National Aeronca Association Bulletin Board

I would like to get all the rust of off my 1940 fuselage and someone mentioned using some kind of shot other than sand be used so as not to take off too much metal. Anyone have ANY info on this? Also: can I X-RAY the fuselage? Will my health insurance cover it? (kidding!) I would like to see where the longerons, etc. need replacing, or perhaps I should say, see if there is anything worth keeping. -stephen

Stephen,

Might look at this thread:

http://joea.com/phpBB2/viewtopic.php?p=11891#11891

David Johnson posted about using a different type of media when cleaning the fuselage tubing that might be worth trying.

Also, what we used to use to check the tubing for rust and such is a automatic center punch. It is spring loaded and when you push it onto something it clicks and leaves a small dimple on the surface that is used when drilling a hole. It also is a quick and good way to check for rusted tubing as when it clicks you can feel the difference between good strong metal tubing and rusted areas.

Have never heard of anyone x-raying an airframe. Hope you have good insurance!

Stephen, there is an older thread with a lot of info from Nathan Hammond about abrasive blasting. You may have to search to find it. His family has been doing aircraft restoration for a long time. He has some very good info there to look at. We did not realize that sand contained some salt residue, and was being blasted into the metal. It would later come back as small specks of corrosion. We always wondered what we were doing wrong! For rusty tubing, Lloyd Thompson taught us to use a small hammer and listen to the sound. Lightly tap the tubing. You can tell a difference between solid tubing and rusted tubing. Lloyd was once blasting wing struts, when he started seeing black specks on the metal. He thought his blaster was blowing something on the strut. Turns out it was holes where the strut had rusted from the inside! David J.

Nut shells and plastic media are better alternatives. Do a Google search and you will find them.

Alternatively be very selective with the grit you use.

Stephen,
Like David said, we learned the hard way about not using sand. The best stuff to use is Glass, plastic BB's, or a cinder base like "Black Beauty" or "Black Diamond" etc... The plastic BB's are about $35 per gallon and reuseable, cinder media (black diamond, black beauty) are usually the cheapest at around $15 per 50lbs bag (about 2-3 gallons) and is reusable for a while. You should be able to get the media from Harbor Freight, Northern Tool, Tractor Supply, etc... Both glass and cinder will start to break-up and turn to dust after several rounds, but the cinder seems to last just a little bit longer.

Keep something in mind about sandblasting:
You're not really taking off material, but simply modifying the surface. Think of it like a piece of 'Play-Doh' that you take a set of drum sticks too. Every where you hit the Play-Doh with the stick, it creates a ridge and valley; you haven't removed any material only modified the surface. And that rough texture is actually a good thing when it comes time to prime, it gives un-breakable tooth adhesion when using an Epoxy Primer.

nkh