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Old 26-04-2016, 12:41   #1
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Radar location on cutter

I am mast-mounting a new radar on our old cutter. Our staysail is self-tacking on its own boom. The leach of the staysail swings close to the mast.

Therefore...

It seems to me the radar unit must be mounted high on the mast above where the inner stay connects to the mast (the tang). This puts it above the second spreader, which is quite high.

Am I missing anything obvious ?
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Old 26-04-2016, 13:46   #2
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Re: Radar location on cutter

Following this as we're trying to make the same decision. We scheduled our mast pull for May 10th and will be adding radar (and a few other things) while it's down. I'd like to get the radar above the foredeck light, which will likely mean we need to go above the inner forestay if we still want the staysail to remain self tacking. I'm not crazy about the idea that the jib will likely contact the radar every tac but I guess that's what guards are for...

For reference we're planning to use a Kato 750 bracket and guard. I've been less concerned with the height than contact with sails/halyards. But will be curious about the feedback you get here.

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Old 26-04-2016, 13:46   #3
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Re: Radar location on cutter

I have a similar layout but with single spreaders.

Been considering fixing a radar bracket to the side of the mast so the scanner's right above the spreader.

Guessing sails shouldn't hang up on it there - on the other hand the flatter side of the mast may be more prone to collapse/buckle than the front face.
Maybe also fixing the (lightweight) scanner to the spreader would minimise the possibility of the bracket damaging the mast.

Can't decide whether it's a daft idea or not.
Wanna try it & let me know how it works out?
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Old 26-04-2016, 15:20   #4
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Re: Radar location on cutter

Quote:
Originally Posted by Mike OReilly View Post
Am I missing anything obvious ?
The radar height and weight will result in some reduction in stability.

I would rather have the radar on a short pylon at the stern but that's just me.

Alain
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Old 26-04-2016, 15:27   #5
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Re: Radar location on cutter

FWIW, Mike, we've had mast mounted radars for many years and miles, no guards, and have never had any problem with sails hanging up on the dome, nor any damage to the dome. On Insatiable II, a fractional Solent rig, the dome is mounted just above the lowest spreader, and the foredeck and steaming light are incorporated in the mount. If you squint real hard you can see it i n our avatar photo.

I've never understood the worry about sails hanging up... it is just the leech sliding by... what's to hang up?

Cheers,

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Old 26-04-2016, 16:46   #6
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Re: Radar location on cutter

Thanks folks. Keep it coming.

Jim, ours is a true cutter with the inner stay well inboard of the outer. I believe a solent rig has the staysail pretty close to the forestay, and not typically on a boom. Have I got this right?

Ours is on its own boom and the leach of the staysail makes a pretty close sweep near the mast. If I had been smart I would have measured the gap, but smart is something I'm not. Now the mast is on the ground, and I can't find any pics to help.

Other than the length of cable, and more weight aloft, is there any other downside to having the radar dome up quite high? It will be 30+ feet above the deck. I'm not at all worried about the weight. Our boat is hefty. She won't feel it at all. But the cable runs are long, and I'm worried (assuming) this will reduce any scanning close
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Old 26-04-2016, 17:46   #7
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Re: Radar location on cutter

Mike, our Solent jib (staysail, whatever) stay is indeed closer to the forestay than your boat's, but the Solent jib's leech does drag across the dome when tacking. It just does not hang up there. But, I guess I can see how with a boomed staysail (which I don't care for), the leech may be a lot tighter as it goes by. But I still can't see it as a problem.

As to problems from the height, well, the cable length is no worry, other than a bit of extra cost for extra length. Loss of detail in close... hasn't been an issue for us, for we don't normally use the radar for observatons less than a boat length away! Seriously, while you might loose a bit of sensitivity in close, the returns are so strong that I doubt that it is an operational difficulty. On our previous boat, the dome was around 30 feet up, and this one around 25. No issues with either one as to short range sensitivity, and I agree that the weight aloft will not be an issue for you.

As to the location of your leech: the staysail boom must clear the front of the mast by a bit, and the leech of the sail will be forward of the end of the boom by an additional bit. You might be able to work out the location from that info.

Jim
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Old 26-04-2016, 18:53   #8
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Re: Radar location on cutter

VALIS is a cutter, and our radar is mounted on the mast above the first spreader but way below the inner forestay. We have a substantial stainless ring around the radar support structure, and we've had no problems with the staysail or halyards getting tangled in the radar. Here are a couple of photos with some details:


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Old 27-04-2016, 06:52   #9
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Re: Radar location on cutter

Mike, for what it worth. We've been checking out boats around the local marinas for several months now. In that time, we've seen many (possibly most) cutter rigged boats appear to have the radar mounted below the inner forestay. This includes that majority of the other IP owners we've met, and the factory staysail setup is very similar to yours with the self tending jib on the hoyt boom. None of them seem to have any problems with it.

My only real concern here on selecting the location for our radar is that to get above the foredeck light we'll need to be very high inside the inner forestay. The space between the mast and inner forestay at that point looks tight for me to fit the radar and still tac a sail though. If I can do it, I'll stay inside the inner forestay as it just seems preferable to me. However if being above the light is also important, so if it's not doable I'm pretty comfortable that going up in the 30sh foot range would be fine on our boat. Our boats are similar enough from a displacement perspective that I don't think either is going to feel much of a difference based on radar location.

Maybe I'm naive here, but that's my current thinking.
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Old 27-04-2016, 07:28   #10
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Re: Radar location on cutter

I should have waited a few minutes before hitting send. Just heard back from our rigger and he said their typical recommendation for our setup is to relocate the light down a bit and mount the radar where it's currently located. So we'll be mounting inside the inner forestay similar to Paul's post above.

Good luck with your project.
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Old 27-04-2016, 09:05   #11
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Re: Radar location on cutter

OK, thanks guys. This is why I love this place ... makes me question my assumptions.

You've got me convinced Jim, Paul, erBrown. I'm going to take some measurements based on mounting just above the first spreader. I might run into the same issue with the steaming light though...

Thanks again for all your help. I'll let you know how I proceed.
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Old 27-04-2016, 11:08   #12
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Re: Radar location on cutter

Quote:
Originally Posted by unclemack View Post
I have a similar layout but with single spreaders.

Been considering fixing a radar bracket to the side of the mast so the scanner's right above the spreader.

Guessing sails shouldn't hang up on it there - on the other hand the flatter side of the mast may be more prone to collapse/buckle than the front face.
Maybe also fixing the (lightweight) scanner to the spreader would minimise the possibility of the bracket damaging the mast.

Can't decide whether it's a daft idea or not.
Wanna try it & let me know how it works out?
That is food for thought.
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Old 27-04-2016, 11:30   #13
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Re: Radar location on cutter

Not had any problem with the radar dome down lower. The sail just tacks right across it, no problem. Mine were similar height as shown in the pic in post 8. Mine had no protection ring etc. You can just barely see it on the pic in my avatar if you blow up the pic.
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Old 27-04-2016, 13:03   #14
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Re: Radar location on cutter

Ahoy Mike,
Another vote for an intermediate location on the mast. Never have had any issue with the staysail being interfered with by the radar antenna. This is also a 37 foot cutter, so I imagine it is somewhat similar to your situation. By the way, you can see in the photo the location of the staysail stay. It exits the forward end of the ready bag going upward to the mast attach point, which is well above the single spreader.
Good luck.
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Old 27-04-2016, 13:16   #15
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Re: Radar location on cutter

Some things to consider when locating a radar antenna.
The Dropbox link should contain 3 PDF docs(copies of a generic radar inst manual) & a blurb (Off.doc) by me after 30+ yrs in the business.
Hope the link works.
Hope it helps someone.

Cheers/ Len

https://www.dropbox.com/sh/bdp7snawf...2aRokB8ma?dl=0
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