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RADAR: Section 3 (cont.)

 
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PostPosted: Mon Oct 27, 2003 6:28 pm    Post subject: RADAR: Section 3 (cont.) Reply with quote

From: Mike (Original Message) Sent: 2/3/2003 6:02 PM

Part III - 2

First to answer some email questions of general interest.

Radar Reflectors. I don't use one and should. I will install one on C-Salt, and installation ideas would be greatly appreciated. A reflector is recommended in all of my recent radar books, and Canada requires (El and Bill note) that you use a radar reflector in low visibility. Anything that will increase the probability of your being seen by the other vessel is a definite safety item. Most radar texts indicate that a reflector increases your reflected return by 2-3 times.

Bibliography. I had originally intended to append my sources and favorites at the end of the collision session, but because some skippers want to read more as we crawl along, and because I'll probably lose some readers during this next boring session, here it is. My basement is loaded with old celestial navigation, navigation, seamanship, and reference books -- all overtaken by progress -- but the following are current and recommended. All of them were used in this pre-school preparation -- with emphasis on the PRE. To boat safely, good or bad visibility, you owe it to yourself, your family, your lovely little C-Dory, and your wallet, to take it from here and move ahead with your study.

Chapman, Piloting Seamanship and Boat Handling (63rd edition). It should be in every skipper's library. A wealth of information, but not much on radar techniques.

U. S. Department of Transportation, United States Coast Guard, Navigation Rules, International - Inland. This is a must, and is required by the Inland Rules to be carried on vessels 39 ft. and over. It should be in your library and I recommend you have it aboard. I like the Paradise Cay Publications version because it is current, with Notice to Mariners through March 15, 2002. Get it, read it.

Bill Brogdon, Boat Navigation For the Rest of Us. A great book. Pertinent, current, and the best and easiest to understand presentation on using the maneuvering board that I've ever read. If I wanted just one book in my library on all facets of small boat navigation, this would be it. This gentleman knows what he writes about. Don't hesitate!!

John Mellor, A Small Boat Guide to the Rules of the Road. Excellent presentation and easy to read. If you can find it, a recommended part of your library.

Tim Bartlett, Radar Afloat. A small, easy to read primer on radar. Nice presentation, and a must for radar newbies.

I can list a few more that I used, such as Bowditch, American Practical Navigator (1995), NIMA Pub 217 Maneuvering Board Manual, and Pub 1310 Radar Navigation Manual, but with "Boot Scootin' Boogie" on the stereo and reading through the first three -- sleepy time. If you want more, ask.

Correction. Did you ever write or say something you wish would go away? I just did, and my procedure for turning to a contact to get a magnetic bearing is a bummer. It is NOT recommended, and is just a sloppy way of doing something that is better done the right way. I used to do it because I boated alone in low visibility so much of the time that I was busy driving, looking at the radar, scanning 360 degrees and too lazy to use the maneuvering board. Forget it, okay? More on this later.

Back to class, kiddies.

Rule 19 is so pertinent to our restricted visibility discussion that I'll include it here. All of those maneuvering rules for clear weather (rules 11-18) that you studied so hard to learn do not apply here.

Rule 19

Conduct of Vessels in Restricted Visibility

(a) This rule applies to vessels not in sight of one another when navigating in or near an area of restricted visibility.

(b) Every vessel shall proceed at a safe speed adapted to the prevailing circumstances and conditions of restricted visibility. A power-driven vessel shall have her engines ready for immediate maneuver.

(c) Every vessel shall have due regard to the prevailing circumstances and conditions of restricted visibility when complying with Rules 4 through 10.

(d) 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, providing 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 toward a vessel abeam or abaft the beam.

(e) Except when it has been determined that a risk of collision does not exist, every vessel which hears apparently forward of her beam the fog signal of another vessel, or which cannot avoid a close-quarters situation with another vessel forward of her beam, shall reduce her speed to the minimum at which she can be kept on course. She shall if necessary take all way off and, in any event, navigate with extreme caution until danger of collision is over.

There it is. I typed it and re-read it. Please read it carefully - make notes - memorize and understand the basics. I'll hit some of the high points in the few remaining sections of collision avoidance, but Rule 19 is the foundation.

What are close quarters? To us little guys probably one-hundred yards would get itchy. For large ships, two miles is close and one mile is 'standby for a collision' time for many of them.

You've got a steady bearing on a closing target, indicating a potential collision, what do you do. Radar is a wonderful tool - it gives early warning of ships around you, shows relative movements, but one critical area is lacking -- the course and speed of the other vessel ('aspect' in many texts). You could be overtaking the other vessel, in a head-to-head meeting situation, the vessel could be overtaking you, or both you and the other vessel could be on different courses that result in a constant bearing with a potential collision possible. You must know the course and speed of the other vessel to take proper action. Brogdon say that an untrained person using radar is a hazard - I agree, and that's why we're here.

Many large ships have an automatic radar plotting aid (ARPA) that finds the course and speed of a target as well as the distance and time of her closest point of approach to you. Raytheon started making a mini-ARPA in the early 90's for small boats (MARPA), and there may be other manufacturers doing the same thing, but if you don't have ARPA or radar with a similar capability, the only choice is to use a maneuvering board. You can get them in pads of 50 from Defense Mapping Agency (DMA Publication 5090). Weems & Plath also makes a plastic one (10855, Radar Collision Avoidance and Current Plotting Board).

Hey, don't run away! They are easy to use once you've practiced a little. Many radar users get along without them (illegally, of course), but if you do much low visibility boating you will be a lot safer knowing how -- and using one. It helps to have a copilot because the maneuvering board adds another task to a one-armed paper hanger operation. Remember, it is easy to practice in good weather, and the knowledge makes you a MUCH safer, and legal skipper in the bad stuff.

We had best recess now because the class is in shock. Maneuvering board next.

Dusty

From: El and Bill Sent: 2/4/2003 4:32 AM
Dusty --
Duane, on Plan B, experimented with a half of an aluminized reflector taped flat to the top of our radar dome. We cruised off a goodly distance and he thought his return signal from us was significantly better than without the jury-rigged reflector. I'll check with him to see if he has carried on his experimentation.
The "half reflector" idea has some real advantages -- easy to mount, inexpensive (his jury-rig was made from cardboard and aluminum foil), and out of the way. What do you think? El and Bill on Halcyon

From: Sawdust Sent: 2/4/2003 9:14 AM
Thanks! If it works -- great. Simple I like, and it can't get much simpler than that. I'll try and check with my Canadian contacts to see if something like that would be acceptable -- if I can find one who has a clue!

Radar capabilities have come a long way in the past three or four years -- a very few years back I had difficulty picking up single 14-15 ft. fiberglass fishing boats at a mile. The new units can pick up kayaks at over a mile, and the return pulses as they paddle! Same power. Apparently there have been some improvements in both transmitter (antenna) design as well as in the receiver section. Not like auto manufacturers, where part of the pitch is a pretty face -- here performance is everything, and the competition is fierce.

Thanks again, El and Bill

Dusty

From: 501-Sealife Sent: 2/4/2003 2:58 PM
Here's a picture of the radar reflector on Sealife. It the verticle tube afair just forward of the rocket launchers. I believe they are made in the NorthWest, but don't know the manufacturer's name. Came with the boat when I bought it used.

Mike - Sealife
Roof Racks.jpg

From: Sawdust Sent: 2/4/2003 3:43 PM
Thank you! It looks great, and guess I'd better do a little Seattle research. Can't believe I've run around this long without one.

Dusty

From: Sawdust Sent: 2/4/2003 7:02 PM
Sealife Mike,

The more I look at that the more I like it. No wind restance, clean, neat and very unobtrusive.

Have you checked it for reflectivity? Probably difficult the way it's installed unless you hang something over it and check with a buddy. I've gotten by for years - usually bigger boats - but the more I read the more I think it's a great idea. Because of weather where I fish, I just about live in fog and rain (on or off the boat). Actually, I think that if you ever had a collision in low visibility the lack of one might be an issue in court. Shucks, everything else is!

Thanks,

Dusty

From: Sawdust Sent: 2/4/2003 7:03 PM
Dang nab it! That's wind resistance!!!

Duster, with un-nimble digits.

From: 501-Sealife Sent: 2/4/2003 7:38 PM
Dusty,

In the times I've been out in fog with other boating friends, as this past saturday when I ran with Fishtales and Islander to Ventura, they have had no trouble following my radar signature, even when deep in the soup with no visual. About a mile outside the breakwater I picked up a target off my port bow that turned out to be a Grady White on a crossing bearing. As we approached each other I could tell he saw me on his radar, as he slowed to let me pass across his bow from starboard. As we passed he loomed out of the fog only about 50 yards away. Bottom line, I think it works fairly well, especially when combined with all the other attachments to my cabin roof.

Mike - Sealife
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