Radar with or without MARPA?

[vyv_cox]

We are investigating which radar to purchase. A very attractive option appears to be MARPA, that gives heading and speed information for any vessels within a pre-set radius. It also alerts if there is a risk of collision.

Buying the Raymarine SL70C appears to be the answer, although it doubles the cost of the display. However, on further enquiry we find that extra kit is required to provide very accurate speed and heading information of the vessel on which the radar is installed. The cost of this gyro compass system is well over 500 pounds, and then you would be stupid not to buy the digital compass display to make it worth having. So the cost of MARPA will be close to 1000 pounds.

Does anyone have any experience of using it? Is it really worth 1000 GBP or can the brain/eye combination do the job almost as well? Grateful for any experience.

 

[Piers]

We use Raymarine's MARPA facility on MBM cruises for two reasons. First, to help judge what other craft are doing (vis a vis collision threat), and second, to target and keep watch on a specific cruise member's boat as we are all going along.

Something to watch for - if a target passes close to another boat which has a stronger return, the MARPA can jump from one boat to the other!

Overall? An excellent aid. Another tool to help decision making.

Piers du Pré
www.playdeau.com

 

[Chris_Robb]

Vyv - Installed the Raymarine Radar 2 years ago. unless you have money to burn I recon it is quite clear enough to avoid colisions, and a bloody site better than no radar at all. so really the question is - is there anything that will give a better return on saftey for the money!

Its also just another bit of electrics to go wrong!

 

[tome]

I've no experience with Raymarine MARPA, but have used ARPA on commercial ships. It's a great tool for tracking other vessels and displaying CPAs and projected tracks. It's likely to be particularly useful if you're short-handed and unable to have someone glued to the radar screen. It can and does lose targets occasionally, and can hop from one target to another if they are in close proximity.

It's used with a gyro stabilised (North Up) display and this is where you need a good compass with an update rate of at least 5Hz. Not knowing the SL70C I cannot be sure but would be very surprised if you cannot display the incoming compass data somewhere? I'm not sure I'd bother with the 500 pound display.

 

[petery]

I have Raymarine with Marpa and it works fine with the fluxgate compass that comes with their autopilots.

btw you can save up to 40% on new Raymarine kit even after duty tax, freight etc by buying on e-bay from the US. Just log on to www.ebay.com and search for Raymarine or Raytheon.

Just bougt an L760 fishfinder with bronze transducer (incl speed and temp), transducer fairing and WAAS/EGNOS GPS receiver all in sealed packages for $2120 + freight $180 = £1464 + £333 duty tax and charges.

That's a total of about £1800. Cheapest I could find in the UK is about £2400 for the fishfinder and about £300 for the GPS.

PM me for specific supplier details

 

[billmacfarlane]

I use mine with the standard Raymarine compass that is included in the package. Initially it takes a couple of minutes to lock on to the target but then it seems to work fine. Incidentally MARPA is the feature I use most with the Raymarine set , I use it much more than the standard radar screen.

 

[Chris_Stannard]

i find that with a fluxgate compass, Raytheon/autohelm and a speed of about 6knots the heading update is not fast enough and the Marpa does jump around a bit. I find it just as easy to put the electronic bearing line on a contact and watch it to see if the bearing remains steady, but if there are several contacts I use the Marpa and then put the EBL on any that indicate they might be a problem

Chris Stannard

 

[Piers]

Is there any difference in the software for the USA market?

Piers du Pré
www.playdeau.com

 

[vyv_cox]

Ebay

Thanks, I tried a search and found one monitor that might be OK, but not for delivery outside USA. Also it looked a bit dodgy, accompanied by a photo of a different model and an apology. Not a deal that I would wish to risk $1400 on.

 

[petery]

Re: Ebay

I have found that some advertisers will ship outside the US if you ask

This one might

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=1873037817

It will be worth looking every day!

 

[ponapay]

What\'s wrong with a chinagraph pencil?

It is cheap, easy, requires no extra hardware, reliable and user friendly.

All you do is put a chinagraph mark on the contacts and then update them at whatever period you think apopropriate - 3 to 6 minutes being best if at a good range, every minute if close.

 

[Piers]

Different software

I have just checked with Raymaine, and their comment is as follows,

"These products are a special promotion package that we (Raymarine) are doing at the moment. They are 'SL' (stand alone series) Pathfinder products i.e. they cannot have repeater displays attached to them via HSB. Consequently they are cheaper than the individually priced items which are being referred to in the cost comparison. Because these are stand alone displays, they are only suitable for those people who want single station units.

"These deals are available world wide. This particular package has a RRP of £2000. Dealers will generally discount off of this price.

Further details of all the 'SL' package promotions are available on Raymarine's web site www.raymarine.com


Piers du Pré
www.playdeau.com

 

[petery]

Re: Different software

I was making a general point about buying fom the US and e-bay in particular.

The unit I bought was not an SL version ( I bought it for HSB2 interfacing) - and it's already interfaced with my Radar/chartplotter.

The items on e-bay tend to be liquidation, trade ex-demo or private sales.

I also got a second-user CE compliant ICOM SSB transceiver and automatic aerial tuning unit for £500 inclucing freight, vat and duty.

I go on my LRC course on Dec 14th.

Browsing e-bay is like browsing this forum - but without the sex, innuendo and bitchiness!!

 

[Opinionated]

Maybe this is a rag-n-stick vs stinkpot thing?

I can imagine that a fast moving boat, with relatively good directional stability given by the engines, would find MARPA highly useful !! But on a slow-moving, directionally unstable thing that most of our yots are, we really don't need such kit.

We, as raggies, use an old-fashioned plotting sheet which reveals not only whether collision is likely (as does the chinagraph) but also what the ColRegs situation is.

In our case, we have to pick and choose what we can afford, and this would be really low on our list.

IMHO, of course.

 

[yachtbits]

Older Raymrine units (pre-marpa) can be upgraded reasonably cheaply by buying the appropriate software upgrade.

US sourced equipment, don't be shocked if UK dealers don't rush to help sort it out if you have a problem. It is not just you that has to pay more than your US counterpart, it is us the dealers too!

From commercial experience, ARPA/MARPA as definate must, particularly for night voyages. It is good to see a manufacturer that is prepared to offer it as standard rather than an add-on.

will work okay with fluxgate, just better with gyro. Heading can be displayed on screen, but if you don't have an autopilot, you will need a compass display anyway and then connect via seatalk. (unless you use a non-raymarine fluxgate that outputs NMEA)

kev
ps, yes we do discount raymarine stuff.

<A target="_blank" HREF=http://www.yachtbits.co.uk>http://www.yachtbits.co.uk</A>
sales@yachtbits.co.uk
marine electrics & electronics

 

[vyv_cox]

Don't know, I've never been on a stinkpot in my life. I have crossed the Maas and Westerschelde entrances many times, day and night, and I confess that I would welcome anything that will assist with identifying the course of shipping.

Unlike you, I find it difficult to see the nav lights on ships at night and therefore to identify their course. How does a plotting sheet differentiate between a ship anchored off Oostende, one entering Oostende, and one continuing up the Schelde to Antwerp? The channels here are only about 45 degrees apart. I have found myself totally confused here on several occasions.

Crossing the Maas is always exciting. Shipping is entering and leaving at a rate of about one per minute, doing up to 20 knots until a short distance from the entrance. It is extremely difficult to judge whether a ship heading towards you, roughly on your beam, is going to be a hazard or not. The slowness of a yacht is part of the problem - if I could do 20 knots the problem would barely exist.

 

[Opinionated]

Well, I wouldn't want to get into an argument about this, but I find it not too difficult to spot which targets on the radar are on a roughly collision course, using the EBL. What is not clear, at night, is what their course is in terms of whether they are crossing, overtaking or what. That is where a plotting sheet comes in handy, but I think some people can do it on the screen either by eyeball or chinagraph.

However, that being said, I have not had the recurrent exposure to traffic such as you describe.

Since I don't have a problem, I have not been really interested in the solution, but I did wonder whether MARPA would be effective with a sailboat whose heading is wandering around all the time - of course I am thinking of wind and waves on the quarter, as they so often are. I spoke with a techie at Raymarine, and it is clear that you have to have an exceptionally good heading sensor to be able to acquire the MARPA target, once you have identified it (which you have to do interactively). It seems to me that you will need a crew member to be dedicated to navigation to be able to continuously work with the radar, identifying the targets for MARPA acquisition, then monitoring their behaviour via the MARPA info. It takes 3 minutes to announce that behaviour, and with your 20kt vessels, that means your targets have moved by a mile by that time - hope you have the searoom to use MARPA.

(Of course, you could do what I do, and avoid being in such a hellhole at night).



IMHO, of course.

 

[vyv_cox]

A few points from your post:

I don't have radar at the moment. The point of my question is whether it is worth having MARPA. The gyro compass, 500 pounds worth, is said to give sufficient signal stability for a yacht.

If heading south from Holland it is almost inevitable that some of the dense traffic parts will be made in the dark. Our normal practice is to set off Friday evening and sail the shallow banks in reasonable safety. By about 1 a.m. we are in the only difficult bit, the assembly area off Westerschelde. Although not a TSS it is regarded as such by some and we have been "ticked off" on VHF. It is extremely difficult to know what is happening here without radar, and for all I know, with it.

Similarly, we crossed the Weser entrance channels in the dark this summer - another very busy and confusing place. We diverted something like 90 degrees for almost an hour to avoid ships making inexplicable manoeuvres. I can't help thinking that MARPA would have helped here.

 

[Opinionated]

It may well be that MARPA is the answer to a maiden's prayer.... Since you do not have radar at the moment, you don't know if you need just radar, or radar + MARPA. I have said my piece, for navigating in general, and, as I said, not in such crowded waters with such highspeed traffic - but the person who can answer your question best is one of your fellow sailors whose sailing profile is close to your own - ie. he sails the same waters and has got radar.

As I said before, it takes 1 minute from you identifying a target (by moving a cursor and pressing a softkey) for the target to be 'acquired'. Then, after 3mins, an indication by a graphic vector of the course and speed. You can then ask for the actual course and speed of the target. You can check on up to 9/10 targets in this way, and I reckon that that is overkill for my shorthanded boat, apart from being worried about getting s/s whilst doing all this work.

If you buy a MARPA radar, let us know...............


IMHO, of course.

 

[petery]

I was reassured about the reliability of Raymarine kit when you confessed in an earlier post in a different thread that you didn't need to stock Raymarine spares as they were seldom needed - so even though I bought the original kit from you I took the risk of buying an add on screen from the states.