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.

(Page 16-02) revisited: stall warning tab

The stall-warning tab, which protrudes from the leading edge of the left wing (second pic), is to be adjusted such that the normally open switch which is actuated by the tab closes with minimum upward travel of the tab a few knots prior to stall, thereby actuating the stall horn.  This adjustment is accomplished by trial-and-error, using the continuity function of a volt meter.  The problem is that the wing skin panel with with the slot for the tab has to be temporarily installed for the adjustment to be

made, since the tab rests on the lower edge of the slot when the airplane is not at the critical angle of attack.  At this point, the tab is supposed to be perpendicular to a tangent to the leading-edge curvature.  If this condition doesn't exist, it is allowable to bend the tab (which I didn't do).  I found it difficult to judge this.  I ended up holding a straight edge at what appeared to my eye to be tangent, then eyeballing the perpendicular.  The leading-edge curvature is not a circular arc, which would be much easier to judge, but appears to have a constantly changing radius of curvature.  Compounding the problem is that the slot cut into the leading edge is much bigger that it needs to be if the builder does as instructed and minimizes movement of the tab.

I ended up doing three trial installations of the skin to get what seemed to be the correct angular

position of the switch (correct meaning the tab was perpendicular to the tangent).  I started with the screw in the center of the housing slot, and that was surprisingly close to what I ended with.  I suppose the adjustments could be made through the access hole (shown in the first pic) thereby avoiding all but one trial fit, but I found this difficult.

With the Skyview providing angle-of-attack information with programmable stall warning (and a female voice saying "angle, angle, push" just prior to stall -- I can't wait to hear this!), some builders are electing to not use the tab stall warning system at all.  I plan to use it.

Kerosene heater is back

Yesterday was the first day of the year that I had to fire up a kerosene heater.  During the coldest nights of the year I use as many as three at once in my uninsulated garage, the fumes from which usually give me a headache.  I did buy a carbon monoxide detector last winter, and according to it, the CO levels are OK.  It can't be good for me, however.  I'm probably being saved by all the air leaks.

Spar bend -- OK or not?

When I unpacked the wing kit many moons ago (way too many) I noticed that the inboard end of the right wing spar bent aft a degree or so at the point where the ribs end and the tapered part of the spar, the part which passes through the fuselage, begins.  Examination of the left spar showed a similar but lesser bend in the opposite direction.  I convinced myself that this had to be by design.  The spars have

individual serial numbers and, being one of the most critical components of the entire airplane, were surely subjected to tight quality control.  As I proceeded through construction of the wing kit, preparing and installing all the ribs, I periodically pondered the very noticeable bends and became increasingly troubled by them.  Before skinning the wings, I figured I'd better get a ruling from the Mother Ship.  In retrospect, of course, I should have done this much earlier, probably before attaching ribs.  I carefully quantified the bends with measurements and sent the results along with the above pic to support at Van's.  The quick reply from Ken Scott was "The ends of the spars always go slightly one way or another, and it doesn't matter at all.  
Once they're installed in the airplane and the pins are through the holes, all will be well."  Instant relief from my self-inflicted worry.

Service Bulletin 13-12-12

Apparently, several flying aircraft have experienced electrical failure caused by water entering the avionics bay by seeping between the upper edge of the firewall and the underside of the fuselage skin.  This Service Bulletin was issued to correct this.

After putting the SB off for six months due to my dread of removing the Upper Forward Fuselage Skin (with all its machine screws), I hit a stopping point with the main build (space to work) and could delay no longer. The instructions call for applying Boelube as a release agent to the underside of Upper Forward Fuselage Skin, then applying a 1/16th-inch bead of Permatex 16BR Black Silicone Adhesive Sealant (#81158) to the opposing face of the Upper Forward Fuselage

Doubler (yellow arrow in pic at right).  After reading the opinions of those who had done this procedure already, I stuck with the Permatex but used O-Ring lubricant as a release agent.  I found this stuff on the aviation isle at WalMart near the pool and spa supplies.

It turned out to be impossible (for me, at least)  to make a nice, uniform 1/16th-inch bead as called for, so I instead made a more or less constant-thickness ribbon between the aft edge of the doubler and the nutplate holes.  I then re-installed the fuselage skin and tightened all the machine screws, the idea being to squeeze the silicone into a continuous, uniform water barrier before it sets up, while preserving the ability to remove the fuselage skin without affecting the water barrier.  I tested this with some scrap aluminum, and it seemed to work after curing for about a week.  No way to know what will happen after it has been cinched up for longer periods.  I'll definitely have to remove the skin at least one more time (and probably multiple times) to make the modifications required for the switch to a Garmin radio.

Pilgrimage to Mecca complete for 2014

It's hard to believe I just completed my 26th trip to Oshkosh.  It's still the high point of my year.  After all this time it's still a sensory overload, at once too much and not enough. Over 10,000 airplanes flew in and over 500,000 people attended.  As I've frequently said, Oshkosh is like sex in that the only way to get enough is to get too much.  After a week of showing up at the flight line at 6:00 am each morning and leaving at dusk I'm energized, inspired, and tired to the bone.  I did manage to get my fourth flight in an RV-12, this time in an S-LSA.  Of course it flew just like my three previous flights in

RV-12s registered as E-LSA.  This store-bought version has been adopted by several flight schools as a primary trainer, but I'm not at all sure it's well suited for that role.  It's too easy to fly.  Student pilots who learn to fly in an RV-12 will have no idea what those pedals on the floor are for.  Even rapid roll inputs leave the ball centered with absolutely no rudder input.  I've never seen anything like it.  The roll rate is astonishingly high (45 degree left to 45 degree right) for a non-aerobatic airplane.  I think it will be very difficult to resist the urge to do aileron rolls in this airplane (my history of resisting temptation is not good).

The picture shows a factory S-LSA with a Ford Trimotor and a Mustang (Bud Anderson's Old Crow, no less) in the background.

Summer school and alien abduction

Teaching summer school in mechanical engineering is like having five weeks surgically removed from my life without benefit of anesthetic.  Each day goes like this: prepare three hours of lecture, deliver the lectures, meet with students, grade papers, eat, sleep, repeat.  No time for building airplanes or much of anything else.  The last time I worked on the RV-12 was about five weeks ago and I can barely remember what I was working on.  The sole reason for doing it, of course, is to be able to afford things like building airplanes.  The pay is good but, at this stage of my life, time is my most precious commodity.  The strange thing, however, is that with one week left, it seems that only about a week has elapsed.  This leaves three weeks unaccounted for.
People who claim to have been abducted by aliens often speak of "lost time."  Inexplicably, the clock has of its own accord sprung forward.  That's how I feel.

The good news is that in about a week and a half I will, at least theoretically, have four uninterrupted weeks to work on the project.  Oshkosh will then consume a week (the high point of my year), then I'll have a couple of weeks before Fall semester begins, which is like a vacation compared to summer school.

(page 16-04) Stall warning tab

With the stall warning switch assembly ready for installation, luck would have it that the wing hanging from the rafters (left) is the one which needs the switch installed.  Also, the construction manual calls for the left wing to be skinned first, meaning I have to get the one on the table up to the rafters and the one in the rafters

on the table.  This is going to require carrying the right wing out to the driveway, lowering the left wing to the table, carrying it to the driveway, placing the the right wing back on the table, raising it to the rafters, then, finally, placing the left wing on the table.  Problem is, there's a construction dumpster (house remodel) blocking the way.  Haven't solved this one yet.

Moving the un-skinned wings around makes me nervous since the ribs are quite frail and floppy in their current configuration, most of them attached only at the spar.  As with the rest of the airplane, once the skins are riveted in place, the structure feels quite solid and substantial.  The skins come next and I'm looking forward to that.  I'm hoping to continue my "one in the rafters, one on the table" procedure after

the wings are complete, since I have nowhere to put them.  Most builders fabricate a roll-around cradle for the wings in which they can be stored nose down.  Maybe I'll do this when I rent a hangar and move the project into it.