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Aileron Counter weight prime?

M

mlwynn

Well Known Member
Hi all,

I am busy prepping the aileron parts. I was trying to decide if the counterweight pipe, which appear to be galvanized steel, ought to be primed. Seems like I have heard the steel and aluminum in contact leads to corrosion. I have thought about priming the inside of the front skin as well as the pipe. Is this overkill?

Also, when riveting the upper skins and spar together, do most people back rivet this or buck?

Regards,

Michael Wynn
RV 8 Wings (ailerons)
San Ramon
 
I would prime the counterweight tube inside and out to be sure. This isn't much trouble and the piece of mind you get alone is worth it.
 
Corrosion

Doesn't it have something to do with dissimilar metal corrosion, as opposed to 'straight' corrosion? (as in, the galv'd pipe in contact with the Al?)

Cheers,
 
I primed the pipe and the nose skin.

Buck. Clamp the assembled ail. to a table (top rivet holes hang over the edge) and have a partner lay on the floor with the gun and you slide your hand through the bottom between the spar and the unclecoed aft skin. Worked great for me.
 
mlwynn said:
Hi all,

I am busy prepping the aileron parts. I was trying to decide if the counterweight pipe, which appear to be galvanized steel, ought to be primed. Seems like I have heard the steel and aluminum in contact leads to corrosion. I have thought about priming the inside of the front skin as well as the pipe. Is this overkill?

Also, when riveting the upper skins and spar together, do most people back rivet this or buck?

Regards,

Michael Wynn

Mike
You are also exposed to dissimilar metal corrosion, as has already been mentioned. Where you countersink the galvanized pipe, the aluminum is in direct contact with raw iron. I suggest that you Mil Spec epoxy or Zinc Chromate prime all parts which come in contact with that pipe. It will also help if you Alodine those same parts. I primed the C/W pipe inside and out. I also dipped the flush pulled rivets in primer just prior to setting them.
I bucked my skins to the spar. I have long arms and it was tough to reach the center of the spar. If you can back rivet the top skins on, do it. However, I suspect that you will still need someone with long arms to buck the lower skin to spar rivets? It's been so long since I did that job!
Charlie Kuss
Click to expand...
 
Specifics of priming the C/W

So how, exactly, is everyone priming the counterweight? Prepping the outside is not that difficult but it looks like all you could really do is rinse out the inside. So, Dawn/Simple Green or MEK? Both?

I have been using AZKO two part epoxy primer on the primed parts of the airframe. I think this is good for steel, as well. Is there a better choice? Is it important to do more than clean and scuff the exterior?

Regards,

Michael Wynn
RV 8 Wings (Ailerons)
 
Rinse it

I'm not a million miles away from that job: I intend to block one end with tape, pour in some mixed epoxy primer, block up the second end and then give it a good rinse out. Remove the tape and then prime the outside as normal. May or may not alodine rinse it as well: don't really know yet. Anyone know if it is necessary? Or even a bad idea for some reason?

Cheers,
--
 
Don't alodine galvanized steel. Alodine is only for alum.. I didn't wash the insides but I put two coats of primer and then just spayed the outside. Set the pipe in its upright position over night to let all the excess primer drain out. Make sure its sitting in a bowl or something (I used a cool whip container), unless you want primer all over the floor.
 
To properly prep galvi, scuff and wash with vinegar to remove the phosphates.

An etch primer or anything suitable for steel is fine. Don't overlook Sherwin Williams DTM finish. It is a one step acrylic coating that can be brushed on and poured inside!

:cool: CJ
 
OH! ...and I had bugs living inside my counterweight/pipe! They were dead and imported from Korea with the pipe! No idea what kind they were. I had never seen anything like them before!

I bent the end of an electrical snake, pinched some maroon scotchbrite in the loop, attached it to a drill and spun the C&@P out of it!

Worked GREAT!

;) CJ
 
Lessons learned

So here's what I did: Ran a piece of maroon scotchbrite on a piece of wire connected to my low speed drill to clean out the inside. I used vinegar first and then dawn. Basically scrubbed the outside with scotchbrite and same.

I bought a can of Sherwin Williams DTM (thats for direct to metal) primer. The sherwin williams folks thought that would be the best option for galvanized steel. I then taped all the holes and one end closed and poured in the primer. Mistake #1: should have thinned it with water. The stuff is pretty thick and left a very thick coat of primer and took forever to drain out. I sprayed the outside, and that went pretty well. All in all, I think the counterweight is adequately primed.

Will doing so other priming with my standard AZKO two part epoxy, I took a piece of galvanized pipe I had lying around. I cleaned it with MEK and then sprayed it with the AZKO. Much better coating. Hard and nails and very well adhered, even though I really didn't prep much.

If I had it to do over again, I would have cleaned, scotchbrited and used the AZKO. I think it is tougher and more adherent. Anyway, lesson learned.

Regards,

Michael Wynn
 
My peices started out looking like Poo!

My Balance pieces (1/2" galvanized pipe) that came from vans loooked horrendous:(

They were bumpy scratchy hot zinc dipped.
They would have certainly had a bad effect on the nose skin for my ailerons.

I bought my 6 wing kit about 7 years ago and all my steel parts were not primed or powder coated from the factory, so.....

I took all those parts and sent them out to be Cadmium II plated, except for the elevator horns I had those powder coated.
The Aileron weights had to be stripped chemically first which was included in the cost of the Cad plating.

They are so purdy:p
 
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