The Tail Boom Repair - Part 2

With the replacement tail boom skin made, it's time to cut away the remaining broken glass and prep the areas for the new skin to bonded to.  








 

The next step was to cut and trim the replacement right skin half and to do a test fit.

The old plastic PE tubing for the rudder cables and TE prop were also removed. I replaced the tubing with new PE tubing.







I reused the static port pressure intakes from the old skin.

I cleaned up the pressure intake and attached it to the new skin using epoxy paste and glass.

The new skin was secured in place using tape, hot glue and clamps. Inside support strips were bonded to the seam lines and epoxy flock and cab-o-sil paste was applied to the outside seam to fill any uneven voids between the skins. 

After the seams had cured, it was time to scarf the area around the seams to create a beveled form to the seam line. There was a fit issue toward the forward seam due to the problems with the mis-matched length between the two PIKs.

I had to grind down the areas with the paste, and reinforce the internal backing to prevent a break through.





The aft seam was much easier to tackle. The scarfing process was fairly a textbook procedure.

After the scarfed areas were properly beveled. I did a final roughening of the surfaces and cleaned and prepped the outer areas before applying the glass.  

Using the PIK fiberglass lay-up schedule, I applied the replacement glass per the overlay repair instructions.

I used a plastic tile trowel to squeegee off the excess resin.

Wooden strips with plastic barriers were clamped in place to hold the glass and Peel-ply during the 24 hour curing time.

There is a final layer of glass that I will need to apply over the repair areas, but I will hold off on that until the repairs are complete and the fuselage is off the jig, so I can verify the contour. 

With the new skin in place, and the resin cured, I re-installed the aft bulkhead with epoxy paste and glass strips. The bond will be better than the original which was nothing but a micro-bubble filler.

Next, I attached the new GRP tubing support straps along the inside of the new skin using the old skin for a placement guide. I pulled new RG58 coax for the antenna back to the cockpit and spliced the break using new BNC’s and a barrel connector. The splice was sealed using shrink tubing. I tested the connection using one of my hand held aircraft transceivers. It was cool to listen to ABQ Center talking to incoming flights to the Sunport. And that was in the garage with the door closed! I also pulled a RG400 cable for the transponder antenna.

The PE tubing used for the rudder cable guides is a little trickier to splice. There is no cement available to bond the tubing (it requires heat to do that). I used a larger PE tube sleeve to cover the slice. I roughed the inside of the sleeve and the outside of the spliced tubes with 50 grit paper and the used super glue to secure it. The spliced sleeve was sealed with shrink tubing.

I created a transponder antenna cradle, using a mold from Robert. The location for the antenna need to be located at the top of the boom The elevator push rod was too close to the antenna if it were located at the near the underside of the boom.



Finally, I placed the antenna ground plate in to verify the clearance.

The RG400 cable was terminated and the antenna distance from the cockpit is 7 feet.


Next, I will be making the left skin and finish the fuselage boom repair.

The Tail Boom Repair - Part 1

The time has come to start work on repairing the fuselage.

I started to cut away the damaged glass to determine how much of tail boom will need to be replaced.   

The aft section had a split under seam to the tail wheel fairing. The pneumatic tubing and antenna COAX were also damaged.

After assessing the damage, and cutting away the broken material, I removed the broken pushrods and sent them to the shop for repair.

The underside of the fuselage was mostly scraped up, and doesn’t look like any major repairs will be needed. 

The top of fuselage had some superficial cracks along the seam, which will require further investigation.

After cleaning out the dirt and debris, I left the most complete side intact, though the glass will need to be cut away after I get the broken plane on the assembly-alignment jig .  

A test fit of the broken boom to ensure the proper length. 

The repaired pushed rods are back. The shop did a great job repairing them.   

Here is what the broken elevator pushrod looked like before,

And here they are repaired… The shorter one is the push rod for the vertical stabilizer.

Now comes the time to make the tail boom skin mold. Robert let borrow his project PIK-20B to make the molds from. The unfortunate thing about this plane is that all of the paint was scraped off with a grinder, so it is uneven in spots, but for the most part it’s useable.

My first step in making the mold was to find the center seam line. A laser line was a good tool for that task.   

Next, tape and plastic were used to mask the mold halves.  

The surface was prepped with PVA and wax, then a layer of tooling gelcoat was applied, followed by several layers of fiberglass, starting with a 6oz ply followed by a 10 oz, 18 oz roving and 6 oz chopped glass.

After the molds were completed, the alignment jig was constructed. I used 2x4’s, although steel tubing would be the preferred material.

  

Here is the completed jig with the broken PIK secured to it.

A special note
After placing the wreck on the jig: I found out that the one I used to make the Jig was 2" longer than mine. Some where in production, they made changes to the design. And down the line, at least 38 airframes between Roberts and mine, they shortened the fuselage. This changed the boom shape slightly, and of course, it would have been in the area that was broken

I have looked at 4 PIK-20's and found changes in the design and materials used. They were not identical, which surprised me, since they were supposed to be the same model!

The first repairs were to the aft portion of the tail boom. The underside seam was split wide open. Robert recommended the use of clecos to hold the seam closed when I re-bond the surfaces. So, after cleaning and roughing up the surface, I re-bonded the seam with epoxy paste.

After the epoxy cured, I prepped the surface, filled the cleco hole with epoxy-flock paste and laid in 2 ply's of 92125 to strengthen the seam.

After the layers cured, I sanded the surface and used bondo filler to even out the seam depression.

After sanding down the bondo to even out the curve, a final layer of 90070 was used to strengthen the filler.

Now the biggest step of this project, making the fuselage tail boom skins. The mold was prepped and treated with PVA and wax, and then a thin layer of white gelcoat was applied followed by the application of the 5 layers of glass that makes up the fuselage skin. I used the layup scheduled provided by the manufacturer.

Finally, after 24 hours of curing, I popped the skin out of the mold, and required little cleanup.

The post cure will follow after the repairs are completed.

And the last repair was to the aft bulkhead. There was a split in the side. I anchored it to a flat surface and patched the crack with glass and flock paste.

  

So this concludes Part 1 on the tail boom repair.

 

The Horror of the Horizontal Stabilizer.

As I have stated, there were some parts I can no longer find for the PIK. I knew there would be a challenge doing the repairs on this plan, since there is no support services out there that cater to the PIK glider needs.

After making the damage assessment, I found that there were a few parts I needed to complete the repairs. The T-mount for the vertical stabilizer which aligns and hold the horizontal in place, a couple of push rods, a bearing mount for the horizontal stabilizer, and the elevator.

As mentioned in the earlier post, the many attempts to locate parts were a total bust. My connection at the airport did not have parts, or the ability to fabricate the parts based on the drawings. But I was given the name of a machine shop that fabricated MIL spec parts, so I approached them with a set of drawings from PIK provided by the Finnish Transportation Dept.

Upon review of the drawings, and advice from my AP-IA, the first part fabrication was improved on and approved.

The first part to be recreated was the T-alignment mount for the tail.

The drawing spec’s a folded and welded structure, ...

.. but as the wrecked piece indicated, the hollow piece is easy to bend.

The machine shop used the spec's from the drawing, including the type steel used, and created a CNC duplicate part. Since we plan on changing the type certification to experimental, the replacement part (lower right) was acceptable and is just like the newer ones used on gliders today.

It was just a tad thinner, due to the available material thickness, but since the part mounts aft of the tail support wall, the horizontal stabilizer aligns perfectly, and fits snugly!

The next repair was to the bearing mount that was broken of during the crash. After removing bearing from the center rib in the stabilizer, I notice that the mounting tabs were torn from the bolt socket.

I had to have a new mount made,


... so back to the machine shop with drawings in hand. They used the original socket, but welded new tabs to the stem. And with a new bearing, we are ready to install it back into the stabilizer!

The mount was painted with chromate and DCC to protect it from oxidation.

With a cleaned out and enlarge opening, I bolted the support mount back on the center rib.

I then created a cover plate using the material from the other wrecked PIK (you will see me doing this a lot over the next months).

The plug was glued in using epoxy paste and taped down till it was cured.

The nest step was to scarf off the old glass around the plug to re-glass the repair.

The glass will be applied per the repair manual, then to the paint shop.

The Flap Control

The first major repair task was to clean up parts, and fabricate new ones to replace the un-repairable parts. I tried to call and email people that I was told once serviced the PIK's, and might have parts, but after several attempts to contact the individuals, I was unable to reach them. I contacted other glider repair stations, and the answers to the availability of parts was the same,... NO. If I cannot get replacement parts, this project will come to a screeching halt!

I spoke with a few pilots and the local repair station, and found there were a couple of machine shops in town that could address the repair of metal parts, and possibly fabricate new parts matching the drawings of parts I received from the Finish Transportation Dept.

With that question put to bed, I decided to tackle the flap control, since this mechanism was partially corroded.

After removing the control from the fuselage, I photographed the control, and then disassembled the mechanism

During the disassembly of the handle, I noticed that there was a crack in the plastic grip due to being worn through over the years of use. As mentioned in a earlier post, replacement parts are virtually unattainable. So, I had a local machine shop at the airport make me a new one out of  aluminum.



After cleaning up the parts, I was unable to get the scale toothed bar re-chromed, I repainted the bar and handle with DCC auto polyurethane, and the reassembled the flap control.

I also painted the back side of the disc gray to aid in keeping the parts cool when in the sun.

The pin hole inside ring of the disc was scratched up, so I buffed off the black coating and polished the exposed aluminum.













The finished flap control looks good as new!






Next, the horizontal stabilizer!