Graham_Wright
Well-Known Member
Are they worth the money?
Self-levelling radar mounts.
- Thread starter Graham_Wright
- Start date
Talbot
Well-Known Member
depends what sort of boat and how you sail. If you make a habit of sticking the leerail so far under water that it is wet foot time every time you walk down the lee side, then there may be some merit in it. However the wide elevation capability on most radars means that the self leveling gizmo is just another source of potential failure.
A
Anonymous
Guest
Undoubtedly the concept will work (Scanstrut) unless it seizes but it is damped so would be useless for normal rolling. It is designed to compensate for heeling so it's only of interest to people who spend a fair bit of time heeling AND needing a radar. We try not to beat when cruising so it would be of limited use for us. If you are like us, forget it!
As for being worth the money, it all depends on how wealthy you are. Some of us have an annual yachting budget of £10,000s to even £100,000s. Others budget at around £1000 or even less. That has to be your call. Since a radar is not, for most people, absolutely essential (unlike a GPS), clearly a posh mount isn't essential either!
As for being worth the money, it all depends on how wealthy you are. Some of us have an annual yachting budget of £10,000s to even £100,000s. Others budget at around £1000 or even less. That has to be your call. Since a radar is not, for most people, absolutely essential (unlike a GPS), clearly a posh mount isn't essential either!
Gunfleet
Well-Known Member
of course, for coastal sailing a radar might be a more reliable way of establishing your position
ps I have 3 gps but no radar. It's a little boat.
ps I have 3 gps but no radar. It's a little boat.
A
Anonymous
Guest
[ QUOTE ]
of course, for coastal sailing a radar might be a more reliable way of establishing your position
[/ QUOTE ]On the whole, no, because the coast at the shoreline does not paint on a radar. You have to determine precise points from which to take a bearing on the radar for any accuracy and there are few accurate points along most coasts. Usually you are talking about hundreds of meters of uncertainty - at least - in a radar position from one to five miles offshore.
Radar is brilliant in really close quarters - entering locked harbours in zero viz for example - but only when you have practiced your technique and have it to perfection. You'll never to that under sail, beating, though!!
of course, for coastal sailing a radar might be a more reliable way of establishing your position
[/ QUOTE ]On the whole, no, because the coast at the shoreline does not paint on a radar. You have to determine precise points from which to take a bearing on the radar for any accuracy and there are few accurate points along most coasts. Usually you are talking about hundreds of meters of uncertainty - at least - in a radar position from one to five miles offshore.
Radar is brilliant in really close quarters - entering locked harbours in zero viz for example - but only when you have practiced your technique and have it to perfection. You'll never to that under sail, beating, though!!
Gunfleet
Well-Known Member
I wrote 'reliable,' not accurate. You switch the radar on and off. You don't control the gps signal. On the whole, if you have electricity, radar is more reliable.
of course, radar and gps would be couilles de chien
/forums/images/graemlins/cool.gif
of course, radar and gps would be couilles de chien
/forums/images/graemlins/cool.gif
A
Anonymous
Guest
[ QUOTE ]
I wrote 'reliable,' not accurate. You switch the radar on and off. You don't control the gps signal. On the whole, if you have electricity, radar is more reliable.
of course, radar and gps would be couilles de chien
/forums/images/graemlins/cool.gif
[/ QUOTE ]
Indeed, round and bouncy ones, too! /forums/images/graemlins/smile.gif
I think we have to assume that GPS - as a source - is more reliable than anything electrical we have on board by a factor of 10 to 100. It is only known to fail in the vicinity of military trials and they are aren't frequent or for long. GPS sets ought to be more reliable than a radar as there is far less to go wrong and all the kit is in the dry. No moving parts, either.
There is concern about availability in time of war and I think that Selective Availability might be re-invoked at any time, but we are still talking about accuracies ten times better than any radar for nav purposes (as opposed to collision avoidance or channel entry).
I wrote 'reliable,' not accurate. You switch the radar on and off. You don't control the gps signal. On the whole, if you have electricity, radar is more reliable.
of course, radar and gps would be couilles de chien
/forums/images/graemlins/cool.gif
[/ QUOTE ]
Indeed, round and bouncy ones, too! /forums/images/graemlins/smile.gif
I think we have to assume that GPS - as a source - is more reliable than anything electrical we have on board by a factor of 10 to 100. It is only known to fail in the vicinity of military trials and they are aren't frequent or for long. GPS sets ought to be more reliable than a radar as there is far less to go wrong and all the kit is in the dry. No moving parts, either.
There is concern about availability in time of war and I think that Selective Availability might be re-invoked at any time, but we are still talking about accuracies ten times better than any radar for nav purposes (as opposed to collision avoidance or channel entry).
KenMcCulloch
Well-Known Member
[ QUOTE ]
On the whole, no, because the coast at the shoreline does not paint on a radar. You have to determine precise points from which to take a bearing on the radar for any accuracy and there are few accurate points along most coasts.
[/ QUOTE ]
I beg to differ. If you know how to use it correctly radar can be a very accurate means of establishing position.
On the whole, no, because the coast at the shoreline does not paint on a radar. You have to determine precise points from which to take a bearing on the radar for any accuracy and there are few accurate points along most coasts.
[/ QUOTE ]
I beg to differ. If you know how to use it correctly radar can be a very accurate means of establishing position.
Richard10002
Well-Known Member
[ QUOTE ]
[ QUOTE ]
On the whole, no, because the coast at the shoreline does not paint on a radar. You have to determine precise points from which to take a bearing on the radar for any accuracy and there are few accurate points along most coasts.
[/ QUOTE ]
I beg to differ. If you know how to use it correctly radar can be a very accurate means of establishing position.
[/ QUOTE ]
I beg to agree and to differ /forums/images/graemlins/smile.gif
Radar paints the point which it hits first on its travel. If this is the point you think it is on the chart, and you get 3 of them, then you will have a reasonably accurate position.
If the shore line is fairly steep, then there is a good chance that what the radar shows is the actual shoreline. However, in many instances, the picture the radar paints is somewhat inshore of the actual shoreline - and there is always the danger that, in moving the position line inshore to take account of this, you generate a false sense of security.
Having said that, going back 30 years, I/we used radar for position plotting on commercial ships, and it usually provided a reasonable aid, (we had Decca, bridge wing compasses, and radar - no GPS), but we had the pitfalls drummed into us.
Steep cliffs and headlands are good, lowlands arent good.
On balance, I would much rather have a GPS position than a radar position - if they turn it off, they turn it off, but that's unlikely. In fact, it could be that the chances of a radar failing are greater than those of GPS being turned off/failing.
As an ex professional, (for what it's worth), I now use the radar for collision avoidance, and the GPS for navigation.
Richard
[ QUOTE ]
On the whole, no, because the coast at the shoreline does not paint on a radar. You have to determine precise points from which to take a bearing on the radar for any accuracy and there are few accurate points along most coasts.
[/ QUOTE ]
I beg to differ. If you know how to use it correctly radar can be a very accurate means of establishing position.
[/ QUOTE ]
I beg to agree and to differ /forums/images/graemlins/smile.gif
Radar paints the point which it hits first on its travel. If this is the point you think it is on the chart, and you get 3 of them, then you will have a reasonably accurate position.
If the shore line is fairly steep, then there is a good chance that what the radar shows is the actual shoreline. However, in many instances, the picture the radar paints is somewhat inshore of the actual shoreline - and there is always the danger that, in moving the position line inshore to take account of this, you generate a false sense of security.
Having said that, going back 30 years, I/we used radar for position plotting on commercial ships, and it usually provided a reasonable aid, (we had Decca, bridge wing compasses, and radar - no GPS), but we had the pitfalls drummed into us.
Steep cliffs and headlands are good, lowlands arent good.
On balance, I would much rather have a GPS position than a radar position - if they turn it off, they turn it off, but that's unlikely. In fact, it could be that the chances of a radar failing are greater than those of GPS being turned off/failing.
As an ex professional, (for what it's worth), I now use the radar for collision avoidance, and the GPS for navigation.
Richard
Dyflin
Well-Known Member
I think you are selling radar a bit short.
I would rather radar for pilotage than gps any day of the week. It becomes obvious very quickly when radar is not giving a good representation of the view outside the window, but otherwise it's an excellent tool for navigation. Range and bearing of known objects is always used over gps position for anchor positions for example. Parrallel indexing is a seldom seen but fantastic aid as well.
Funnily enough we always had the errors of gps (signalm chart datum etc. etc.) drummed into us as well as radar discrepancies.
I would rather radar for pilotage than gps any day of the week. It becomes obvious very quickly when radar is not giving a good representation of the view outside the window, but otherwise it's an excellent tool for navigation. Range and bearing of known objects is always used over gps position for anchor positions for example. Parrallel indexing is a seldom seen but fantastic aid as well.
Funnily enough we always had the errors of gps (signalm chart datum etc. etc.) drummed into us as well as radar discrepancies.
Slow_boat
Well-Known Member
[ QUOTE ]
Since a radar is not, for most people, absolutely essential (unlike a GPS), clearly a posh mount isn't essential either!
[/ QUOTE ]
Is GPS essential? Would you not sail if wasn't working?
How did anyone manage before it was invented?
Since a radar is not, for most people, absolutely essential (unlike a GPS), clearly a posh mount isn't essential either!
[/ QUOTE ]
Is GPS essential? Would you not sail if wasn't working?
How did anyone manage before it was invented?
Richard10002
Well-Known Member
[ QUOTE ]
I think you are selling radar a bit short.
I would rather radar for pilotage than gps any day of the week. It becomes obvious very quickly when radar is not giving a good representation of the view outside the window, but otherwise it's an excellent tool for navigation. Range and bearing of known objects is always used over gps position for anchor positions for example. Parrallel indexing is a seldom seen but fantastic aid as well.
Funnily enough we always had the errors of gps (signalm chart datum etc. etc.) drummed into us as well as radar discrepancies.
[/ QUOTE ]
You are, of course, correct!
Thinking about it, I am coming from my own perspective where the radar is at the chart table, so cant be seen from the cockpit, whereas the GPS plotter is at the wheel, and turns through 360 degrees.
I also have a concern over power consumption under sail, or at anchor.
Would I use radar for pilotage if I had both at the wheel? - I would use both. If I could only have one which would I choose - radar.... for its' navigation and collision avoidance features.
Which would I prefer for navigation and pilotage only? - GPS plotter, (and depth sounder).
On position - agreed, with known objects, but there is the power issue.
On errors - agreed
I cant remember what parallel indexing is - it rings a small bell, and I recall it is powerful.
I guess if I had a Raymarine all singing and dancing set up, with radar on a C80 or whatever, I would probably make more use of radar, but GPS would win for navigation and pilotage.
Richard
I think you are selling radar a bit short.
I would rather radar for pilotage than gps any day of the week. It becomes obvious very quickly when radar is not giving a good representation of the view outside the window, but otherwise it's an excellent tool for navigation. Range and bearing of known objects is always used over gps position for anchor positions for example. Parrallel indexing is a seldom seen but fantastic aid as well.
Funnily enough we always had the errors of gps (signalm chart datum etc. etc.) drummed into us as well as radar discrepancies.
[/ QUOTE ]
You are, of course, correct!
Thinking about it, I am coming from my own perspective where the radar is at the chart table, so cant be seen from the cockpit, whereas the GPS plotter is at the wheel, and turns through 360 degrees.
I also have a concern over power consumption under sail, or at anchor.
Would I use radar for pilotage if I had both at the wheel? - I would use both. If I could only have one which would I choose - radar.... for its' navigation and collision avoidance features.
Which would I prefer for navigation and pilotage only? - GPS plotter, (and depth sounder).
On position - agreed, with known objects, but there is the power issue.
On errors - agreed
I cant remember what parallel indexing is - it rings a small bell, and I recall it is powerful.
I guess if I had a Raymarine all singing and dancing set up, with radar on a C80 or whatever, I would probably make more use of radar, but GPS would win for navigation and pilotage.
Richard
A
Anonymous
Guest
[ QUOTE ]
I beg to differ. If you know how to use it correctly radar can be a very accurate means of establishing position.
[/ QUOTE ] From my Raymarine HSB Series LCD display spec, range accuracy is better than +/- 1.5% of the max range scale in use or 22m whichever is the greater. The Range Discrimination is 23m which, I presume, has to added to the basic accuracy. The problem is that a radar works out the distance by measuring the time it takes a pulse to return from the target and the timer cannot be perfect at the outset and will not be stable over time. I would expect at least %5 drift over time, could be much more, and some drift with temperature. The Bearing Accuracy is +/- 1 degree. So let's assume that you are 3 nm off the coast (were were talking about coastal position finding?)
Range = 3nm = 3 x 1852 = 5556m 1.5% of that is 83m Plus the 23m discrimination = 106m You also have to allow 1 degree azimuth and by the 1 in 60 rule you get 93m inaccuracy from that. So, 106m in range and 93m azimuth on the 3nm scale. It gets worse as the range increases.
And remember that these are ideal conditions; a perfect reflector and no age or thermal timebase problems (highly unlikely).
Please explain why you think this is better accuracy than a GPS?
I beg to differ. If you know how to use it correctly radar can be a very accurate means of establishing position.
[/ QUOTE ] From my Raymarine HSB Series LCD display spec, range accuracy is better than +/- 1.5% of the max range scale in use or 22m whichever is the greater. The Range Discrimination is 23m which, I presume, has to added to the basic accuracy. The problem is that a radar works out the distance by measuring the time it takes a pulse to return from the target and the timer cannot be perfect at the outset and will not be stable over time. I would expect at least %5 drift over time, could be much more, and some drift with temperature. The Bearing Accuracy is +/- 1 degree. So let's assume that you are 3 nm off the coast (were were talking about coastal position finding?)
Range = 3nm = 3 x 1852 = 5556m 1.5% of that is 83m Plus the 23m discrimination = 106m You also have to allow 1 degree azimuth and by the 1 in 60 rule you get 93m inaccuracy from that. So, 106m in range and 93m azimuth on the 3nm scale. It gets worse as the range increases.
And remember that these are ideal conditions; a perfect reflector and no age or thermal timebase problems (highly unlikely).
Please explain why you think this is better accuracy than a GPS?
A
Anonymous
Guest
[ QUOTE ]
Is GPS essential? Would you not sail if wasn't working?
How did anyone manage before it was invented?
[/ QUOTE ]Like a high proportion of other forum members I was sailing across large chunks of water (around 3 days at sea) long before GPS arrived and before Decca was affordable. We used Consul and RDF with crossed-loops and a goniometer; the ocean chaps were using sextants.
But things move on. Small GPS are as cheap as chips - literally. You can buy a functional GPS on Ebay for the cost of feeding a McDonalds to the family and FAR less than the cost of a tank of petrol in the car. Pre-GPS the biggest reason for having to call the coastguard (Mayday) was that the yachtie was tired, lost and demoralised. Today, you can put a point on a chart to within a few metres of the correct point and know exactly which way to head for safety or calm.
I am not saying that one cannot go to sea without a GPS - we all used to do that - only that given the affordability of GPS it has become a due diligence item - you would be lacking in due care if you went to sea without one.
I bet that there isn't a single forum member who sails out of sight of land and who doesn't have a GPS of some kind?
Is GPS essential? Would you not sail if wasn't working?
How did anyone manage before it was invented?
[/ QUOTE ]Like a high proportion of other forum members I was sailing across large chunks of water (around 3 days at sea) long before GPS arrived and before Decca was affordable. We used Consul and RDF with crossed-loops and a goniometer; the ocean chaps were using sextants.
But things move on. Small GPS are as cheap as chips - literally. You can buy a functional GPS on Ebay for the cost of feeding a McDonalds to the family and FAR less than the cost of a tank of petrol in the car. Pre-GPS the biggest reason for having to call the coastguard (Mayday) was that the yachtie was tired, lost and demoralised. Today, you can put a point on a chart to within a few metres of the correct point and know exactly which way to head for safety or calm.
I am not saying that one cannot go to sea without a GPS - we all used to do that - only that given the affordability of GPS it has become a due diligence item - you would be lacking in due care if you went to sea without one.
I bet that there isn't a single forum member who sails out of sight of land and who doesn't have a GPS of some kind?
Sequoiah1
Well-Known Member
Yes if you are doing a long spell beating, though i would suggest you have a couple of tilt control lines. If you go for the scanstrut stern mount unit it looks quite snazzy but expensive, otherwise go for mast mount type.
Richard10002
Well-Known Member
[ QUOTE ]
Undoubtedly the concept will work (Scanstrut) unless it seizes but it is damped so would be useless for normal rolling.
[/ QUOTE ]
Sitting here looking at my gimballed cooker, I am wondering why the mounts need to be damped. In all but the most atrocious conditions, the cooker doesnt spill a drop, so must stay pretty level during normal rolling, as well as heeling.
What am I missing?
Undoubtedly the concept will work (Scanstrut) unless it seizes but it is damped so would be useless for normal rolling.
[/ QUOTE ]
Sitting here looking at my gimballed cooker, I am wondering why the mounts need to be damped. In all but the most atrocious conditions, the cooker doesnt spill a drop, so must stay pretty level during normal rolling, as well as heeling.
What am I missing?
A
Anonymous
Guest
"What am I missing?"
Wind? /forums/images/graemlins/smile.gif
Wind? /forums/images/graemlins/smile.gif
Richard10002
Well-Known Member
[ QUOTE ]
"What am I missing?"
Wind? /forums/images/graemlins/smile.gif
[/ QUOTE ]
Would Fray Bentos Steak and Kidney Pie and beans for tea help??
I wonder if there is a level of damping which might help with the wind situation, but allow it to keep up with the rolling about - probably not - didnt see much point in the gadget anyway.
Internal gimballing??
"What am I missing?"
Wind? /forums/images/graemlins/smile.gif
[/ QUOTE ]
Would Fray Bentos Steak and Kidney Pie and beans for tea help??
I wonder if there is a level of damping which might help with the wind situation, but allow it to keep up with the rolling about - probably not - didnt see much point in the gadget anyway.
Internal gimballing??
Ric
Well-Known Member
Yes, it does depend on what you use radar for. I use radar primarily as a ship lookout when offshore and solo. With a fixed mount, in rough weather, if I tuned out sea clutter on the leeward side, the radar could hardly see even quite big ships on the windward side. In rough weather I thus couldn't use an alarm reliably as it was always being triggered by sea-clutter, or not spotting ships. With the self-leveller fitted I could filter out sea-clutter much more effectively, and thus"check the brandy bottle" more readily.
Mind you, that was with an old Furuno analogue radar. Some of new generation digital radars can apparently filter sea-clutter by sector, as opposed to trying to average it out over 360 degrees, thus the self-levelling mount might not be as useful with a digital radar.
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Ex-SolentBoy
Well-Known Member
Congratulations. You win the prize for taking the longest ever on YBW to answer a question. 5 years!!!!!
Can anyone else beat that?