THE VERTICAL STABILIZER
On Friday, June 7, I started preliminary work on the vertical stabilizer. Before I did anything else, I laid all of the parts on the work bench so I could take the picture at left below. After that, the work began.
The first step was to smooth the edges of the ribs (de-burr) and spars and flute them as required (no picture). Then I put the assembly together with clecos to see how it all fit together (upper right). Everything fit very well so I disassembled the stabilizer and commenced with the completion of the pre-assembly details.
The first operation that I decided to attempt was to install the optional lightening holes in the rear spar re-enforcement plate P/N VS-808PP. I put tape on the plate so that I could mark the hole locations with a pencil (left picture). Then I clamped the plate to the table of the mini-mill (see “Tools.) with a block of wood underneath it. I installed a fly cutter in the chuck and set it to cut a 2” hole. The wood is needed to keep the fly cutter from contacting the mill table.
There are 2 each 2” holes and 5 each 1.5” holes in the re-enforcement plate (above left. After the holes were added, the plate was attached to the spar and all of the fastener holes were enlarged. Several fastener holes were dimpled in the spar and counter-sunk in the plate (above right). These fasteners are flush where the spar will attach to the fuselage.
Here is an “oops.” These are the lower rudder hinge brackets (above). I installed the upper of the 2 in the wrong location and added a fastener hole. The right photo shows three holes in the lower row. The middle hole is not supposed to be there. To solve the problem I purchased a new hinge bracket. It cost $5.01 with a $2.50 handling charge (not including shipping). If this is the most expensive mistake I make on this project I will be satisfied.
Let the dimpling begin. I dimpled all of the ribs and the outer edge of the skin on June 10. I had to leave the project for business purposes and did not dimple the holes where the skin attaches to the ribs until June 14. The right picture shows the skin with the “C’ frame dimpling tool. This tool needs to be used with some caution. If the part is allowed to slip in the slightest in between hammer blows while using the tool, it is possible to enlarge the hole and move its center. This can cause assembly problems. The tub of clecos is on the skin to help hold it.
This is a close up of the dimpling process (above). The left photo shows the pin of the dimple die through the hole. Two raps with a dead blow hammer and the dimple is done. This is where a problem can occur. I caught the skin moving ever so slightly out of the corner of my eye between blows. Before the second blow I managed to stop myself. I manually moved the mandrel down to mate up the dies. The female die did not engage the male die square. I moved the skin back where it was and continued with this dimple. I performed a little test on a piece of scrap metal. If I put side pressure on the metal the hole was enlarged and the dimple was not symmetrical by the time the second blow was applied. The fact that I had not had this happen to this point I attribute to luck.
There was one more thing that I learned from the dimple process. The picture on the left shows the mandrel on the “C” frame dimpling tool. There is a spring to retract the mandrel after each blow of the hammer. The height of the female die from the male is controlled by an “O” ring on the shaft of the mandrel. After about 2 dimples the “O” ring slips up the shaft and the mandrel does not retract. I came up with a simple solution: tape around the “O” ring with the mandrel set at the desired height. This increased the speed at which I could dimple holes considerably.
These are the vertical stabilizer parts after etch and alodine. The alodine turns the metal a golden color. What this does for you is to remind you that you have applied alodine. I used Alodine 1201 on some parts and DuPont 226S on others. The 1201 turns the part more gold than the 226S. The parts have to be “etched” prior to the alodine treatment. The etching process thoroughly cleans the metal. The alodine neutralizes the etch or it could corrode. This is an interesting concept. In order to help the aluminum to resist the corrosion process, you must first put the aluminum at risk of corrosion???? Anyway, this is an important step.
And now it is time for paint. But first, here are some thoughts from Mother Nature. On this day it was raining like a cow ……………… you know the rest. It was not raining inside the paint booth though so I decided to continue on.
When I primed the horizontal stabilizer parts some primer passed through the filter. I decided to add one more layer to the filter for a total of three layers. I added a lip around the inside of the filter box (left) to hold the filters in place (instead of masking tape). When this filter material is used up I will get a better grade of filter material. What I have came from W. W. Grainger and they sell a better grade I am told. If not I know a professional aircraft painter and he uses some material that is a lot heavier. The filter material I am using will last at least until the empennage is completed. At any rate parts are primed (right) and all of the primer over-spray stayed inside the 3 layer filter.
What is nice about the wooden frame paint booth is that I can put a hole in one of the cross braces and hang parts that shouldn’t be painted on the screen, like the rear spar re-enforcement. When the painting is done the paint gun needs to be completely disassembled for cleaning (right). If this step is skipped, a $200 paint gun will be wasted. I use a Binks gravity feed HVLP “touch up” gun for priming parts. It does a good job so I take care of it.
Its assembly time. The photo at left (above) shows the pneumatic squeeze with the “flange nose yoke” attached. Notice that the spar is clamped to a 2 X 4. I did this to keep the spar straight while the re-enforcement is attached. Otherwise it would be easy to twist the spar and final assembly would be difficult. The photo on the right shows the rear spar assembly complete, including the rudder hinge brackets.
The photo above left shows the VS-707 rib attached to the VS-702 front spar. The right photo shows the vertical stabilizer skeleton ready for installation. Note the tubing attached to the forward side of the front spar. The plans tell you to think about wiring before you close the stabilizer up but they really don’t tell you what to do. I know that I am going to want a strobe or a beacon atop the tail. I installed this ½” O.D. tubing on the front spar in order to run electrical wires after assembly. I installed a grommet on each end rib and I clamped the tube to the spar with two Adel clamps.
I installed a ¾” hole in each end rib to accommodate the grommets. This is a little small for a -13 grommet but I did not want the tubing to be loose in the grommet. The grommets and the tube had to be removed to assemble the skeleton. After the skeleton was riveted together the grommets and the tube were re-installed. I made sure to double check the rivets and the clamps. This area is not accessible after the stabilizer is closed.
Riveting the Vertical Stabilizer is straight forward. I installed a cleco in every other hole. The rear spar is not attached until all of the forward spar rivets are installed. I riveted the rear spar except for the left lower corner (bottom left photo above). Note the block of wood holding the skin up so that I could reach through with a bucking bar. I reached through this opening and put solid fasteners in the center rib. I then closed this section. If you block a section of skin up like this, be careful about putting a kink in the skin at the first cleco or rivet from the block of wood. By the way. I was able to rivet this assembly together by myself. I know that this will not always be the case but sometimes it is enjoyable to be by yourself when working on a project like this. "Recreation and Education" is what this exercise is all about. The vertical stabilizer is complete. The Rudder is next.