§21-06 Fuel Tank Inspection & Wash

Well, I got all prepped and studied up for doing section 20.  I got the tanks out of their containers & unwrapped them and was pleasantly surprised that section 20 was completed by the factory.  One more down w/o any effort!

Section 21 is all about prepping the tanks and sealing them up.  I inspected the insides with a video scope and found them to be spotless.  There were no 'hanging chads' of sealant, any debris to be found, and all of the specified internal passages were open. 

The book says to fill each tank with 3 or so gal of 100LL and throughly rinse the insides, including turning the tanks upside down.  I looked at the 4 big open inspection plates and decided that it would be a good idea to put the plates on, otherwise we (Lada & I) were going to just pour all that avgas all over the garage.  There are two fuel pickups (6D) and two vent lines (4D), but the kit only included 1 each of the end caps, so fuel did make a bit of a mess.  Lada took the brunt of  the spill but didn't complain because she has a curious appreciation for the smell of oil & gas and stuff.

I did try to stem the mess by hand threading the fuel vent lines into their ports.  The L tank was straightforward, but the right side wouldn't thread.  I gently applied some torque w/ a wrench and promptly sheared the first couple of threads inside the coupling in the bottom of the tank.   I did some research and verified that it's a 1/8" NPT which is readily available at Harbor Freight.  I'll pick up a tap in a couple of days and will very gently chase the threads and try again.

Left Flap completed, §36-24 thru -26

Well, yesterday I said that I had estimated it would take 3 hr to complete the Left Flap.  I must be getting better at this (or at least lucky) since it took 2:50 to finish the job.   Lada helped during the pro seal application and fitting the trailing edge.  It's much easier with 4 hands instead of just 2.  I propped the skin up with some rags under the skin and against some ribs.  I only used about 1/2 of the jar of proseal and made essentially no mess.  Then both of us flexed the trailing edge around the back and it was done.  I spent the rest of the afternoon pulling the rivets, putting the ailerons & flaps into moving blankets and then cleaning the garage.  All in all, a very satisfying afternoon.

 completed Left Flap

both ailerons & both flaps

All wrapped up!

about 1500 pop-rivet mandrels

Right Flap completed §36-25, 26

I got off to a late start today because I worked a night shift last night and then had a 4 hour morning course to renew that pesky ATLS certificate.   I slept until 5:00pm before heading out to the shop.

I left off yesterday with the right flap fully skinned but not yet riveted, so all I had to do this afternoon was  pull rivets and finish the FL-15500-002 Right Flap.

FL-15500-002

Close up of the vortex generators on the upper surface

Once that was done, I got to work on the left side.  The lower/training skin was peeled & deburred.   I hadn't deburred the vortex generators on the leading/lower skin so that got done, too.   I've fully clecoed the leading edges of the skins, but will stop here.  Tomorrow, I will rivet the leading edge & generators together.  That will provide excellent alignment for the one-and-done fitting of the trailing edge once the B2 sealer is placed on the rear lip.   It should take about 3 hours (so I'll budget 6) to finish before I go back to work tomorrow night.

§36-05 through -20 (Left), §36-21 thru -23 (both)

 It's been a very productive couple of days.   I built up the substructure of the Left flap, installed it into the forward/lower skin and verified that the upper/rear skin fit on both flaps.  I fully riveted the forward/lower skins on both of them.  

close up of typical cleco and rivets prior to pulling

overview of same state of construction

Dale came over and helped me bend the upper/rear skins.  The general portion of the KAI recommends using two boards that are hinged together to make a tool to bend the sheet metal into the final shape.   It didn't work worth a damn.  Bending the trailing edge all of the way to touch the other side did nothing; it simply sprang back to its original shape.   Following the advice of a VAF post, I ended up putting the flap skin on the floor, laying the board over it and literally walking on it back and forth and even springing up & down for good measure.   This produced about 75 % of the desired decrease in radius of curvature.   It was enough that it was not difficult to cleco together,  In fact, it was much easier than the leading edges of the ailerons, so I suspect that I'm in the correct ballpark.  I will enlist the opinions of other RV builders regarding the final shape of the trailing edges.

Last night I tackled the dreaded fuel sealant step and actually didn't make too much of a mess.  I had already riveted the forward/lower skin.  I scuffed the area that would get the fuel sealant.  I slide the upper/rear skin under the forward skin and fully clecoed it in place.  The natural spring in the sheet metal kept the rear edge away from the lip that got the sealant.   I smeared the sealant in place in about 12 minutes (out of a 30 min working time) and had a pretty easy time of clecoing the upper skin down onto the sealant.  I flipped it over, and clecoed/riveted the underside.  I was about half way through finishing all of the riveting (boring, but very satisfying) before having to close shop and go to work.

I'm expecting that I'll finish up both of them with another solid day in the shop.

RV-12 myth busted

 A few months ago I read a comment that you could tell your non-flying partner that in the event of pilot incapacitation, they could close the throttle and trim the plane full-up in order to achieve a controllable, low speed (and hopefully survivable) forced landing.

I had my doubts since the RV-12 has a very powerful stabilator and I can't recall ever getting close to full-up or full-down.  I took her up and tried it out.  Yep, it's not a good idea to put in full up trim. Even without power (prop wash over the stabilator), the plane was nearly in a trim stall with only 75 % trim.  I didn't push it any further and went home to continue building.

§ 34-14. Ailerons complete

Right now, it's about 3:00 on Saturday the 20th.  I'm pretty busy working on the plane and haven't bothered to update this for a while, so there's going to be a series of posts that cover the last few days. 

I finally finished the ailerons!   The replacement AN509-8R16s arrived.  I still can't remember what the new MS designation is, but the last two digits in that code do not match the AN suffixes.  In other words, I had several collections of the wrong size sitting around before the correct ones arrived.  I primed the lead because I have no idea how well the priming covered the inside of the steel tubes.  I realized that there was actually a fair amount of binding on the steel tube rather than the lead.  I used a #19 drill bit and re-drilled the factory holes and used a lot of 'English' (precessing the drill bit while drilling through the hole) and viola! -- the AN509's slipped in easily.  The left side went together w/o problem.  The right side was noticeably loose since I had chased the lock nuts so I used blue lactite to securely hold them in place.

The photo shows the completed ailerons.  In the foreground is the Right one and its uninstalled lead weights.  In the background is the completed Left one.  Note the fact that it is clearly nose heavy and has tilted forward since the center of mass is now in front of the center of rotation.

§36-05 thru -20 (R)

It's been a busy two days.  First, let's get the bad news out of the way.  (It has nothing to do with the plane, so, relax.) In order to be legally allowed to do my job I have to hold a set of "merit badges" such as BLS (CPR), ACLS, PALS, NRP and ATLS.  That last one, Advanced Trauma Life Support, is good for 4 years.  My current certificate expired on the 11th and I was informed that day that I was not allowed to work until I get it renewed.  I had received a warning, that I would be "locked out" of the schedule but I took that to mean that I could not be scheduled for any additional shifts.   I was never told that I had to stop working.   This has thrown a major monkey wrench into the ER's of two of my hospitals.  They are scrambling to find people to cover  4 shifts of 24 hrs each.  I've done what I can and will trade one shift to work at a hospital where I'm allowed a grace period to renew my ATLS.  Interestingly, I'm being told that the mandate is system wide, yet I'm allowed to work at Grady.  Go fig.   I renew on Saturday the 20th.

The good news is that I suddenly have an entire week off and I'm going to make good use of it!

As the title says, I got 16 pages done on the Right wing.  We're making progress.   Marking a page off in the book doesn't convey the prep work that goes into just assembling parts.   Most of yesterday morning & afternoon was spent clecoing all of the flap ribs onto the spars.  It went great, with only a few expected moments of head scratching ensuring that I was on track for L vs R.  Again, I would greatly appreciate Van's making explicit direction marks on their instructions and maybe a few comments to help orientation.  For example, on the flap spars a comment such as "The inboard side of the spar has two lightening holes between the 1st and 2nd rib.  The top webbing faces forward."     Anyway, after a false start or two I got both sets of ribs fully assembled. 

Ribs attached to the wrong spars

I looked at it and get ready to rivet.  Then I paused.  Then I pulled out the skins and laid them on the table and inserted the L rib subassembly into the L leading edge skin.  Everything slid together perfectly.  Happiness.  Just because I'm anal-retentive, I decided to cleco everything together so it would have some structural rigidity.  The ribs fit right in.  

Then I realized that the the holes in spar did not align with those of the skin.  I spent about an hour trying to figure out what had happened.  I never figured out how I spun myself into that circle of mistaken L vs R parts, but eventually I got both spars into both skins and then reattached everything.   The left flap (assembled w/ clecos) went onto the shelf and I went to work on the right.

Left flap assembly, correctly oriented

Last night I finished up deburring and fluting all of the ribs and hardware attach points.  Today, I tackled bucking the larger rivets that are what hold this plane together.  All in all, I think I did a pretty good job, but I'm nowhere near being consistent.  Oddly, I think that I may be holding the bucking bar too tightly.   The physics isn't completely clear to me but it might be that if I hold too tight then a lot of the impulse goes into moving my fingers against muscle force and that dissipates energy into my hand.  Maybe by letting the bar absorb all of the impulse, more energy is reflected back into the rivet to cause it to set.   I'll think about it later.

Typical driven rivets.  Factory head (on top) has a "smiley" 

which is only a cosmetic defect.

The 3 shop heads are acceptable. 

At least 80-90 % of them look pretty close to the text book pictures.  A few are ugly but serviceable.  One is clearly a basket case, but drilling it out will cause more damage to the flange and actually weaken the final joint so it stay.  In case you're curious, it stays hidden because this all internal stuff that will never be seen again after I close it up.

I'm taking a lunch break and plan to write more later tonight.