I use 1/8" "Closed-End Blind Rivets" with an aluminum rivet and a STEEL mandrel. Why a steel mandrel? More shear strength and you get more clamping force before the mandrel breaks away!
Example:
1/8" aluminum w/aluminum = 105 lbs shear strength.
1/8" aluminum w/ steel = 305 lbs shear strength.
These rivets have a special solid end that seals tight against vapors and liquids. Once set, part of the mandrel stays in the rivet to give you more shear and tensile strength than standard blind rivets of the same size and material. Shear strength (listed in chart) is the amount of force applied against a rivet that will cause it to break. Tensile strength (listed in chart) is the amount of pull a rivet can withstand before breaking.
Here are a couple of pictures of the bottom tube of the I-10K. This piece has 2 layers of aluminum tubing to strengthen the bottom section. I always replace the stainless steel screw with a 3/16" closed end pop rivet. Notice the end is not like the regular pop rivets you get in the local hardware store. These rivets are weather tight and won't become loose with vibration which is why they are used in the aircraft industry....unlike your standard pop rivets.
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As I said above, I use 1/8" rivets for the elements. I use
3 rivets per joint which gives me over 900# of shear strength. On a 4" overlap I space the rivets at 0.25", 2.0", and 3.75" from the end of the tubing. This gives me a solid joint across ALL 4" as opposed to only the first 1" when using a clamp.
I use
Noalox on ALL my aluminum to aluminum joints which improves my conductivity plus eliminates air (oxidizer) getting into the joints! You can get "Noalox" from Home Depot in the electrical section. One 8oz bottle will last a lifetime! I do not further seal the joints with a sealant.
Using rivets is NOT my idea. You can read about it in the ARRL Handbook and Antenna Book. It was Force 12 who made me a believer however.....
http://force12inc.com/F12-ele-ex-r1-0.htm
and also from Force 12.....
RIVETS Yes, rivets! Force 12 is the first manufacturer to provide riveted element construction. The rivets used by FORCE 12 are from the aircraft industry and are called "closed end" rivets, since they are solid aluminum, with no hole. They are designed specifically for applications with vibration. If necessary, they can be drilled out for repairs or transport and new rivets installed for re-assembly. The use of sheet metal screws tends to render disassembly difficult at best, since material from the inner tube is pulled into the hole and into the space between the tubes. Hose clamps can break or become loose and present a nuisance when erecting the antenna.
You can buy closed-end pop rivets from McMaster Carr. Go to.....
http://www.mcmaster.com/
and type "3157" in the search box on the left. I use the three following part numbers:
97524A020 (1/8" .063 - .125 thick)
Used for double wall thickness (.058 x 2 = .116" thick) on all your standard element joints.
97524A021 (1/8" .126 - .187 thick)
Used for triple wall thickness (.058 x 3 = .174" thick) on main radiator joints.
97524A106 (3/16" .063 - .125 thickness)
Use only 1 at the base of the main radiator to replace small stainless steel screw.
NOTE!
I have yet to see a failure of a single I-10K using the clamps supplied with the antenna. Jay and Steve use the best quality clamps available! I should know, I remember having that conversation with Jay and pointing him towards Breeze all SS clamps. My choice to use rivets (which I tried to talk Jay into all the way back in 1997) on the I-10K is more of a personal choice rather than a necessity. Besides, the clampless elements looks real good also! Still, I believe pop-riveting element joints is still better than clamping. I also drill an 1/8" drain hole in the main radiator just above the solid fiberglass rod of the base assembly.
Same applies to the Maco antennas.
