Contouring, FIlling, Priming, and Finishing

So, the sad story of fiberglass airplanes...

You have to finish them!

Sanding, filling, sanding, sanding, swearing, sanding, sanding...

You get the idea.

I am using the technique which Dennis Ohlman published to the Cozy maillist. 

Contouring:  Wet out surface with pure West system.  Put 1/3 gallon kit of West into 5 gallon bucket.  Mix with drywall paddle.  Add 1 gal bag of micro.  Mix with drywall paddle.  Adjust epoxy or micro to get the consistancy of frosting.  To dry and it is hard to get it to spread decently.  To thin, and it is really hard to sand.  Better to be too dry, but after awhile you learn just how you want it.

Throw the mix onto the surface to be contoured.  Spread with a notched trowel (metal carpet glue trowel).  Spread across the surface to create even distribution.  Follow with heat gun/ hair dryer and flat trowel.  I like to use a 14" drywall trowel, but sometimes  6 inch or 4 inch squeegee works better.  Don't mess with it too much, once it starts to kick over troweling it just cause it to peel up and makes a mess.  After it has set, you can add micro to any missed spots or low areas.

After cure, time to make a lot of dust!  I used a belt sander to knock off the ridges and really high areas.  Once you take off the glaze, the bulk of the material sands really easy.  So don't expect to use the belt sander much.  It is too easy to dig a hole that will need more fill.  Next up, I used a 6 foot aluminum straight edge with sheets of 36grit fileboard on it.  Leave a section on each end without paper to hang onto.  One person each end, bow the tool across the surface, and make dust.  Saw back and forth and work from one edge to the other.  Then cross at a different angle.  This worked very well to knock down high spots and identify low areas.  Once it is to rough shape, then I used assorted blocks to make sure areas were straight and flat.

Next step, Sloppy Slurry.  This is a shell coat to seal the micro, fill imperfections, and give you a nice hard shell so your filler/primer doesn't soak in forever.  This is squeegeed off as much as possible.  Sand with 80 and 180 to bring the surfaces more into line.  When it looks really good, and you just can't stand it any longer, it is time to fill it.

A lot fo people would call this priming, but since you sand most of it off and continue filling, I think it is more correct to call it filling.  Also, the product that I am using is called surfacing/filler and it does not seem to be ashard as what you would call a primer.  Anyway, I am using a RM material that is supposed to be the cat's meow.  It fills and floats really nice.  If I was using a PPG product, this would be the K38 high build primer.  This stuff is heavy!  Lots of clay in the filler.  If you think you can save time sanding early on and just let the filler take care of it, you are going to pay for it with weight.  I spray this on with an HVLP gun that I bought.  Per plans, I mixed 25% micro in as well.  Really makes for a fluffy fill, and gives you some serious depth if you have low spots.  Easy to identify the low areas when you block sand it.  But I get ahead of myself.

You have sanded your plane until you think it is perfect.  So time to spray the filler.  As you spray it, you begin to see in the wet surface every scratch from the sandpaper, dips, hollows, high spots.  It looks like someone finished your plane with a HOE!  You start crying, but keep spraying the material.  It will get better.  Really!

As the material sets up, it floats out and fills!  The next day when you look at the plane, it looks pretty darn good!  The scratch marks are gone!  The surface is rough, but time to get the sanding block after it!  This stuff sands easy compared to micro!  You find a few low areas (still rough and darker after sanding), and a few high spots.  But allin all, it looks darn good once you get it all block sanded (180 grit).  A bit of micro fill if you have some big low spots, or some Evercoat for some pits and little stuff.  A lot of people get upset about the Evercoat because it is a polyester based material, but think about it- this is what all the body shops use.  If my paint bubbles, I'll come back and erase this paragraph...

Anyway, that's where I'm at for now.  Next step will be to hit it with a coat of K26 primer, then finish paint.

UPDATE:  If you have any Evercoat in the garage, throw it away!  I have some bubbles that will need to be sanded out and repainted!  Basically, I am going to fly the plane with the paint that is on it now, and in a couple years, I will refinish it.  I have no more sanding ability, and no help available. A lot of the really nice looking planes have been refinished.  The other piece of the puzzle is that if you need to reset the canard incidence, or if the wings need to be adjusted, then you have to resand and refill anyway.  So I am going to fly this plane.  The quality of the finish is not bad, but it is not a show winner either.  I'd rather fly it!