Backstay radar mount

Electronics, Navigation, Rigging, etc.
bshirk
Posts: 19
Joined: Sun Jun 17, 2007 8:49 pm
Location: San Diego, CA

Backstay radar mount

Postby bshirk » Thu Aug 28, 2008 9:59 am

We're about to plunk down the money for a backstay mount for our radar but before we do we'd like to hear from any of you regarding the pros and cons. What do you have? (We're looking at Questus and ScanStrut.)
Did you install it? Any problems, words of wisdom????
Thanks,
Betsy
s/v Andastar
Baba 30 #236

RBEmerson
Posts: 236
Joined: Sat Jun 16, 2007 8:46 pm
Location: Skippack, PA, USA

Postby RBEmerson » Fri Aug 29, 2008 9:20 pm

Er, why do it? OWTW's scanner is about 25' off the water, on the mast, and does just fine (last radar was there for 15 years, the "new" R70CRC Plus' scanner is in the same spot).

First and foremost, the scanner's beam (which spreads from the antenna) must be above where anyone standing on the cabin house, or possibly reaching up the mast to set a halyard, might be in the beam. That puts the scanner well up the backstay. And that doesn't bode well for avoiding things twisting about in a strong wind.

Unless you have rod rigging, I'd pass on the whole thing.
We are all just a battery failure away from the age of sail.

bshirk
Posts: 19
Joined: Sun Jun 17, 2007 8:49 pm
Location: San Diego, CA

Postby bshirk » Sun Aug 31, 2008 2:53 pm

Where is your radar mounted in relation to the inner forestay? We're looking at backstay mounting partly because we've been on too many boats where halyards and headsails get tangled on the radar. We think it will also be an easier wire run. Did you do your installation, including wire run?
s/v Andastar

Baba 30 #236

Michael of Cambria
Posts: 31
Joined: Tue Jul 03, 2007 4:37 pm
Location: Cruising - currently Mexico

Radar mount

Postby Michael of Cambria » Mon Sep 01, 2008 11:05 am

We agree - better coverage from higher up and you won't blind your crew if they get in the beam. Ours is a 36 mile Furuno mounted just below the spreaders (on a Panda 40); the dome is large so it brushes the leach of the staysail when tacking, but after ten years the sail shows no wear, so it's a non-issue. Halyards just don't get caught in the bracket or dome...
Most units have a twenty-five degree apature, so when level, radar emission goes twelve and a half degrees above and below the plane of the dome. If you are heeled over more than that, you are looking for fish on one side and airplanes on the other, but on the other hand rarely does one have a sailing breeze concurrent with a need for radar. Fore-and-aft will always work, but in swells a self-leveling mount can't keep up anyway with sideways motion...
Michael & Elizabeth
S/V Cambria Panda 40

RBEmerson
Posts: 236
Joined: Sat Jun 16, 2007 8:46 pm
Location: Skippack, PA, USA

Postby RBEmerson » Tue Sep 02, 2008 9:36 am

With a radome (spinning thingie inside a plastic "cake cover"), sail snagging shouldn't be an issue (just add wear patches to the head sails). With an open scanner (spinning thingie without a cover), a pair of stainless rings, above and below the antenna, should keep the sails out of the way. However, I'm not 100% sold on that point and less so on the rings keeping lines out of the way. In short, "radome good, open scanner bad".

The scanner sits on a strut (made from cast aluminum pieces powder-coated - built by PYI, the same folks who do other boat toys including dripless stuffing boxes) secured to the mast by 14 screws. It's not going anywhere in any conditions I hope to see.

The cable is about 1/2" thick and passes through a 1" hole in the mast at the butt and and near the scanner. The latter is sealed with a grommet/gasket supplied by PYI and back up with a lot of Life Caulk. As we replaced an existing installation with another, running a snake for the new cable was part of lowering the old cable (hint: using 3/8" or 1//4" line is a good thing). Otherwise, invest in an electrician's snake lowered from the hole near the scanner's new home. It'll go straight down and can be fished out of the hole near the mast butt (long forceps, bent coat hanger, etc.).

At least Raymarine "allows" cutting the cable and joining the ends with terminal strips. Needless to say, use good crimped terminals on the wires, particularly the shield and core for the video data. Thus, it's possible to have a mast mounted antenna and still be able to pull the stick without major trauma (cutting or pulling the radar cable just to let the mast loose from the boat).

One encounter with a radar beam isn't likely to do much harm. It's the repeated doses, particularly with people on the boat often, that raise the risk level. Also, remember there's "splatter" from the transmitted signal hitting rigging, and particularly the mast, that need to be considered, too. A low scanner, mounted on the mast or backstay, is just not a healthy idea.
We are all just a battery failure away from the age of sail.


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