[Bill]

Bill,

I have penetrated the roof on previous coaches a couple of times. Both times were to add an antenna. I started on the inside to determine where I needed to be so when I was routing the wire it would be out of sight.

Once I determined where I needed the wire to come through I measured and then went outside to verify the interior location did not interfere with anything on the outside, such as a seam or another device on the roof.

After marking and measuring a couple of times to be sure I drilled the hole. All the entry points were behind finished panels. In both cases I had to dig out insulation to make a more open hole to add a backing plate so the antenna was not attached solely to the aluminum or fiberglass cap. I replaced the insulation after the antenna was mounted.

I sealed the antenna base and hole with RTV sealant. After it was installed I used ProFlex on the exterior of the antenna base to further seal it.

In each case I removed enough panels on the interior to expose the Prevost sprayed insulation and all wires were run behind the panels so there was no sign of the wiring.

[Paul]

Bill

I am converting a 1991 XL 40 from a seated coach to a MTH version. I have been at it for 7 years on weekends, evenings and any other time I have. I have penetrated the roof for satellite cables, black tank vents, skylite, etc. The key, just as Jons’ sage advice said, measure at least twice and drill only once. Here are some other things to think about before you get to that stage. Most antennas have a threaded mast that penetrates through the skin and then a cover, usually plastic, that slides down over that somehow. Separate those and seal each stage of the process. For example, the center threaded mast usually has a disk about 1/2-3/4″ up from the bottom of the threads. Cover that disk with clear silicone on the underside that will come into contact with the coach skin and fill the hold you drilled with a “gob” of silicone, then shove the threaded mast through the hole. Hold it in place while someone on the inside threads on a fender washer with the right size hole to slide up the threaded mast and come into contact with the inside coach skin, then screw on the the nut and tighten it. There should be enough silicone in the hole in the “gob” that you should not need to coat the fender washer that comes into contact with the inside coach skin, but if not add just a little bit more to it. The fender washer, rarely supplied by manufacturers, just gives a little more support and sealing power. The fender washers are available at hardware stores like Ace for 50-60 cents. Then coat the top of the disk with silicone where the mast cover meets the outside antenna disk and tighten it down. BTW, it is always better to buy a fender washer with a smaller hole and drill out the proper size hole to go over the threaded mast than to buy one with to big of a hole and have it wobble around the threaded mast. Now, “Let it sit and dry for 24 hours”. Once dry, come back with a sharp pin knife and trim away the silicone around the mast cover. DO NOT pull it away!!! It is not hard and will not leak if you take your time and seal each stage of the process. In another 3-5 years, depending on how much time your coach is in the sun and how the roof is washed, run a small 1/8″ size bead of silicone around the mast cover on the outside, let it sit for 24 hours, then repeat the sharp knife trim again to make sure there are no pin holes that have developed.

HTH

Rob

91 XL 40

Missouri