Mount electronics in a sailboat?

[Winnipesaukee]

I have a 20 foot catamaran. Obviously, it has no electronics system. This spring I wanted to install a VHF radio and possibly a small stereo system. Obviously, I will need some sort of power source. I'm thinking a battery.

Questions:

-About how much power will I need to last an 8 hour day? I want a fixed mount 25 watt VHF.
-Any suggestions on a battery that is as lightweight as possible? I mean under 20 pounds.
-Would there be any realistic way to charge the battery while out on the water?

Thanks!

[TomC]

if you want to run equipment for a specific time, you need a battery that can deliver the required energy in watt-hours. A 25 watt radio for 8 hours requires 200 watt-hours. Add in whatever stereo you are thinking about, as well - stereos can be power hungry if you like to crank it up. Add in a safety margin if you want to be sure. A solar panel to charge would be the only practical way to charge the battery but they get physically large for any reasonable current capacity. A 1-2 amp panel can approach 2 sq ft in size - and cost $200. At 25 watts your radio will draw approximately 2 amps at 12v so keep that in mind. To charge your battery, the solar panel (or whatever you use to charge it) wil have to supply current in excess of whatever you're drawing from the battery.

Finally, battery and battery life. You would need a deep cycle battery for this application. Capacity is proportional to size, so light weight is challenge. The energy-to-weight ratio for conventional (lead acid) batteries is around 30 watt-hours per kilogram. So assuming that you selected a battery with a rating of 600 wh to run your radio, stereo, and provide a safety margin, you are looking at a weight of 20 kg or 44lbs.

Like most engineering problems, this is one of selecting the best compromise for balance of features that makes the most sense to you.

[Skip]

Originally Posted by TomC

...A 25 watt radio for 8 hours requires 200 watt-hours...

Excellent information, but a clarification on power requirements.

The 25 watt radio referenced by the original post is for a VHF marine two-way radio. The 25 watts specifically refers that at high power output the radio produces 25 watts of RF power. To do this requires approximately 6 amps DC at 13.8 volts, or about 83 watts hours while transmitting.

Obviously actually transmitting is only done during a very small portion of the unit's on time, the vast majority of the time the radio is receiving or just in stand-by mode. Receiving a signal at full volume requires about 1 amp DC at 13.8 volts or 13.8 watt hours. When in stand-by (neither transmitting or receiving) the unit consumes about .25 amps at 13.8volts or less than 4 watts. Since the radio spends the majority of it's time actually drawing around 4 watt hours it changes the storage batteries requirement drastically.

The concern to me would be the type and power requirements of the stereo system being considered. Wattage will increase with volume selected, type of display used and length of time it is operated. In my experience with mobile and marine electronics it would be the stereo system's requirments that consume the majority of the calculated wattage.

In my experience your suggestion on solar panels is an excellent option to minimize battery consumption while the boat is being operated, and to recharge the battery during off time.

Ah, but the battery. No way around that one, you will need a deep cycle, prefereably a gel type with no spill capabilities. Therefore you are looking at a battery in the 50 pound range.

Or, you could always by a portable boom box and a decent handheld marine vhf with an external antenna installation!

[Lakegeezer]

The biggest issue I think you'd have in a catamaran is mounting the battery. The smallest ones that will do the job are going to be 10 lbs and its easy to get to 40 lbs. Where are you going to mount it? Think of the slamming a cat takes and the potential for turning over (or turtle). The battery mount has to take the jolts in all directions. Can you get inside the pontoons? That might be a good spot, and you could also mount the speakers from the inside. Watch where you put the weight - a battery makes a big difference - both front and back and side to side.

If you can't get the battery figured out, buy a waterproof VHF hand-held and store it a small winch-crank pouch near or on the mast.

Solar chargers work, but the inexpensive ones are slow and the fast ones are expensive. You have mounting issues with them too. There are flexible forms, but its not the kind of think you can walk on.

[fatlazyless]

For about four or five dollars the Saint Vincent de Paul store in Laconia occaisionally has second hand, am-fm-stereo cassette players made by Sony, Panasonic or Emerson. Powered by four 'c' batteries, these are relatively small boom boxes.

And, pre-recorded stereo cassettes sell for either 10 or 25 cents each.

Have never seen a vhf, two-way marine radio at Saint Vincent's but you never know what one will find there, or where all the stuff comes from?

Maybe, M & M Marine Salvage in Meredith has second hand, vhf radios & antennas?

[Winnipesaukee]

Thanks for the replies. I'm definitely going to scrap the stereo idea and just put a shower radio in it.


The insides of the hulls are accessible, but only through 7" diameter holes... Still thinking of a solution for a battery.

I wanted to run a coax to the top of the mast to the antenna. Let's say it is 30'. How would a 5 watt handheld VHF compare in range to a fixed-mount attached to the same antenna at the top of the mast? I understand that VHF waves are line of sight, but will the wattage make a difference? Will I lose any gain in the ~35' length of coax?

[Silver Duck]

You would definitely get more range from a 25 watt fixed mount VHF than from a hand held.

But, that said, antenna quality and height are very much the controlling factors for range in a line of sight situation such as VHF. With your antanna at mast head height, I suspect that even with a hand held unit you will have more range than the typical fixed mount VHF setup with the antenna only a few feet above the water!

Silver Duck

[Skip]

Gotta agree with the 'Duck....

One thing to remember, with the antenna placement you describe a quality 5 watt handheld will receive just as well as the 25 watt fixed mount. However, the 25 watt output on transmit will definitley improve range over the handheld, but you will be amazed at the performance of a handheld utilizing an external antenna.

The determining factor in your proposed set-up? The quality, and hence the loss factor, of the coax cable you intend to use. Do not scrimp here, as cheaper cable can have double or triple the loss of good quality marine grade RG-8 or highr loss RG-58 cable.

Frankly, if you are doing all your sailing on Winni I think that a quality handheld with external antenna option coupled with a portable stereo system is your best option. Not only does it give you many portability options, but when you leave the boat you can take your electronics with you and cheat the thieves out there!

[brk-lnt]

Another option to consider would be a 15W solar panel and charge controller ($200 last time I bought a kit from Northern Tool), along with an alarm panel battery mounted in the Cat. You can get a 12AH (amp-hour, I don't generally see batteries labeled for watt-hours), battery for $50 or so. It's a sealed gel unit and will handle normal discharge cycles easily (I've done similar arrangements for other purposes).

Setup a waterproof quick disconnect so that when the boat is docked you can connect the solar panel to charge the battery. (In my experience a 15W 12V panel is about 18" X 40" or so, too big to mount on your cat). Keep the battery basically for backup juice in case the batteries in your handheld VHF get low.

Or, even simpler, get a kit like this: http://www.amazon.com/Midland-NTVP1-...QNHSSXP8N96PK7 and drop it in the charger when you're not using it.

For use on Winnipesaukee, I think that a quality handheld VHF will give you all the coverage you are going to need.

[Winnipesaukee]

Thanks again for the replies. I think the benefits of the extra Tx range with a fixed-mount are not worth the headache of dealing with a power/charging setup. I'm going to go with a handheld radio with an external antenna mounted on the top of the mast. Some more questions:

-Any suggestions on a handheld radio that is submersible (does not have to float), has a great battery life, and an external antenna adapter? Cost is not an issue; I'm not skimping on a safety device. I prefer Standard Horizon because of their excellent customer service, but any brand will do.

-What grade of coax should I get? I will be running about 35'. Again, cost is not an issue. I want the best quality.

-What antenna/mount should I get? I want to keep weight as absolutely light as possible.

Thanks again!!

[Dr. Green]

Sustain Ability, 50 Canal Street, Laconia, sells solar panels, including lightweight ones that can be used on (some) boats. I'm not sure what you could mount the panel on on a catamaran, but these do not have glass, so no danger of shattered glass on the boat - rather a polymer covering.

[Skip]

Your best bet is to visit the retailer you intend to buy from. There you can sample and see everything you are interested in.

Most of the West Marine stores I have used are well stocked, carry everything for your particular job and usually have an electronics person available to answer all your questions.

Or, check with regular posters here who have a local store they may recommend...and any references for competent installers unless you plan to do the job yourself. The trickiest part of this installation would be the proper installation (soldering) of the RF connectors on each end of the cable.

[brk-lnt]

You're going to be hard-pressed to find a handheld that is water-tight while connected to an external antenna. Most are "splash-proof" and offer a vinyl bag setup for true waterproofing.

[ApS]

1) If you're looking for a "shower radio", be sure to check the quality of the speaker(s). I bought one that is unintelligible right next to my ear!

2) On most 20-foot catamarans, the portable VHF radio would be relatively dry if located in a pocket at the mast "dolphin striker". It would definitely get some "splash" there, but would be relatively dry and available for almost any event I can think of. (And out of the way).

3) The connector to the antenna coax could be taped next to it for quick access.

4) While your antenna may be over 30' above the water, one emergency contingency in a catamaran could have it between 1' to 30' below the surface!

[Mee-n-Mac]

Originally Posted by Winnipesaukee

Thanks again for the replies. I think the benefits of the extra Tx range with a fixed-mount are not worth the headache of dealing with a power/charging setup. I'm going to go with a handheld radio with an external antenna mounted on the top of the mast. Some more questions:

-Any suggestions on a handheld radio that is submersible (does not have to float), has a great battery life, and an external antenna adapter? Cost is not an issue; I'm not skimping on a safety device. I prefer Standard Horizon because of their excellent customer service, but any brand will do.

-What grade of coax should I get? I will be running about 35'. Again, cost is not an issue. I want the best quality.

-What antenna/mount should I get? I want to keep weight as absolutely light as possible.

Thanks again!!

I'm not sure which is the "best" handheld for you but before you go mouting an external antenna and associated stuff, you might just want to try out the handheld all by itself. It's not like it's going to be that far from you to any likely receiver.

As for the "stereo" I'd ask what you're trying to do. If all you want is music for yourself when out, one of those solid-state MP3 players with earbuds would seem to make a lot of sense. Almost waterproof, easy to secure, and cheap. I think some also come with an FM radio too. If you're looking for sounds to entertain the whole crew ( ) then there are battery powered portable devices in all shapes, sizes and capabilities. You can even get a "waterproof" case w/speakers for your iPod. I'd just worry it would find it's way overboard in no time on a 20' cat.

Whatever you do carry spare batteries for both items in your hull. I'll guarantee that when you go to use the electronic device the battery will die.