Electrical Tape Tips

Tricks of the trade

Electrical Tape Tips

Postby George Dowell » Sun Sep 04, 2011 10:34 pm

Electrical Tape Tips by K0FF



Did you ever notice that electrical tape, like a hammer, comes with no instructions? Perhaps the makers figure that everyone automatically knows all the ‘tricks of the trade”. Read on, you may pick up a new wrinkle.



Vinyl electrical tape has been around since 1945, but for a long time after it was introduced, black cotton friction tape was still used for most applications, partly because of the cost difference, partly because of tradition. I remember tearing long strips of half-inch friction tape into quarter-inch wide strips as a cost savings. A unique feature of the adhesive on the friction tape is that it gives off an eerie blue light when the tape is peeled from the roll. It is bright enough to be easily seen in a darkened room. Aside from that trivial fact today’s friction tape is used for special applications only as a topcoat for delicate rubber tape as used on high voltage cable spices. Modern materials are superior in every respect. The first vinyl tape I ever saw on the job was gray in color, not black, I suppose it was a telephone company spec.





Today I recommend using only Scoch 33+ tape for all ham radio uses, except as noted at the end, as it has predictable characteristics and is good for every indoor/outdoor application. The temperature range is zero F to 220 F.

Make sure to get the type with the + sign, as there is also a plain type 33.



3M also makes product called Temflex, but again type 33+ is suitable for every application, especially outdoors.



When taping over coax connectors, or coax splice kits, it is helpful to first wrap the connector with a self-amalgamating Silicone Tape product. The 3M version is Type 70, and Radio Shack also sells it in small rolls under the part number 64-2336.

This is NOT the same product as the coax-seal, or Radio Shack #278-1645 “sealant for RF connectors”. I do not care for that sticky material, dum-dum, or any other putty type material that is hard to remove later. The silicone-tape peels off cleanly and easily, so easily in fact that it needs to be covered with a topcoat of Type 33+ to protect it. This two layer approach, when applied as explained below will give a waterproof seal that is weather resistant, and stays flexible for years, but can easily be removed if changes need to be done to the system..



Any time you wrap tape on a threaded component, make sure you wrap it in the direction that tends to tighten the screw threads, not the other way. That means if you are taping a splice, for example two PL-259’s screwed into a double barrel female (PL-258/83-1J) you must tape each connector from the cable end to the barrel center.



Always run the tape “uphill” that is from the smaller diameter to the larger diameter.

Start at the smallest end, make several tight turns of one-quarter lap for a good seal, then run the tape in one-half laps to the center, with moderate stretch so the diameter of the 33+ is reduced to about five-eighths of it’s original width. On the last few turns reduce the stretch tension until it is zero at the last turn, to prevent flagging. Use a scissors to cut the tape end square, as a knife or ripping will add stretch to the last lap and cause it to come loose. Repeat the same strategy from the other side, and meet in the center ( if it is a splice kit) , overlap the left hand side tape with the right hand side tape. If the connection is to be removed at a relatively short timeframe, fold the last ¼” back onto itself, sticky side to sticky side, making a flag that does not stick. If the tape job is permanent, simply lay the last lap down flush. Now for the best-kept secret, spray the entire assembly with clear coat enamel or other dielectric spray. I use Krylon Crystal Clear. The overspray absolutely seals the joint and keeps the ends flat.



Non-electrical uses for electrical tape.

For taping cables to tower legs and other such jobs, consider using the Temflex or straight Type 33 as they both are less expensive and have a slightly higher breaking strength. The superior conformal qualities of the 33+ are not needed in these applications.

One of the most common non electrical uses of vinyl tape is to secure rolls of wire, bundles of tubing, cables to rungs, and many other odd jobs that use the material for other than it’s weatherproof or electrical qualities. To tie up a roll of cable, the cheapest grade of black vinyl tape is adequate, except that it leaves a gooey mess behind when removed. The secret here is to make the first full two turns with the sticky side OUT. Then simply twist the tape around on itself and continue making a few more turns with the sticky side IN. This same trick can be used with cellophane tape to secure hardware store bundles of conduit, pipe etc, so that it removes cleanly. Wish I had a nickel for every minute wasted trying to get that sticky mess off copper water pipe before soldering!

Another slick idea Scotch came up with is the color-coded vinyl tape. I’ve tried many schemes over the years of using red, blue, green white and other color tapes to identify certain cables, for example coax cables in a bundle run up the tower. After toughly confusing myself, I decided to simply use the white tape, and mark the ID on it with a Sharpie permanent marker. Foolproof, and lasts for years.

A final note, the better tapes like 33+ have a shelf life rating of 5 years, but still be careful of “surplus finds”, as the age and storage conditions are unsure. Best to buy fresh tape from a known, trusted source.



Have Fun

Geo>K0FF
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Re: Electrical Tape Tips

Postby Doug Coulter » Mon Sep 05, 2011 12:59 pm

I moved the real version of this one down to shop tips and kinks, since it's a keeper. If you have responses to it, please put them there so they won't autodelete like they do here.

Thanks Geo!
Posting as just me, not as the forum owner. Everything I say is "in my opinion" and YMMV -- which should go for everyone without saying.
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Re: Electrical Tape Tips

Postby Joe Jarski » Mon Sep 05, 2011 2:38 pm

Thanks for the tips Geo! I've always hated using electrical tape because of the goop left behind when you try and remove it, so I usually use the silicone tape when possible. I'll have to try the 33+ tape though - sounds like good stuff.
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Re: Electrical Tape Tips

Postby chrismb » Mon Sep 05, 2011 6:00 pm

I can't say I have experimented with removing electrical tape, but I'd hazard a guess you'd do it the same way either that you take labels of CD boxes or chewing gum out of the carpet. Not sure which one the properties of electrical tape are most like.
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Re: Electrical Tape Tips

Postby Doug Coulter » Mon Sep 05, 2011 8:16 pm

Over the years, going way back to me as a kid in my dad's shop, the "good stuff" was the 3m, and pain be to anyone wasting it - back when gasoline was under%0.30/gal, this stuff wasn't cheap. All the stores had this bogus black tape that had all the goo problems as well as other deficiencies, like easy to puncture, weak adhesive, or well, wouldn't stick to what it was supposed to, but was yes, hard to remove off everything it wasn't.

Over the years, assuming you stay out of the cut-out bin at Harbor Freight or other "dollar store" -- it's not so bad as it was. I must have a dozen half used rolls around the shop from various sources, and as long as they say "UL listed" on the cardboard inside the roll and have the right "feel", they're the good stuff, it seems. I never have issues with the stickum being troublesome and leaving a mess.

I've found it only a somewhat better than duct tape out of doors here - it maybe lasts 2-3 times as long, which still isn't so great. Sun especially renders it brittle and variably unstuck - though I freely admit, applying it correctly as Geo suggests is key, as well as not touching the sticky at any time while doing it - finger prints at one end, and it will unravel there, so you develop a technique that doesn't touch the very end, ever (or cut it off if you do). I will rarely use it as the only thing on an outdoor splice for that reason. I will have something else as a minimum, and one or the other substance will be the sacrificial one ruined by UV/oxidation to save the other. The older caulking silicone has given decent service in some cases, but of course not on RF kinds of things - the ammonia really kills copper. The newer GE Silicone II - avoid for everything, even caulking. It's either hard in the tube, or won't get hard later, the stuff just stinks, or it's a way to find out just how horrible something can get before the public won't buy it anymore -- utter fail as a product for any use I can imagine (maybe that's why Lowes has box after unopened box of it on display). Permatex sells some great silicones -- the blue gasket maker emits no ammonia and has low vapor pressure (eg, a decent vacuum sealant). Their hi temp red stuff is iron oxide filler and here it's withstood red heat on a patched woodstove - got a little crunchy, but that's it. It's the ammonia type though. The red stuff is ideal for making blue sensitive phototube assemblies light tight, however.
The blue gasket maker is good candidate for outdoor connections, either over or under the tape. I don't have a ready source for the self welding stuff Geo mentioned, though I've seen it, and it's good.

I've become a fan of gorilla tape. That stuff is what duct tape should have been -- it's even better than the pricey 3m stuff (and way way better than the Chinese cheapo stuff). Good adhesive, good quality cloth, sun resistant. Very strong stuff. We've used it to repair torn body-fabric on a jeep and it really does withstand the elements and a lot of continued flexing in the wind (current test is 6 months). If you get a rip in your convertible roof, this is your stuff. Being what it is, you can sew it after sticking it too.

One thing I've found about black tape generally - it's transparent in near IR, and so useless around phototubes that are IR sensitive. Most black stuff is black from carbon/graphite, and that's the issue - it becomes transparent just below where you can see and many phototubes and diodes can see right through it. If you've wondered why some IR remotes don't have a hole with the led sticking out (or the receiver doesn't) that's why -- almost no attenuation at a micron or so wavelength, so the manufacturer gets to save a step in fabrication.

Nowadays, I use some slick adhesive containing heat-shrink for most outdoor joints as perhaps even the only layer. That stuff really works well. If I'm splicing, say, 3 conductor #10 wire, I stagger the splices though, so each splice will sit against original undisturbed insulation in the other two wires. Then perhaps goop it a little so water won't creep up in the jacket, and tape the whole thing up once the goop hardens. I've done that on some splices out here on my land, wire just sinfully laying on the forest floor, and it's lasted decades, no problems.

Rf is of course its own world -- it's not the bulk thickness of the wire as much as it is the resistance of the skin that carries the RF, so there things have to be a heck of a lot nicer to get good performance, especially if you have antennas high up on long runs where attenuation is going to negate the advantages of the tower height if things aren't all just right. And in that case, you REALLY want to keep the copper dry -- water will eventually get into the entire length of the coax and ruin the nice shiny skin if you let it. Such coax is mainly useful for high voltage DC after that's happened, and that's a scrounge tip as it can often be had very cheap as its ruined for RF, but not for DC (the seller only knows about the former).

The other super cool tape 3m makes that I use all the time is their copper foil tape. It's got a scotch tape-like adhesive, not too much, and you can solder it if you're quick about it without unsticking it. Just ideal for EMI kinds of things, very impervious to weather as well, though it won't conform to things leak tight - it wrinkles. But if you need to shield something that is hard to do any other way (think the pickup pockets of an electric guitar) -- it's the magic stuff for certain. Also good for an outer shorting turn on transformers to cut the stray H field (you put it all the way around the core and everything, not inside like a turn on the transformer) and a host of other related uses. For whatever reason, their aluminum tape that otherwise seems the same stinks -- the adhesive is no good - comes off a perfect clean joint in about a month with no provocation, just falls on the floor. Go figure -- and of course you can't solder it either.
Posting as just me, not as the forum owner. Everything I say is "in my opinion" and YMMV -- which should go for everyone without saying.
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