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Best Plastics, Composites, Rubber for structural antenna parts

90179 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 bought these electrical conduit straps (in the sched. 40 - electrical dept at HD) and glued them together using ABS cement - yellow quality.

Will this hold up outside, and is it UV resistant?
Hmmm, yes, good idea...

I was thinking of using a small metal screw with nut, but from what I read it's preferable to not have ANY metal near and in between the phase lines...

Then I was thinking about nylon screw/bolts, but I couldn't find any, plus I dont rhink this would be UV resistant either!
Alright thanks, I'll check out a marine shop, I hope that's quite common, thanks
Thank you johnpost,

Yes, I sanded the each contact surfaces flat, but this is not easy to get perfectly flat.

So, I guess, HD must sell the PVC glue also...
Thanks johnpost,

I will need to set up my old vice.

I bought some nylon (plastic?) bolts with nuts which are used to fasten a license plate to the car (Canadian Tire sells them). I assume they are UV.

I drilled a hole through the center of each strap and passed the bolt thru to fasten them tightly together, but I dont understand why when I tighten the nut against the strap it just keeps turning, never really tightening up. I checked and the bolt was not stripped, I even tried another one and same thing. I assume these are not meant to get really tight, especially without any kind of washer???

PVC gluing with PVC primer and PVC glue is solvent welding. The glue has solvent and PVC resins which dissolves some PVC and then it reforms new polymer chains fusing the pieces together.
the guy at the HD told me that the CPVC glue will not bond the electrical straps properly. This product was actullay in the plumbing section.

However, in with the electrical conduit section, there was another type of glue, which I believe mentionned solvent and PVC, I assume this would be the correct one.

Is CPVC and PVC the same thing? Thanks
Following 300ohm's suggestion,

I have sashed together the 2 straps using 3 tie-wraps, I think with a little glue this will be very sturdy for a stand-off...

I also placed the small strap passed underneath the larger one.
Some toilet seat bracket nuts/bolts are fairly lengthy and made of nylon, so if you can get used to the backwards threading on some of them I think they'd be a good option for someone needing non-metallic joiners for antenna building. I have no idea if they're UV-resistant though.
been there, done that...they dont work...dont waste your money & will have to buy a toilet accessory kit just to get a couple screws if you cant buy them individually (which is the case in Montreal at least!).

And when you tighten them they dont get tight...same thing for license plate fasteners, they dont work....

BTW, toilet fasteners are NOT UV, whereas license plate fasteners ARE UV..
the plate fastners can be up to and more than 1" sometimes...but they dont tighten, they ONLY FASTEN (big difference!), also at close to $2 a screw - a real rip-off...

as for marine derlin, thats a no-find here in surprise...ironical considering we are SURROUNDED by marine!
PVC, CPVC, Fittings UV protection

My understanding, is, for the fittings, they need to be dark pigmented, which are inherently UV resistant, thus the darker Schedule 80 PVC fittings would be recommended - but these run at least 3x more expensive than the white or the CPVC fittings...

However, when post-purchase protecting for UV, the suppliers recommend to coat them with LIGHT colored, 100% LATEX based, outdoor paint, for increased UV resistance...apparently LIGHT colored pigmentation provided the most Titanium Dioxide for UV protection.

Does this make sense ?
Black Tie Wraps

Thanks 300ohm, thats a good review!

Yes, I guess fuchsia wouldn't be an option :eek:

Are ALL BLACK tie wraps considered UV resistant...I've used some which were specified UV resistant, but many which are not specified, in either case after several years of wear they are still doing the job...
Balun protection

I have noticed, that the balun connection feedpoint screws area on the DIY bow-ties are somewhat sensitive to the elements over time, specifically corrosion whereby the balun leads break off

Are there any recommendations for a simplePVC type enclosure built in at the feed point to cover the connection (it seems rather complicated to build into the structure and stand-off, and doesnt appear to create a perfect seal anyway since humidity/moisture will still work to the inside) ?

Typically I use dielectric grease for minimum protection, on a brass coated wingnut, washer, and screw.
I guess im trying to protect the connection itself, as opposed to the balun alone, like on the commercial antenna, CM4221HD

I tried to recreate the balun box protection, but it become too complex
yes, im of 2 minds on that also, after all, the old CM4221 was exposed, then again they werent using brass screws and copper wire

I guess either way, it can be expected that eventually you may need to change out a balun
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