Chapter 25
Filling and Finishing
 

I'm going a bit out of Plans Sequence (AGAIN). I'm going to fill and finish the wings thru primer/mechanicals, then hang them in  the garage. This will give me much more maneuvering room when I mount the Main Spar. I know there will be finish issue between the spar and the wing, but those will be realtively easy to fix as compared to all the moving I'd have to do working on the wings having the fuselage w/strakes to work around. All of a sudden, 20'x22' doesn't seem all that large.

9/16/04

Do yourself a MAJOR favor and go to this website for finishing information:

http://curedcomposites.netfirms.com/finish.html

Today, I'll tell the story of my first real good mess up in finishing.

I decided to use Alphapoxy as my primary material for filling.  Jeff Russell, of AeroCad, told me Alphapoxy passes the "thumbnail hardness test" while still retaining easy sandability. An added benefit is Alphapoxy can be shipped without being classed as hazardous material.  So, you save a few bucks there as well. Anyways, after a couple of small batches, I decided to tackle the left winglet and rudder.  I used an 8" and 12" drywall trowels to spread the micro.  I found that if you heat trowel with a heat gun you could make a final pass on the micro you've applied and make it look pretty smooth.  I did the inboard side first then the outboard and then one side of the rudder.  The next morning I sanded it all down, and I must admit I was pretty pleased with myself.  The next day though, I noticed the micro wasn't hardening up as fast as I thought it should.  (This is where the little guys started running around my head at various times during the day screaming Fire! Fire!)  The next day, I was brushing my teeth, getting ready for work, and suddenly realized that I was mixing the epoxy 1:1 as opposed to 2:1 resin/hardener ratio.  I didn't even notice the white spots of toothpaste that had been spewed onto my mirror by me verbalizing in a quite loud and profane manner how stupid I was. Well, to make a long story short, I ended up scraping off all of my beautiful micro work with a 1-1/2 scraper and the heat gun.

Good thing, I didn't do it to the entire wing!

Well, I tried my hand at filling and finishing the bottom of the left wing. 

I know, I know... I'm supposed to only do new things on Debbi's wing.  But, it was just too much of a hassle to move her wing from the wall and put my wing on the wall, so I could put Debbi's wing on the worktable. So call me lazy!!
I used Alphapoxy in a 4.5: 1 by volume micro to epoxy mix.  For this big of a job, I mixed 3 quarts of mixed epoxy to 14 quarts of micro.  You really have to work fast with this stuff.  Ambient temperature was about 87 to 88°, and as I was finishing, the stuff was just beginning to heat up.  I had about a quart of micro left over.  Better to have too much than too little.  I applied it using a 12 inch drywall trowel with moderate to pretty heavy force.  I truly believe you should use an 8" blade instead. I found more than a few voids after final sanding, which required me to do a " poke test" which found quite a number of voids, which I'm sure, would come back to haunt at me at later date.  I found I can leave a nice smooth finish if I use my heat gun to make one last pass after I've gotten the whole wing covered with at least a ¼"of micro.  WARNING!  Do not try this without heating up the drywall trowel.  You'll only drag up the ¼" of micro you just laid down.  It took me all about 2 hours to cover the entire bottom of the wing.  Approximately 12 hours later, I went out and sanded for about four hours, until I was happy with the feel and look.  I then filled the various little divots with a 50-50 mixture of micro and Cabosil.  Tomorrow, I'll go out and touch up sand the Cabosil spots and apply a pure epoxy skimcoat.  Then, if things look cool, I'll flip the wing over and do the top.  I must admit, my shoulder is pretty sore.  But hopefully, with the techniques I learned from a really cool web site: (http://curedcomposites.netfirms.com/finish.html), I'll get through this stage, of what most Cozy builders generally find to be the most labor-intensive, in pretty good time.

Below, I've included a few pictures of the voids I was able to detect.  If they were large, I filled them with micro.  If they were smaller, say, the size of the tip of my little finger, I filled them with the 50-50 mixture of micro to cabosil.  My plan is to fill/finish the bottom of this wing, then fill/finish the bottom of the other wing.  This should give me enough practice, so that when I trie the top of each wing, the final product will not be too embarrassing. ( Heh, heh.)  So far, I'm pretty happy with my performance.  Now, all I have to do, is wait for the paint to flake off 1 to 2 years after I'm flying.

I later decided to make smaller batches of micro so I wouldn't have to work so fast and make so many mistakes. It works out to 3-4 cups epoxy to 12-16 cups micro.

Above is the dehumidifying setup to stop those embarrassing water blobs from ruining an otherwise mediocre paint job in the Florida humidity.

My plan is to use a 4-5 coat primer system.

1st: Squeegeed coat of pure epoxy.

2nd: Off-white High build primer

3rd: Same

4th: Maybe same, maybe regular grey primer... depending on how much of the high-build I have to sand off to get a decent look.

To the right, you can see I've flipped the wing over and am working on filling the top.  I've learned the few things since I wrote the above paragraphs.  Number one: using 8 inch drywall knife.  A 12 inch drywall knife requires too much pressure to keep bubbles from forming when you're laying down the micro.

I'm finding I'm getting much better at this as I go along.

Above, you can see my continuing efforts to make this thing more aerodynamically agreeable.  The fuel sump was filled and faired according to plans.  I would recommend getting the fuel sump fairings from Aerocad.  You'll probably have a much more professional looking outcome than I did.  All in all though, this went off pretty much as easily as the wings did.

At left, is a shot of "Web Slinger" ready to be flipped over right side up again.  I learned a good lesson on the initial flip.  Do not make the half-moon pieces of plywood so large.  The first time, I had to have two guys help me.  After adjusting the size of the half-moon pieces, (see below) Debbi and I were able to flip the plane by ourselves with relative ease. (Clear as ketchup, right?) .

1/23/2008

It's been quite some time since I have made an addition to this chapter. I decided to use the Zolatone color Admiral Blue. It comes closest to a Spiderman color that I could find.

I used the Harbor Freight $50 pressurized 2QT HVLP spray gun. 
The hard part was figuring out the pressures that work best with the Zolatone.
I know, I know. There are a couple of what may look like thin spots, which I will repair, if necessary, at a later date. I purposely left some areas in bare primer, which will later be covered with seatbottoms/cushions/what-not.

Not too shabby.

At left, is a picture of Webslinger with his first coat of High-build Primer. I'm using US Paint's Awl-Grip products.

D9002 Yellow High Build Primer 
D3002 High Build Converter
D1001 Gray Finish Primer
D3001 Finish Primer Converter
T2006 Reducer

I've used about  3 gallons of the high build stuff and maybe 2 gallons of the finish primer on the plane. (NOT counting the converters... so double actual quantities.)

They worked pretty well on the wings and the fuselage bottom, so I couldn't see a reason to change systems mid-stream. It really is amazing how many errors/blebs in finishing I've missed! That's the good reason for using the method here.

1. Get the surface as best you can with micro. Use your hand for leveling, rather than your eye.
2. Skim-coat the glass with pure epoxy to fill any pin holes you missed.
3. Do a cursory sanding to rough up the surfaces for the primer.
4. Put a nice thick coat of the high-build stuff using HVLP. Thin it at least 25% with the reducer. It's pretty thick stuff, and thinnig it will reduce the amount of sanding needed to get rid of the orange-peel.
5. Sand it down to the point where you see the high points in the surface.
6. Chase the pinholes you'll find when painting if you thought you didn't need to skim-coat the surface with pure epoxy.... and also fix the various dents/dips you couldn't see before painting with micro.
7. Spray again with the High-build primer.
8. Sand again.
9. Spray the finish primer. Voila!

11/29/2008

Well, I finally get the plane in finish primer.
I learned how to paint upside down during this period. It sure is a shame to be learning all these things just to build one airplane.

My plan from here is to remount the engine with new engine bushings, look up fuel, electric, and oil lines, and start the engine. Once I get the engine and propeller working properly, "Webslinger" will be ready to go to the airport for finish paint and high-speed taxi tests.

We'll see how it goes.......

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