snooks
Well-Known Member
Follow on from the test of the self-levelling radar in the March 2010 of Yachting Monthly....here's a video
Video of the results...clicky
Video of the results...clicky
The effects of heeling on radar
- Thread starter snooks
- Start date
Ubergeekian
Well-Known Member
How much damping is there on the mount? In the shot of it there seems to be very little - would that not risk the whole caboodle rocking around wildly in choppier water? Clearly it's a good idea in smooth conditions.
NorthUp
Well-Known Member
The radar is in north up- what was the heading, as the effect of heeling will be much more pronounced athwartships?
snooks
Well-Known Member
There's quite a bit of dampening, it wobbles slightly, before the dampening takes effect, but it doesn't sway even in rough weather (2-3 metre swell 25-30 knots off Jersey this summer)
snooks
Well-Known Member
It was in north up because we wanted the images to look the same. Heading was IIRC 320º-350º we were anchored off Gill kicker
Here
elton
Well-Known Member
I've often thought about the effect of heel on the reflective characteristics of the target. I would imagine that a vertical surface (eg a mast) at 90 degrees to the radar beam would produce a good echo. But any degree of heel would result in an (essentially) infinite number of reflections, each a different distance from the source; and each reflection from a point above the centre of the beam would have an equivalent echo from below the centre of the beam. The reflections from points above the centre of the beam would be out of phase with reflections an equal distance below the centre of the beam, and of near equal amplitude and equal but negative phase difference (relative to the reflections at the centre of the beam), thereby cancelling them out. If my theory is correct, then self leveling radar won't be much help in spotting sailing boats. Only a boat fitted with a good parabolic reflector (or active reflector) will be visible to radar, even a self leveling type.
Twister_Ken
Well-Known Member
So, a pole on the other quarter, with a gimballed parabolic reflector then?
snooks
Well-Known Member
Funnily enough I didn't get radar to spot plastic yachts doing 5 knots, I got it for the big metal thing that don't have AIS transponders and catch fish
Ubergeekian
Well-Known Member
Thanks. You have this fitted on your boat, then?
onenyala
Well-Known Member
Gimballed radar
If the strength of the wind was giving a 30 degree list the visibility would probably be OK and the radar not required.
Normally it's bad visibility when I use the radar there is no wind and the engine is on.
If the strength of the wind was giving a 30 degree list the visibility would probably be OK and the radar not required.
Normally it's bad visibility when I use the radar there is no wind and the engine is on.
snooks
Well-Known Member
Yep, that is Pixie's pole and radar
Ex-SolentBoy
Well-Known Member
Who are you kidding. Have you heard of rain or dark nights?
Talbot
Well-Known Member
most people keep the angle of heel to less than the radar beam elevation specifications. Therefore a levelling device would be just additional weight and point of failure.
However, if you heel to the extremes there might be some point.
For most people it is an answer to a non-existent problem
However, if you heel to the extremes there might be some point.
For most people it is an answer to a non-existent problem
Ex-SolentBoy
Well-Known Member
Graham. Loved the article and the video. I have the backstay self-levelling thingy, mainly because I did not want the radar on the front of the mast (lots of other reasons, let's not start a thread on that!).
Anyway, I have wondered whether there was a performance improvement and it's great to see a proper test on something.
I do occasionally get a return from the boom or the mast, but it never lasts for long.
Regards
onenyala
Well-Known Member
snooks
Well-Known Member
Of course it's very easy to judge distance, speed and direction at night in a breeze when you're heeling over
snooks
Well-Known Member
What's Chuck Paine's 20,20,20 rule?
20 degrees of heel is hardly extreme, well not for older designs going to windward any way
Ubergeekian
Well-Known Member
Of course it's very easy to judge distance, speed and direction at night in a breeze when you're heeling over
It's easy enough, with a handbearing compass, to establish the only thing which actually matters: Will it hit me?. I dunno, kids today, all this technology, might as well just use a simulator and be done with it.
Voice tails off, mumbling...
Ex-SolentBoy
Well-Known Member
I thought radar was for collision avoidance. Not everything you collide with can be seen with a handbearing compass.
Unlit buoys? Land at night? Everything in fog? Please PM me when you are out in bad weather so I can avoid the area.
Ubergeekian
Well-Known Member
I thought radar was for collision avoidance. Not everything you collide with can be seen with a handbearing compass.
Unlit buoys? Land at night? Everything in fog? Please PM me when you are out in bad weather so I can avoid the area.
If you are too scared to sail with non-radar craft nearby, you won't go out very much. Incidentally, there is a technique for avoiding unlit buoys and land. We call it navigation.
