Tuesday, December 07, 2004

Time to make some junk

One of the biggest hurdles to starting a homebuilt airplane project is the mindset that every part you make must be "flight hardware".

That attitude MUST DIE if you are to make any progress at all. So, your task begins with making some JUNK. Say you start your scratch built all-metal airplane by beating out some ribs (which is a very good place to start). Before you waste your good material, get some stuff that you don't really care about, if you can.

Some caveats. Scratches are OK when Making Junk, but big dents and bashes make the sheet harder to work than it needs to be, hard enough that learning will be impeded. And cheap aluminum (like flashing) generally works differently than the real goods. In particular, flashing is dead soft, and take a lot less beating over the form block than say 2024-t3.

Where do you get cheap crap to experiment with? Well, I get some of it by dumpster diving, but then I work at an industrial facility. Flashing is available at Home Improvement big box stores everywhere. It comes in various thickness, from about .010 inch to about .032 inch, and is generally 3003 aluminum, but is sometimes dead soft 1001 pure aluminum. I suggest the 3003, as thick as you can find it. If there is a scrap dealer in your neighborhood, they might have odd lots of sheets, but watch your mill marks carefully, you can end up with some strange alloys and tempers. Ask me how I know....I thought surplus 2019 would be fine, but it turns out it was -T8, fully hard, and a bitch to form. 3003, 6061, 6063, and 5005 sheet is all relatively cheap, and may be available at your local sheet metal, or heating/ventilation/air conditioning shop. And who says you have to use alumium? Mild steel sheet, galvanized or not, is pretty readily available, and forms about like tempered alumium if you drop the thickness a little bit. It's actually a bit more forgiving of error, and doesn't need as much spring-back allowance, but still, it forms, and it's cheap.

Some sources to check out for cheapo aluminum can be found at Aluminum Sources

In making junk, you seek to make as many mistakes as possible. The caveat here is, again, if you're using flashing, it's not as sensitive to things like sharp internal corners as 2024. But bust it up. When you're done, toss it in the recycling bin.

There are a lot of web sites that show/describe forming a rib. Search for Zenith or Sonex sites. I'll probably go into a laborious descrpition in a later post, the purpose of this post is to get you off your ass and out into the shop.



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