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Best Plastics, Composites, Rubber for structural antenna parts

90285 Views 212 Replies 43 Participants Last post by  300ohm
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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I guess im trying to protect the connection itself, as opposed to the balun alone, like on the commercial antenna, CM4221HD
Condensation is going to last longer inside that plastic box, so it may actually speed up corrosion. On the other hand, it would protect the dielectric grease from drying out / washing away sooner from the sun and rain.
I came across this CPVC FAQs:

How long can CPVC systems be exposed to sunlight?

CPVC can easily withstand the ultraviolet exposure commonly experienced during the construction phase of a project, provided on-site inventories are turned regularly as would be anticipated. If CPVC is used in above-ground, outdoor applications, protection from ultraviolet attack can be achieved by shielding or by painting the system with an exterior-grade latex paint.
I used solvent based paint on some white PVC fittings in my GH build,
Yeah, I used the cheapest flat 96 cent indoor/outdoor spray I could find on my first GH build that used white pvc (that was before I discovered the grey stuff, heh). After 3 years, its held up very well outdoors. I only used 1 thin coat, just enough to cover. Using many or thick coats it will peal, whereas 1 thin coat will just slowly fade. Ive also done the same on outdoor white pvc trellises and sump pump drains for over a decade, and theyre still in great shape. Kelly green blends in nicely with leaves and grass. :)
Zinsser 1-2-3 latex primer is good stuff and I use it on wood. But for pvc its probably overkill.

PE and PEX cannot be joined with solvent cement!
Plumbers Goop works fine with PEX, at least for antenna usage. Maybe not for water pressure though. Im not really a big fan of using PEX for water usage either. The connections just seem weak and flimsy.
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I picked up some of these usb devices cheap today: Spec Sheet 10-08.pdf

Heh, usb stands for universal slider bracket. :p

These would be great for clamping on a CM4221 type mesh reflector onto a round pipe from 1/4" to 1 1/8" OD. Not good for a GH mesh model because of the need for a split screen.

Another thing, the clamps on it are UV resistant plastic. They clamp down on both sides just like electrical wire ties do.
Polyurethane glues like Elmers Glue All Max or Gorilla Glue work great for joining styrofoam and metal. :p I had been wanting to test this out and just recently did. It holds the piece of coat hanger to the styrofoam panel extremely securely and most importantly, it does not eat its way into the styrofoam.

So if building a GH for attic use on a styrofoam panel, all you would need to do is apply a small drop of the polyurethane glue every six inches or so. The polyurethane glues expand to about 3 - 4 times the size of the original drop as it dries. A slightly damp, but not wet, surface also helps.
It holds the piece of coat hanger to the styrofoam panel extremely securely and most importantly, it does not eat its way into the styrofoam.
Its also great for joining or repairing Styrofoam end to end. :D I just repaired a custom cut piece I had that the wind broke. If it breaks again, it wont be at the original break point, the joint is that strong.
I did some experiments using Gorilla glue on vinyl siding and plastic outdoor lattice. The result, very poor bonding on those materials. The amazing world of plastics, I guess. Next test with Gorilla glue, grey pvc pipe to white pvc fitting.
Update on black "UV resistant" Walmart nylon wire ties

The black "UV resistant" Walmart nylon wire ties aren't as UV resistant as I had hoped they would be. After 4 years outdoors, they are starting to fall off and are getting brittle on my DBGH gen1 mesh reflector antenna. Of course, that's still 4 times as long lasting as the white nylon wire ties outdoors in my area.

Ill probably use aluminum wire to secure the mesh to the pvc pipe instead of nylon wire ties.

All the 1/2" pvc pipe pieces and even the cheap 96 cent flat black spray paint (thin coat) I used on them and the mesh reflector are in fine condition after 4 years. Just starting to get that right touch of dark greyness in them. :)

Darn it, I just remembered I used black nylon wire ties to secure the fiberglass reinforcing rods on the CM1221. Ill have to redo them too, crap. :(
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For indoor use, you could skip the pvc frame altogether and just go with 3 levels of Styrofoam with Styrofoam spacers.

Personally, with a fairly simple design as the GH2n2, I would go with the traditional center pole method. The 2 center sets of uhf reflectors would go into thin tubes (to hold the spacing between them) and then go into a hole in the 1" diameter center pvc post. The 3 vhf-hi back elements would be mounted from tees and pipe in the center post. The front driven element would be mount on 3 sets of tees and pipe from the center post. I would use 1" to 1/2" reducers out from the center post tees to reduce cost and wind resistance. The NAROD to stub separation would be held in place with scrap vinyl siding spacers. The top of the top hat NAROD would be attached to the center pvc post.
I would not glue the pvc joints, but rather use a small #4 screw to hold the fittings in place.
If built this way, using the cheaper grey electrical pvc pipe, it would be durable and wind resistant to use outdoors in the future.
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The single T standoff just seems "wobbly", so that is where I was thinking about supporting both ends of the reflectors.
I always glue in an old broomstick in the center of the 1 inch pvc mast to add rigidity. :cool:
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