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.