Radar dome - mounting options

[SalishAire]

We are FINALLY to the point of installing electronics on Hyacinth (A25). She came to us with an unmounted fairly large radar dome. Clarice has been dreaming of a nice stainless radar arch over the aft cabin that also supports kayaks or a folded Porta Bote and provides a support for the back of a canvas cabin. I'm thinking that may be a spring project unless someone can suggest an A25 to look at with a really nice looking setup that we just can't resist making a copy of.
That said: Has anyone mounted their dome on the cabin roof (ours is now converted to a hardtop with good strength)? My question is does the lower position really affect how much you are "seeing" with the radar? I think that this position would keep the lines of the boat more original, the anchor light (which is now mounted on the tip of the wooden forelight mast) would shine over the top of it, and it would be easy to do so it might provide us some usage in the next couple of months if we get some clearing over Puget Sound.

[DesertAlbin736]

The first Albin 25 we looked at and almost bought back in 2012 had a radar dome mounted & looked like this. Before that time I didn't know such a thing as an Albin 25 existed. I had been looking to switch over from the Catalina 25 sailboat we had at the time to some sort of power boat so we could trailer beyond Lake Pleasant to coastal cruising grounds without having to deal with mast raising. At the time there were so many other issues with that A25 for the price the seller was asking ($17K) that we ended up walking away from the deal. We went as far as using my own truck to trailer it out the 25 miles from the RV storage yard where it was parked in Surprise, AZ to Lake Pleasant, launch it and have the owner take us out for a check ride. None of the electronics including the radar were hooked up & working. It had been recently repowered with a 40 HP Volvo (I don't recall the model number) and there was something wrong with the alignment such that it vibrated so violently we couldn't run it above idle RPM. That and a number of other issues spooked us when the buyer refused to lower his asking price by more than $1K so we walked. But that was my intro to Albin 25's which eventually led to the boat we have now. Ironically the amount we would have spent on that first boat is a drop in the bucket compared to what I've spent since.

Anyway this is what the radar mounting looked like. This is the only remaining photo I have of this boat. Within a few weeks someone else bought the boat & took it out of state somewhere. As I recall it was a 1977 or '78 de Luxe. Unfortunately from this angle you can't really tell how the short mast the dome is mounted on attaches to the roof. But you can see that the top is the stock opening with canvas cover. It must have been bolted to the side or back of the doghouse. That boat did have some nice features including a propane Hiller Range 2 burner stove & oven cut into the galley cabinetry, a split stern rail with pad for attaching a small outboard motor for a dinghy, a divided swim platform & really nice boarding ladder. Another issue that caused concern was how low the exhaust outlet was. That was nine years ago & I'm still driving the same Dodge RAM truck.

Albin (1280x960).jpg

O_Flow_San Diego.JPG

DSCN0572 Mooring at Avalon 7-11-714.jpg

[DesertAlbin736]

This is more like what you might have in mind. The former owner of Leighway posts on AOG once in a while.

AlbinwithAdvancedElementsKayak.jpg

[Ambler27FC]

I have a radome mounted directly to the hardtop of my A27 on the stock stand (maybe 6” tall). The main obstructions are the VHF antennas (unavoidable) and a hardtop over the aft section that is about 4” taller than the forward hardtop the radome is mounted to. It works ok, but it is my first radar so I don’t know if it could be better.

No problems at all mapping the shoreline, spotting channel markets, and commercial ships. Tracking small fast-movers requires concentration .

I believe A25’s have hatches above the pilot house? If so, wouldn’t you want to raise the radome so that you’re not getting face-full of radiation sticking your head out? At night I am constantly sticking my head out the window with a flashlight and those hatches seem perfect for it. The kayaks also seem like they want to raise the mounting of a radome.

[WillieC]

Salish Aire,

What radar and plotter have you landed on? We are considering upgrading, having had a couple fog incidents this season. (We really need radar here in the PNW. That, and decent heat could really extend our boating.)

We currently have a Garmin 741XS plotter, bought new '18 and low hours, and it is compatible with some Garmin radomes. The 7 inch screen is too small in my opinion, but we may just get a radome and hook it up and see how it works. There is a bit to wade through to understand compatibility issues, but so far I've learned that Garmin works with Garmin, sort of.

I'm following this thread closely. Keep us posted and thanks!

BTW, is Leighway's radome off center or is it just me?

[SalishAire]

WillieC:

You might get a look at it soon if we have a break in the weather. Hopefully we will launch for the first time next week but I'm not sure when we can get up and down Hood Canal. In any case we ended up mounting the dome just 3/4 inch above the cabin top. The boat came with a pulse style radar that doesn't use a magnetron and is supposedly much safer as to RF exposure and much happier being down closer to the water. Please give a holler if you are in the Olympia area and you can come and take a look. (PS we have a long way to go before she looks as good as WillieC but she is definitely well on her way to being rehabbed.)
Norman

[LopezMike]

Until recently I would always recommend getting your radome as high as possible. The reason being that I've found the most wonderful part of radar was spotting buoys and the like in strange harbors. And knowing where you are in channels. The chart says that there is a rock that is 40% of the way from one side to the other of a channel. I have no way to judge such distances by eye. The radar made it obvious. Spotting alarming stuff like container ships is pretty much not affected by your radome height!

With the advent of GPS and cheap electronic navigation programs such as Navionics and others, the issue of knowing your relationship to fixed objects like land and documented obstructions such as nav aids is largely solved. Knowing where the damned oil tankers are going and staying aware of current drift is still a big deal but a lower radome location works fine for those cases.

The old bugbear of cooking your brain or eyes with the energy of a small boat radar is just that. Not supported by the evidence. In support of that assertion, I call to your attention that home microwave ovens and therapeutic diathermy machines used in hospitals use the same magnetron. Same part number even. Better than an infrared lamp as it is more penetrating.

I have personally done tests with an ordinary oven with the door and interlocks removed and at a distances of fifty feet the levels are below those recommended by safety organizations. During those tests I horrified an attending marine biologist by warming my hands in front of the oven. Yes, the fluid in your eyes absorbs a bit more energy than other tissues but recreational boat radars are fairly low power. If you don't behave like a complete idiot, you will be fine.

To make it clear, the possible hazards of 10 gHz. radiation are thermal not ionizing. Your genes might get cooked like a steak but you won't get cancer or have kids with two heads.

Mike
Caprice

[WillieC]

Mike, interesting points about mounting height but I will continue using my microwave oven with door closed. I did wonder about sticking my head out the hatch right next to the dome, with the cell phone glued to my ear breathing in the lovely aromatics emanating from the ancient Volvo Penta watching the two part paint on the roof dry mere inches from my nose. As to the kids, well that is all history at least for me.

For our little 6 knot A25s, is the 24" radar dome (with a narrower beam) worth the added expense over an 18 incher? I've seen the videos where the narrower beam will distinguish two objects close together where the wider beam may well see them as one object. When I approach an unfamiliar harbor, I generally take it out of warp factor 7 well before any possible impact.

Apologies to Salish Aire, I should prolly start a new topic. Let's hear more about height and mounting options. For the A25, scale is critical, so as to not upset the feng shui achieved by Per Brohall (other posted topics notwithstanding...) I am trying to incorporate the running and anchor lights and it seems it all should be on the centerline just above and/or maybe behind the radome. Surely Mr. Kirsop solved all this long ago, as he sits in his twice or thrice heated cabin up in the Broughtons in November...

[DesertAlbin736]

The thing about microwave ovens is the RF radiation produced by the cavity magnetron is prevented from escaping by the metal sides of the box and the bug screen-like grid you see in the door window. That effect is known as a "Faraday Cage". That's why Gene Hackman's character in the movie "Enemy Of The State" had his hideout in an abandoned warehouse surrounded by copper wire chain link mesh fencing, functioning as a "Faraday Cage" to shield his clandestine spook-gone-underground activities from NSA electronic surveillance and wiretapping.

On Garmin 741xs chartplotter compatibility with Garmin radar, the 741xs is the same unit we have. It's already semi obsolescent & discontinued. The latest and greatest is is the 942xs, available in 7", 9", & 12" screen sizes. MSRP $999.99, $1,299.99, & $2,699.99 US respectively. I really like the touch screen feature. We upgraded our built in maps this year, which we might as well not have bothered with because we didn't do anywhere as much as originally planned as far as cruising & in the end only did about half of the Erie Canal, and none of Hudson River, NJ coast, or Chesapeake Bay.

20190617_150246.jpg

[WillieC]

The Garmin radome I am considering is compatible either both the 741 and the 942 series. I am thinking we could upgrade later if we so choose. I need to pick cheaper projects. But with this project I’ll get to learn all about NMEA 2000! Yee haw. On a nearly 50yo boat.

Why do I need a heading sensor? They’re cheap too. And cabling and tees. Stop the insanity!

[dkirsop]

Any radar issues I might have had were addressed by the Previous Owner as my boat came equipped at time of sale. He was quite good with carbon fibre and made an excellent mount that attached to the mast on the wheel house. It is now an older unit with dedicated display. It is quite good for testing one's eyesight.

Small vessels often appear as a fast approaching pixel if they appear at all. Chances are you will actually see them first and then confirm your sighting with the small, dim pixel on the screen. Larger vessels such as freighters, ferries, barges and tugs usually appear as small islands gradually traversing across the screen.

Port Side.jpeg

Pilot House.jpeg

With practice it is useful for a range of up to 3 miles but I find it user unfriendly. Beyond 3 miles the image is too small for good definition. So here are my thoughts on the subject.

I mostly run with the range set at 1.5 miles.

I tend to run my radar and GPS with range rings of corresponding distance. This helps when interpreting the radar image. I also keep a chart on my dash to get the "big picture". My chart plotter is equipped with a 7" screen and I know I would find this too small if I was to use it for a combined radar/chart image. If I had a choice my preference would be a 12" screen.

User friendly, intuitive controls are important. I still can't operate the Relative Bearing Line (RBL) without reference to the manual and fumbling with fussy knobs. Too awkward, so I do not use it. Not good if trying to avoid a collision in fog.

A lot of small craft will not appear on the screen, even if they have a radar reflector. From talking with other boaters this is not unique to my unit. So vigilance remains the order of the day. Logs and other floating debris capable of ruining your day will also not show. So you still need to travel at a speed that allows you to stop within your range of vision.

I still think it is useful. Knowing where the large craft are gives some stress relief. The Virtual Bearing LIne (VBL) has acceptable accuracy for keeping one's course and avoiding large objects.

It makes a great rear view mirror.

Make a point of using it in good visibility so you get used to interpreting the image.

The bottom line is: do not buy without trying, so pay a bit extra and go to a store that is set up for this. Make sure the image remains visible in strong sunlight and that the controls are intuitive.

[WillieC]

Thanks, David. Great points all.