Fog, Radar Installation and Visibility

[TenMile]

Hey all,

Last month, my wife got me a new radar system for my birthday (a Raymarine C70 with 18" dome). Got the system up and running and it works like a charm. Used it for the first time 2 weeks ago at Swiftsure in the Oatmeal Fog and it's real handy.

I've got a couple of questions for you radar veterans. I've mounted my dome on an aluminum mount that has a 6 degree down-tilt. When the boat is sitting stationary in the water, the raydome looks downward towards the water -- but while up on plane, it will be more or less horizontal. I've seen other installations around where the domes are level while the boat is in the water. Is there a preferred method?

I'm also finding that visibility of sport boats is pretty dicey at anything greater than 1km (even 500m in some cases). I'm assuming that this is due more to the low profile and relative lack of reflectivity of fiberglass? Interested in what others see out there.

Finally, has anyone done any tests on radar reflectors to see whether they make a sport boat show up on radar? I have one of the tube style reflectors installed up high on my boat (about 10' off the water) but have no idea whether it helps or not. For $30, I'm figuring it's a pretty low cost safety device if it allows you to see me on the water.

Will be out at Swiftsure this weekend if anyone is interested in conducting a few visibility tests. Look for a 26' Striper Sport Cabin (Pilothouse) called "Made Glad".

 

[beemer]

Hey Ten Mile. Congrats on the new system. Your present scanner setup should not make a huge difference to your performance. The key is scanner height. The usual equation for recreational style scanners is for every three feet of height you get 1 nm of clear reception. Big targets may show up at six miles but small ones won't. Tuning your radar properly is key , I would suggest picking up a book called Radar basics by Captain Kevin Monahan, local guy with tons of practical knowledge. I have seen lots of boats flying around in the fog with radar and either it wasn't turned on or it wasn't tuned properly. A radar reflector is always a good idea. I like the small tube type , but the reality is that if a guy with radar is not picking up a 18' plus fibreglass boat at under a mile he probably will not be picking you up with a reflector.

 

[ratherbefishing]

I spend some time out at sea in larger fishing boats and let me tell you, if you are in a sport boat you want every chance to be seen on a radar of a bigger boat. I think $30 for a tube-style reflector is a great investment! Would also encourage you to use the radar on days when the visibility is good so you learn to interpret what the radar is telling you and to play with the settings to optimize the set-up.
Sweet set-up by the way.
Good luck and be safe in the 'soup'
RBF

 

[Coyote Spooner]

I have the same set-up on my boat. The radar overlay function is great. It takes the guess work out of what is land and what is a boat, etc... The fact that it only shows targets about one mile out is ok depending on how far out your gps/plotter screen is ranged to. You can adjust the strength of the signal by adjusting the gain. But I usually leave this on the auto setting. Most times when I am trolling I have the radar and plotter set to about 1 mile. If anything shows up on my screen that should give you lots of time to react. Get your sound signaling device at the ready. you can also set the proximity alarm, so if any targets get within the area of you boat, it sound an alarm. This can be adjusted to your specs, in the set-up menu. I agree that it's a good idea to learn with it before you are in the thick of things.

 

[TenMile]

Thanks for the advice guys.

Coyote, is your setup the C70? I've been trying to figure out how to activate the overlay function (I know, I know, R-T-F-M but I can't find that section). I have a Navionics Gold card in the unit and would like to overlay the radar images on the chart. Do you recall how that's done?

For those interested, the reflector I got is really called a "Mobri" style. I picked it up on eBay from a guy on Bowen Island called BoaterBits for $30 and have seen them at Trotac or Westmarine for about $50.

 

[Bushbear]

A link to a site that has a lot of information on radar reflectors. Worth looking at and evaluating what kind you want to run on your vessel.

http://theradarreflectorsite.org/

 

[beemer]

Hi Ten Mile to activate the overlay , you must be in head up mode in the menu unless the radar is stabilised with a fluxgate compass. Press the dispay button to highlight GPS and activate the overlay function in the bottom corner.

 

[Slabby20]

Probably the most important tip I can give you is always make sure you have your radar tuned in properly every time you turn it on. Always check it!! Just because it was tuned right the last doesn't mean it's tuned in right now. I'm speaking from experience. I almost learned the hard way out at Swiftsure when I almost hit another boat (about a 50 footer) with my radar on. I had it on an hour earlier but it the fog had cleared so I turned it off. Then I turned it back on before ducking into a fog bank and a little while later the near collision. As I moved away from that large boat I reached up and adjusted the gain slightly and there he was, huge on my screen.

 

[TenMile]

Hey Bushbear,

Thanks for that link to the radar reflector site. It has a couple of great links to other forums and discussion groups.

There is a good discussion here that has some input from a Navy radar operator: http://www.woodenboat.com/forum/showthread.php?t=70504&highlight=radar+reflectors%2522 -- his comments reinforce what others have said above -- assume you are completely invisible and tune your radar.

One of the members has a super-easy DIY radar reflector. Take an empty milk jug and fill it full of aluminum foil strips cut 1/2 inch wide and 1.5-3" long. The aluminum strips will resonate and provide a very positive return along the radar path. The key seems to be lots of strips randomly oriented.

The results were very disappointing for the Mobri style reflector. It seems to indicate that it will help one sport boat see another sport boat (and that's good) as they are basically at the same level, but a big ship with a radar oriented much higher than the water is still very unlikely to see you.