(Page 40-01) Cutting holes for the lighting kit

I'm beginning to seriously question my decision to install the lighting kit: way more time than anticipated.  I'd probably skip the landing light if I had it to do over.  All three holes have full-size templates included in the build manual.  First step was to photocopy these and double check that the copies overlaid exactly on the originals.  I have in the past encountered copies which were slightly bigger than the originals.

I also think that paper expands or shrinks a bit with changes in atmospheric moisture, not good when the rivet holes shown on the templates have to match up with pre-punched holes in the hardware (landing light).  The holes for the wing-tip strobes are not critical since they will be covered by the fiberglass fairings which the strobes actually attach to.  In fact, the large hole specified could be replaced with a 3/4-inch hole easily done with a step drill.  A large hole is specified because the write up for the entire lighting kit assumes that the kit is being installed on a completed airplane and there's a need to reach in to the wing tip enclosure.  This job is made considerably easier when done during the build process.  In fact, it's hard to imagine doing the landing light installation after the fact.  The strobes wouldn't be a problem.

I cut out the cross-hatched areas in the template with an Exacto knife, taped the template to the aluminum, marked the hole with a Sharpie, then cut out the metal with an abrasive disk in a Dremel tool.  The last cutting pass was with an abrasive drum in the Dremel, followed by a 2-inch Scotch Brite wheel in a die grinder.  If I were doing it over, I'd put the Scotch Brite wheel in a drill since the die grinder has the potential do damage owing to the high speed.  Although the build manual doesn't say this, the template obviously must be flipped over when going from left wing to right wing.

I followed the same procedure with the landing light cut out.  This required temporarily clecoing the appropriate wing skin to the ribs, then making the cut.  I once again used the Scotch Brite wheel in a cordless drill for final smoothing, and was quite pleased with the results.  The problems arose after I drilled the rivet holes, which have to match up with stiffeners which have the holes pre-punched to accept nut plates (to be detailed in a following post).

The cut was tedious, the good thing being that there's only one of them.

The Scotch Brite wheel can be seen in the cordless drill.  I should have ordered one of these small wheels much earlier in the build.  From the start of the build I have made extensive use of a six-inch Scotch Brite wheel in a drill press for deburring, but access is limited for large parts.
                                                                                                                                  

Pilgrimage to Mecca complete for 2015

My 27th trip to Oshkosh ended with me in my usual happy/sad state.  Can't believe it's over for a year, but my daily routine of getting up at 4:00 am in order to be at the show when the gates open at 6:00 has worn me down.  I'm toast physically, but mentally I'm fired up to work on the -12.  Great photo gallery here: https://www.flickr.com/photos/eaaairventureoshkosh/    From that link, a P-51, P-38 and F-35 fly in formation.

The highlights of the week were getting my 5th flight in an RV-12 and attending every forum Burt Rutan gave.  Burt officially presented his latest (and last, he says) design, the SkiGull.  He had planned to fly it to the show, but didn't quite make it.  Can't wait to see it next year.  The plane will, according to Burt, land on snow, dirt, pavement and water, with water being its preferred habitat.  It uses a pneumatically actuated pair of skis which pop down during the take-off run, lifting the hull clear of the water.  The skis are extended for water landing to absorb shock.  Apparently, it will handle ocean landings, allowing the owner to land, then taxi up onto a beach.

On the builder front, the big news is that the Mothership has given their blessing to using a split bulkhead behind the baggage compartment.  Van did this on his personal RV-12 and most people building E-AB did it, but until now those of us building SLSA couldn't.  Without this, the builder must remove the fuel tank for each yearly condition inspection.

The RV-12 shown is one of the most beautiful I've seen.  The builder has a Cobra painted the same color.

SB 14-12-06 completed

Complying with this SB involved drilling out ten pulled rivets, six of which are through relatively thick aluminum plate.  The accepted method of removing this size pulled rivets (LP 4-3) is to drive out the center mandrel with a 1/16th punch, then drill out the rest with a 1/8th bit.  Problem is, in order to drill out the rivet without enlarging the original hole requires that the drill be exactly perpendicular to the plate containing the hole.  Even with my trusty Tight Fit Drill Kit I couldn't make this work.  Not enough distance from the rivet centerline to nearby structure.

I've always used a different procedure, when possible, for removing pulled rivets, one which eliminates the possibility of enlarging the original hole.  I carefully drill off the manufactured head with a 1/8th or #30 bit, then either pull the rest out by grasping the shop head with needle-nose pliers or drive it out with a 1/8th punch.  In this case, the metal was too thick for this method to work without modification.  I drilled off the manufactured heads, drove out the mandrels (lacking a 1/16th punch I used the shank of a 1/16 bit, worked great), then drilled out the remainder of the rivets with the right-angle attachment (shown next to the drill in the pic).  For the two which were too close to adjacent structure, I used an old drill chuck (shown between the right-angle attachment the drill) and turned it by hand.  The chuck was still a bit too fat for perfect alignment, so I used a smaller bit and went through at a slight angle.  This loosened the rivet enough to be pulled out with pliers.

Free advice for other people building airplanes.  Don't lose momentum in the build by going for long periods with no work.  Getting back up to speed is a huge waste of time.  Example:  yesterday I had to reacquaint myself with the tool and procedure for properly crimping Molex connectors.  Had to go to EweTube (they're a bunch of sheep politically) and watch a couple of instructional videos, then destroyed the first connector I tried.  I'm taking a solemn vow to never again take a break from the project.

The completed part for the SB is shown at left.

Off topic - or how I've learned to love the carburetted 912.

Partial explanation for why I've made no progress lately.  Read this only if you're interested in antique cars.

Said car has consumed a substantial chunk of my time (and an even larger chunk of my money) for the last year.  With the engine installed the car can actually propel itself down the road, though much work remains to be done with the engine management software.  Full throttle operation is awesome

(borderline scary), but anything else leaves a lot to be desired.  It's making 544 hp and 500 ft-lbf on the engine dyno, numbers that this chassis was never meant to handle.  Next step is to put it on a chassis dyno and try to  improve the drivability with the help of noted engine gurus Luke Woroniecki and Wes Kiser.

It says Chevrolet on the valve covers, but nothing in the engine, including the block, was made by Chevrolet.  100% aftermarket.  I used a vertical throttle body (costing horsepower) to give it an old-school, carbureted look (the barrels even open progressively, like the carbs of my youth).  If I'd had any brains I would have actually used a carburetor, where the spark map is controlled simply by flyweights on a spinning shaft and manifold vacuum.  If ever there was a mature technology, it's the four-barrel carburetor.  In fact, this experience has caused me to completely re-think the carburetor vs. fuel injection question for the Rotax 912.  I was initially unhappy that the 912is was not being made available for the RV-12.  In fact, I think that earlier in this blog I opined that I had assumed that the four carbs on my Honda motorcycle were the last carbs I'd ever have to balance.  Now I say bring'em on.

Work resumes tomorrow on the RV-12.  First up is SB 14-12-06.  I'm completely out of excuses.  The spousal unit (my beautiful and super-fit wife, Karen) is spending the summer in Boulder, CO training for the Boulder Iron Man (2.4 mile swim, 110 miles on the bike, 26.2 mile run, all at altitude in mountainous terrain).  My plan is to finish this airplane by the end of next summer (Voice from the Future: Boy, was I naive, bordering on stupid, to think I could finish that soon).  Oshkosh is in two weeks and will consume a week of my time, but I will more than make up for the time loss with the inspiration and enthusiasm I'll bring home from the show.