Covering the next task

I received a "current" price list from betteraircraftfabric.com dated March 2015, with unchanged prices from Feb 2014: $109.95 for a 1.8m width, per meter.  That's just bonkers considering the changes in the world economy in the last year alone.

Direct from oracover.de is 69.96E ($77.30 at 1.11). I did contact them asking if they updated their price list each year, but did not ask about exporting directly, since they already have a US distributor.

From a UK distributor named G-TLAC, the price list from May 2013 from their website lists 60.42 pounds ($77.94 at 1.29), though I am unclear if/how VAT plays into the price.  They emailed back and said they are unable to sell to the US.

All this is to say that the price from BAF is high and I don't get it.

Another couple Oratex blogs:

• http://avidsimonini.blogspot.co.uk/2015/10/returning-to-initial-topic-of-this-blog.html
• http://www.avidfoxflyers.com/index.php?/topic/3147-oratex-covering/&page=3

So after all of this back and forth trying to find a good price for Oratex, it was time to research some other options.  I've read internet posts about using the normal polyester process and then latex house paint.

• http://www.wienerdogaero.com/Latex.php *** good
• http://43012weed.blogspot.ch/p/wing.html *** good
• https://groups.yahoo.com/neo/groups/Airchairgroup/conversations/topics/18281
• https://groups.yahoo.com/neo/groups/Airchairgroup/conversations/messages/17313

The covering option that looks good to me is Stewart Systems.  It is water-borne and has no real smell.  Looks like Ecobond is the same as 3M Fastbond 30NF.

• http://www.avidfoxflyers.com/index.php?/topic/2003-ekobond/
• http://43012weed.blogspot.ch/p/tail-group.html *** good
• 3M Fastbond 30NF testing - http://www.teamkitfox.com/Forums/showthread.php?t=7109
• http://www.homebuiltairplanes.com/forums/finishing-techniques/2239-latex-paint-fabric-covering-4.html

Looks like the Ekofill layer (the filler and UV blocker) is made from coal ash, according to this guy.  It only gets about 300 ft2 of covering per gallon, and so would take around three gallons at $180/gal from spruce, that adds up quickly.


After all this research, I've decided to go with the the 3M 30NF and sprayed latex primer/paint.

I ordered a quart of 3M 30NF from Amazon for experimenting by covering the rudder.  Turns out their quart quantity only comes in neutral color.  No matter as long as I'm careful to get the right coverage.

 I started by cleaning the structure very well with alcohol.  It was mostly dusty from sitting in the garage.  This part was originally built in Feb 2009!  Next I took cloth tape and covered over all the sharp edges, to include the rivets and exposed ends of the tubes.

The uncovered rudder with cloth tape weighs 537g for reference.

I trimmed a piece of polyester fabric a couple inches large and it weighs 45g.

The first step was to brush adhesive on the structure around the perimeter and let it mostly dry.  Then I laid the fabric over the rudder (slitting for the control horn) and hand-pressed it against the semi-tacky adhesive, all the way around.  A small heat iron set to 250 deg F helped set the adhesive around the edges.  I brushed another layer of adhesive around the perimeter, wiping the excess off, and let that mostly dry.  A quick trim of the excess and ironing down the inside finished the first side.  Trimmed first side weighs 588g.

Flipping it over and doing a gentle 250 deg F shrinking pulls the fabric taut enough for doing the second side.

Repeating for the other side using pinking shears to keep the edges clean, and it's ready for patches.

If I'd known it was this easy to cover with polyester, I wouldn't have put in all the effort on acquiring Oratex.  Maybe I'll be singing a different tune while painting, but only time will tell...

I have not forgotten about the load test.  I wanted to get myself spun up for covering as a way to encourage myself to do the math for the load test.

Other than that piece of business, I cut out the rest of the leading edge shells.  Whew that was some CNC time, but tolerable using the variac to help knock down the noise levels!  I also tried to cut the strut fairings on the CNC.  The fairings would be much easier to cut using a hotwire, which I don't currently have.  But I can see the shapes and cut templates for borrowing a hotwire from a friend.