drilling into fiberglass

[Diane G.]

my husband would like to install an antenna on the side of our Scamp. Any advice on drilling into the fiberglass?

[Eddie Longest]

If you use a hole saw run the drill in reverse. It will still go through the fiberglass an it won't tear up the fiberglass. You also might want to put painters tape over the area where you plan to drill the hole.
Eddie

[rabbit]

Don't most antennas have a big mounting flange and/or escutcheon which covers a rough opening? There will be some chip out of gelcoat with any upclearing cutter (twist drill, saber saw blade, hole saw) and it doesn't matter a whit IF it's confined to an area which the trim/bezel/escutcheon overlaps. As for hole saws, always make sure you have sufficient protrusion of the pilot bit to bore the center hole before the teeth of the saw hit the surface. Sometimes it's not a bad idea to simply drill the pilot hole with another twist drill. Either way, you want to ease the holesaw in initially to allow it cut a track for itself before you apply real force. Plunging thru relatively thin material (such as the glass in trailer hull) with a pilot bit and then aggressively engaging the teeth on one side of the saw can produce some shuddering of the saw and a less than perfect hole. Same for engaging teeth and then skating away on the surface because the drill motor isn't plumb to the surface and the teeth engage before the pilot. You really won't like that result because you will very likely overrun the area that your trim will cover. Never hurts to rehearse on scrap or a similar material. Here's another hint: down clearing sabre saw blades and router bits reduce surface chipout.

jack

[Tim Wood]

I had a bad experience from a previous egg that I had which had one of these TV antenna's installed. Long story short there was a leak there that I did'nt notice when I looked at the trailer. So I have never installed one since that bad experience and have seen many installed on the back bumper instead made from pole extensions, now that I would do. The fewer things installed in the roof of my trailer the better I like it, but that's just me.

[841K9]

I usually cover the area with painter's tape and then run the drill slowly.
If you're worried about chips you could use a carbide hole saw that basically sands the hole through.
Remember to hang on to the drill. They tend to grab on things when using a hole saw. I have a nice scar from a bad day with my Milwaukee 28v.

[Bobbie Mayer]

Here's how I was told to drill into my boat. Drill a slightly larger hole, fill with slow-acting epoxy. Let that harden and drill through the epoxy for the "real" hole. The epoxy has some give so helps prevent future cracks around the hole and you get a more watertight screw. It's essential to do that with balsa-core fiberglass but it should help any time you put a hole through where leaks or cracks might occur (and yes, use masking tape for the first hole.)

[Darwin Maring]

Do what 841K9 says in covering the area with painters (Masking) tape.

I don't think you should require a Hole Saw for an antenna and will use small drill bits found in any drill bit set so make sure you use the tape as it will help to prevent the gell coat from chipping, take your time and drill slow. You might want to wear a dust mask to keep the GLASS dust out of your lungs.

What I would do on the inside of the shell would be to install a larger plate to beef up the holding strength of the installation so when the antenna whips around it will not crack the fiberglass around the antenna on the outside.


If you are drilling a LARGE hole then use a hole saw that has a pilot drill bit in the center. The hole saw is more expensive than the one without the pilot drill and is well worth it.

Use some Butyl Caulk around the outside mount B 4 you tighten down so you maintain water tight integrity.

[rabbit]

I've seen most of the tool bits that cut and/or score on the circumference (multi-spur, Forstner, hole-saw, brad point twist with spurs, spade bit with spurs, spur auger) and haven't seen any without a pilot drill or point. The "one without the pilot" would be the most "expensive" imo. Pilot bits are usually held in the bore of the hole saw arbor by a setscrew. Make sure that the pilot is present in the arbor; that there is reasonable protrusion beyond the saw; that the pilot is secured by the setscrew.

jack

[Darwin Maring]

rabbit, The hole saw without the pilot is usually sold in those multi tool bins in low cost stores and go for less than $10 and have about 10 saw blades of different sizes with the arbor. I would give Junk a bad name if I called them that.

[rabbit]

I actually had one of those mult-diameter blade tools with the cast potmetal base with the grooves yrs. ago. Even it had a 1/4" dia. solid pilot/shank. It required drilling the pilot hole with another twist bit. Perhaps a shipment arrived in the junk barrel without the center rod.
That wouldn't surprise me and, as you say, they would be useless.

jack

[mary and bob]

Like Tim said, I mounted a Winegard fold out TV antenna on the rear bumper. I'm trying to avoid anything on the trailer body that can leak, or flex and cause cracking

[Bob Miller]

FWIW: Anytime I use a hole saw I always try to cut from both sides to reduce tearing as the saw breaks through. In the case of fiberglass I try to start the hole saw part from the inside, even if I have to put a pilot hole through from the outside for location. After making a deep groove with the hole saw from the inside, I go to the other side to finish the cut.
BTW: A hand held hole saw will almost always cut a slightly oversize hole.