Radar vs. Spotlight

maryswensen · Posted: Wed Jun 27, 2007 1:12 pm Post subject: Radar vs. Spotlight

We are about to purchase and mount a spotlight on the overhead. The radar is on a five inch mount and most lights will stand 6 inches. Ideally we would like to mount it on the centerline. Absent that location, would could mount it to the starboard side.

What are the chances that we will encounter major problems with the radar?

Any thoughts will be appreciated!

Ed

journey on · Posted: Wed Jun 27, 2007 1:48 pm Post subject:

OK, a couple of thoughts> Radar is a transmission and receipt of electromagnetic waves, right? If you put a metal plate in front of it, the electomagnetic field will be absorbed and reflected. This will both heat the metal object and reflect some energy. The first is what happens in a microwave oven, which is a radar, when you put a metal cup in it. The second will give you a blind spot in the radar return. It will not show up because of the radar gateing, ( it only receives signals in the selected range time,) but may screw up the internal circuitry.

Basically, why put a metal object in the radar scan path, which is a 360 deg field, ~30 deg above and below the horizontal, around the radar antenna. Mount it above or below the antenna, or at least 6' away. I think the radar is more important than the spotlight. One can even use a hand held spotlight.

Boris

drjohn71a · Posted: Wed Jun 27, 2007 2:11 pm Post subject:

Ed,

As a person who has mounted spotlights on several boats, I think you need to first preview what results you'll be getting.

My experience with outside cabin spotlight mountings is that they cause such bright light on the foredeck, railings, etc., that you are effectively blinded. In all of those cases, I simply could not use the mounted light much at all due to several problems.

Some C-Brats have mounted their spotlights on the bow pulpit - that would eliminate the worst reflections. Even there, however, you don't have the control over the beam that you would in a hand held unit. You can purchase remote controlled, suction mount units that would allow you to preview the situation.

To my knowledge, it is not legal to just turn on a mounted spotlight and simply drive your boat around in the dark. Such bright lights blind other boaters and should only be used sparingly, limiting the "on" time, limiting the area covered, and avoiding illuminating other craft. I actually got stopped and recieved a "warning" years ago for constant illumination of the lake shore while fishing.

Good luck on your installation,

John

patrick and linda · Posted: Wed Jun 27, 2007 3:02 pm Post subject:

ALL GOOD RESPONSES. I'LL TAKE A SLIGHTLY DIFFERENT ANGLE OF ATTACH. IF MONEY IS NO OBJECT, FOR AROUND $700. YOU COULD PURCHASE A RADAR ARCH, THERE-BY ELEVATING THE RADAR DOME 20" TO 24". YOU COULD THEN MOUNT THE REMOTE SPOT LIGHT FORWARD AND CENTER ON THE CABIN ROOF. THIS CONFIGURATION GIVES A VERY SALTY LOOK. WITH THE RADAR ARCH ONE COULD ADD ADDITIONAL EQUIPMENT, GPS AND TV ANTENNAS, AS WELL AS AIR HORNS AND THE LIKE.
MY BOAT HAS THIS EXACT PROFILE AND MANY BOATERS HAVE MADE FAVORABLE COMMENTS REGARDING THIS.
GOOD LUCK
PAT

Sneaks · Posted: Wed Jun 27, 2007 3:17 pm Post subject:

First off, I'll have to gently disagree with Boris on this one.

First, if your dimensions are correct, the spotlight will not be in front of the actual radar antenna, which is centered on the radome. Sounds like your light is about 2" below that point. Should have zero effect on range and sensitivity.

Second, recreational radars have roughly 35 watts worth of average power to accomplish everything - including the 2-4kw pulse. Not enough to disturb a bug walking on your radome, let alone a spotlight several inches away.

Third, as Boris correctly pointed out, the receiver is gated and just doesn't see any signals that close to the radome.

AFAIC, go for it, subject to the caveats others state about using spotlights for other than actually docking at night.

Don

lloyds · Posted: Wed Jun 27, 2007 3:19 pm Post subject:

No matter how many times I have tried to use a spotlight, I always end up turning it off because of causing night blindness. I always do better in total darkness. A handheld is good for signaling, and for lighting up landing areas though.

patrick and linda · Posted: Wed Jun 27, 2007 4:07 pm Post subject:

IF CONVENIENCE IS IMPORTANCE, A REMOTE SPOT LIGHT IS THE WAY TO GO. I HAVE USED REMOTES FOR YEARS AND WHEN NEEDED THEY HAVE PREFORMED EXTREMELY WELL. I TEND TO USE THEM A BURST AT A TIME. NEVER LEAVING IT ON FOR EXTEND PERIODS. IN DARK LIMITED AREAS ALL I'LL NEED IS JUST A TOUCH OF LIGHT TO DEFINE THE SHORE LINE OR DEBRIS IN THE WATER.
THE CD-22 IS ABOUT AS LIMITED ON SPACE AS IT GETS. I HAVE BOTH HANDHELD AND REMOTE, THE HANDHELD BECOMES A BACK UP TO THE REMOTE.
WHAT EVER WORKS BEST FOR YOU WILL BE THE RIGHT WAY.
AS ALWAYS, BEST REGARDS
PAT

Jimbo · Posted: Wed Jun 27, 2007 9:48 pm Post subject:

I just installed a remote controlled spotlight a couple of weeks ago and used it the first time last weekend when we left our cabin in total darkness.I mounted it on the centre line of my boat as far forward as I could get it. It actually bolts through the brow in front of the windows. I thought this would be good but unless I paint my bow black it will have to be moved right up to the bow. It did work great for following the shoreline and got us out of our bay safely.
Jimbo

El and Bill · Posted: Wed Jun 27, 2007 11:39 pm Post subject:

Down on the Gulf, we heard tow skippers refer to their spotlight as "Cajun Radar." So, perhaps you need either a spotlight or the radar? And you can 'see' those tows coming for miles as they sporadically sweep their powerful spots.

We have used a handheld spot and they are great! El holds it out the side window or sits on the bow (when we are traveling at 1 mph). She turns it on for a few seconds when we think we spy something in the water ahead(while I close my eyes, to protect them from night blindness) and reports what she sees and I watch radar and GPS (with screen light turned way low) and use my eyes. Once she 'lit up' a flock of geese. They panicked and all the water ahead was white on their take off -- looked like rapids in the darkness.

Has worked well for us on the few times we have been 'caught' by darkness. Only time that has happened to us is when we've been delayed by locking times.

starcrafttom · Posted: Thu Jun 28, 2007 1:03 am Post subject:

the sea sports have lights in the hull at the bow. Has any one done this to a C- dory or been in a sea sport while under way with the lights on. only good for going slow into a port but having the lights out front and low seems like a good idea and they look good.

Sea Wolf · Posted: Thu Jun 28, 2007 6:32 pm Post subject:

Here's my solution (a common one) to the problem on a C-Dory.

Costs about $350-$450 for the remote controlled light, and another $100 or so to fabricate and weld the stainless plate to the bow pulpit.

The wires go into the pulpit tubing and come out down under the center of the rear starboard stanchion plate in the v-berth.

The lamp has two filaments, one for spotlight use, another for flood.

Additional lights on the brow are for docking, retrieving on trailer.

Similar light set up on rear of cabin makes backing up trailer and launching at night much easier.

More photos on page 1 of my album.

Joe.

Sea Wolf · Posted: Thu Jun 28, 2007 7:24 pm Post subject:

Here's an alternate view on night vision and viewing:

Would you like to drive your car at night without lights and depend on your night vision? In town? Out on the unlit highway in the mountains?

Why not just use powerful lights on a boat and light up the water like we do with our cars? Do you think two 45-55 amp headlights and a spot/flood light would be better than your night vision?

I know it's definitely true that water doesn't reflect a lot of light back to the viewer (just like wet pavement), but anything you'd want to see and avoid, like the shore, a rock, a bridge abutment, or marker should stand out against the background, right? Other boats are lit up so you can see them, so they're not a problem.

I've done this on dark lakes at night, and it seens to work out OK, sometimes combining it with radar to see the outline of the shore, which is usually unlit unless there are houses.

Joe.

westward · Posted: Thu Jun 28, 2007 7:57 pm Post subject:

Sea Wolf: Your bow light is an awesome bit of rigging! To what extent does it interfere with your field of vision during the daytime? How has the light held up? I'm definitely interested. Mike.

El and Bill · Posted: Thu Jun 28, 2007 9:03 pm Post subject:

This is an interesting topic, and a good discussion. As always, the adaptations we do to our boats depends upon their use. Certainly, those who are routinely on the water at night (for fishing, or driving a tow boat at 10 knots along a narrow winding canal) have a different use and a different need than those of us who are only out at night when they have misjudged time or had an unplanned event delay them.

Comparing a boat to a car is, for our use of the boat, similar to comparing a boat to a 747 -- two totally different animals with totally different uses. A car is routinely used at night -- we rarely use our boat after dark -- two or three times -- in 6 years. Our car we often drive at night at 75 mph; our boat, the few times we have been forced to travel at night, we rarely exceed 2 knots. Our boat is equipped with night eyes (the radar) and our car is not.

Radar (observed with good night vision) 'sees' all the major landmarks (like the shore, a rock, a bridge abutment, or marker), better than a 55 amp light when off a 1/2 mile, and can be used for navigating into harbor or cove a few miles off far better than the light). Our handheld spot turned on every minute or so 'sees' smaller objects (logs, etc) in the water when traveling slowly.

With a car, you are driving a narrow strip -- with a boat rarely -- Do airplanes fly with spotlights? No, they have space around them and use lights only when landing or taking off. We usually have space around us and, of course, use the handheld spot for 'landing.'

Since our boat use is in daylight, a spotlight is only for the rare time when out at night -- and we don't want a large object mounted ahead of our vision for the 99.9% of the time we do use our boat.

So, we think having mounted spotlights are a great idea for those who do a lot of night travel -- but not necessary for those who do not.

journey on · Posted: Thu Jun 28, 2007 9:37 pm Post subject:

As for mounting headlights, as on a car, a boat doesn't go down a well defined road sticking to the right side. You need flexibility as to where the light is pointed; such as seeing the breakwaters in entering a harbour, picking out the shoal sign, etc, not just illuminating the road ahead. Either a remote controlled light or a handheld does that job. Fixed headlights don't.

Once, when entering Oceanside Harbour at about 1 am, we encountered a dredge which kept its spotlight on us, for some god-forsaken reason. This completely blinded us, and we nearly hit the breakwater, before we figured out (1) it was a dredge and (2) how to get around. The moral of this story is that if you have a spotlight, please be careful where you shine it, so as not to blind the object of your illumination.

Boris