My antenna doubler!

captain_john · Post by **captain_john** » Mon Dec 24, 2007 3:01 pm

Hey all,

Per usual, I have noodled over this subtlety WAAAAY too long and have finally put it to bed. Here is a pic:

I gotta say, I am thrilled with the outcome and this thing is MIL-Spec all the way!

I have one on each side and it is DIESEL!

I have no doubts that it will withstand the test of time and have great signal propagation.

It is in the outermost seat rib bays and as you can see, ties the floor into the ribs nicely!

Thanks to Kevin J. and Mitch B.!

CJ

Post by **Spike** » Tue Dec 25, 2007 9:44 am

Schweeeet!!!

Wicked Stick · Post by **Wicked Stick** » Thu Dec 27, 2007 8:32 pm

Hey Capt'n,

How about posting a picture or at least more info on the tool you used to makes those nice round swirled grounding circles.

WS

tmbg · Post by **tmbg** » Thu Dec 27, 2007 9:58 pm

I'm gonna take a wag at it and say that he used round sticky colored dots from the office supply store before he primed it

captain_john · Post by **captain_john** » Fri Dec 28, 2007 4:14 am

Ian, you zigged when you should have zagged!

I used a bonding brush. Kevin J's bonding brush to be exact. He has some tricks up his sleeve and this was one of them!

This is what it looks like:

You chuck it in the drill and the stainless steel brush cleans away everything in it's reach!

It looks like Sky Geek has 'em. I am sure others do too.

Why you need it is this; In order to get adequate signal propagation you need a good ground plane. This is hard to achieve in a plastic airplane. In our metal ones it ain't hard. The problem is, you need metal to metal contact. Having primed the skin and doubler for corrosion protection, we need to scrape away the contact points.

The bonding brush cleans the points of contact nicely! Once clean, use a little bit of alodine on the fresh surfaces and you are ready to assemble. I also cleaned the 4 outermost rivets and alodined them as well for a broader "short circuit" of the ground plane. This will mitigate any capacitive effects of the insulating properties of the primer.

CJ

tmbg · Post by **tmbg** » Fri Dec 28, 2007 11:12 am

ah well, life would be boring if I were right 100% of the time!

captain_john · Post by **captain_john** » Sat Dec 29, 2007 7:36 am

Ian, Once I thought I was wrong... but I was mistaken!

CJ

BrickPilot · Post by **BrickPilot** » Sat Dec 29, 2007 2:26 pm

captain_john wrote:You chuck it in the drill and the stainless steel brush cleans away everything in it's reach!

You could fab a mini sanding disk out of some non-metallic sandpaper and bond it to something chuckable as well. I'm thinking that would be preferred because couldn't the steel brush leave behind some microscopic ferrous particles in the aluminum, leading to some possible corrosion issues down the line?

Wicked Stick · Post by **Wicked Stick** » Sat Dec 29, 2007 5:36 pm

I suppose that could happen, but if you wash n prep it afterwards and then etch the surface, it should last just fine.

TomNativeNewYorker · Post by **TomNativeNewYorker** » Sun Dec 30, 2007 2:50 am

BrickPilot wrote:couldn't the steel brush leave behind some microscopic ferrous particles in the aluminum, leading to some possible corrosion issues down the line?

Taken from my corrosion manual:

Wire brushes are used to
remove heavy corrosion deposits or paint that is not
tightly bonded to the metal surface and are available
with aluminum, steel, stainless steel, and brass bristles.Thick, short, and/or stiff bristles are more effective for
rapid corrosion removal. The brushes must be
compatible with the metal surface to prevent galvanic
corrosion. Stainless steel can be considered to be
neutral, and can be used on all aviation equipment. Do
not use a wire gage or diameter above 0.010 inch, as
gouging of the surface may occur. Remove the corrosion
with a linear motion; do not cross-hatch. This will
unnecessarily damage the surface. After wire brushing
soft metal (such as aluminum or magnesium) the surface
areas must be polished with fine abrasive paper.

captain_john · Post by **captain_john** » Sun Dec 30, 2007 8:07 am

Well Tom, that works!

Soooo, the Bonding brush is okay, hit the area with a little aluminum oxide sandpaper and then clean (acid etching is probably optional because mechanical etching is already extensively performed) and then an alodine treatment.

I think that is enough minutia!

CJ

BrickPilot · Post by **BrickPilot** » Sun Dec 30, 2007 11:32 am

TomNativeNewYorker wrote:Stainless steel can be considered to be neutral, and can be used on all aviation equipment.

Awesome! Great information Tom. Thanks.