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HSH Yacht Articles

Radar

By

Jeremy R. Hood

How times change! When I first started dinghy sailing in England I recall a friend telling me how they had just fitted a VHF radio to their boat and it seemed amazing to us all that you could use the VHF to make a phone call when out at sea. That was over 20 years ago, and today every well equipped boat will have at least one VHF radio and probably several. Now Radar has become almost standard on vessels equipped for offshore sailing. And unlike the radar units of old the new units are so much easier to read, are reasonably priced, and do not consume half as much electricity aboard your boat. With these advantages, it is not surprising that many sailors are now fitting radar to their boats and are then faced with the prospect of actually using it.

In 1997 I took an Island Packet down to the Cayman Islands from Clear Lake. The trip was a fast one with a northerly wind taking us most of the way and we made the passage in record time. Overall, everything was relatively straightforward though our trickiest navigation was when passing through the Yucatan Channel at night. Because of the strong north wind I chose to transit the channel on the Eastern side close to Cuba where the water is deeper and the current less strong. However around the western end of Cuba there is a considerable amount of shipping and I was aware that an international Traffic Separation Scheme was in operation there (see Nav Rule 10) but I had no details on my charts or in my books of the exact location of the lanes. Transiting the area that night took two of in the cockpit at all times keeping a lookout and taking bearings on the vessels that appeared to be coming close. But what made the whole thing easier and safer was the cockpit mounted radar display. Although its bright screen (even fully dimmed) was really too bright, having it there and being able to see vessels below the visible horizon was invaluable. Throughout our passage through the channel we were able to see seven or eight vessels at all times on the eight mile range and being able to track their progress using the EBL (electronic bearing line) and ERM (electronic range marker) made collision avoidance that much easier. In such situations I would always like to have a radar available!

It is beyond the scope of a short column such as this to teach how to use a radar (books, videos and CD-ROMs are available for this) but it is possible to discuss some of the navigational features that new radar owners need to be aware of.

NAVIGATION RULES IMPLICATIONS

One of the most important considerations when fitting radar is that once it becomes operable then you are required by the navigation rules (Inland and International) to use it in certain circumstances: not knowing how to is not an excuse!

Navigation Rule 5 (Inland and International) states that:

“Every vessel shall at all times maintain a proper lookout by sight and hearing as well as by all available means appropriate in the prevailing circumstances…”

While radar in not mentioned here, the implication is clear: it should be used when the circumstances would make it helpful such as at night or in poor visibility.

Rule 6 (which deals with safe speed for a vessel) has a specific section (Rule 6(b)) which applies to vessels with operational radar. The requirements are the same for both sets of rules and are:

“…In determining a safe speed the following factors shall be among those taken into account:

(i) the characteristics, efficiency and limitations of the radar equipment;

(ii) any constraints imposed by the radar scale range in use;

(iii) the effect on radar detection of the sea state, weather and other sources of interference;

(iv) the possibility that small vessels, ice and other floating objects may not be detected by radar at an adequate range;

(v) the number, location and movement of vessels detected by radar;

(vi) the more exact assessment of the visibility that may be possible when radar is used to determine the range of vessels or other objects in the vicinity.”

Rule 7 is concerned with assessing risk of collision, and specific mention is made about radar. Section (a) states that:

“Every vessel shall use all available means appropriate to the prevailing circumstances to determine if risk of collision exists. If there is any doubt such risk shall be deemed to exist.”

The Rule then continues with sections (b) and (c) which relate specifically to the use of radar:

“(b) Proper use shall be made of radar equipment if fitted and operational, including long-range scanning to obtain early warning of risk of collision and radar plotting or equivalent systematic observation of detected objects.

(c) Assumptions shall not be made on the basis of scanty information, especially scanty radar information.”

Rule 19 relates to the conduct of vessels in Restricted visibility and here, as you may have imagined, radar is again mentioned. Section (d) reads:

“A vessel which detects by radar alone the presence of another vessel shall determine if a close-quarters situation is developing or risk of collision exists. If so, she shall take avoiding action in ample time, provided that when such action consists of an alteration of course, so far as possible the following shall be avoided:

(i) an alteration of course to port for a vessel forward of the beam, other than a vessel being overtaken; and

(ii) an alteration of course towards a vessel abeam or abaft the beam.”

These navigation rules, which are in easy-to-read language, not only tell you how you are required to use your radar, they tell you what type of information you can expect to obtain from a radar. You can detect other vessels when they are far off and often below the visible horizon and you can determine if there is a risk of collision. But from Rule 6 you will deduce that radar can give false or misleading information also!

RADAR NAVIGATION AIDS AND CHART SYMBOLS

Besides being able to identify other vessels and potential collision situations, a radar can be extremely helpful when entering a channel or navigating in a restricted area. Buoys and navigational marks often have radar features to them, and the main ones to be aware of are Radar Reflectors, Ramarks and Racons.

Radar Reflectors

Just as many small craft have a radar reflector which is hoisted in the rigging to make the vessel more easily visible on a radar, buoys and marks are often similarly equipped. The appreciation Ra Ref will be seen on a chart often accompanied by the symbol

Ramarks

A Ramark is a radar beacon that transmits continuously. They are not that common but can be extremely useful. A ramark is shown on a chart as . On your radar display it will show up as a block or blocks indicating the morse code signal for the transmitter (see Fig 1)

Racon beacons

These are fairly common and their are several in the approaches to Galveston (as there are at most major port entrances). A racon only transmits when it picks up your radar signal. When it transmits it sends out a signal in your direction which will show up on your radar screen (as with a Ramark) indicating its morse code identification. With this information you can positively identify the beacon and from the radar you can easily obtain your its range and direction and thus your position.


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