Drilling a hole in the roof for a cable.

[tetranz]

I know that's a scary subject line

This is a continuation of a thread I started here about a month or so ago. There seems to be a much bigger audience here so I thought I'd post here too.

I want to mount a cellular antenna on the roof of our Winnebago Minnie Winne and need a cable entry hole through the fiberglass roof. I still haven't quite had the sunny day and courage to drill the hole but I need to do it if I want to get this show literally on the road.

I think I have the technology and everything else pretty much sorted out. Following the two videos I linked to there, I'll have a plastic cable entry box and some conduit coming down into a cupboard above the kitchen counter. I think I have the correct sealant, cable glands for the box, adhesive tape etc.

Drilling the hole safely still freaks me out. I'm basically a newbie starting with nothing in terms of tools etc so I've been buying stuff, mostly on Amazon.

I bought a set of these hole saws first https://www.amazon.com/gp/product/B07FVN82B2 but based on advice in that thread, I then got some of these diamond hole cutters https://www.amazon.com/gp/product/B0778NND9D without teeth. I can see how the teeth could catch and rip a chunk out the roof. Both those videos use a cone shaped drill and make it look so simple but people are telling me not to use one of them either. I can see how their single cutting edge could catch and cause problems too.

I tried the diamond saw on a piece of plastic and I found it impossible to hold steady enough to get started since it has no center drill so I'm very nervous about trying to use that on the roof.

I'm looking for any further advice or opinions. I'll drill a small hole up first. I'm thinking now that I might just draw a circle the size I need (1 inch diameter) and then drill lots of small holes around the circumference of the circle so I can pull that piece of fiberglass out. Then I'd probably use the normal hole saw with teeth for the wood below. Does that sound like a reasonable plan?

[450Donn]

You probzbly dont need a hole saw to drill a small hole. A wood spade bit should do just fine. Be sure to tape the area first to prevent cracking.
Instead of drilling more holes I just glued a piece of sheet metal to the roof, got a magnetic mount antenna and placed it on the roof. Ran the cable down and around the slide room rubber seal. Worked fine for me if you want a semi permanent situation you could always apply dabs of Dicor every few inches to hold the cable down. Those magnet mount antennas are designed to hold at highway speed so no worries about it falling off.

[tetranz]

Thanks. I'm doing something similar with a metal plate. That will give the antenna a ground plane too for better performance.

I've been warned away from using a spade bit. The suggestion is that it could catch and rip.

Tape around the area sounds like a good idea.

[AlanTerry]

I have a different roof EPDM but I called fleetwood technical support and they mentioned to drill a small hole and use a coat hanger to work on the styrofoam to enlarge the hole up towards the roof that way you will find any wires and be able to work around them than drill into them. Probably a different roof structure in yours but thought this might apply.

Good luck!

[Joe_Camper]

Unless you need a hole bigger than 1/2" or so, you shouldn't need a hole saw. If drilling larger 1/2", use the regular hole saw and run it in reverse. You will want to drill a pilot hole the same size as the pilot in the hole saw first.

[HarryStone]

Absolutely no spade bit. As mentioned above, use a regular drill bit unless drilling larger than 1/2". Tape your cable to a stiff wire and use that to 'thread' the wire thru the hole, then you can pull the cable thru as well.

[Dav L]

The "right" way is to use a metal hole saw as the teeth are finer than a wood set and less prone to grab. Takes less than 10 seconds. - if the hole is more than say 3/8". Use a common twist drill for less than that.

If you really wanted to be careful, then get a 3/4" thick board, drill a hole in it with the hole saw, and then put blue 3M painters tape on the top of the RV, place the board on that and use the board as a guide. But generally that isn't needed as the pilot drill will work fine.

When using a hole saw in thin material, drill through the pilot hole and then slightly angle the drill so the edge of the saw cuts in first. Once that has started, you can bring the drill back to straight on (vertical) to the surface. Helps so the bit doesn't grab.

Once you feel the bit is passing through, minimize the pressure (you really don't need much at all for fiberglass). Hold the drill with both hands and support it's weight so when it does cut all the way through, it doesn't move downward into the insulation. Keep your finger loose on the variable speed trigger.

The above is pretty overkill description and something that only takes a few seconds in practice. go for it!

And definitely don't use a spade bit. Wrong tool for sure. Hole will end up a rectangle...

[tetranz]

Thanks all. I want to make about a 1 inch diameter hole to do the same as this.

https://www.youtube.com/watch?v=aB8ic6x9DAM

My Poynting MIMO antenna has quite a bunch of cables, probably about 1/2 inch but I want room for more cables later such as a ham radio antenna without needing more holes.

The fine tooth metal hole saw sounds like the way to go.

[Teamfoxy]

When I installed my cellular antena, i just drilled a 3/8" hole through the roof at a 60 degree angle so that the cable led out easier. I used Dicore to seal the hole and then covered it all with 4" wide eternabond tape. I used 2" eternabond tape to hold down the cable back to the antenna so that I did not need to drill holes for cable clamps.
The worry is always to not hit any wires or other things in the roof. I chose to drill through in the space over the microwave because it was easy to remove the valence and see what was up there. It worked out because there was 12V wiring that I could use to power the booster.
Be careful if you need to drill through the ends of any cabinets to lead the cable to the indoor antenna. They are double walled with wires inside that you will want to avoid.

[dp7]

I have drilled two holes in my fiberglass roof for cable runs. Both times I used a Milwaukee Shockwave hole saw https://www.homedepot.com/p/Milwauke...9820/204994422 . This hole saw cuts a very smooth hole thru the fiberglass & wood sub-structure. Much better surface finish than coarser toothed hole saws.

It even cuts a smooth burr free hole in metal.

[sibe]

I have used hole sawas for this over the years,, I have run a 5/32-3/16 pilot first .. just incase you hit a meal beam and have to back out.. then seal and move.. LOL has happened.

Then from top with hole saw, low pressure pop thru roof skin. then i go inside and drill up..

This was you dont tear up inside ripping thru. nice clean holes each way..

If you are doing a fast feed of TV coax with a 3/8 hole and dicor with no feed tru device.. go for it