Restoring aluminum skins

[GARY HILTON]

Hi all, as I am in the process of getting my PV-2 home (piece by piece) I am wanting to start the process of restoration . I have the cowling panels at home, as there is not much in the way of corrosion on the alum. panels, there is a lot of rust and corrosion of the steel dzus fasteners on about every cowl panel I have...some are pitted rather badly.
I was thinking about a blasting operation on the whole panel, but was told to not even think about it, because it would stretch the alum. skin. The panels are two sheets pressed together, with what looks like the dzus fasteners sandwiched between them. I was at the museum in Pueblo,Co...and noticed on their B-29, that they had completely cut out some of their dzus fasteners and made some rather crude looking patches to replace the fasteners...is this the remedy I will have to use to make mine nice, clean, shiny, and operational?
Any help on the care and treatment of the alum. on Annie would be appreciated...I don't know how I'll end up presenting her as of yet, but it seems obvious that being in the humid climate of Missouri, and being kept outside for the time being, that I will need a protective coating/paint. Believe me....suggestions are welcome! Thanks!

[bdk]

Dzus fasteners are installed by swaging alumninum collars to hold the rotating steel part in place. Remove that collar (cut it carefully) and the fastener will pop out. If the hole is worn out in the cowling itself you will have no choice but to install a doubler as you describe and then install a longer Dzus stud.

DZUS FASTENERS: Almost all Dzus installations utilize a grommet, which acts as a retainer for the stud. By working the grommet from the backside of the panel and bending inward enough to slide through the panel thus removing the stud with it, you can remove this permanent grommet. Reinstallation of new grommets requires special tooling. A separate tool set for each size and head style is required. See 'TOOLING REQUIREMENTS' below. In order to lift the aluminum grommet material from the backside of the panel, you can use a nail cutting type of tool or a large end cutting pliers. Please take special note that old, bent and rusted spring receptacles will hinder proper fit and the engagement of new Dzus studs, especially stainless studs that are generally softer than the steel studs being replaced. Replacement spring receptacles are available.

http://www.performanceaero.com/cgi-bin/ ... .fasteners

You might try Alumiprep 33 to clean and Alodine 1201 to protect for painting.

http://www.chiefaircraft.com/airsec/Air ... odine.html

[GARY HILTON]

Thanks BDK, will be picking up the alumiprep and the alodine very soon. Any suggestions for sprucing up the steel dzus fasteners that are still in good shape?

[bdk]

Thanks BDK, will be picking up the alumiprep and the alodine very soon. Any suggestions for sprucing up the steel dzus fasteners that are still in good shape?

Send them out to get re-cadmium plated (and baked per the MIL-SPEC to prevent hydrogen embrittlement). Failing that you can wire wheel any rust off and preserve them with the anti-rust compound of your choice.

http://www.corrosion-control.com/acf50.html ?????

By the way, forgot to mention that Alodine will leave a yellow/brown surface finish. Doesn't look that good by itself but that doesn't matter once it is painted.

[GARY HILTON]

Yeah, that's what I was reading on the alodine add...and you are right, if painted , it wouldn't matter...By sending them out for cad plating, are you refering to taking them apart? I'm not home now to take a look at them...you mentioned something about a collar, I am assuming that they can be removed without tearing up the aluminum?

[Sully]

To get an idea of the collar see this.

http://www.aircraftspruce.com/catalog/h ... -00849.php

and from here for the stud, about half way down the page.

http://www.aircraftspruce.com/menus/ha/fasteners.html

The tools are expensive but worth every bit if you are doing enough of them.

Sully

[bdk]

Yeah, that's what I was reading on the alodine add...and you are right, if painted , it wouldn't matter...By sending them out for cad plating, are you refering to taking them apart? I'm not home now to take a look at them...you mentioned something about a collar, I am assuming that they can be removed without tearing up the aluminum?

Yeah, you have to remove the stud as you can't cadmium plate the aluminum skin!

The collars (or grommets) are aluminum. They can be carefully removed as indicated below:

DZUS FASTENERS: Almost all Dzus installations utilize a grommet, which acts as a retainer for the stud. By working the grommet from the backside of the panel and bending inward enough to slide through the panel thus removing the stud with it, you can remove this permanent grommet.

[bdk]

To get an idea of the collar see this.

http://www.aircraftspruce.com/catalog/h ... -00849.php

Something is messed up up about that price quoted!

Try here (full grommets):

http://www.aircraftspruce.com/pdf/2008I ... t08105.pdf

You'll probably need the "GF" type.

[GARY HILTON]

thanks for the insight...yeah, I knew that you don't cad plate aluminum..I have never worked with these fasteners before, and didn't realise that the grommets could be removed, and the studs replaced...and thanks to all, I have learned , just need to master the process now!

[Sully]

The reference for the collar was for a visual only. It was the better picture. That particular part number is a deep unit and probably not the one needed for his specific application.

Sorry for any confusion.

[Cvairwerks]

Gary: Check around for the prices on the tools. Not super expensive, but prices can vary pretty wildly. They do show up on fleabay on occasion. Also, get a copy of the installation data for the correct hole sizes. If you have a collar that is being difficult to remove, use a reamer that is a few thousands undersize for the minimum hole diameter to cut the collar out.

Craig C.

[gary1954]

Gary, I saw your post that you were trying to get a PV2 home, and were working on the panels etc. What the status man? The PV2 is a cool aircraft, I love the drone of a Radials. Pictures, you have pictures, we need pictures

[GARY HILTON]

Craig, thank you...makes mose sense....I am getting the big piture now...I have an outlaw-bro-in law that works for a major airline...was talking with him tonite, and he suggested the same thing as you...plus, he tells me that he'll grab a handfull of different sized dzus fasteners and the springs, to check the size....might be able to get a bunch of freebies! And thanks Pooner...I will probably take you up on the springs as well!

[GARY HILTON]

And thanks Sully, as well...By the way, what part of Ms are you in? Any where close to Corinth or Tupilo?

[The Inspector]

Just reading your post about dzus fasteners. If the metal around the fastener holes is distorted but not excessively worn, search the field for someone with a plannishing hammer or an english wheel (also try local hotrod builders as they also use these tools) and have the metal shrunk back.
One of the courses I teach to Boeing new hires is alodine application. firstly the piece to be alodined MUST be water break free,meaning lightly scuffing with a red scotch brite pad, then pouring water on the piece while it lays flat, any 'pullback' ffrom edges must be removed as wherever pullback occurs, alodine will not apply correctly.
Be very very careful with alodine, the stuff is about #2 on the list of things not real good for the human filter system (kidneys, liver, spleen, tec. last time I was in POOPBOYS I didn't see human filters on the shelf next to the ones for Chevies) Look the stuff up in an MSDS book, its chromium flouride, it is very easily absorbed through the skin or eyes if splashed. It can cause partial to complete loss of vision depending on how much you get hit in the face with. It causes what are called 'chrome sores' that are skin lesions that get a very hard, white edge crust and the center stays an unhealthy looking dark red for a very long time, they break open easily and can cause bleeding around the sore that can be hard to stop.
Boeing recomends a maximum of three minutes wet on the surface for adequate protection, what it does is combines with the surface aluminum oxides and hardens the surface of the metal. rinse with tap water in a bottle but be aware that this stuff and everything you've used with it is now haz-mat and must be disposed of correctly. Recommended gloves would be PVC as they are good against alodine for up to 8 hours.(and also work great for mixing a meatloaf for dinner)
You are not looking for a golden shiny finish, just some indication of color shift! Be aware also that the alodine remains very fragile for about 6 hours after application and you can easily rub it off with your fingers and could ingest it (not good for the filters). Use alodine in a very well ventilated area as the fumes will displace oxygen, Boeings painters wear what amounts to a full pressure suit when doing an alodine wash including forced ventilation masks.
You can alodine a bare metal airframe with alodine 1000, every shiny, glistening AMERICAN AIRLINES 777 is alodined in the paint shop. The trick is to do a test piece, apply 1000 for three munutes and neutralize, if any color shift is noted, try 21/2 minutes on another test strip, backing the time down to as little as 30 seconds, remember, you're not making wheat toast here.
The fasteners can be sent to anyone of several platers (that can replate to FAA specs)who will strip and replate the fasteners, bad ones throw out as thy just become a source of later agrivation. I hope this info helps you and others out on the evils of alodine.