Questions about Radar on smaller boats?

sail sfbay · Jun 8, 2020

rgranger said:
.............I do a lot of coastal cruising.............I have been caught out in fog. I would have loved to have had radar in those conditions............

Lots of good questions!!

Why don't you see more RADAR on smaller cruising boats.....because these small boat sailors do not want to spend the money and do not sail/motor at night or in the fog
- Does the dome add to much weight aloft? (you could put it on a pole on the stern)............consult with a rigger or install on a stern pole
- Do they draw too much power............no (I had one installed on my Hunter 31 with a small house battery
- Other reasons?................cost
If you have Radar on your smaller boat...
- Where did you mount it?.................stern pole
- Why did you want it? .......to safely sail/motor at night or in fog
- What model did you go with and do you like it?..............Garmin HD radar since it was compatible with my Garmin chartplotter.

Rick D · Jun 8, 2020

I put one on a stern pole (Garhauer) on my 32' after getting caught in dense fog in the shipping lanes a couple of times. Furuno. 30 years ago; they are a bit more sophisticated now

Pizzazz · Jun 8, 2020

Radar is expensive ($2,000+) and only useful if you do overnight cruising. Many sailboats are used as day sailers and the owners would stay at the dock if the weather is bad. If you have radar, you get used to it and cannot live without it. It helps with weather, measuring distances, avoiding other boats, measuring the speeds of other boats.

The biggest problem with radar on a small boat is not height (minimal impact) but the reflections of nearby waves in bigger seas. You can adjust the settings but it only helps a bit. Another way is to limit the radar movement, which means mount it lower on the mast, not above the fractional jib. Typically, you would mount it above the first spreaders, not higher, to give enough room for the genoa to tack. A stern pole is visually unappealing imho.

Power draw is manageable, about 1.5A for the new solid state units, 2.5A for the older analog radars plus the draw of the chartplotter, usually 0.5-1.0A. It does add up but it is manageable. You can use an iPad or Open CPN to view your radar image but I do not find it satisfactory most of the time. Sun readability is not so much of a problem because typically, when you need to use the radar, the weather is cloudy or dark but the integration and the update rate is not so good. Just get an integrated Garmin or Raymarine system for $2K.

SV Pizzazz

Crazy Dave Condon · Jun 12, 2020

What is the weight of a radar. Would it impede the mast raising due to weight?

Capt jgw · Jun 12, 2020

Mounting the radar on the mast puts it way higher than it needs to be. Some big ship radars can reach out 72 miles and they need to be high above the water to achieve that range, but typical small boat units are only 16 to 24 mile range. 6 to 10 feet above deck on a pole will work fine for that. Installation is easier, cables are shorter, etc. Plus if you ever have to run the boat with the mast down or removed, you will still have radar capability.

sail sfbay · Jun 12, 2020

rgranger said:
............have always been curious how a pole mount would work...............

Pole mount worked fine on my Hunter 31 and ple was there when I purchased the boat. When I purchased my Hunter 386 I installed radar on the mast since a radar mast mount was considerably cheaper than a stern pole and the the arch and davits would have been in the way.

tfox2069 · Jun 12, 2020

The higher the radar transmitter is mounted, the further you will see (within the limitations of your radar's power), and - perhaps counterintuitively - will increase the MINIMUM range at which you'll be able to see (to see rocks, pilings, other boats close in during periods of limited visibiity such as fog or night). Radar is largely a line-of-sight, though that is affected by a number of factors - not the least of which is the reflectivity of the object for which you're trying to see, and math will tell you how far you'll be able to see a reflective object. There is also a "dead zone" around the boat which gets larger as the transmitter gets higher off the water. At the heights that pleasure craft mount radars, max range is WAY shorter than the advertised and capable max range of modern radar. For example, if you mount your radar at 6 ft off the water on a pole on your stern, assuming the reflective object was another boat with a reflective surface 6 feet off the water your ability to see that object on radar would be roughly 6nm. If you mount that radar at 40 ft above the water on your mast you'll probably paint that boat at nearly 11nm. If your radar transmitter is on the mast at 40 feet and the other boat has a reflective survace 40 feet above the water (sailboat with a radar reflector that's effective or a big honking ship) you'd likely detect them at 15nm. Here's a link to a simple calculator that does the math for you:

Horizon calculator - radar and visual

There's also a good article on the West Marine site which provides the actual formula used, and some other very good information about the capabilities and limitations of marine radar:

Marine Radar for the Recreational Boater | West Marine

Marine radar is the best collision avoidance system ever developed for boaters. Visit West Marine to learn about the latest radar technology available.

www.westmarine.com

In short - buy a good modern radar with as narrow a beam as you can afford, mount it as high above the water as feasible on your boat, and spend the time getting to know its capabilities and limitations during good weather when you can visually correlate radar returns with actual objects, and you'll be ready to use it when its most needed. Bonus points if you can overlay your radar on top of your chart on your chartplotter - and extra bonus points if you can also overlay weather on top of that for a full picture of everything around you.

Kings Gambit · Jun 12, 2020

I have radar on a stern pole. It’s a relatively small one. I think its range is about 16 n.mi., at least its useful range. In practice, 6 - 8, maybe 10, n.mi. is enough along the coast here. I use it to get a good range & bearing on commercial ships approaching me whenever I’m crossing the lanes. Otherwise, to navigate around the anchored container ships at Long Beach, both inside and outside of the federal breakwater when there is fog, and to see other (recreational) vessels approaching in fog. However, I don’t commonly do this b/c I’m not out in those conditions very often. While helpful, you don’t need radar to navigate in fog if you have a GPS chart plotter and a depth finder. There are other “fog” tools. Namely, the fog horn signals via a fog hailer. But I doubt the smallish vessels have that item either.

If you are caught in fog with no radar, no GPS, no depth finder, and no fog hailer (how could this happen?—small boat like a 20-ft day sailor, for example), and you have no clue now which way is which, the best thing to do IMHO is to anchor, turn on your lights, plumb the bottom manually if near enough to shore, go look at your chart, then issue a Pan Pan (hand-held VHF) your approximate location, and lack of signaling capability. Maybe if other boaters are listening, and know where they themselves are, you won’t get hit

!

tfox2069 · Jun 12, 2020

Kings Gambit said:
I have radar on a stern pole. It’s a relatively small one. I think its range is about 16 n.mi., at least its useful range. In practice, 6 - 8, maybe 10, n.mi. is enough along the coast here. I use it to get a good range & bearing on commercial ships approaching me whenever I’m crossing the lanes. Otherwise, to navigate around the anchored container ships at Long Beach, both inside and outside of the federal breakwater when there is fog, and to see other (recreational) vessels approaching in fog. However, I don’t commonly do this b/c I’m not out in those conditions very often. While helpful, you don’t need radar to navigate in fog if you have a GPS chart plotter and a depth finder. There are other “fog” tools. Namely, the fog horn signals via a fog hailer. But I doubt the smallish vessels have that item either.

If you are caught in fog with no radar, no GPS, no depth finder, and no fog hailer doh: how could this happen?—small boat like a 20-ft day sailor, for example), and you have no clue now which way is which, the best thing to do IMHO is to anchor, turn on your lights, plumb the bottom manually if near enough to shore, go look at your chart, then issue a Pan Pan (hand-held VHF) your approximate location, and lack of signaling capability. Maybe if other boaters are listening, and know where they themselves are, you won’t get hit!

Or...compass and smartphone (doesn't need a cell signal to tell you your GPS position - iPhones for sure, can't speak for others) and paper chart to plot your position given by your smartphone. And if you downloaded your local chart onto a chartplotter app on your smartphone, you don't need a cell signal to use that as a pretty accurate and real-time chartplotter in lieu of plotting on a paper chart.

Noodat Lady · Jun 12, 2020

My Seaward's radar is ancient, bought new with the boat in 2000. It is a Furuno 1622 with a neat small dome. Works fine and is useful. The dome is mounted 7' above the cockpit sole, clear of the boom (good idea!), on the helm binnacle.

Kings Gambit · Jun 12, 2020

tfox2069 said:
Or...compass and smartphone (doesn't need a cell signal to tell you your GPS position - iPhones for sure, can't speak for others) and paper chart to plot your position given by your smartphone. And if you downloaded your local chart onto a chartplotter app on your smartphone, you don't need a cell signal to use that as a pretty accurate and real-time chartplotter in lieu of plotting on a paper chart.

Yeah, with the technology of today, it would seem that even the least prepared boater in experience and equipment could mostly stay out harm’s way with everyday items in possession.

smokey73 · Jun 12, 2020

@tfox2069 I think the practical application of range with the radar, especially for a small mostly coastal cruising sailboat, might give you a different perspective on the need for height. With a 6 foot height above the water and a 4 foot effective height of the target, the range is about 6 miles. Are you really concerned about a 4 foot high target at even this range? What action would you take to "avoid" this target? Would you do anything different if you detected it at 11 miles? Probably not. If its a 40 foot high BFT (Big Floating Target

) you would detect him at 12 miles. Again what action would you take for that target different than if you detected it at 17 miles? For most coastal cruisers, 6 to 10 feet above the water is fine for general navigation and safety in fog.

Now, when it comes to which radar to buy. Of course, buy the best you can afford and justify. However, for a small pocket cruiser with a limited budget a good working used radar compatible with your existing chartplotter that you can buy from somebody who "upgraded" to the latest and greatest would be fine.

Where to place it would be based on convenience and cost of installation as long as you can get it above 6 feet. I would, however, not put it where it you will routinely be standing right in its beam so get it as high as you can if you have to put it on a pole. (Probably just my paranoia from Navy days when sending peopoe aloft)

Capt jgw · Jun 12, 2020

rgranger said:
I've never had active radar and have always been curious how a pole mount would work. Doesn't your own mast create a massive reflection right in front of the receiver?

No. The radar can't "see" anything that close, and there isn't an appreciable shadow either. If it did have an effect, mounting the scanner on the mast would make it blind to the stern, which it is not. They work through 360 deg regardless of how they're mounted.

tfox2069 · Jun 12, 2020

smokey73 said:
@tfox2069 I think the practical application of range with the radar, especially for a small mostly coastal cruising sailboat, might give you a different perspective on the need for height. With a 6 foot height above the water and a 4 foot effective height of the target, the range is about 6 miles. Are you really concerned about a 4 foot high target at even this range? What action would you take to "avoid" this target? Would you do anything different if you detected it at 11 miles? Probably not. If its a 40 foot high BFT (Big Floating Target ) you would detect him at 12 miles. Again what action would you take for that target different than if you detected it at 17 miles? For most coastal cruisers, 6 to 10 feet above the water is fine for general navigation and safety in fog.

Now, when it comes to which radar to buy. Of course, buy the best you can afford and justify. However, for a small pocket cruiser with a limited budget a good working used radar compatible with your existing chartplotter that you can buy from somebody who "upgraded" to the latest and greatest would be fine.

Where to place it would be based on convenience and cost of installation as long as you can get it above 6 feet. I would, however, not put it where it you will routinely be standing right in its beam so get it as high as you can if you have to put it on a pole. (Probably just my paranoia from Navy days when sending peopoe aloft)

Smokey73 you make some good points about convenience and cost - those are nearly always factors to us recreational boaters. I'm most definitely not dissing anyone who uses a pole mounted radar on their stern at all - just understand the inherent limitations and work within them. I've sailed off the east coast on a J42 with pole mounted radar through shipping lanes, and from NY to Maine and Bermuda to NY multiple times on a Hinckley 42 with pole mounted radar. That particular boat has done 13 Bermuda races, a transatlantic and the FASTNET race configured that way - with no chartplotter in the cockpit (or canvas protection for the cockpit). It was built as a race boat and the owner likes it that way. And it works.

I would just say that distance = time to react. Detecting a gofast doing 30 knots at 6 NM while you're doing 6 kts toward the target gives you 10 mins to work through the cycle of detecting (mmm this coffee is good..whoa..what's that on my radar - or you're napping at 0300 because you're singlehanding and you hear a radar alarm, so you shake off the fog of sleep and try to focus on what's happening), classifying (that's a fast moving object - probably a speedboat on plane; is he on AIS - yup, let's see what he is...ah, commercial fishing boat - I'll assume he's fishing, so he has right of way), determining CPA (without course or speed change he'll pass .75nm off my bow **or** looks like we're gonna come close to intersecting), and take evasive action (call on VHF to determine intent if unclear; change course/speed to avoid as necessary, deploy sound or light to deter if other measures are ineffective). And working through this process while you're sailing/navigating/otherwise distracted, possibly at night and in limited visibility, maybe at 0300 near the end of your watch, and maybe through bumpy seas - which also may cause a target to intermittently disappear due to wave height and your radar tilting its scan below the horizon. Sure, under fairly normal conditions this is a pretty easy situation to work through. But I like to plan for when things aren't fairly normal, and if I can put my radar 40' off the water to double my reaction time, I think that's worth seriously considering.

Kings Gambit · Jun 12, 2020

A commercial fishing boat making 30 kt while fishing?