Best Plastics, Composites, Rubber for structural antenna parts

90331 Views 212 Replies 43 Participants Last post by 300ohm, Oct 10, 2013

stampeder

Discussion Starter · Nov 26, 2008 (Edited)

Just a warning note about using ABS for structural parts that I've mentioned many times before - hopefully what you're planning to use is the thick walled stuff that has little or no flex. If you go to Rona or Lowe's or Home Depot and shake a 10 foot ABS pipe like a sword it flexes a lot.

It seems to be rigid, but its not. If you shake a length of PVC like that it will seem like a wet noodle, so avoid using PVC for structural use either, except when recommended in build plans.

From experience I'm clarifying that ABS should never be used as a pole or mast, and it should be carefully considered if you're thinking of using it as a horizontal boom of any length more than a meter or a few feet.

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300ohm

· #2 · Nov 26, 2008

Yeah, if its more than a meter in length for 1/2 inch stuff, a dowel (or a broomstick for 1 inch stuff) etc should be stuck in it and glued with something like polyurethane construction glue to give it stiffness. A thick walled fiberglass tube would be ideal, but theyre hard to find and expensive.

Speaking of plastics, Ive noticed the Chinese plastics getting stiff and brittle a heck of a lot quicker than the plastics from other places, even when used indoors. For example, like in wire coverings. They start supple and soft when new, but quickly stiffen in a few years.

stampeder

Discussion Starter · #3 · Nov 27, 2008

Yes, one of the complaints I've come across here about the recent use of enclosed baluns from China is that the plastic has a tendency to crack or break off.

300ohm

· #4 · Nov 28, 2008

I think I know what happened.

All the melanine that was supposed to go into plastics got diverted into baby formula and pet foods. The Chinese probably figured that since rugrats and pets like to chew on plastic toys anyway, including it in their diet seemed like a good idea at the time.

ctgottapee

· #5 · Nov 30, 2008

the stuff they add to make plastics stay softer are generally polluting and/or cancer causing so they might be using less of it

and it costs money too

i'd say you notice it more now as overall things are built lighter (shipping) and cheaper so the overall product is more flimsy

johnpost

· #6 · Jan 5, 2009

concerning electrical pvc conduit

300ohm said:
Also a better choice. Its sunlight resistant and 50% cheaper than the white plumbing choice. The only downside is that its just a little floppier than the the white plumbing stuff.

do shop around for the electrical pvc conduit.

some brands are a bit floppy, nice where you could use the play for electrical power installation, over a long run you can skip using offsets.

there is a brand that has about maybe 80% to 90% of the stiffness of plumbing pipe, so good for short length structural use like this.

then only the plumbing fittings (L, T, caps) are subject to greater UV deterioration.

i have painted those plumbing fittings with expensive PVC use primer and paint in the hopes of having it last longer.

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stampeder

Discussion Starter · #7 · Jan 5, 2009

Thanks for that, johnpost. Is PVC-primer paint readily available? Also is PEX suitable too?

300ohm

· #8 · Jan 5, 2009

You can get vynil-color paint at Pep-Boys and other automotive places. I noticed my Lowes is now selling paint for plastic too. Its really more of a dye than a paint, in that it soaks into the plastic a little.

PEX is not UV resistant, it says so on the label, so its best to paint it too.

But that cheap 96 cents a can Walmart spray is very tenacious and lasts a good long time, especially in places where you dont want it to, heh.

johnpost

· #9 · Jan 5, 2009

stampeder said:
Thanks for that, johnpost. Is PVC-primer paint readily available?

I used a spray paint that was listed for substrates that included PVC.

I used a spray primer that I recall was listed for PVC but no longer have can nor recall brand. It was a non-antenna project a couple years ago.

Got both at large home improvement or farm supply store.

fmw63

· #10 · Feb 26, 2009

Fiberglass rods

I've found some fiberglass rods at Lowe's (home improvement chain here in the US) disguised as "driveway markers".

Some are fluorescent orange and some are yellow. $1.99/4 ft. $3.78/6 ft.

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hawken45

· #11 · Feb 27, 2009

Are they rods or tubes?
Where would you use a fg rod in construction?
Inquireing minds want to know

300ohm

· #12 · Feb 27, 2009

Theyre solid rods. I too saw them at Lowes and Wal Mart has bicycle flags about 6 ft long too. I bought 4 ft solid fiberglass rods, 3/8 in diameter, at Tractor Supply (used for electric fencing) for $1.29 each.

Heres a couple of interesting pieces of plastic for about 60 cents each :

The one on the left is a J 1/2 inch pipe hanger available at Home Depot. Dont know if its UV resistant or not, so if used, should probably be painted.

The one on the right is called a rebar chair. I got it at the local cement supply dealer. Its made by the ReBar Stakes Company, they have a website. Its listed as corrosion resistant, but nothing said about UV resistance. It is very strong plastic. The clips fit 1/2 inch pvc, and the distance from the back of the pvc to the flat part is just about right for the reflector to element distances in the GHs.

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johnpost

· #13 · Feb 27, 2009

the fiberglass rods i've seen

the driveway markers and bike flags have a plastic coating.

the white electric fencing rods are uncoated and very durable. they will have glass slivers especially as they weather.

all will produce glass slivers when cut.

adhesive tape is the best removal method i've found for glass slivers.

300ohm

· #14 · Feb 27, 2009

the white electric fencing rods are uncoated and very durable. they will have glass slivers especially as they weather.

The stuff I bought was light gray electric fencing rods.

Also, green plastic garden stakes made by Woodstream (makers of tackle boxes) are sold at Wal Mart, Lowes and other garden centers. They vary in thickness depending on length. They should be UV resistant, but have bumps.

300ohm

· #15 · Feb 28, 2009

I found this tube at Ace Hardware Stores today. Its a 5 inch grey plastic ferrule (used for rain gutter installation) made by American Home Products and its overpriced at 12 cents each, heh. It is stiff and should be UV resistant. It also has ridges on the inside, so that when a common 3/8 inch aluminum element is inserted, very little of the plastic is touching the aluminum, yet it holds perfectly. A little glue or pop rivet would make it permanent. This should be a help to a lot of people. I wish I knew about it when I built my colinear rod model, heh.

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northyork

· #16 · Feb 28, 2009

I have used "Krylon fusion" on coroplast on my model airplanes around 3 years ago and still in the same shape as when painted. The difference is that the planes are under the sun only when I fly them, the antenna is to be exposed to the elements all the time.
Anyhow, Krylon fusion is made specifically to paint plastics.
Here is some info I've got from their website:

"The revolutionary no-prep, superbond Fusion for Plastic® now makes painting plastic possible.

* No sanding or priming required
* Bonds easily to most plastics, PVC, resin and more
* Fast dry; fully chip resistant after 7 days
* Features EZ Touch 360® Dial Spray Tip

Dry to Touch
15 minutes
Dry to Handle
1 hour

For use with
Wood, Metal, Wicker, Wrought Iron, Plastic, Hard Vinyl, Glass, Plaster, Ceramic, Paper, Paper Mache. "

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northyork

· #17 · Mar 1, 2009

stampeder said:
Just a warning note about using ABS for structural parts that I've mentioned many times before - hopefully what you're planning to use is the thick walled stuff that has little or no flex. If you go to Rona or Lowe's or Home Depot and shake a 10 foot ABS pipe like a sword it flexes a lot. It seems to be rigid, but its not. If you shake a length of PVC like that it will seem like a wet noodle, so avoid using PVC for structural use either, except when recommended in build plans.

From experience I'm clarifying that ABS should never be used as a pole or mast, and it should be carefully considered if you're thinking of using it as a horizontal boom of any length more than a meter or a few feet.

As many of you already know I have used square 2 1/4"X2 1/4" PVC gutter pipe. What I am trying to say is that no all PVC is equal. I have lined the interior of the gutter pipe with 1/2" ply with gave it extra strengh and made it easier to attach all the antenna parts to it. Based on the description found at Home Hardware:
"- Won't rust, chip, dent, peel, corrode or leak
- It stands up to winter ice and snow, salt air, desert heat and heating cables
- Easy to work with, maintenance-free and lightweight
- Never needs painting"

I am all for the square Vynil gutter pipe.

On top of all the benefits of using the square PVC gutter pipe I was pleasently surprise when I read on the sticker....... Made in Canada..Fait au Canada..... It has been a while since the last time I have seen a Made in Canada sticker on a product........ Everything seems to say China,

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300ohm

· #18 · Mar 1, 2009

I have used "Krylon fusion" on coroplast

Ive used the Vynil Color paint sold at Pep Boys and other places for modding computer cases. These plastic paints arent really paints, but rather dyes in that they soak into the plastic a little, hence they can be used even on vynil upholstery. On another note, Ive redone marine vynil seats in a stuff that they used to sell in marine stores, not sure if they still do. Its really like another coating of vynil. The stuff they sell for dipping tool handles in (and electrical tape paint) is similiar.

On the otherhand, that stuff is probably overkill for this purpose. Just look how long the cheap 96 cents a can spray stuff lasts by observing graffitti, heh.

Grand Audio

· #19 · Mar 1, 2009 (Edited)

Yea 300ohm, I bought a couple of cans of flat black at wally world today. 96 cents a can.

I got lucky today and found an old mop handle (thin metal) that is a perfect fit inside my 3/4" schedule 40 pipe. I had to get the paint off of it before it would fit inside the pvc. I finally got it in with the help of a 2x4 and rubber mallet. You can't make it flop or bend now!

opilion

· #20 · Mar 15, 2009

ABS or PVC mast & lightning

Would a 6 foot tripod-mouted mast made of ABS of PVC be less likely to be struck by lightning than a metal pole?

op

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