How To: Run wire under "Rat Fur" without cutting it

[peterh]

Something that comes up on the forums now and again is "How do I run wire underneath the 'Rat Fur' in my Scamp or Casita?" There have been a few answers, but not a lot of "how-to" instructions & pictures. This weekend I've been running new electrical wiring in my trailer for my new roof-mount solar panel, so I thought I would take some pictures and do a narrative on how to do it.

Tools of the trade: You only need five tools: a utility knife, nylon string, a screwdriver, a glue gun, and a specialty tool called "fish tape." A fish tape tool is a spool of spring steel with a hook at one end that electricians and communications wiring guys use to "fish" cables through pipes and other inaccessible spaces, like the space between the studs and the wallboard for a wall in a house or office. (There's a picture of a fish tape below.)

First, pick a spot near the middle of the rat fur where ever it is you want to put your light, appliance, or disco ball and use a sharp utility knife to cut a deep 1" slit through the rat fur and Reflectix insulation that's perpendicular to the general direction you want your electric cable to run.

Next, unwind enough fish tape to make it to your wire destination plus about a foot, then get a feel for what direction you want to point the fish tape by running it along the surface of the rat fur from origin to destination while keeping the reel perpendicular to the wall. This'll give you an idea of how you want to hold and orient the fish tape reel while you ram the hook end through the Reflectix insulation under the rat fur.





The fish tape is readily flexible in only one direction, the direction it winds onto the reel. So, if you point your fish tape the right way and ram it down through the Reflectix, it'll more-or-less go the direction you point it, taking the path of least resistance through the Reflectix bubbles.

More-or-less. Something to keep in mind when you're running wire under rat fur is that, if you have one exact spot where you'd like the wire to end up at -- such as a specific place for a light -- it is best to start feeding the fish tape through at that end because the fish tape has a tendency to drift a bit to the right or left of where you aim it, and the longer the wire run the more the drift will be.

In these pictures I'm running a new wire from the hole in the corner over my dinette where there is a pre-existing light down to the dinette bench. I've lined up my fish tape up and rammed it through the hole at the top, following the seam tape line down to the dinette, where I've cut a second hole just above the bench.

It's easier to run the fish tape along a pre-determined line when the wall is flat along the direction you want to run the wire, but my target was not where the fish tape came out. When the tape bottomed out on the top of the dinette bench I had to feel around for the hook head under the rat fur while wiggling the wire reel back and forth. The hook actually bottomed out about an inch from my target, and I had to use a pair of needle nose pliers to yank the hook over to where I wanted it to come out.

Next I tied a nylon string to the fish tape hook and simply pulled the fish tape back out, pulling the string with it.





With the string pulled through I attached the string to the wire I wanted to pull, first by tying a big, bulky knot about the diameter of the wire I'm pulling about 8" from the end of the string, then tied the string to the wire bundle with a very tight square knot a couple inches from the end of the wire so my big, bulky knot was touching the end of the wire, and tightly wrapped the loose end of the string around the wire as many times as I could to trap the string to the wire and tied down again, then taped the whole thing from just ahead of my big, bulky knot down. (Usually I use electrical tape, but the clear packing tape I used here does the job just fine, too.)





Then I pulled the wire through from the bottom hole to the top. You have to pull hard and you have to pull as close as you can along the rat fur, because if you don't you'll raise the rat fur up off the wall or tear a hole in it along the string. It's easier on your hands if you wrap the string around the handle of a screw driver several times, then use the screwdriver as a pulling handle. The big, bulky knot making a nasty tearing noise clearing the way for the cable as you pull it.





This wasn't the end point where I wanted my wire to come out. It was just a convenient way-station that was close to my actual intended destination, so I repeated the process. Remember I said it's easier when you're running the wire along a straight, flat line? This time it took several attempts from both directions before I go the fish tape to go exactly where I wanted it. Then I repeated the process of pulling the string then my wire through the holes. Then I fed the cable through the hole in my shell, riveted on a "clamshell" wire access way cover (the closed end always points up and into the wind so water runs down and around it) packed with marine silicon. (These rivets, by the way, are aviation-grade rivets with closed ends, so they won't leak down the mandrel/pop head.)





Once the wire is run you can use the glue-gun to patch the rat-fur back into place around the holes you've made. If you've been careful about the whole process you won't be able to see or even feel the wires under the rat fur.

--Peter