PS Advisor July 15, 2005 Issue

PS Advisor: 07/15/05

Radiation from Radar?
I would be interested to know if you have any information regarding the safety of radar use on a typical 30 to 45-foot sailboat.

In your review of the Hunter 38 (PS May 1, '05), you fault the radar arch for offering extra windage, but it does a great job holding a small radar unit well away from the helmsman's head, much the same as a sturdy dedicated pole, spar, or mizzen mast would.

Radar is powerful and it's on for long periods of time. While I know these units provide great information and increase safety for piloting, how much cause for concern is there regarding radiation?

Joe LaFreniere
Falmouth, MA


The health hazards of exposure to high-frequency, non-ionizing radiation—including radar transmission—have been studied extensively for many years by such agencies and organizations as the EPA, FDA, the National Institute for Occupational Safety and Health (NIOSH) and the Occupational Safety and Health Administration (OSHA). Essentially, the effect of such radiation on tissue is heating; the same effect that makes microwave ovens work. The amount of heating depends on the transmission power and the distance between the transmitter and the tissue.

OSHA has established a recommended maximum safe level of exposure to microwaves at 0.2 milliwatts per centimeter squared (which carries a built-in safety factor of 10 or so).

Obviously, not all marine radar units put out the same power. A large radar unit putting out three kilowatts, operating at 3-1/2 feet from and at the same height as the scanner, can create an average intensity that can be as high as 0.8 (milliwatts per centimeter squared) if the scanner is stationary. At a distance of 7 to 10 feet from the scanner, the average intensity drops to safe levels (i.e. below 0.2 mW/cm2). During actual operation, the average exposure is reduced, because the scanner rotates and a person in the path of the beam is exposed only when the beam sweeps past. This can reduce radiation levels by more than 80%.

When the scanner is rotating for normal radar operation, average exposure is below the recommended safe limits; even at points as close as three feet.

Further, almost all of the output of a radar transmitter—though it isn't uniform—is concentrated in a narrow beam of 25 degrees, 12 1/2 degrees above and below the horizontal axis of the scanner. Radiation levels outside that narrow beam are very low; and directly below the radome, they're virtually zero.

We wouldn't recommend that you work aloft near the radome when the system is on, particularly if you wear a pacemaker. Otherwise, though, you shouldn't be at any particular risk.

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Restoring Anodized Hardware
My 1982 O'Day 34 is generally in good condition, but the bow cleats are worn and the original anodizing appears to be wearing off. I have seen products to fix sun-faded car bumpers and wanted to know if there was something similar to fix the anodizing on a cleat?

Peter Sidewater
Boston, MA


Anodizing is an electro-chemical process which physically alters the surface of the metal to produce a tough oxide layer. There are several kinds of anodizing, but Type III, known as hardcoat anodizing, is what you want for most aluminum items used aboard sailboats, particularly something like a cleat that's intended to withstand contact with line and will receive minimal maintenance apart from the occasional fresh water rinse.

We don't know of any products that restore anodizing, but you can have items re-anodized. Before doing so, it would be prudent to weigh those costs against the cost of replacing those cleats with similar sized new ones.

We contacted International Hardcoat in Detroit, MI, and their representative told us that any item can be re-anodized, but it must first have all the initial coating removed, either chemically or mechanically (by blasting). The quality of the results in that process, he told us, are directly related to the quality of the material you start with. So, if your cleats are banged or scratched, the new coating may not hold up well.

Then there's the matter of cost. Most anodizing firms, he told us, begin with a minimum charge for coating products. For his firm, that's somewhere between $75 to $100. Given that you can purchase 6" aluminum cleats from Schaefer for roughly $30, your best bet is to buy new cleats.

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