(page 17-06) Wingtip close out

I had dreaded starting on the wingtip close out, because with all those tabs to be bent to all those different angles, I figured there would be lots of trial-and-error fitting.  A wooden tool was required to be built, which greatly facilitated the physical bending of the tabs, but the amount of the bend was

left up to the eyeball.  As can be seen in the picture, the amount each tab needs to be bent is specified to one degree.  At first I took this to be more Oregonian humor, but decided it's the perfect angle that the CAD model spit out, and the builder is to come as close as he or she can to this ideal.  Fortunately, close is good enough.  The tabs can easily be bent with the fingers to fine tune everything during installation.






I sketched the angles in five degree increments on a piece of cardboard cut from a white paper plate  (shown on the second pic) and eye-balled it as best as I could.  Worked great.  The only two tabs to

require a bit of fiddling were the forward-most two (left in the first pic), with one being a bit greater than 90 degrees.  I straightened and re-bent those two a couple of times, finally lining the holes up with the ice pick enough to insert clecos.









Overall, this was nowhere near as bad as I expected.  The cleo insertion was fairly typical, requiring the usual tools (ice pick, 1/8th inch punch

used as a reamer and, on a couple of holes, the hand held #30 drill bit mounted in an old chuck).  Now, the only thing left on the right wing is the strobe light fairings and electrical connectors.  The fiberglass fairing has to be bonded and riveted to the aluminum.  Doesn't look like fun. Then I get to do it all again on the left wing.

Service Bulletin 14-11-03: Wing Skin Doubler

One of the Mothership's higher time RV-12s used as a demonstrator was found to have a few "smoking" rivets on the lower inboard wing skin.  This condition arises when a rivet loosens and allows fretting corrosion (very small scale relative motion between mating surfaces due to vibration) and subsequent oxidation of the resulting aluminum dust which is produced.  The loosening was no

doubt a result of the high stress in the skin at this location.  Putting on my engineer's cap for a moment, I'd say this location has the highest skin stress of the entire airplane.

The fix involved installing a rather robust (0.04 inch thickness rather than 0.03 inches for the wing skin) doubler plate with four different rivet types, eight of which are 5/16th inch rather than the usual 1/8th inch diameter rivets.  I was thinking "Wow, it's great that I received the kit for this service bulletin before I installed the wing skins.  Now I won't have to drill out 20 rivets per side like many builders are having to do because their skins are already on!"  Then I proceeded to install all the rivets in the right wing skin, then had to drill out the aforementioned 20 rivets.  This required the invention of several new, stronger swear words since I have essentially worn out all of the customary ones during previous mistakes in this project.  I won't (I hope) make the same mistake with the left wing.  I'm astonished at the strength and complexity of this fix (four different rivet types!), considering that the fix isn't mandatory.

The plans call for final drilling the holes for the 5/16th rivets with a #22 bit, which I did using a bit from my new #1-through-#60 bit set, obtained from Amazon rather than Spruce or one of the other "name brand" aircraft suppliers.  The rivets would not fit into the holes.  Upon measuring the bit diameter I discovered that the #22 bit was considerably smaller than spec, and that the #21 bit in the set had a smaller diameter than a proper #22.  You get what you pay for!  I had checked the bits with a go/no-go gauge, but that didn't catch it.

At last, a valid reason for making no progress on the RV-12

All of my other lame excuses pale compared with this one.  On September 27th, while riding my bicycle in the rain (first act of stupidity for that day), I fell while crossing a railroad track and broke my femur into three pieces.  The railroad track runs at about a 45 degree angle to the road, simply requiring that I slow down and steer the bike so that I'm crossing the rails at a 90 degree angle.  Cycling 101, right?

Instead, as is my usual habit (second act of stupidity), I attempted to bunny hop over the track and fell as if smacked down by the hand of god (I said smacked, not shmacked -- even if I do spend part of the year in Boulder). This resulted in a new titanium rod in my leg, extending from my knee to my hip.  The titanium structure below the knee is a result of a car wreck in 2005, and extends from ankle to knee.  In all future bike crashes, I'll try to fall on that side since it would be difficult to break it again with all the titanium in there.  I suggested to the Spousal Unit (my beautiful Ironman wife, Karen) that when she has me cremated she should retrieve all the titanium and put it on the mantle over the fireplace.  She didn't see the humor in that.

The good news is that after going from a walker to two crutches to one crutch, I'm now able to stand long enough to actually make progress on the airplane.  I still can't stand for long periods, but it's a start.

I ordered the finishing kit (a deceptive name since when it's finished I'm nowhere near finished with the airplane). The kit arrives in one month, which means the wings have to be finished and on the wing stand before the finishing kit arrives.  The right wing requires only that I finish the wing tip, then I have to repeat the entire skinning process for the left wing (except for the landing light, thankfully -- anyone who installs a landing light in both wings is a glutton for punishment).  Looking ahead, it seems that money will be the limiting factor in the completion of the project.  When I look at what I've built, it seems that I'm way more than half way done.  From a cost standpoint, however, I'm not.  The engine kit and avionics kit are horrendously expensive.