[TowerTalk] Force12 rivets

Fri Feb 18 13:32:42 PST 2011

1. Aluminum and stainless steel are dissimilar metals and will corrode when
in contact with one another.
2. The physical construction of a screw is that it has fairly sharp ridges
for threads. When in contact with a soft metal surface and subjected to
mechanical vibration like wind action or antenna rotation, these ridges wear
on the holes in which they're used and abrade the soft aluminum - they
"round out" the hole.

Better to use a backing structure (fiberglass/pvc, etc) that holds the screw
threads or a backing nut, or a hose clamp.

Many of these rivets are aluminum or alloy that won't cause galvanic
corrosion (as in case 1) and their contact surfaces are relatively smooth,
to solve case 2.

Rivets are a good mechanical solution when properly set and when a high
quality rivet is used. The trouble comes when they're not tightly applied
when pulled, contamination (sand/salt, etc) permeates the joint and the
joint or rivet wears from mechanical or galvanic action.

All designs are compromises. The designers of Force12 antennas have chosen
rivets because they're cheap, light and effective. Rivets hold airplanes
together very well, but few of them are the type you get at the hardware
store.

73,

Mickey N4MB

On Fri, Feb 18, 2011 at 2:30 PM, Fernando EC1CT <ec1ct at esbesaya.com> wrote:

> Wonder why don´t you upgrade and insert a good stainless steel screw with
> nuts instead those failing rivets. Optibeam is using this system and works
> fantastic in their antennas
> having a similar size and design as Force 12. 73!
> Fernando EC1CT // KD0IGJ
> E-Mail: ec1ct at esbesaya.com
> KR DX Group
>
>
> --------------------------------------------------
> From: "Mickey Baker" <fishflorida at gmail.com>
> Sent: Friday, February 18, 2011 5:07 PM
> To: "Chet" <chetmoore at cox.net>
> Cc: <towertalk at contesting.com>; "Barry Gross" <n1eu.barry at gmail.com>;
> <n8de at thepoint.net>
> Subject: Re: [TowerTalk] Force12 rivets
>
> > I have seen several Force12 antennas that have failed in my part of the
> > world in a tropical salt water environment due to corrosion and
> mechanical
> > wear from wind.
> >
> > If I were assembling one, I'd be tempted to use swaged collar rivets:
> > http://www.aircraftspruce.com/menus/ha/rivets.html
> > These would hold better - they grip the tubing tighter because they
> deform
> > the aluminum more under the collar of the rivet.
> >
> > I'd also use something to chemically protect the rivet
> > (Boeshield/Corrosion-X) after it was installed.
> >
> > Careful drilling "perpendicular holes" - better to go down the length of
> > the
> > tubing a few cm so as not to provide a weak point in the element.
> >
> > 73,
> >
> > Mickey N4MB
> >
> > On Fri, Feb 18, 2011 at 10:13 AM, Chet <chetmoore at cox.net> wrote:
> >
> >> F-12 antennas are pre drilled at the factory. The instructions with mine
> >> say
> >> if there are 3 holes, use 3 rivets and insert all 3 rivets in the holes
> >> and
> >> don't pull any of them until you know all 3 line up. If they don't line
> >> up
> >> you probably have that particular element reversed.
> >>
> >> On some of the driven elements they drill a 4th hole in case you need to
> >> adjust the SWR and on these elements only 3 of the 4 will line up. My
> >> instructions didn't say anything about a 2 rivet rule.
> >>
> >> If you still have 2 out of 3 rivets,insert a new one. Not sure what kind
> >> of
> >> failure you had. Did the problematic rivet fall out, did it get pulled
> >> all
> >> the way through? Just put a new one in.
> >>
> >> 73
> >>
> >> Chet N4FX
> >>
> >> -----Original Message-----
> >> From: towertalk-bounces at contesting.com
> >> [mailto:towertalk-bounces at contesting.com] On Behalf Of
> n8de at thepoint.net
> >> Sent: Friday, February 18, 2011 9:38 AM
> >> To: Barry Gross
> >> Cc: towertalk at contesting.com
> >> Subject: Re: [TowerTalk] Force12 rivets
> >>
> >> I believe that the rule is:
> >>
> >> put two rivets at each location .. perpendicular to each other.
> >>
> >> Someone told me that in the past.
> >>
> >> 73
> >> Don
> >> N8DE
> >>
> >>
> >> Quoting Barry Gross <n1eu.barry at gmail.com>:
> >>
> >> > I'm not sure if Force12 still uses riveted construction of yagi
> >> > elements.
> >> >  In any event, I just experienced my first rivet failure on my C3S
> >> > (great
> >> > timing, huh?) and would like to avoid repeating this experience.  What
> >> > is
> >> > the tried and true wisdom on preventing rivet failure on these
> >> > antennas?
> >> >
> >> > Thanks & 73,
> >> > Barry N1EU
> >> > _______________________________________________
> >> >
> >> >
> >> >
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> >>
> >>
> >>
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> >
> >
> >
> > --
> > Mickey Baker
> > Fort Lauderdale, FL
> > “Tell me, and I will listen. Show me, and I will understand. Involve me,
> > and
> > I will learn.” Teton Lakota, American Indian Saying.
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-- 
Mickey Baker
Fort Lauderdale, FL
“Tell me, and I will listen. Show me, and I will understand. Involve me, and
I will learn.” Teton Lakota, American Indian Saying.