest way to find out if it makes you visible on a ship’s radar is to ask a fellow yachtie who has a good radar to check and see what you look like on their radar screen.

Additional resources

There is a vast amount of information on the internet about radar reflectors, and if you read it all you’d likely be more confused than when you began.

We found a lot of conflicting information but did find the following websites useful:

www.theradarreflectorsite.org and http://offshore.ussailing.org/SAS/General_Information/Safety_Studies/2007_Radar_Reflector_Study.htm

However, overall we learned more from talking to other sailors around us and looking at what they had. This doesn’t need to be yet another expensive necessity. Safety can sometimes come at a more reasonable price that doesn’t break the bank.