Radar question

[lumphammer]

I don't have radar and if I fitted one it would mainly be because I sail mostly single handed and I would use the 'watchman' facility as an extra lookout.
Not knowing anything about the practical use of radar it seems to me that with the boat heeling over and the mast swinging around any time the radar wakes up to have a look around it could be looking at the sea one moment then the sky the next.
How realistic is it for the radar to pick up a ships echo in the one minute or so that it is active?

 

[bobgoode]

Most radar sets have a fairly large beamwidth in the vertical plane, around 30 deg. This takes care of most heeling but in essence you are correct for those times when sailing well heeled.

 

[simon_sluggett]

gimballed dome mount like this may be the answer!
http://www.scanstrut.com/products/product-page.php?range_id=10010&type=Sailboats

 

[sailorman]

mine is on a pole about 12 ft above the wl, works fine

 

[Talbot]

Those gimballed struts are a bit of a con unless you normally sail at well over 30 degrees to the upright. The standard boat aerial has a vertical beamwidth that is designed to be able to cope.

 

[pvb]

Vertical beamwidth is generally around 25deg, so radar returns are dodgy at 12.5deg heel from targets abeam.

 

[boatmike]

That would seem logical. I have my Pathfinder book at hand and can confirm a VBW of 25 degrees. However the standard definition of BW is "the arc over which the power output is more than 50% of the maximum rated output". In practice the return you get will depend on how much power is transmitted at higher angles and sets will vary in this respect. However, in conditions of minimum vis it's often (though not always) the case that there will be little wind. If worried the simple answer is roll the sails and motor.... Gimballed scanners are unnecessary IMHO even if you do have half a boat and sail at stupidly uncomfortable angles of dangle /forums/images/graemlins/wink.gif