Stabilator Tips

Santa Claus was kind enough to deliver some genuine Texas-made stabilator tips under our Christmas tree, so I just had to install them with the abundance of free time during the holidays.

First step was to temporarily fit the mounting bracket to the stabilator end rib and mark the bend line on each of the bracket's 10 tabs.  The objective was to have the tab lay 1/8 inch below the surface to allow for the thickness of a J-nut and the tip itself.  After the tabs were marked and bent, the unit was prepped and primed as shown below.

Next, the tips had to be marked for alignment with the pre-drilled holes in the mounting bracket tabs.  Careful measurement was required and a 1/16 inch hole was drilled at each of the tab locations into the tip.  The blue masking tape allowed for better visibility of the marks.

The end rib of the left stabilator is shown below, with the 5 holes to be used for fastening of the bracket.

I added another 8 rivets in strategic locations in an attempt to minimize any potential flexing of the bracket with the end rib.

Finally, the holes in the tip were drilled out to 1/8 inch and were fastened to the tabs of the mounting bracket with number 6 screws.  I managed to get a perfect match between the tip's edge and the end rib of the stabilator...on the underside!!!!  The top side, unfortunately, is not a great match and features a 1/16 to almost 1/8 inch gap along the length - just enough to be noticeable.  Sometimes the seemingly easiest tasks are those that turn out to be the most frustrating.  At least I get another shot at the right tip.  I'll try to get that one perfect.

Apparently I did not apply enough upward pressure on the tip (my wife's analysis) as I was measuring/marking the hole locations on the tip.  She's probably right.

Wing Tanks! (Fuselage Components)

Yes, it's true - there will be no box fuselage fuel tank in my RV-12.  I believe Viking has a viable and preferable alternative.  It consists of a small standpipe in the corner of the baggage compartment which interconnects to 4 tube tanks, resting in the lightening holes on either side of the main spar of each wing.

The process begins with removal of the box tank and then cutting a hole in the baggage compartment floor, designated by the bracket shown in the second picture below.

Aforementioned bracket cleco'd into place from 3 drilled out rivets in the baggage floor.  The standpipe is temporarily jigged into place on the longeron, where it will call home for the foreseeable future.  The bung at the top of the standpipe will be for a vent.

The standpipe as it projects below the baggage floor.

The third bung on the right is for the engine fuel feed line.  A large finger strainer is screwed and sealed into place.  Later, the supply line itself will be screwed and sealed into the female threads of the finger strainer as it runs to the fuselage center line where it will intercept the existing supply line.
The bung of the end cap of the standpipe will be for a drain sump valve.

Here is a potential mockup of the right wing's supply line fitting.  I don't yet know if this is feasible as I have not built the wings and do not know if there is 1.5+ inches of clearance between the fuselage side and the root wing rib.

Closeup shot of the nipple, coupler and elbow fitted together for the geometry imposed by the standpipe and bung.

Loosely screwed together to see if I'm in the ballpark for clearance between the fuselage and wing root.  The answer is still a long way off.  I have to build the wings first!

Shown below is the termination of the engine supply line, that will run from the lowest bung of the standpipe.

 A shot of the left wing's supply line as it runs from the standpipe.  The 3/8 inch aluminum tubing clears the top of the lightening holes by 1/16 - 1/8 inches.  The horizontal white lines are actually strings that will be used to route control cables for the rudder and stabilator.

 The photo below shows the three lines (from bottom to top: engine supply, engine return and left wing supply) from the standpipe, running toward the center line of the fuselage.

Another view from slightly further aft (near the exit of the right flaperon torque tube), looking forward.

 More to come, so stay tuned.

 

Upgrade to the Upgraded Flywheel

The Viking factory reported some incidents of ring gear slippage on the new flywheel assembly that I recently upgraded to.  The recommended remedy was to remove the unit and separate the ring gear from the flywheel and make some changes.

So, off to drain and then remove the radiator, then the PSRU and finally the flywheel/ring gear assembly.  The remedy begins by bonding the ring gear to the flywheel with green Loctite.  After some research, I resolved to use Loctite 620 which is the most viscous and highest shear strength of the green Loctite family for this application.  But alas, I'm getting ahead of myself.

The ring gear had to be separated from the flywheel first and then the two components cleaned thoroughly with acetone prior to bonding with Loctite.  The first two photos below show the nice bead of Loctite that resulted from dropping the heat soaked (to 350 deg F) ring gear down onto the flywheel.

The final step of the process involved the replacement of the smaller washers with some AN970-3 washers that had a larger outside diameter for greater surface area contact.  I also used some red Loctite on the nuts, which are also secured with lock washers.  See below.

Now it was time to bolt the flywheel back onto the engine, after scrubbing the 6 bolt's threads clear of the previously used blue Loctite.  As usual the bolts were torqued back down to 80 foot pounds per Viking and secured with blue Loctite again.

I like to refer to the next shot as the "sacred geometry".  The rubber isolators have to be oriented as shown with the factory sketch ON the flywheel, below.

The next major step of the process involves aligning the PSRU studs of the spider gear and driveshaft to the rubber isolators and the crack bushing.  The business side of the PSRU as it is readied for installation.

PSRU in place.

Oil line from the engine galley plumbed into the top of the PSRU.

Then the gearbox temp probe is installed too.

The last major step in the process is to plumb the gearbox oil discharge line from the former location of the siteglass back to the oil tank.

It takes careful orientation of two elbows at the site glass location to negotiate the path around the coolant tube as shown below.  After running out of room with the cowling in my original configuration, I had to re-route the oil line aft of the coolant tube.  It worked out okay, but I was really sweating it to get to this perfect arrangement.  Four pictures to show the various angles of this tightly configured area.

It looks like I'm back to where I started again....hopefully that is the final install of the upgraded flywheel.