Purpose

This is a blog containing the build history of an experimental home built airplane. The RV-7A is a two place, piston powered, low wing, tractor configuration, tricycle gear, aluminum and composite aircraft. The original purpose of this blog was to document the construction of my experimental category aircraft in order to satisfy the build log requirement for the FAA. Now it's just for the amusement of friends and family as I document some of our aviation experiences. For more information on the RV series of aircraft see www.vansaircraft.com.

Tuesday, June 16, 2015

Step 13.0, Time out for a disaster

Gravity sucks.  Yes, it is the weakest of the four fundamental forces, but it still manages to wreak havoc on a macro scale.  While preparing to spray the epoxy primer on the right elevator I somehow caused it to fall off of the hook and slam on to the concrete floor.  Can we say with the telephoto lens of hindsight that its position on the hook was precarious and replete with gravitational potential? Yes, if we must. And since I was holding the other end of the elevator at the time, a far too honest assessment might conclude that I had something to do with the accident. However, we should not fail to toss a wary eye at gravity itself, lest it escape blame entirely.


















Did that just happen?  I just stood there in stunned disbelief while my brain worked feverishly to assemble the appropriate profane response.  Fortunately, I had the forethought to stockpile a great reserve of emergency profanity for just such an occasion.  Logistically though, it's not such an easy thing to do. That is, to launch in an instant, the mother of all swear storms that common sense demands.  In a second or two my paralysis fades and I spring into verbal action.  At least that is what I thought would happen.  But I find that I am unable to form intelligible words as I attempt to unload my entire arsenal at the same time.  That ever so small portion of the profane artistry which finally makes it past my vocal cords intact is just one tiny, weeny, almost imperceptible, "shit." All the while, in in my mind, I keep seeing the Hindenburg going up.  Over and over.  Oh, the humanity!  

Now the moment has past and I move on to survey the damage. It seems that the aluminum carnage stops at the first rib tip and there is no sign of bending anywhere except at the inside corner as shown. My first thought is that I will have to build a new elevator or at least re-skin it.  I really did not like the thought of re-skinning because removing rivets often causes as much damage as the original problem.  Since the elevator is small, it might be better to just make a new one.

Then I think, not yet accepting the stark reality of the situation, that perhaps I could just unbend the corner using a screw driver and some pliers.  Well, I had nothing to lose so I gave it a go:




















As expected it cracked in several places as the folded metal was pulled out.  It was pretty clear that this was not going to work, so I moved on to plan C.

My next idea was to cut off the corner and replace it with fiberglass.  The photo above shows the cutting process already begun.





Here is the elevator with the corner cut off and the edges smoothed.


The next step is to build a foam core for the corner and epoxy it in place.





Then build up the corner with fiberglass.


And sand it down smoothly feathered into the aluminum.


So I end up with a fiber glass tip and a few hours wasted, but the fix is very strong and virtually invisible.  At least from the top or bottom.  From the end the plug is visible, but I don't think it's obvious what kind of horrors went on there.  It's kind of like some scar you carry from childhood that you laugh about now, but was just short of amusing at the time.


So next time I'll continue with more painting and, hopefully, fewer mishaps.

Friday, June 5, 2015

Step 12.9, Painting begins

And the winner is...


After an extended period of agonizing indecision I've finally made my selection regarding the paint scheme.  My next step is to try and calculate the amount of paint I will need.  The paint store says I will need about 1 gallon per 350 square feet.  Having painted a few cars in the past, I know that I will probably be unable to achieve the very light coats and good coverage that a professional would do. I've had pretty good results with the lay it on heavy and then sand off every thing that doesn't look like a car method.  I'll try that with the airplane.

But how should I estimate paint required?  Hmm... How big is my airplane, I think.  I decide to break the problem down into very small pieces a, la, Leibniz and Newton.  Summing the infinitesimals I arrive at the value 470 square feet.  


There are many possible ways to calculate this, and consequently, many possible sources of error. My confidence in this number is fairly low.  Never-the-less, I trundle off to the paint store and return with this:


There's 1.5 gallons each of primer and base coat, plus two gallons of clear coat.  I have 1/2 gallon of the blue base coat and a quart of the gray.  I figure I will just get started and see how far the paint goes.

I'll start with the small pieces and work up to the Fuselage.  First scuff with a Scotch pad.  Here is an aileron:


The first coat is epoxy based primer

Here are the flaps and ailerons getting there base and clear coats.  The white is a three part process: Two coats of white base coat, then two mid coats with pearl, and finally two coats of clear over the top.

And the mad painter himself:


Finally, here is the horizontal/vertical stabilizer fairing. All purdy and everything.


The small pieces came out just fine.  I'm now confident that I understand the processes well enough and am ready to move on to the larger and more complicated parts like wings and fuselage.