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-   -   Radome Mast Mounts: Should They Pivot? (http://www.sailnet.com/forums/gear-maintenance/39736-radome-mast-mounts-should-they-pivot.html)

Valiente 01-09-2008 01:03 AM

Radome Mast Mounts: Should They Pivot?
 
A sailing buddy sent me a link to the Edson technical website. They are known primarily for steering, pedestals, quadrants, etc., but I saw that they made a mast mount for radomes.

Does anyone care to comment on what the advantage is, if any, to having a pivoting mast mount for one's radome? A lot of the pole mount or backstay mounts pivot, but the mast ones don't (in general), and given that the range of "swing" is going to be more pronounced the higher you go up the mast, I wonder why I haven't seen pivoting mounts that often.

I ask because I am weighing the pluses and minuses of pole mount vs. backstay mount vs. mast mount.

Idiens 01-09-2008 04:22 AM

I wonder how the pivot system handles the genoa pushing on it every tack.

Also, the pivot system is likely to weigh more than a fixed installation, and that's top-weight. It's more complex and so more likely to fail, particularly the bit of cable that bridges the pivot.

Finally, marine radar's do not suffer too much from moderate heel angles and when they are seriously needed, one is advised to reduce speed and hence heel angle.

Sasha_V 01-09-2008 04:23 AM

It has to do with weight aloft issues. In order to pivot and keep the raydome level, there needs to be a counterweight also held aloft...and because you do not want it to tangle with sails, that couterweight has to have a fairly short lever-arm, so it has to be considerably heavier then the raydome itself. Frankly, that is reason enough...BUT; The cabling that is actually designed for constant flexing as the raydome swings around is also much heavier and bulkier, so smaller vessels (which are also prone to care much more about weight aloft) usually do not run masts that have enough room on the inside of them to have all the halyards, the masttop wiring stuff and the raydome's springy cabling all fitting in.

Does having your raydome always pointing level and not alerting you to the darting of fishes and the flights of seagulls, YES, absolutely....But on a smaller boat it often creates more problems than it solves to have that optimal system...so you have to weigh it in the balance of your needs and wants. As a test, though, Find out how heavy the entire setup you propse is, add about 10-20% because they never include mounting bolts and plates and such. Measure off that much weight of water or something into a jerry can and using a downhaul, run that up the mast to the height you wanted the raydome. Secure the downhaul line and then tension the halyard as much as possible....Now go for a real sail....Can you notice any difference in performance and boat heel?

That may help you decide.


Sasha

Idiens 01-09-2008 04:35 AM

Although the horizontal beam width (50% power) of a typical small marine radar is in the single digit degrees (say 3 to 4), the vertical beam is nearer 45 degrees. At 30 degrees heel, a lot of energy goes into the sea and sky, on a fixed installation, but this is always the case, even upright. The near sea clutter is rejected and the sky offers little return, so the remaining reflected signal still comes from targets, rain and longer range sea clutter.

Sasha_V 01-09-2008 05:09 AM

And dolphins wearing aluminium foil beanies!

sailingdog 01-09-2008 09:20 AM

Personally, unless you have a habit of sailing at 30˚+ of heel, you really don't need a pivoting radome mount. As others have pointed out, it adds significantly more weight aloft, is far more complicated and more prone to failure.

Most modern boats are much happier if they're sailed relatively flat anyways, with less helm problems and handling problems as a general rule—so if you've got radar on the boat, try to reduce sail, instead of heeling way over. You'll be more comfortable, safer and the boat will generally handle better—which are all pluses.

Sasha_V 01-09-2008 10:17 AM

Your credibility on discussing heel is suspect, SD.
Mr Multihull here thinks it is extreme heel if the martinni sloshes out of his glass.


:)



Sasha

sailingdog 01-09-2008 10:35 AM

Sasha-

That's not accurate... everything I said about most modern monohulls sailing better and generally faster at less extreme angles of heel is true. They're also safer sailing flatter, until they sink. :)

Besides, I don't drink Martinis. :)

Quote:

Originally Posted by Sasha_V (Post 247616)
Your credibility on discussing heel is suspect, SD.
Mr Multihull here thinks it is extreme heel if the martinni sloshes out of his glass.


:)



Sasha


Faster 01-09-2008 12:15 PM

True story, and recent too.

A friend ordered the full suite of radar, plotter,GPS, LCD etc etc, all the bells and whistles. He opted for a gimballed radar mast mount. It all got installed and seemed to work fine and so he headed off to the West Coast and Barkely Sound.

After an uneventful but enjoyable couple of weeks there, he was sailing back through Juan de Fuca in lumpy foggy conditions. After a while he noticed that his radar overlay on the LCD plotter wasn't matching his track, and further, was nearly 90 degrees off. Cycle power, turned the boat played around a bit and no matter what the radar overlay was 90 deg out.

He finally thought to look aloft, and there was his radar, sitting nicely on the starboard spreader, pointing off the to left.

It seems the gimbal mount released, and due to the motion of the boat when the radome slipped off the gimbal, it got "flipped" up onto the spreader instead of dangling by the cable and bashing the mast.... lucky, what?

Anyhow a duck into Sooke harbour and an hour in the bosuns chair and he had it back together and temporarily lashed in place. The installer properly fixed it later.

Anyhow, probably due to sloppy installation in the first place, but it is another potential failure point.

Valiente 01-09-2008 02:07 PM

Quote:

Originally Posted by sailingdog (Post 247587)
Most modern boats are much happier if they're sailed relatively flat anyways,

Heh...I should post the camber of my decks...I'm not standing on a flat surface unless the boat's heeled 15 degrees or so.

The other points are good ones. Perhaps I should just go for a 2 KW higher up (I fly a yankee, so it's not likely to snag), so I can have a decent range and a little bit of a power savings.


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