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Old 24-03-2009, 20:43   #1
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Masthead Antenna Cable

I am planning to install a masthead antenna on my Beneteau 281. My last boat was a Tanzer 22 and the wind speed cable made a slapping noise against the inside of the mast on a calm night at anchor or at the dock. I want to avoid this disturbance to my neighbours for the antenna cable. Are there any suggestions out there on how to eliminate or reduce this?

Or is a rail mount antenna nearly as good?
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Old 24-03-2009, 21:26   #2
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Waterborn...Are you going to put it inside the mast or on the outside???
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Old 24-03-2009, 22:34   #3
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The official way is to install a PVC pipe. The quick and dirty way is to put a plastic cable tie on the cable every foot or so, without trimming the excess length.

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Old 25-03-2009, 05:10   #4
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Use groups of three tie-wraps, fixed at 120 degrees (making a horizontal tripod). The tension they provide against the inside of the mast keeps the cable (more or less) centred, prevents the harness from slapping, and allows free-running of internal halyards.
When pulling a new cable (or wire harness) into the mast, it’s essential to ensure that the cable does not wrap around any existing lines (halyards, wiring).
Pull the ties “snug”, but not so tightly as to compress the cable insulation, which creates pinch points in the co-ax, that will affect the impedance resulting in more power reflected back from the antenna to the radio.
You also want to install some means of supporting the weight of the cable at the mast head.

The (high) masthead is a much better antenna location than the (lower) rail.

A conduit inside the mast not only controls the slapping, but adds protection from internal halyard chafe. As Nick notes, this is the “right” way to do it - but it’s a big job, especially if you already have wiring installed.
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Old 25-03-2009, 05:26   #5
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Thanks guys,
A very clear explanation.

I have an in-mast furling, so there is limited space inside the mast. This might be beneficial to a snug fit though. Maybe it will stop raining and I can go over to the yacht club and have a closer look eh Gord?
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Old 25-03-2009, 06:34   #6
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It's possible that there is already a conduit in there. If you have a light a top the mast it probably is in one and you probably can get the antenna wire in the same.
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Old 25-03-2009, 06:40   #7
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... Maybe it will stop raining and I can go over to the yacht club and have a closer look eh Gord?
Rain's just water, not as good as whiskey, but no fear.
Give me a call before you go, and I'll meet you there.
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Old 30-03-2009, 20:32   #8
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How would one go about installing the conduit in an aluminum mast? I have 3 internal halliards plus two loose cables in there and I'd like to make some changes. My last boat had no internal halliards, and was a lot smaller so the wire tie trick worked just fine. This one is bigger being about approx 9x5 inches.

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Old 31-03-2009, 06:12   #9
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How would one go about installing the conduit in an aluminum mast? ...
Don Casey has a pretty good description of this painfully finicky procedure, on pages 100 ➛ 102 in his book “This Old Boat”

Beginning here:

This Old Boat - Google Book Search
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Old 31-03-2009, 18:13   #10
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Oh boy, I can see where thats going to be great fun. My mast cap is welded in place. Otherwise it makes perfect sense. Thanks for pointing me in the right direction.

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Old 01-04-2009, 03:43   #11
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... My mast cap is welded in place...
Which will likely make “back-fishing” the only practical way to thread the co-ax out of the conduit, and through the (bushed & sealed) exit hole in the mast. In this case, I would stop the conduit sleeve about a foot short of the exit hole.
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Old 01-04-2009, 08:02   #12
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I really love this forum and spend way too much time here.

Hope this does not hijack the thread. I know I caught myself doing that recently.

I recently tried to pull a new cable with an old one thru the conduit. My help at the bottom of the mast had to pull the splice back down when things snagged. My splice held. The wire above ths splice just broke. (which tells me that I'm the one who broke it).

Bottom line is, I lost my path inside of the conduit. So I've been laboring on whether or not to just go outside of the conduit. Now I'm feeling better about it. The cable ties idea works for me.

So with no current leader, a small hole at the top and a small hole at the bottom, what'e the best way to string a new tail thru the mast. I think a electricians fishtape would be difficult due the the exit point. The other trick of a vacuum at the bottom to suck in a light string that I feed down from the top seems my best option. Then attaching a much heavier pull cord of course.

I used that method to string a small gauge wire thru a tiny hole for a brake light in a roll bar I installed once. That seems a lot more difficult than this. Anybody else had experience doing this in a mast?
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Old 01-04-2009, 10:29   #13
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Hope this does not hijack the thread. I know I caught myself doing that recently.
No problem Minggat. Once the person who posted the threads original question has been answered thoroughly, then its fine to ask a second question that is somewhat related to the original question. A little thread drift is fine.
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Old 01-04-2009, 10:30   #14
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Back-Fishing:
Once your fish tape has been pushed through the conduit (and a few inches out the end), insert another short tape, bent into a “Z” shape, in from the other side. Crank the bent short tape, so that it entangles the end of the long fish tape, then pull gently (with someone feeding from the other end) out your exit hole. Sometimes a few loops of string on the fish tape’s end hook help to snag it.

Quote:
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... So with no current leader, a small hole at the top and a small hole at the bottom, what'e the best way to string a new tail thru the mast. I think a electricians fishtape would be difficult due the the exit point. The other trick of a vacuum at the bottom to suck in a light string that I feed down from the top seems my best option...
The vacuum is unlikely to develop enough suction to pull a Jet-Line messenger up the mast. Proper use of an air pull or push device requires that the conduit (or mast section) be plugged with a foam mouse (pictured below), to which the light messenger string is attached.
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Old 01-04-2009, 12:39   #15
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A light line with a length of dog-tag chain at the end can be pulled thru a small exit hole with a magnet Just make sure you get the cheap chain made of steel instead of the nice chrome plated brass one!
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