GPS / Radar mount

[Roger Long]

I spent yesterday whipping up a mount for the Garmin 3205. Got it wired up today and turned it on. Pretty cool to see it jump from Taiwan to the Portland waterfront.

Here is the unit mounted in the position for stowage and inside use:

It swings around for viewing from the cockpit. Since the mounting surface isn't quite square, it needed a level adjustment. This was required anyway as it prevents the mount from being torn out if someone fall against it going up and down the companionway.

Here it is in the outer position:

The upper companionway slide is Acrylic so I can button the boat up tight and still see the display. I can also turn it just 90 degrees and sit in the companionway out of the wind working it while still keeping watch.

Tomorrow I'll wire up the computer connection and maybe try the radar with a temporary mounting in the shed.

 

[Stu Jackson]

Great addition

and good viewing angle possibilities.

What's the "swing" mechanism? A bolt through with washers, or what?

 

[Roger Long]

What's the "swing" mechanism? A bolt through with washers, or what?

It would have been a bolt through with the brass slide strips for the companionway covering up the upper end but I can't get the slide strips off now without disassembling the whole companionway and turtle cover.

So:

Used a 3/4" flat bit to drill about 1/16" into the hatch trim. Drilled through trim and fiberglass at the size that a 1/4 x 20 machine screw will self thread. Drilled for a T nut shank and drove the stainless T nut in flush. I had made up a 2" x 2" square of 1/16" brass with a hole for the pivot and four FH screws. This went over the T nut and was screwed in place with the pivot (a 1/4 x 20 S.S. thumbscrew with fender washer under the head) screw in place and centering it.

There are basically just the four screws holding it with some help from the T nut prongs, drive fit in the hole, and the self threading of the pivot into wood and fiberglass. The strain is limited by the friction of the leveling feature so it should hold.

 

[sailingdog]

Roger--

that's a 3205...I just got one in UPS today. Looks great.

 

[Roger Long]

Roger--

that's a 3205...I just got one in UPS today. Looks great.

Oops. You can tell it was a long day curled up in the quarter berth wiring a new terminal strip for the NEMA outputs from two GPS units and the computer interface working over my head and backwards. Post edited.

The antenna seems very sensitive on these units. All the small GPS units I've tried work fine on a shelf over a berth where they are outboard under the side deck but sometimes have weak signals on the main cabin table. I tried this one on top of the battery box way down in the engine room and it seemed unfazed. Since that's right next to wiring central, I'm going to mount it on a small board and tuck it under the hold down strap for the top of the battery box. I won't have to disassemble more joinerwork to run wires and I'll be able to experiment easily if it doesn't work so well heeled or in rain. I'm going to leave the full length of cable tied up. If I'm then out in very heavy rain with poor satellite coverage, I'll be able to quickly move the antenna outside to the cabin top.

Incidentally, I'm leaving the NEMA connection to the DSC VHF on my hand held. My reasoning is that the handheld has a battery backup and I'll eventually have a small 12 volt emergency battery with a plug for the radio in case fire or flooding takes out the main power.

 

[William12213]

Roger I did something similar when I had my C&C 27. I made a swing out panel that I mounted the radio, chartplotter and radar screen on. When we got under way we just swung it out into the companion way and we had access to everything in the cock pit. It worked great and it kept things locked up inside when we were not on the boat.

 

[sailingdog]

Oops. You can tell it was a long day curled up in the quarter berth wiring a new terminal strip for the NEMA outputs from two GPS units and the computer interface working over my head and backwards. Post edited.

LOL...yup...been there, done that...

The antenna seems very sensitive on these units. All the small GPS units I've tried work fine on a shelf over a berth where they are outboard under the side deck but sometimes have weak signals on the main cabin table. I tried this one on top of the battery box way down in the engine room and it seemed unfazed. Since that's right next to wiring central, I'm going to mount it on a small board and tuck it under the hold down strap for the top of the battery box. I won't have to disassemble more joinerwork to run wires and I'll be able to experiment easily if it doesn't work so well heeled or in rain. I'm going to leave the full length of cable tied up. If I'm then out in very heavy rain with poor satellite coverage, I'll be able to quickly move the antenna outside to the cabin top.

The increase in apparent sensitivity may have a lot more to do with the GPS receiver chipset than it does with the actual antenna design. The new SirfSTAR III and newer chipsets are far more sensitive and lock onto satellites far better than did the older units. They also seem to have far better noise rejection/discrimination and can work with a weaker signal because of that.

Incidentally, I'm leaving the NEMA connection to the DSC VHF on my hand held. My reasoning is that the handheld has a battery backup and I'll eventually have a small 12 volt emergency battery with a plug for the radio in case fire or flooding takes out the main power.

Good idea, my handheld also has an NMEA connection to it... redundancy is never a bad thing IMHO.