stripping the fuselage: bead blasting, buffer, or chemical stripper?

[noelcragg]

I've been reading threads for the last several days, trying to come to a decision on how I should strip the fuselage on my project. There seems to be conflicting information about which method is best.

Bead blasting seems like it would be fastest, with the downside that it requires quite a bit of setup (enclosed space, blast rig, full-face supplied-air respirator, etc.). Some folks say that blasting will remove and distort the tubing, while others swear by it as the most gentle way to remove everything except the metal. One source warned about not being able to spot cracks after blasting.

There's not much written about mechanical buffers, but it appears that using one would be relatively speedy. (http://www.youtube.com/watch?v=Sd3sw0OppWM shows one being used to clean up tubing before welding in a replacement longeron.)

Other writers say that chemical stripping is the only correct way to prep a tube fuselage for repainting. They say that the chemicals react only with the coatings and not the metal itself, leaving the structure in a condition where cracks and rust can be easily spotted.

Anybody care to weigh in with an opinion on this topic?

[PACERGUY]

Blasting the fuselage will often make bad tubes very easy to see. Might be worth farming out to local shop.
DENNY

[Steve Pierce]

You can buy an inexpensive sandblasting rig from Harbor Freight or Tractor Supply. I did it that way before buying a big, fancy, expensive pot. Rent a gas powered commercial compressor cause you will use lots of air. I use the black iron slag that Tractor Supply sells. I put down a tarp to catch and reuse the sand after I sift it through a screen. Cleans everything to white metal, I blow off the dust and spray epoxy primer and a catalyzed polyurethane top coat. I have used stripper on tubes with a lot of dope on them but then you have to get the stripper off which means using water. I use a small propane torch to remove glue and the black tape Piper wrapped around the tubes.

[Jason Gerard]

Sandblasting with the proper grit and material type is the preferred and acceptable method by professional mechanics and the FAA. Properly done it will not harm the structure and provides the best surface for max corrosion removal and improves the adhesion of primers. Carburizing the coatings on the structure by burning them with a torch makes for quick and easy removal with the least effort when blasting. Chemical Stripping can leave reside and contribute to corrosion, buffing can imbed contaminates. There are acid treatments for new bare steel but that's not for use on corroded or painted steel.

All steel should be top coated with paint and not left just in primer


Jason

[noelcragg]

Thanks for the input, folks. I'll see if I can get my hands on a small sandblasting rig and practice refinishing a chromoly bike frame before trying my hand at the fuselage.

Time to start reading up on how to spot cracks or other tubing problems...

[tnowak]

Jason,

When you say "All steel should be top coated with paint and not left just in primer", I assume Randolph W2248 Epibond epoxy primer (or equivalent) is okay without further top coat?
TonyN

[Steve Pierce]

I top coat the Epibond. Primer is primer and not a good sealer. I work on some newer Maules and Huskys and they are all top coated. I don't see rust showing through the top coated parts like I do the parts that are just primed.

[tnowak]

Steve,

What top coat do you use that won't "melt' when Ceconite Superseam cement is used? Next year I need to recover my PA17 fuselage and will be using the Ceconite process (rest of Vag recently recovered in Ceconite).
TonyN

[Steve Pierce]

I use Randthane. The glues and MEK have no effect on it once cured. Aerthane is the same I just prefer Randthane because of the way it shoots. Helped a friend cover a Clipped wing Cub once. He didn't follow my recommendation and bought some high dollar automotive top coat. As we were glueing the fabric to the second longeron the first one started coming off like paint stripper. Needless to say he had a few choice words.

[Jason Gerard]

All primers are just that... Primer. The function of a primer is to provide a surface for paint to bond to and in most cases some corrosion protection as well. This is true of any product that is labeled as a primer, epoxy, sealer, wash, etch, what ever type it is it's just primer. The benefit of an epoxy primer is that the solvent based glues will not melt them which is fine on things like aluminum wings parts. The reason for epoxy wood varnish is to keep the solvent based glues from lifting the varnish off the wood.

Aluminum does not corrode anywhere near as fast as steel so leaving aluminum in primer is fine for most aircraft parts. Steel parts need a high quality catalyzed paint to seal and protect them from the environment. Remember fabric jobs now last 30 years so protect the airframe to last 30 years too :)


Jason