[TowerTalk] F12 C19XR Rivets

[Jim Thomson]

Date: Mon, 7 Mar 2016 23:52:31 -0500
From: "Roger (K8RI) on TT" <K8RI-on-TowerTalk at tm.net>
To: towertalk at contesting.com
Subject: Re: [TowerTalk] F12 C19XR Rivets

Good advise Jim,

My C19XR uses 3 rivets in a row at each element joint.  I understand 
that they may have gone to 6 using two sets of 3 opposing rivets.  
That's the way I plan on repairing the ends of the 20 m reflector.

IIRC it does use larger rivets in the boom, but I don't remember the 
size as I had forgotten the size for the elements..
After tomorrow (63F and 55 F for a low, 59/43 and near an inch of rain 
Wed) The snow should be gone giving me easy access, if a bit squishy, to 
the antenna.

These are what are called a "Blind Rivets" in that, unlike regular pop 
rivets which have the mandril go all the way through, the end of the 
rivet is solid to prevent water from leaking through, much like the 
"Cherry Rivets" used in aircraft.  The "Sonex" little single seater has 
all riveted joints using these "Cherry rivets" instead of the typical 
flush rivets requiring a bucking bar.

As Jim says, do not tap rivets in by taping on the mandrel. Usually you 
only forget once as the mandrel may just fall in and you no longer have 
a blind rivet that may be a bit difficult to remove.  Trying to drill 
out a failed rivet can be frustrating as they often just spin in the 
hole instead of holding for the drill bit to cut metal.

73 es thanks Jim

Roger (K8RI)

##  I have yet to see any issues with the 3 x rivets in a row on ele joints.   It was an issue
on my EF-180B 80m rotary dipole where they drop from 2 inch OD down to a smaller size, 
with this huge swedge.   I ended up installing rivets  every 90 degs,  but every 120 degs
would have sufficed....and .1875 rivets were used in that one off case. 

##  the rivets f12 uses are called closed end rivets, the mandrel is embedded into the solid
Aluminum rivet.   They are easy to drill out, if required. Use a 1/8 inch drill bit, and you can easily
drill them out 20 times, and the new ones just slide right into place. 

##  On my shorty 40m eles, the 44 ft long ones, they are triple walled on the inner sections.  The way they
do that is to 1st rivet the inner  pair of sleeves 1st, then  grind the rivet heads right off so all that is left is 
the mandrel pin, and its flush to the ele.  Done that way so the 3rd and biggest outer sleeve slides right over the
inner 2 x sleeves, then the  5 x really long .125 inch rivets are used to go through all 3 x sleeves, with the 
5 x holes provided.   Ingenious method..and works good.   But that is another one off case. 

##   3 x rivets slid in, and the 1st one riveted.  If the  2nd + 3rd rivet jumps out a bit, they can easily 
be put back flush, using a real small xcelite  nut driver.. or the edge of a T square, etc.... that goes on the
domed portion of the rivet.   3 x rivets is plenty, and 6 is  overkill.   Where F12  really beefed things up is
on their new style  ele to boom brackets.  the new style are a full  1/4 inch thick.... and wrap  around the boom.
The old style used a .1875 or .125 plate, with 2  x 90 deg bends in the plate, where it goes around the boom.
Mew style use the wrap around style, and uses a total of  20 x 1/4 inch  rivets.  5  down each side,  5 on the top, and
5 more below.   They install a horz plate below the boom, that straddles the new style  wrap around ele to boom bracket.
this horz plate just touches the bottom of the boom..where the 5 rivets  go down below.   The new style assy is  bomb proof. 

##  I have never had a problem with the old style brackets, nor the 3 rivets for  ele joint.   Where I did a have an issue was the 
boom slices.  f12 used a 6 inch long outer sleeve,  which had  8 x  3/16.rivets on one end, call that the factory end.  End use
opposite end used a pair of  1/4-20  SS bolts and nylocks.  Done that way since the hand rivets  will not pull a 3/16 inch rivet.
Mine had too much slop in the boom slice joints  so beefed it up with an additional  4 x rivets, so a total of 12 on the factory end,
they are every every 90 degs, and now 3 rows, instead of 2 rows.    User end beefed up installing 3 x new 3/16 inch rivets
down each side....and one more 3/16 inch rivet on top, and one ton the bottom, between the  1/4-20  SS bolts.  OEM  1/4-20
bolts were oriented vertical.   Old style  ele to boom brackets all had a 5th un-used  1/4 inch hole dead center.   You can use it
as a drill guide and drill out the boom with a 1/4 inch drill  bit, and install a 1/4-20 SS  bolt + nylock, or install a 1/4 inch rivet 
on each side. 

##  I like  1/4 inch rivets  vs  1/4-20 SS bolts myself.   Rivets  suck from the inside out.  A  1/4-20 ss bolt  just crushes the boom.
A  3/16 rivet is damn strong..and a 1/4 rivet is  stupid strong.   IF  you have an air compressor, do urself a favour and get the
optional attachment that pops rivets, it makes things go 100 x faster.   I buy the closed end rivets in either 100  qty..or in 250
qty.   Local industrial supply place had thousands of em, identical to what F12 uses.   Slightly domed heads, al rivets, and mandrels
embedded into the solid rivet. 

##  The F12 ants atre easy to beef up.  And the larger 3/16 and 1/4 inch rivets are far less weight vs  1/4-20  SS bolts +  nylocks.

Jim   VE7RF