Support Electrical Wire Inside the Mast.
INDEX - cap/foot, wire harness, through mast, through deck, connector.

There is nothing more frustrating than intermittent electrical wiring, especially if it's inside the mast.  Picture this, you are motoring along during the evening in a busy seaway or harbour and you are converging with a tug boat pulling a heavy barge.  To avoid the tug you alter course to give a reasonable margin.  Just then your steaming light goes dead.  Not the type of situation you want since you are now blind to the tug boat.  This is one of those situations that makes hair turn white, quicker than normal. You quickly signal the tug with your flashlight and confirm your heading with him via VHF.  All is OK between you and the tug BUT, your boat is now basically invisible to everyone so you better pay extra vigilance as you proceed along the edge of the traffic lane.  Careful though, a flickering flashlight may give a wrong signal to converging traffic.  What started out as a romantic moonlight trip through the harbour has become a downright dangerous situation due to an intermittent wire.  The next morning you decide to do something about the mast wiring!  Since repairing the wiring requires you to open the mast, you may as well inspect the halyards and sheaves as well.  (See Tech Tip F03).  The description that follows is a technique for supporting the electrical wiring inside the mast so it doesn't get damaged and works all the time.  The system on Panache has operated without fail since 1998.

INSTALLATION CONSIDERATIONS - Determine which type of electrical connectors you will install at the ends of the wires.  This may determine where you can install them or may restrict the layout of the installation.  If you have internal halyards then it is extremely important to separate the wiring from the halyards inside the mast.  This can be done by keeping the halyards on the aft side of the spreader compression bolt and the wire harness on the forward side since this is where the steaming light is located.  Don't consider the mast kerf as a place to install wiring.  There isn't enough room to accommodate both mast slugs and wires.  I've tried it.  If you have to temporarily install a wire up the mast I suggest taping it to one aft side.  Not elegant but it works for a while.  Keep the electrical connectors at the bottom of the mast outside the mast.  This way you can maintain them and make it easier to isolate a problem without having to drop the mast.  

REMOVE THE CAP & FOOT - To start this job you should remove the mast cap and foot.  The factory attached them with aluminum pop rivets or sometimes machine screws.  The head of a pop rivet can be removed with a drill and the shaft can be driven inside the mast with a drift punch.  If the screws are so corroded that you can't remove them, pour some strong vinegar on the thread and have a beer, or two, before you tackle them again!  The alternative is to use an "easy out" (poor man's impact wrench, hammer driven) on the head of the screw.  Quicker than beer but not nearly as much fun.  This tool is equipped with interchangeable drive tips to match the screw and has an internal reverse thread that turns the screw out when you hit the end of the tool with a small sledge hammer.  Don't be afraid to drive it really hard.  A single heavy blow will work where a bunch of light taps don't.  In the worst case situation the screw head strips and you have to  grind the head off flush so you can drill or punch the stud through to reuse the hole.  Another technique is to use high quality penetrating oil with mercurochrome that will soak into the corrosion to loosen it.  I have removed some really stubborn bolts with this stuff.  Be patient, it takes time.  Don't be afraid to drink another beer!  Lastly you can apply heat to loosen the screw but I'd be tempted to try another shot of vinegar or penetrating oil first.  Applying heat to an aluminum mast will require a torch and a magic touch as the aluminum conducts the heat away so quickly.  The danger with a torch is that you could liquefy the aluminum and "blow" a hole through the mast.  Hardly desirable considering the cost of the extrusion not to mention the delay time of waiting for a replacement! 

If your mast head or foot fitting was attached with pop rivets or sheet metal screws, replace them with 1/4" stainless steel machine screws.  Screws are stronger and easier to remove/install in the future.  Read the note from Dave Clark at the bottom of  Tech Tip F17.  I'd tempted to install four screws for ultimate strength.  It's OK to install a slightly oversize screw (relative to the pop rivets) since you will have to drill out the hole to get clean metal to tap the new thread.  Drill the hole through the thickest metal of the mast foot to hold the screw since it will be under considerable shear load when stepping the mast.  Smear the thread and underside of the head to prevent galling or corrosion.   While you have the cap off, you may as well inspect the sheaves and dividing plate as per Tech Tip F03.

You should consider installing LEDs at the masthead for lower power consumption and greater reliability. With the low power consumption you  can also install lighter gauge wire saving weight aloft. It is nice to know that the Windex or anchor light won't drain the battery after an overnight sail.

WIRE HARNESS - Insert the wire harness inside yellow hollow braid polypropylene line.  This braid is perfect for supporting and protecting electrical wires inside a mast.  Buy at least 50' of line to cover the bundle of wires and co-ax after it is pushed together.  
When you push the ends of the braid together it opens the core so you can push the wires through.  Having done that, splice a 2" diameter loop of braid at the top end by tucking at least two feet of braid back inside itself, similar to splicing yacht braid.  Now you should have a nice strong loop with 2' of wire ends sticking out the top end of the braid.  Draw the remainder of the loose braid tight along the length of the cable harness, working the slack towards the bottom.  Attach the top end of the braid to an eye strap fastened to the underside of the mast cap and feed the free wires through the mast cap. I drilled a hole through the top horizontal side of the cap and sealed around the wires with sealant.

Extend the harness along the full length of the mast.  About 2' from the bottom of the mast, pick the wiring out through a hole in the side of the hollow braid, just above where the electrical wires will exit the mast.  I suggest you exit the mast close to the bottom.  Now splice a  loop in the bottom end of the braid so the end is about 12" from the foot of the mast.  Pull three loops of high quality 1/4" bungee cord through the eye of the braid.  Mount an inverted J hook to the inside bottom of the mast. Since all my wires are installed at the front of the mast, I installed the J hook at the front as well. This way I keep clear of the internal halyards. 

THROUGH THE MAST - Pull the harness through the mast, ensuring NO twists around other lines. This is easier said than done.  I'm assuming that the mast is down and you have it horizontal as shown above.  It is impossible to push a line through the mast, even if it is empty.  I've tried many times and never been successful.  It is also impossible to see down the length of the mast without both ends off.  For all these reasons I removed both ends and pushed a 25' long pole (3/4" white PVC is cheap) through the mast to pull the cable and a messenger line.  The pole will slide along the bottom of the mast, fore or aft side, depending on which is at the bottom.  Pull the line from the mast cap to the foot.  Slip the cap (with harness and braid attached to the under side) on the mast and temporarily mount it in place.  At the bottom of the mast, tension the bungee loops and slip them over the J hook attached to the side of the mast.  Use a strain relief inside the bungee loops to protect them from long term strain.  Tensioning the harness prevent it from slapping inside the mast and beating itself to death.  Push the loose wires through the exit hole out of the mast. 

NOTE - Here is a slick trick I learned from a buddy.  Because he couldn't find hollow braid to support the wire harness, he surmised that by strapping on two opposing 8" long tie wraps every 4' along the harness it would prevent the harness from slapping against the mast.  Snug them up leaving the tails sticking out, opposing each other.  The tension they provide against the inside of the mast prevents the harness from slapping. While you don't have the vertical support of the poly braid, pulling the top and bottom ends through rubber grommets should ensure no fatigue. Seal the top hole with a sealant to prevent cable movement and water entry. The cable at the bottom exists the mast through a hole in the sidewall, close to the bottom and away from halyards. If you wish to include the co-ax in the harness, DON'T tighten tie wraps tight around the bundle.  This creates pinch points in the co-ax cable that will affect the impedance.  Instead, attach the co-ax to the side of the harness with separate tie wraps set only snug. Now your voice won't come out of the antenna sounding squeaky!  
Just kidding about your voice, but the pinch points will change the impedance of the cable resulting in more power reflected back  from the antenna to the radio. 

At this point of the installation you should have at least 1.5' feet of loose wire ends beyond the mast ends to terminate the external electrical connectors to.  Now you have only to terminate the top wires to the instruments and lights and the bottom wires to a connector that will feed through the deck.  I prefer to feed the wires down the compression post and under the floor, so my deck hole is very close to the tabernacle. 

THROUGH THE DECK - Once you have the connectors on the wires you have to direct them into the cabin to the power distribution panel, bulkhead instruments or radio as the case may be.  Probably the best technique is to drill a suitable sized hole through the deck close to the tabernacle.  Then run the  wires down inside the compression post as shown at left and come out again at the bottom as shown at right.  (This was a previous configuration that has since been cleaned up, but it demonstrates the technique. I'll replace the photo when I have a chance).  Here the previous owner ran the wires over the floor and down under.  A better path would have been to run the wires through the "rise" of the floor.  This path would would have been les strain on the wires and created a neater installation.  It was simply too much work to rearrange. 
NOTE: Leave several feet of slack wire coiled under floor by the head as you will need it to move the compression post if you ever decide to remove the port bulkhead.  See Tech Tip B07, Sealing a Leaking Chain Plate and Replace a Rotten Bulkhead.  
Run the wires under the settee, up near the top so they stay dry, corrosion free and out of harms way.  They can't get damaged from stuff stored down there.  This cable path clears the working area of the boat of clutter. 
IMPORTANT: To prevent wood rot YOU MUST SEAL THE WOOD CORE AT THE EDGE OF THE DECK HOLE WITH EPOXY, then seal the inside of the hole around the wires with a sealant like Sika-Flex. 

WIRE HARNESS CONNECTOR - So now you should have wires hanging out of the mast and sticking up out of the deck.  To connect them and facilitate testing you must install the electrical connectors.  Don't connect the wires directly to the deck.  Sooner or later you will have to step the mast! You have several choices; 

1. Install a free hanging connector at the end of the mast and deck cables. (this is my preference as the advantage is maximum access for trouble isolation and minimal corrosion inside the connector.  Given enough slack, a connector can always be replaced). 

2. Install a connector on the deck that the mast cable can plug into. (If you choose to do this then install the deck connector horizontally, up off the deck on a block of some sort.  This keeps it out of most of the deck water to minimize corrosion inside the connector).

3. Install a connector on the mast that the deck cable can plug into. (Not my preference as humidity inside the mast will corrode the connector.  It may also be difficult to service).

4. Assign the female connector to power and the male connector to the mast lights, etc.

Of course there are variations of the above techniques.  By the way, I use the automotive four pin trailer connector.  It is rugged, is capable of handling the current, is easiest to clean and cheapest to buy.  I've only occasionally had an intermittent connection which was easy to solve by unplugging the connector and then plugging it back together.  Something that can be done out on the water.  The wiping action cleans the corrosion.  If you want excellent corrosion protection, apply a thin coat of water proof grease to the pins once a year, which I had forgotten to do.  

STEAMING LIGHT - If you wish to connect a steaming/deck light at the spreaders, it's best to install a separate wire harness inside the mast for it. Beside being easier to install, this eliminates many of the following problems: 

• If wires protrude half way up the mast head harness they will flex and eventually break with the movement.

• The worn insulation will create an electrical short to the aluminum mast.

• It is difficult to seize the wire harness and attach it to the inside of the mast to prevent movement.

• The mast head harness can be removed for service without disturbing the steaming/deck light.  Independent wiring is always superior.

Isn't this the problem we're trying avoid? 

The advantage of using hollow braid line is that the wires have no strain on them and the braid provides side impact protection.  I installed the wiring inside Panache's mast in 1995 and have experienced absolutely no electrical troubles.  This way that tug boat will always be able to see you!  Now where is that tug boat! 

Return to Techtip Index. . . . . . . . . . . . . . . Have a Question?