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Muroc 04-21-2007 09:00 AM

Hi all.

I'm new to this forum so apologies in advance for any inadvertent transgressions.

I'm looking at getting a Jeanneau 42DS in the next 12-18 months and as a new purchase the boat comes pretty well 'bare bones'. I'm new to the world of radar and so my question(s) are:
  • or a 42 foot yacht, which I plan to use for mainly coastal cruising, should I be looking at purchasing a 2kw or 4kw radome?
  • is mast or transom mount best? (pros and cons)
  • any suggestions about combo products (radar/depth/speed/wind/gps etc.) and which company provide best value for money?
Any views on the above is greatly appreciated.

Cheers and happy sailing !

Lighthouse 04-21-2007 09:19 AM


Welcome aboard - enjoy your stay.

Harbor_Pilot 04-22-2007 05:02 AM

Welcome Aboard Muroc,

You made no transgressions. That was most considerate on your part.>/smile.gif

Your question is technical in nature and rather specific. We understand it is most important to you, and I do not want to steer you wrong.

Keep checking back for responses from those with expertise on this topic. Meanwhile feel free to explore, ask more, contribute, and participate.

The water is warm, and shark free, jump in,


Muroc 04-23-2007 11:12 AM

Thanks guys for the warm welcome.

For others reading my opening questions about radar please feel free to offer your opinions. I understand that people may be a little hesitant in giving opinions on my questions about the 2kw/4kw and mast vs transom questions etc., but I really am only looking for other peoples experiences and opinions. That is the best way to learn. I believe you should listen to everybody.

I really don't care if you come back with "if you can see another boat then that's your radar" but please I'm listening>/rolleyes.gif. My background is in sailing competition dinghy's from a very early age - including a couple of national competitions in NS 14's (early on the 'fast and furious' but slowing down, as you do, as age determines) moving on finally to owning my first keel boat four years ago (albeit a 21' clunka). Now as I can afford and am looking at a serious big keel boat I'd like to get other peoples input... so please.. please... I'm listening.

Auzzee 04-23-2007 12:26 PM

Hi Muroc,

Purely taking a guess here, but I think most cruisers have experience with mainly one radar set. For example, I got my JRC off the arc when Noah had finished with it. It works fine, chews up the juice a bit, but it sees in the dark. Some of our members have vast maritime experience in merchantmen, but the sets they are used to, are vastly more powerful than the sets we use on sail boats. I think this may be contributing to the uncharacteristic paucity of respondents to your query.

I think if I was to equip my boat with new gear, I would stay with a low power radar with a 16nm range, the money I would save would be invested in forward looking sonar, which these days is becoming highly accurate and can now produce good operating data up to 1600 feet ahead at an arc of 15 degrees either side of the bow at that range.

There is something to be said with the fully integrated systems of say Raytheon, where the radar overlays on the chartplotter/ depth sounder etc....but I am a bit of a luddite and if I can see a black hole in a sea of green clutter, I am happy to head for it.

I think perhaps Stephen off Nausikaa may be able to help you a little.....

But I would avoid Lighthouse at the moment....He's South African....and the World Cup Cricket....well...he's not a very happy cricket fan......enuf said


Lighthouse 04-23-2007 01:40 PM

I don't know too much about electronics. We had a 16nm radar (Raytheon) which we were very happy with and was trouble free for the five years that we had the boat. I my mind, the horizon is about 15 miles off so what would you need anything more powerful for. The bigger ones have better features, etc., but are also a lot more expensive and use more power. We had the radome mounted on the mizzen mast just above the spreader and the screen at the nav desk below. I would have loved to have been able to see the screen in the cockpit though. I'm afraid that is as far as I can help.

"Auzzee" is trying to watch the World Cup cricket on his radar screen and no matter how much he fiddles with the dials he is not going to get it - I'TS ON THE TELE! (Don't tell him - the "fiddling" keeps him busy)

Nausikaa 04-23-2007 02:32 PM

Hi Muroc,

I have been keeping quiet on this one for the very reasons that David mentioned. I have a lot of experience of operating RADAR sets on both merchant ships and coastguard vessels and on a few warships too. Radar sets fitted to large ships are very different to those available for the average cruiser. However there are a few very important, basic commonalities.

On ships, RADAR sets are placed as high as possible (with the exception of berthing RADARs) to give maximum range. There being unlimmited power, in this context, the size of the set is not restricted by the available power. Nor is weight nor windage a consideration.

The parameters for a cruising yacht are very different. There, generally speaking, is always a lack of available power and size and weight as well as windage are also important considerations.

Given that the greatest limiting factor is usualy that of power, I would sit down and calculate how much power is available to power the RADAR and what the battery recharging intevals would be. Once this has been found and the established recharging intervals have been accepted then you have the maximum power available to power your set. At this stage your available power might limit you to a 2KW set or you may find you have enough to go for the bigger 4 KW set. Don't make the choice yet though.

Your next consideration is where to mount the set. As you mentioned, generally there are the alternatives of mast mounting or mounting at the stern on a dedicated RADAR mast or on some form of gantry. Let us consider these alternatives for a moment.

The higher you mount the RADAR antenna the greater the distance to the RADAR horizon. The actual distance can be found using the formula

d = 1.64 . the root of h, where d is the distance to the RADAR horizon in nautical miles and h the height of the antenna above sea level in feet. So, if you want to "see" further mount the RADAR dome higher. But there are some other factors to consider. Just putting a RADAR antenna higher and higher only increases the distance to the RADAR horizon so long as the set has the power to transmit and receive an echo. A more powerful 4KW set will give you a greater range than a less powerful 2KW set.

On the other hand, unless you can mount a 4KW set's antenna high enough, the distance to the RADAR horizon will be limited not by the set's transmission power but by the height at which it is mounted. In this case, a 2KW set is just as good as a 4 KW set. I suppose then, given that you have sufficient power and mast height, a 4 KW set mounted on the mast will give you the greatest range. Unfortunately, it is not as simple as that. There are other considerations such as is their sufficient space to mount the dome on the mast so that it will not be fouled by sails or rig, what will the effect on stability be, what will the effect of the increased windage be?

Because of the problems of mounting the dome on the mast, you may choose to mount the dome on a dedicated mast at the stern or on a stern gantry. Again, we have the problems of windage etc. but fewer issues with stability and available space. There is another issue though. The antenna must be mounted high enough so that the brains of people in the cockpit are not frizzled when the RADAR is in use.

Once the decision of where the dome is to be placed is made we need to consider something else. A RADAR sends out a radio signal. This radio pulse is limited in time, width and height. The lobe, as it is called, will have a vertical angle of 15 degrees or pretty close to that. That means that when you are sailing heeled say 25 degrees to port, you will see nothing to starboard except low flying aircraft! Of course the boat will roll a bit but you get the idea. This means that to be as effective as possible the RADAR antenna should be mounted on gimbals, at least in an athwartships direction. You should "budget" for this too in terms of weight, space and windage if you want optimal performance.

In the "good old days" when RADAR sets used cathode-ray tubes, professional seamen spent weeks on RADAR simulator courses. These were needed as it was difficult to operate a RADAR set and correctly interperet the information received. With the advent of modern displays and ARPA technology interpreting RADAR information has become easier. However one still needs to practice using the RADAR in good conditions in order to be able to effectively use it in bad conditions. If you do fit a RADAR then use it often.

Another issue with RADAR is that a low-lying coast may not be seen whereas the slightly higher land further inland will. This can give a false sense of security if the echo is taken to be the coast-line. You will be closer to the shore than the RADAR seemingly indicates. Danger! This probably is not a problem round Tazmania though.

Also, beware that whilst a big, flat-sided, tanker will be clearly visible on RADAR a smaller, wooden vessel may not. The shape, size and form of a target as well as the material it is constructed from all affect the "quality" of the echo. Remember too that in snow or heavy rain you will not see many echoes as they get lost in the "clutter". The same applies to a lesser extent in heavy weather when echoes dissapear in the "sea clutter" (clutter is simply the mass reflection of RADAR signals by wind, snow or waves).

I would always, when fitting out, invest in a RADAR transponder. e.g. SeaMe, before going for a RADAR set. If I had the space and the money I would have both.

Combined plotters / RADAR are excellent - as long as they work. If the main unit goes south, you will loose both plotter and RADAR. Also, if you choose a combined unit, as David mentioned, beware so that you do not interpret the chart display as a RADAR display. It has happened!

Finally, RADAR is probably the greatest aid to navigation since the magnetic compass (at least for big ship sailors) It has helped to prevent numerous groundings and collisions but its missuse has also given rise to a number of serous incidents - take the collision of the two passenger-liners Andrea Doria and Stockholm as the ultimate lesson in RADAR assisted collisions.

As far as the cost of the comboined units is concerned, I can not advise. You must do some local research but remember that you will remember quality long after the price is forgotten. IMHO, FURUNO make great pieces of kit. Many swear by SIMRAD too and RAYTHEON is reputed to a producer of quality products. There are other, cheaper units too. Your money - your choice.

Best of luck with the boat!



Nausikaa 04-23-2007 02:43 PM

@ Auzzee & Lighthouse,

RADAR is great but nothing beats the "eyeball mark 1". Spent most of the day sitting at a pub on the Waterfront watching the scenery go by. Who cares about the cricket - South Africa has so much more to offer!>/biggrin.gif>/cool.gif>/rolleyes.gif




Lighthouse 04-23-2007 02:50 PM


I have read many replies to a radar topic on many forums but yours has to be the best by far. Thank you for the great post - I have learned a lot.

Nausikaa 04-23-2007 03:03 PM

SeaVenture 04-23-2007 03:27 PM

Stephen, I second the thanks for a well-written, informative post.

I'm still practicing with our Furuno radar/chart plotter (glad to be married to an ex-Navy pilot who's my teacher), though I certainly enjoyed it as we crossed the Sea of Cortez and would have loved to have it working for the few hours of fog we encountered on our trip down the San Juaquin River in Dec. (Something about cables? It wasn't the unit's fault but ours. Fortunately the fog burnt off before we arrived in unknown waters or woke up any ships. Until then, we went VERY slowly at the edge of the channel where we could duck out of the way of anything threatening. And we LISTENED. "What was that? Did you hear a prop? Is that an engine?" "It was a fish jumping, dear." "But, Michael, are you sure?" I can promise you, he wasn't going out with me again without those cables working. We did have a Garmin in the cockpit that worked beautifully.)

I don't know enough about the various units to say one is better than the other, but the Furuno people have been very supportive with any technical questions. Now that they've bought MaxSea (I have a wonderful time with that program, sailing in virtual time when I'm not sailing in realilty), we can use our radar/chart plotter in the cockpit and tie it to our computer in the nav station, which is located in the pilothouse. We also have our dome attached to the mizzen mast.

I've heard difffering comments about the benefits of a gimballed dome, but I'm afraid my brain isn't calling them into focus right now. Are there any reasons you can think of that would make not gimballing a good idea? Ours is on a fixed mount, though I know Michael toyed with the idea of gimballing it.



Nausikaa 04-23-2007 03:38 PM

@ Normandie,

Sorry but this has to be a quick reply - I am just about to dash out.

In short, I would not go for a gimbled dome just to keep things simple. What the effect will be of not gimling is that of poorer echoes but, boats do roll..... I sailed on a topsail schooner many years ago and we had one of the seamen go aloft every time we tacked to "trim the RADAR".

The main issue with RADAR in small boats is that, appart from in fog, when it is most needed, i.e. stormy weather, it will to a very large extent be wiped out be the amount of clutter. Hence my claim that a transponder would be my first choice. At least you would be seen by large vessels.

Sorry for the brevity of this answer ........ must dash




SeaVenture 04-23-2007 07:16 PM

Thank you for the reply, Stephen. A transponder, eh? Another query for my husband. Thank you for the advice.


Muroc 04-24-2007 12:19 PM

Phew !, many thanks folks - especially Nausikaa (very impressive response) - that has certainly given me quite a bit to mull over. I'm glad I asked before I just launched (pardon the pun) into a purchase, probably guided by some mis-informed chandlery salesperson.

I suspect a 2kw mast mount unit (thinking about power requirements, windage, fouling of sails etc. - as rightly pointed out by Nausikaa) is a likely candidate, probably fitted at the first set of spreaders, which would make it about 10 metres above waterline. A transponder eh... hmmm.... may need to do some more homework. I have looked at the Furuno units and they do spec. up well so I'll take a closer look.

I may also need to look at alternative power for recharging batteries when not on shore power... wind? solar? maybe that can be my next question. Any takers?

Auzzee 04-24-2007 12:40 PM

Hi Muroc,

Alternative power is a huge subject and may be worthy of a separate topic. However. If you are going to be cruising mostly around the Apple Isle, you can't afford not to have a wind generator. New Airex marine sets are available through the manufacturer on EBay for an astoundingly low cost. Main problems...You need to mount them high to avoid the possibility of injury and although modern units are much better, there is still a problem with them resonating through the hull (harmonic vibration?).

Solar is great if you are cruising tropical latitudes. No matter whether you use solar, wind, 240v alternator, genset, inverters or whatever, it is necessary to link them to your battery banks via smart regulators.

There is a degree of science involved in determining your power requirements, and determining the appropriate charging system and capacity. Add-ons can be a real nuisance in the future, so get good advice from someone heavily involved in marine charging and storage systems, and build it big enough to allow for a future expansion of power needs.



Nausikaa 04-24-2007 03:50 PM

Hi again Muroc,

I am pleased you found my answer helpfull. It has occures to me though that I should have added a little more about transponders, such as SeaMe. These devices are not cheap, costing about 400 but they are good. The great advantage with a transponder, apart from being seen, is that in normal operations it draws very little current as it operates in "receive only" mode. Once a RADAR signal is received it goes into transmit mode. Alson, it gives a signal indicating that it has picked up a vessels RADAR signal, which is a good warning of trafic in the vicinity.

What is the disadvantage? Well, apart from not being a RADAR as such, thus not being able to indcate the direction and range of the vessel from which a signal has been receved, it operates only on one wavelength. Maritime RADAR operates on either 3 or 10 cm. wavelength. Normally ships use 10cm but at shorter distances 3cm. The advanced RADAR sets big ships use change the wavelength automatically as the range is changed. This means that the transponder will only be picked up on the 10cm. wavelength. Is this a problem? Well, not normally. Looka arround at big ships and you will see that they are fitted with at least two RADAR sets. They usually have one set at longer (10cm) range and one at closer 3cm. range.

Once again, good look with the boat.




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