Radar/Lightning

Inquiry*** Does the average size trawler, say between 35'and 50', with an average fly bridge or PH height, provide an adequate radar target or do you use a radar reflector located up higher?**** KJ

-- Edited by KJ on Monday 24th of January 2011 06:48:39 PM

-- Edited by KJ on Tuesday 25th of January 2011 09:09:59 AM

RE: Radar

I've always heard that radar sees the biggest hunk of metal on your boat...your engine(s). That is, unless you're a metal boat.

RE: Radar

We have a radar reflector but we've noticed that we sometimes get good returns from boats that don''t have one. It all depends on the mass of the boat, what kind of radar reflective surfaces are on or in it, how the boat is oriented relative to our boat, and how our radar is tuned.

When it's foggy we run in the fog, but when we do one person (usually my wife) drives and navigates using the GPS plotters and compass, and the other person (usually me) works the radar on an almost full-time basis. In order to make sure we don't miss something we are constantly adjusting the radar following radar operation procedures we've learned from a couple of books, one of them being a Royal Navy "how to use radar at sea" book. Strong and weak gains both show you things and overlook things. So the trick to seeing everything, from commercial crab pot buoys to Washington State ferries is to keep varying the display unit's adjustments.

We've gotten weak signals from boats that when we saw them proved to have a radar reflector installed and strong signals from boats that had no reflector, like the smaller sport fishing boats that are very numerous up here.

I think a radar reflector is very definitely worth having but I would not assume that just because you have one you will show up as a big, obvious target on everyone else's radar display all the time.* Lots of variables at work here, and some of them are in the hands of the operators of the boats around you.

RE: Radar

I have one of the common metal Davis round shape reflectors strapped just the spreader of the mast. No idea if it helps, it can't hurt unless they are a lightning attractor. That reminds me there is a last years wasp nest up inone of the corners I need ot take out. i have thought about asking a tow how my reflection appears on his screen, haven't done it yet maybe next cruise. One of the boating magazines did a comprehensive study comparing different passive reflectors a couple of years ago sorry, I can't remember which maybe a google search will bring it up.
Steve

RE: Radar

KJ,

We have a reflector on our boat.* I've asked boats around us how we show on their radar.* Most say we are clearly visible.* I have*no way of knowing whether it's the reflector or our boat (our bridge height is about 14 feet and we have twin engines and a generator) or both.* I wouldn't take it down to find out!* Like Marin said, we can't control how other boaters use and maintain their radar equipment and their ability to know what they "see", or "don't see".

I've attached a photo of the reflector (the "drum" shaped cylinder just below the anchor light on top of the mast).* I like the idea that it's high up on the mast.* The top of the mast is 22' 6" so the reflector is about 21 to 22 feet above the water.

RE: Radar

WESTERLY has a Davis Echomaster mast-mounted in the catch-rain position.* Prior to permanent*install, we*went outside the marina and asked other mariners to look at our radar return with the unit up and down.* Even with our un-scientific test, it was clear that it aids in providing a good radar target, except when the mast blocks the radar signal from the reflector.

If the unit cannot be installed with a 360 exposure, a second unit*mounted in*the*weak/hidden*vector*may be helpful.

RE: Radar

Steve wrote:

I have one of the common metal Davis round shape reflectors strapped just the spreader of the mast. No idea if it helps, it can't hurt unless they are a lightning attractor.** Steve

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I think I can hijack my own thread.
I've been meaning to ask, has anyone, particularly in the tropics, ever had their boat hit by lightning. I vaguely remember something about sailboats running a copper (?) strip down mast to the bottom of the hull as a ground, so that if hit, it wouldn't fry all the electronics.* I would imagine with a lower profile, trawlers wouldn't be at the same risk as a sailboat. So again, has anyone been hit or heard of a trawler being hit?*** KJ**

*

RE: Radar

Haven't had it happen or seen it happen but at least one person on the GB forum has had it happen. It hit the mast and toasted all the boat's electronics.

I am curious if areas that are more prone to lightning strikes like east coast (Fla, NC), have any incidents of boats getting hit.* KJ

Last Summer a guy in my Marina was offshore in his 40' Viking with a tower.* His boat got struck- 30k damage to electronics.* That day his fishing buddies included a Roman*
Catholic Priest.** Makes one think.*

Mike wrote:

I am curious if areas that are more prone to lightning strikes like east coast (Fla, NC), have any incidents of boats getting hit.* KJ

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Sure. Several boats a year get struck here in central FLA.

There is sailboat on my dock that has been struck twice in the last 4 years.

The first time it was struck my DeFever was in the slip next to it.

I reported the strike on the boat next to me to my insurance carrier and they sent a surveyor out and paid to haul my boat to inspect for damage.

We could not find any evidence of a strike on my boat, but every electronic device was kaput - instruments, chart plotters, radios, battery chargers, transducers, alternators, etc.



Mike
Merritt Island, FL.

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Did you have to replace the boats wiring?*

JohnP wrote:

Last Summer a guy in my Marina was offshore in his 40' Viking with a tower.* His boat got struck- 30k damage to electronics.* That day his fishing buddies included a Roman*
Catholic Priest.** Makes one think.*

Click to expand...

Now, that is really thinking.* I had never thought of having a Chaplain on board.* Makes sense!

*

Moonstruck wrote:


JohnP wrote:

Last Summer a guy in my Marina was offshore in his 40' Viking with a tower.* His boat got struck- 30k damage to electronics.* That day his fishing buddies included a Roman*
Catholic Priest.** Makes one think.*

Click to expand...

Now, that is really thinking.* I had never thought of having a Chaplain on board.* Makes sense!

*

Was anyone injured?* Any other damage to the boat?

*

Clergy on boats/ships is a no no. As bad as women aboard. Bad ju ju. My father, an (Anglo) Catholic priest, told of boarding a steamer in the 1930's in his clerical duds and having the crew spot him, roll their eyes and cross themselves. Sure enough, it was a rough trip weather wise.

Glad I don't boat in Florida with its surplus of lightning. ... Perhaps a Marina with tall hills/mountains/buildings around has something in its advantage.

The best radar antenna is still the biggest thing with precise 90 deg corners.

The surplus life raft folding units from WWII surplus are cheap and really effective.

There were no injuries on the Viking (Thank God)

The electronics were toasted, and a lot of the wiring on the tower was damaged.

Some work was done on the panel to replace breakers and gauges.

The weather was wet and only the Captain was on the bridge the rest of the crew were in the deck house.

The boat was returning to the inlet at approx 18knots.


-- Edited by JohnP on Wednesday 26th of January 2011 07:56:03 AM

When I lived at A&B marina in Key West, a sport fisher came in after being hit by lightning, the bolt exited the dashboard on the upper helm and blew a huge hole. The Capt. was sitting there under way and he looked like he had been shot with a shotgun,fiberglass shrapnal. He survived with lots of scars. Last summer here in Belize, a dive boat headed out to the blue hole was hit at the upper helm and exited through a crewman on the lower deck, he did not live. We are the highest thing aroun when were on the sea , and make pretty good targets. BB

Again, if you*do your boating*in a lightning prone area, is it possible to shield your electronics from damage if you get hit? Aren't aircraft instruments shielded?

is it possible to shield your electronics from damage if

YES BUT , to do a proper job they would all need to be disconnected from power and antennas and probably kept in a Faraday Cage .

FF wrote:

is it possible to shield your electronics from damage if

YES BUT , to do a proper job they would all need to be disconnected from power and antennas and probably kept in a Faraday Cage .

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Should*I look it up, or can you tell me what is a Faraday cage?

*

KJ, it's just an electromagnetic shield, which may be how military equipment is protected - I don't know.* On board, the only ready to use Faraday cage is your microwave.* However, stuffing your electronics into the microwave is a bit inconvenient every time you hear thunder, and most boats aren't built with perhaps the next best option, which is a very straight path for a strike to follow to ground.* Even then, there is no guarantee you'll avoid damage.

Faraday cage
* It is generally accepted that this cone of protection extends 45 degrees, all around, from the tip of the metal protrusion.
This means that if the aluminum mast of the average sailing vessel is properly bonded to the vessel's other major metal masses and is given a direct, low-resistance conductive path to ground, the entire boat should fall within the protected zone.
*If the vessel has a wooden or composite mast, a marine electrician can achieve the same effect by installing a 6 to 12 inch metal spike at the top and running a heavy conductor down the mast and as directly as possible to ground, usually through the engine and propeller shaft.
.

Basically just a lightning rod*attached *of the tallest place on the boat grounded to the water.

The 45 deg thing is important as the top needs to be able to cover the entire boat so it is like a cone.**To short and the bow and stern may not fall within the protected barrier created by the. Lightening rod

SD

-- Edited by skipperdude on Friday 28th of January 2011 10:24:26 AM

KJ wrote:

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Should*I look it up, or can you tell me what is a Faraday cage?

*
The reason you are safe in your car if it gets hit by lightning has nothing to do with the rubber tires.* Lightning is so powerful it will get to the ground despite the tires.* The reason you are not cooked is the car itself is a Faraday cage.* The British TV series "Top Gear" did a fairly dramatic demonstration of this in which one of the hosts (Richard Hammond) sat in a car under the most powerful lightning generator in the world, which happens to be in Germany.* Even this thing generates a lightning strike only a small percentage of a real strike.* They fired off the rig and car lit up like a neon sign.* But Richard inside--- who had been instructed to NOT TOUCH any part of the car's body--- was perfectly safe.

A Faraday cage dissipates lightning's energy by spreading it out.* An airplane (a metal one) is a perfect example of a Faraday cage.* Planes are hit by lightning all the time, but the damage, if any, is minimal.* I've seen close-up the result of a lightning strike on the upper fuselage of a 747 (the plane had been stripped of it's paint so you could see the metal) and all there was was a slight discoloration of the aluminum.* Composite airplanes present a bit of a problem in this regard, so to ensure the same Faraday cage characteristics a fine wire mesh is embedded in the composite fuselage panels.* The 787 fuselage is wound, not made of panels, but while I don't know how they do it its fuselage stll has a "Faraday cage" of mesh embedded in it.

*


-- Edited by Marin on Friday 28th of January 2011 06:00:40 PM

Wow. Great info. I didn't know any of that stuff other than the metal spike or strip in the mast.* So, I guess I would have to weigh the odds of getting hit*against the considerable effort of preventative*measures.*Thanks again for the info.** KJ

Sounds like you would want a sailboat in the next slip with a mast tall enough to include your boat in the cone of protection.* JohnP

Will*the aluminum in a fixed canvass enclosure act as a Faraday Cage?*

Last Summer I got scared ****less as we went through storm after storm.* Electricity is not predictable, and so I was scared I was going to die.

Egregious wrote:

Last Summer I got scared ****less as we went through storm after storm.* Electricity is not predictable, and so I was scared I was going to die.

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Just make sure you have completed "final business" with your attorney before boarding*a boat.

By the way, just how many boaters have been killed by lightning during the last decade?* I'd bet it is much fewer than deaths of mountain climbers or motorcyclists.

Still, I can't understand why Floridians*even go outdoors to dare the lightning gods.

*

Fishing skiff hit by lightning on a lake in Louisiana.
Two guys were in the boat.* One guy was putting the anchor away when the boat was hit. He was killed on the spot. The other guy was sitting in a plastic seat, got his butt seared a little, but walked away. You can see the exit hole in the third picture.*KJ

Almost a*hit. *That'll teach'm to own a sailboat! Thanks Keith.



*

-- Edited by KJ on Sunday 30th of January 2011 01:50:07 AM