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.