What is the issue?

Small boats cannot rely upon a larger ship's watch systems seeing them, especially at night. Larger ships tend to rely on radar for watchkeeping support. The problem with this is that radar signals reflect best off flat metallic surfaces and not the fibreglass that leisure yachts are mostly made of. Worse, radar systems typically require a minimum of three consecutive radar ‘blips’ or ‘hits’ before they acquire a target which further reduces the chances of a pitching or heeling yacht being picked up. All of these result in sailing boats easily getting lost in the sea clutter and not being spotted.

Why address this?

Being safe is a function of being seen. Radar is the primary equipment used by all commercial vessels for collision avoidance in busy shipping areas, or during bad weather, poor visibility and at night. Everything possible must be done to maximise the radar signature for ships as you cannot rely on being seen visually. A passing ship's radar system will only identify objects that are radar visible and those that are highly visible will remove the risk of being run over.

How to address this?

Mount a passive radar reflector in a permanent posting reflecting ship's radar signal so a vessel can provide a strong return, and a consistent signal to passing ships. A passive radar reflector is a low-cost, or easily self-manufactured, device that requires no power and is a 'fit and forget' project. Though they tend to look highly unattractive and add a little windage, they may save your life.

There are numerous different models of passive radar reflector on the market, but it is important to note that many will only give their best results under very specific conditions, and generally, the cheaper the radar reflector, the poorer its performance. Passive radar reflectors also require some judicious positioning. The RORC recommend a mounting height, where possible, of 4 metres above sea level. In short, due to the curvature of the earth the higher you can position the radar reflector the better. They also need to be kept clear of sails and running rigging as their edges eat through anything that rubs against them, especially so once they oxidise and become pitted.

Below are several examples. The poorest example being the aft backstay mounted radar reflector that has just attained a minimum height requirement of 2 metres above sea level. A good position for a vessel with radar is just beneath the radome as the established radar brackets make it easy to fasten the reflector in place and position it correctly. The outreach of the radar cover above tends to kept the headsail clear when it passed in front of the mast and it is also less conspicuous to the eye. Two alternative positions are also shown below between the top crosstrees and cap shrouds, and below the crosstrees, which gives height and safely removes it from its harmful potential.
The positioning of the radar reflector is often overlooked. Most radar reflectors only give their best results when they are positioned top V up to the sky, so the lower Vs are pointing the radar signal directly back at the ship. Each product should be fitted according to their optimum position according to their instructions. This optimal position can be difficult to maintain on a sailing yacht on account of heeling but when running downwind, powering up a fairway or at anchor, the boat is mostly vertical and the optimum reflector position can be obtained.

There are more expensive radar reflector options available that appear like fenders as they are enclosed in polyethene cases. These are specifically designed for yachts have a symmetrical arrangement of interacting corners to generates an echo with the largest possible reflective area, whatever the angle. Being enclosed, they are weather tight, are streamlined and do no harm to sails and running rigging.

With thanks to:

Michael Harpur, Yacht Obsession.




Learn to Sail Safer - How to Use Radar Reflectors




Radar Systems Reflectors and Computer Simulators

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