Vertical Stabilizer - assembly begins

4 hrs. - This post combines about three separate days of activity spread over as many weeks, interrupted by my trip to LA when I got to fly the Sling 4.

First steps were unpacking the VS parts, then prepping and priming (did this before my trip).  I then started to assemble the the spars and ribs...and riveted the front spar, nose ribs and main ribs 1-3 together.

I plan to build my Sling to IFR capabilities, so the tip rib of the VS gets a VOR/Localizer/Glide Slope antenna for navigation and landing aid.

The last picture is my helper...our German Shepard "Bear".  He likes hanging out at the hangar!

Flying the Sling 4!

Wanted to give a quick update.  Visited with Matt and Jean at TAF on December 6th.  I planned to take a lot more pictures and videos...but:

Once we got in the airplane, Matt  pulled up the electronic checklist, and let me do everything from engine start, to taxi, run up, takeoff, and we flew for a good 45 mins. 

I did three landings - two were touch and goes, one was to a full stop on the short runway (29L).  

With two of us aboard, OAT was around 60F, at 115% power and the electronic prop control on T/O we climbed initially at 80 knots around 1200 FPM.  The sight picture isn't good at that pitch, so we nosed over for better sight over the front, at 90-95 knots, and we reached the pattern altitude before even turning to the downwind leg after takeoff for the departure to the west.  

We went out over the edge of the Pacific Ocean and flew down to Long Beach harbor - I did a few steep turns.  Then we slowed back down, hung out full flaps and did a power off stall.  It buffeted a little and dropped the left wing at 50 knots...The recovery was easy, it didn't have any adverse Yaw or reaction to stall recovery.  Simply drop the nose and it starts flying. Add power and start climbing again.  

Full power (100%) without the engine in the extra boost phase used for takeoff, we leveled out at 4000' and cruised at 126 knots IAS.  TAS was 135Knots.  You change the prop control to climb after you leave the pattern and it reduced RPM to 5500.  We dialed the control back to cruise and the RPM came back to 5200 +/- and the fuel burn reduced to around 5 gph.  

It's a very quiet engine/ airframe, reminded me of a turbo prop, or a video game. Very little engine vibration, climbs very well with just two aboard, and has distinct handling (no slop).  

Landing was Similar to the Sonex, but it's hard to slow the airframe down.  Flap extension speed is 85 knots.  It takes full flaps to get it dirty enough to descend without gaining airspeed.   I greased 2 of the 3 landings.  The first one Matt had me come in pretty high over an oil refinery that's on final, and then I slipped it down about 800', on short final.  The rudder has a lot of authority and reacts quickly when you bring it back around.  The toe brakes that they have as an option worked very well in conjunction with the direct nose wheel steering.

Did get a few pics after we landed!

Elevator Tips

1.5 hrs - this post is about completing the ends of the elevator- not about hints (tips) for building the elevator!  The directions are fairly simple and clear for this step.  Wrap the tip rib (with attached counterweight) with the forward elevator tip skin.  Cleco and rivet.  Then insert the fiberglass composite tip, position inside the aluminum skin, then drill and cleco the tip in place.  Once it's fitted then clean up the holes as needed, insert the rivets and complete the assembly (pull the rivets).  The fit was pretty good, looks like the trailing edge of each tip will need to be faired/filled to match the profile of the elevator aluminum skin better.

Elevator Skin (Left side)

2.5 hrs. - Today Liam and I worked on the left elevator Skin, which is more complex than the right.  Made sure we inserted all of the doublers for the rear channel that supports the trim tab.  Everything fit together pretty well.  The last items to do on the elevator is the outer forward skin and the composite tips.

Elevator Skin (right side)

2 hrs. - Removed the right skin fm the shipping crate, pealed off the inside film and cut away the rivet hole lines...and primed the inside.  Carefully attached the skin to the right elevator structure and only had to open up a few holes on the top of the #1 ri to avoid the trailing edge deformation as shown in the plans.  Once both sides were clecoed - I began riveting!

After finishing both sides - I then clecoed and riveted the leading edge where it wraps over the top and bottom skin.  I had contemplated dimpling this rivet line and using CCC-42 (flush rivets)...but decided to just do as the plans call for.  Once finished I trail fit the elevator to the horizontal Stabilizer...and it fits!

Happy Thanksgiving! Elevator assembly continues...

2 hrs.  Continued installing and riveting the ribs #2 and #3.  Unfortunately I mixed up the location of the Left and Right sides since I was building this upside down (to allow for the elevator control horn to face up).  Had to drill out about 12 of the larger alum. rivets...move the ribs to the opposite side, and re-rivet.

Moving on to the outer Ribs, now it gets a little more fun.  Had to cleco and then updrill the counterweight to allow for the extra large 4.8mm rivet to fit.  These are rivets on and I'm going to only do one side at a time for the outer rib, and skin since my work table is only 6' long.  I'm finding the counterweight is torquing the last rib and entire elevator structure if it's not supported.

Elevator parts prep and begin riveting spar

3 hrs. - I've consolidated a few separate sessions into this post.  Began by prepping the elevator spar, ribs, attach angles, doubler channels, etc. by removing the plastic film, and deburring edges and holes as needed.  Primed all of the parts with self etching primer.

After the primer set it was onto following the steps in the book for item #1 and #2.

And a detailed picture of the elevator control horn and center hinge bracket with the inner ribs (rib 1 -  left and right) now attached with rivets and the AN-bolts/nuts.

Elevator Trim Tab

1 hr. - Assembled the elevator trim tab per the plans.  The instructions are a bit confusing as they indicate the need to modify the rivets (for the whole assembly?) due to them being too long.  We only found the first to rivets on the control horn tab needed shortening.  All of the others were fine.

Horizontal Stabilizer complete

1.5 hrs. This week I was able to rivet half of the top side, and today my son and I completed the remaining rivets.  For some reason I had extra 4x10mm rivets and ran out of the 3.2x8mm.  Hopefully there is enough in the empennage kit to balance this out.

My thoughts so far on the Sling 4 kit compared to the Sonex.  No fabrication!  No pilot hole drilling, and upsize drilling, a lot less debuting, and very little hole reaming is required.  The kit so far is going together well. I'm sure if the kit were home in my garage workshop where I built the Sonex the empennage would be done by now.  But building at my hangar is slow, and mostly limited to weekends.

Riveting skins on the horizontal stabilizer

3.5 hrs. - Today was the first time I've worked on the Sling in a few weeks, been busy with work and Boy Scouts.

Completed riveting the forward ribs and spar together.  My son Liam helped again today and used the rivet gun to pull the rivets for me while I reamed holes and inserted the rivets for him.

To prep the skins I removed the plastic film on the inside and deburred the punched holes with 320 grit sand paper (quick and easy way to do this).  Cleaned the surface and sprayed the mating surfaces with etching primer.

Next was clecoing on the left and right skins, and checking the tips for level (to each other).

My measurements were good so no warp is built in to the Horizontal Stabilizer.

Riveted the left skin on...

And the right skin...need to flip the HZ over and rivet the top another day.

Horizontal Stabilizer - front spar & ribs

1.5 hrs.  Prepped and primed the parts for the front spar, doubler plates, and nose ribs.  Components are clecoed together ready for riveting.

Horizontal Stabilzer - rear spar & ribs

2 hrs. -   Completed priming, and installed some carpet tiles on my workbench.

Was able to reassemble the 1st page of the horizontal stabilizer plans/parts with clecos.  It's now ready to rivet together.

Riveted and completed:

Empennage progress - Horizontal Stabilizer

3 hrs. completing the inventory for the empennage kit, my son and I jumped right into the first page of the build manual:

Gathering up the parts, we temporarily fastened them together with the appropriate sized clecos (black and copper (5/32" and 1/8").  It went together quickly and was impressed with the "match hole" tooling and parts forming.

I took all of the pieces apart, and made sure the edges and holes were properly deburred...this is important for eliminating future stress cracks/fracutures.  I'm following The Airplane Factory recommendation for priming the mating surfaces.  Used a process of cleaning with Simple Green and scotchbrite pad, then dry, and spray with a self etching primer.

Work bench for empennage

1.5 hrs. - Today I constructed the work bench to assemble the empennage.  Similar to when I constructed the Sonex several years ago, I recycled part of the shipping container.  This gives me a work surface roughly 0.7M x 2M (2.7' x 6').

What is a Sling 4?

About the project.  After completing my first experimental amateur built (E-AB) aircraft, which is a Sonex 2-place aluminum low wing light sport, my wife mentioned it was too bad the plane wasn't big enough for the family to all fly in.  We discussed selling the Sonex and getting a used certified airplane (i.e. a Cessna or similar).  Stepping back from a new airplane I can work on to a 40-50 year old plane only a certified aircraft mechanic can touch...wasn't that interesting to me.

After researching the various 4-place "kit" aircraft currently offered, I narrowed my search down to then Van's RV-10, a Cozy MkIV, and a newer entry to the market - The Airplane Factory's "Sling 4".

This airplane has flown around the world twice since it's inception in 2011, and is developed in South Africa.  They have a US distributor based in Torrance, California, who are affiliated with MGL Avionics (I have their EFIS and COM radio in my Sonex).  See the company website for more details:  The Airplane Factory

I found this to be a very interesting airplane and project.  Modern, efficient, attractive, roomy, great range and load capacity.   Turbo Rotax 914 UL, giving 120 knots, at less than 6 gph.  1000 mile range and service ceiling of 15,000'.

Stay tuned and follow my built blog as we build our dream project...