Adding radar - on pole or arch?

SaltyC said:
Hmmmm, confused! I understand fishing boats - they do NOT want to be found on AIS. You previously stated you use Plotter and electronic navigation, not traditional nav - Why do you need to do 'the old way' and find a lighthouse? You aren't looking for the 'confirmation of position' because GPS may not be correct?
Click to expand...
I explained at the time, there was a 10 degree compass variation in the area so I overlaid radar on the plotter. Traditional navigation with a compass and chart would have had us on the rocks very quickly at 10+ knots in the strong currents. We couldn’t see the land, lighthouses or any other feature and turning back wouldn’t work in those currents so I was glad to have such a capable system.
 
lustyd said:
I explained at the time, there was a 10 degree compass variation in the area so I overlaid radar on the plotter. Traditional navigation with a compass and chart would have had us on the rocks very quickly at 10+ knots in the strong currents. We couldn’t see the land, lighthouses or any other feature and turning back wouldn’t work in those currents so I was glad to have such a capable system.
Click to expand...
???? But your gospel GPS is irrefutable? So Radar is superfluous.
 
johnalison said:
Probably very good, but for me it would have been a bit of overkill. Almost all my fog adventures have occurred while motoring in calm conditions, so any loss through heeling would not have mattered much.
Click to expand...
True, and overkill perhaps, but it was of most use 4hrs into a Channel crossing heeling under sail when forecast fog patches become in reality much denser fog. I was short handed, just me and a very seasick chum, so having counted half a dozen black blobs marching steadily down on our port bow I dumped all valour and turned back.
 
You can hang it from the backstay as one poster suggested. Those backstay mounts are normally also gimballed, another benefit.

I would not personally want my radar lower than about 10m above the waterline, and you should not ruin your boat (and her upwind ability) with one of those ghastly solar arches, in my humble opinion.
 
Dockhead said:
You can hang it from the backstay as one poster suggested. Those backstay mounts are normally also gimballed, another benefit.

I would not personally want my radar lower than about 10m above the waterline, and you should not ruin your boat (and her upwind ability) with one of those ghastly solar arches, in my humble opinion.
Click to expand...
As I said, the backstay mounts are really only suitable for larger craft where the stay is beefy enough and there is enough space between the stay and the sail, though many are fitted with a support from the deck. I agree about arches' looks but I suppose if you want solar panels they make sense. The chap who bought my last boat fitted an arch, but that wasn't his worst crime; he renamed it Miss Piggy.
 
Dockhead said:
……

I would not personally want my radar lower than about 10m above the waterline, and you should not ruin your boat (and her upwind ability) with one of those ghastly solar arches, in my humble opinion.
Click to expand...
It is a matter of priorities - a lot of other things will “ruin .. her upwind ability” a lot more than a solar and radar arch - eg a long keel, bilge keels, furling mainsail, baggy genoa etc. An efficient modern boat with good laminate sails will slice upwind far faster with a solar arch than most other boats without one.
Radar high up on the mast has most adverse impact on windage and stability, but not noticable on our boat unless racing against an identical sistership.
 
I suspect the radar stability debate dates from when boats were generally less stable. Quite a bit of received wisdom in yachting is dated, but very hard to change.
Even the furling sail debate I’d argue isn’t as clear cut as many suggest. Slightly less efficient for “spherical chickens in a vacuum”, but infinitely adjustable reefing can keep the right amount of power and heel set more often than slab reefing ever could, and the slowest boat of all is the one where crew fell off the foredeck while changing sails!
 
What concerns me about free gimbled radar is the constant movement of the ratar and the possible movement /chafing of the radar connection wiring,

This is why I designed my adjustment to to be fixed in place once adjusted.
 
It does mean there are fewer forces on the internal moving parts though, and a spinning platform is effectively a gyro when rocked side to side.
 
johnalison said:
I can’t tell you what set offhand but as you can see it’s Raymarine, and I changed it from an older one over twelve years ago. It came with an e7 display and I think calls itself digital. I’m not sure about pot markers, certainly not the lemonade-bottle types we get locally, but mooring buoys and middle-sized birds show up.

The specification and performance required will no doubt depend on the type of sailing undertaken. Obviously, some modern sets can given great range and tell you if a wasp is about to land on your boat, but for general offshore cruising decent collision avoidance and general view of the land is enough. Although I have Marpa, this has really been superseded by AIS.
Click to expand...
Older radars fired a fixed frequency high energy pulse, then switched in to receive mode. You couldn't detect anything close in as you had to wait for the unit to switch to receive, and there was ambiguity over the distance.

More modern sets constantly send low power frequency sweeps and distances are calculated by the offset between send and receive frequency. As the set is always receiving, there's no loss of imaging close in.

The mast has an effect on the radiation pattern, the closer it is to the antenna, the greater the effect.

As for height, the safe operating distance calculated for Ship's Radio Licence compliance can be used to work out a useful minimum. It needs to be high enough that people on deck, walking past on a pontoon etc. are not within that.
 
st599 said:
Older radars fired a fixed frequency high energy pulse, then switched in to receive mode. You couldn't detect anything close in as you had to wait for the unit to switch to receive, and there was ambiguity over the distance.

More modern sets constantly send low power frequency sweeps and distances are calculated by the offset between send and receive frequency. As the set is always receiving, there's no loss of imaging close in.

The mast has an effect on the radiation pattern, the closer it is to the antenna, the greater the effect.

As for height, the safe operating distance calculated for Ship's Radio Licence compliance can be used to work out a useful minimum. It needs to be high enough that people on deck, walking past on a pontoon etc. are not within that.
Click to expand...
I don’t know what you mean by close in. I never had trouble picking up craft or even mooring buoys a few boat-lengths ahead..
 
johnalison said:
I don’t know what you mean by close in. I never had trouble picking up craft or even mooring buoys a few boat-lengths ahead..
Click to expand...
To give context, Raymarine Pathfinder (Old, old one) was 40m minimum while the quantum (current) is 6m. There was also an improvement in resolution along the way so easier to see what you’re looking at, and if it’s moving with the much improved doppler stuff.
Realistically it’s the difference between useful for pot markers and mooring buoys and not very useful. Most won’t notice the difference anyway and don’t use radar for that.
 
lustyd said:
To give context, Raymarine Pathfinder (Old, old one) was 40m minimum while the quantum (current) is 6m. There was also an improvement in resolution along the way so easier to see what you’re looking at, and if it’s moving with the much improved doppler stuff.
Realistically it’s the difference between useful for pot markers and mooring buoys and not very useful. Most won’t notice the difference anyway and don’t use radar for that.
Click to expand...
“There’s a bloody maniac 6m ahead of us on Radar - he keeps changing course to stay on a collision heading. “
“Erm, love, are you sure that’s not the anchor on the bow roller you’re seeing? Do you need a nap?”
 
Minerva said:
..., are you sure that’s not the anchor on the bow roller you’re seeing? ...
Click to expand...
Of course the type of anchor will determine the strength of the radar contact. The wrong type of anchor won't show at all and you will be left wondering if it has gone missing🤣
 
You must log in or register to reply here.

Share this page

Top