Chapter 25
Filling and Finishing
Do yourself a MAJOR favor and go to this website for finishing information:
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.
1st: Squeegeed coat of pure epoxy.
2nd: Off-white High build primer
3rd: Same
4th: Maybe same, maybe reg grey primer... depending on how much of the highbuild 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.
1/23/2008
It's been quite some time since I have made an addition to this chapter. I decided to use the Zola tone 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 coverwed 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 poducts.
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!
Hint: When you spray the High-build, leave time in your schedule to sand the very next day. This stuff gets VERY hard to sand as time goes on. So, if you want to save yourself 6 months or so of shoulder pain. HEED MY WORDS!!
