[TowerTalk] Fiberglass rod

[Grant Saviers]

Fiberglass rod is a generic statement.  Often for pultruded 
glass/carbon/kevlar fiber and a polymer.  So that leaves a lot of 
choices including if the polymer is UV resistant.  Glass fiber plus 
polyester resin is the most common and cheapest.  Probably UV resistant, 
but worth checking with the supplier.  A large hexbeam I was given had 
all of the pultruded support tubes painted.  steppIR has all trombone 
fiberglass painted. So acrylic paint is one fix.  I've used 
glass-polyester on several beam driven element restorations.

Generic epoxy-glass material (eg FR4) is not UV resistant so unless 
spec'd UV resistant needs painted.

Delrin (acetal) is an excellent polymer, but as others noted not likely 
strong enough on its own as a 40m beam element insulator.  A black 
delrin sleeve over 6061 rod is another choice. My W6NL designed 40m 
Moxon uses pvc sch 80 pipe inside and outside 6061 tube at the center.

Things to avoid - ABS pipe as it has a foam core and deforms.  Nylon and 
UHMW unless UV grades.  Blue nylon has held up well for me as driven 
element saddles and black UHMW for radial mast bearings.

Grant KZ1W


On 3/8/2020 10:09, Dave Sublette wrote:
> Follow up Question.  My browser now works.  Go figure.  Question:  Is 
> there any other material (Delrin comes to mind) that you would recommend 
> for this application?  The rod will be 1.5 inches in diameter and insert 
> at least 6 inches into each half of the dipole. This is a 40 meter 
> dipole and is heavy (75 pounds).  It is supported by strut ropes, but 
> will be subject to bending horizontally and to some us flexing as the 
> wind generates lift. Some torque will be present for the same reason.
> Keep in mind, I have a similar material that has been in service 
> satisfactorily for over a year on my pair of two element Moxons (without 
> strut ropes).  So I'm sure this will work.  I am  just curious to have 
> the benefit of your experience.
> 
> Thanks,
> 
> Dave, K4TO
> 
> On Sun, Mar 8, 2020 at 12:52 PM Dave Sublette <k4to.dave at gmail.com 
> <mailto:k4to.dave at gmail.com>> wrote:
> 
>     Well....it appears that something is out of whack with my browser. I
>     will try another flavor.  I have two more available.
> 
>     Thanks everyone.
> 
>     Dave, K4TO
> 
>     On Sun, Mar 8, 2020, 12:42 PM Grant Saviers <grants2 at pacbell.net
>     <mailto:grants2 at pacbell.net>> wrote:
> 
>         McMaster.com  FR4 to 4" diameter
> 
>         Grant KZ1W
> 
>         On 3/8/2020 09:29, Dave Sublette wrote:
>          > Some time ago (two years) I bought some 1.75 inch diameter
>         fiberglass Rod
>          > to use as a center insulator for my 40 meter Moxon project. 
>         I bought the
>          > material from Max-Gain Systems, somewhere in Georgia.  I now
>         get an error
>          > message indicating that the web page no longer exists.  Does
>         anyone know
>          > where they went or where I can buy large diameter fiberglass rod?
>          >
>          > Than ks,
>          >
>          > Dave, K4TO
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