The World Models 1/6 Scale Piper Pawnee Kit Review – Part Two – Covering with Toughlon Iron-On Covering

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For those of you just joining, here’s what you missed – Part one of the Pawnee review covered building the basic airframe. I would suggest reading that before diving into covering. If you’re only interested in Toughlon covering material, and plan to use it on a different project, then by all means, carry on! Toughlon is the World Models’ brand of covering. It’s very similar to UltraCote, but I like it more than UltraCote for a couple of reasons: 1) It shrinks more, and 2) It’s less expensive. Toughlon comes in a wide variety of colors, and costs about $11.00 per 800mm x 2 Meter roll. It’s approximately two-thirds the price of a roll of UltraCote, and you get a little more covering too!

Tools

To apply an iron-on covering, you’re going to need an iron. I have been using this 21st Century covering Iron for approximately 10-15 years, and it’s been great! The adjustable thermostat makes it great for different covering materials, which are all applied at different temperatures! I also keep my straight edge on hand – this one has a strip of cork on the back side, so it stays in place when drawing a line or cutting. The cutting mat is a tool I have added in the last couple of years, and it really saves on bench top. When cutting the covering, I prefer using single-edge razor blades – they’re cheap, disposable, and I can glue different scraps of balsa to them to make spacer-guided cutters. A small scrap of balsa stick in 1/8″ and 1/4″ are great tools for cutting a nice overlap for edge trimming. My trusty old Robart foam airplane stand has seen better days – in fact, this was its last project before being replaced. These foam stands are really nice for holding the airframe at different angles when covering. Lastly, I used some tag board for making templates for the trim. I made a ‘hot poker’ from a small piece of music wire and a piece of 3/8″ square basswood stick. I’ll talk about this tool in a bit. Lastly, I used my 12″ x  2″ sanding bars – they are sold by Great Planes, and are immensely helpful for smooth, flat sanding!

My Inspiration!

This is a full-scale Piper Pawnee of roughly the same vintage and profile as my kit. I really liked the lines of the blue, and since the canopy I had was already blue in color, this design lent itself very well to my model. I wasn’t terribly fond of the white, so I changed the white to Cub Yellow. (Photos courtesy of Fault Line Flyers – www.faultlineflyers.com)

It’s best to have a design idea in place before you start building, so you can order the covering and have it before you actually NEED it. With that said, keep an open mind as your building – another trim scheme might pop into your head – just roll with it! It is, after all, YOUR new airplane!

Before Covering Begins…

One thing I cannot stress enough is that every little blemish in the wood’s surface will show through the covering – this is not a fault against Toughlon, but rather ALL covering materials! The surface MUST be properly prepped before covering! I started by sanding the entire airframe with 120 grit sandpaper on a sanding bar. After a good sanding, I checked the whole airframe and applied small amounts of lightweight spackling filler to any dents in the surface. When the filler had dried (about two hours), I sanded the entire airframe again – this time with 400 grit wet-or-dry sandpaper. Because this is not adhesive backed, I wrapped it around the 120 grit on my sanding bar – it got the job done! With the outer surface of the airframe completely smooth and dent-free, I moved on to covering!

Applying the Covering

The kit building instructions have a section on covering the Pawnee, and there’s some good advice in there. I did not cover my Pawnee with the color scheme they did, so I was left to my own experience for covering. I will be using two different colors of Toughlon – two rolls of Cub Yellow (Part# STL331) and one roll of Blue (Part# STL250).

I started by cutting a piece of Cub Yellow that was a little wider than the bottom of the fuselage and laying it in place. With my covering iron set to 225° F, I tacked the covering down at the corners and then along the edges. Once it was stuck all the way around, I used the razor blade tool I made to trim the covering to have 1/8″ of excess around the edges. This excess was then ‘folded’ over onto the fuselage sides and ironed in place.

The large, flat sides of the fuselage went on in the same manner, and had the same 1/8″ overlap at the bottom and 1/4″ overlap at the vertical tail. That overlap was then folded onto the bottom and ironed in place over the bottom covering. The vertical tail overlap was ironed one layer on top of the other.  Each side of the rounded tail block got a small separate piece of covering – this was a MUCH easier job than trying to cover the whole yellow area in once piece!

The horizontal stabilizer, elevator halves, fin and rudder were all covered on both sides. As you can see, the top of the rudder is not covered – there will be a color change here, so I didn’t have to cover all of the rudder in Yellow.

Here is the basic fin and rudder two-tone color scheme. The blue covering was laid over the top of the yellow and ironed in place – when putting one layer directly over another, air bubbles can develop. When this happens, a very small pin can be used to poke a hole in the covering to let the trapped air escape. as the air leaves, the bubble will lay flat, and the covering can be stuck in place again with the covering iron.

Being as I was on a roll (no pun intended) with the Cub Yellow base color, I decided to move on to the wings. I started by covering the small inside parts of the wing – these have a 1/8″ overlap that got ironed to the surrounding surfaces, just like the larger fuselage pieces. With those done, I cut a large piece of covering for the bottom of the wing. As you can see, I didn’t cover the wing tip, as it will get the blue trim color. The larger piece was laid in place, and ‘tacked’ or spot -ironed in several places around the edges first, followed by sealing the leading and trailing edges and all the 1/4″ overlapped edges. with a good seal all the way around, I ran the iron over the entire piece of covering. When it had been sealed to all the underlying wood structure, I turned the iron temperature up to approximately 275° F to shrink the covering tight. The key here is to get a good shrink and tighten the covering without pulling the covering loose or warping the wing.

The top of the wing was done exactly like the bottom – I really like Toughlon covering – it’s easy to work with, and looks great! The aileron and flap were done with two pieces of covering each (I laid the flap and aileron on the back side of a piece of covering and traced around the part with a 1/4″ spacer and a #2 pencil).

The covering was cut and removed from the four aileron/flap servo hatch areas, and a piece of covering was attached to each of the hatches. I tried using the iron and had limited success, but I found that a little medium CA smeared on the hatch corners and edges before applying the covering worked really well!

After designing and cutting my template, I transferred the design to my blue covering. The blue covering for the wing tip was done in two pieces – one each for the top and bottom of the wing tip! Toughlon covering is great to work with! Even after trying as hard as I possibly could to get the covering on without a single wrinkle, I still ended up with a couple. Thanks to the covering’s ability to dramatically shrink, I was able to get rid of 99.9% of the wrinkles! I was extremely pleased!

A piece of the blue covering was cut over-sized and applied to the middle of the battery hatch. Remember the ‘hot poker’ I mentioned? I used it to melt a hole in the covering for the latch. With the covering stuck to the middle of the hatch, I simply rolled the hatch to each side and drew corners and outer edges on the back side of the covering.

I rolled the hatch from side to side again, and marked the edges on the front and rear of the hatch. With all the edges marked, I trimmed the covering to shape and started ironing it to the hatch. The edges were simply overlapped in the corners.

The rounded, front and rear were a little more tedious, but the end result was nice. with all the edged stuck, I shrunk the rest of the covering on the hatch. It fit perfectly in place!

The top blue was applied in three pieces, starting at the rear of the fuselage. Instead of tag board, I used the backing material from the covering to make a more flexible template. This allowed me to apply the covering in one piece from the cockpit forward. I left approximately a 3/8″ overlap seam where the blue was laid on top of the Cub yellow. With the fin and rudder in place, it’s starting to look really nice!

Since I happen to own a vinyl cutter, and I had a piece of vinyl that matched the blue, I made some custom N-numbers. Instead of black, I opted to paint the cockpit floor a light grey to help keep the temperature inside the cockpit (from the sun’s rays beating in) to a minimum.

While  not included in the kit, I decided to add an instrument panel, complete with ‘crash pad’. Some Ag-places had this crash pad to keep the pilot from smashing their face into the panel in a crash. The gauges were made from printing some Piper Cub gauges on a piece of copy paper, trimming them, and sticking them into the wet paint on the  1/16″ light ply instrument panel.

A simulated roll cage was made from a 1/8″ dowel. This was all done by eye, and the pieces were all glued together using thick CA. I painted the roll cage with some olive drab green acrylic paint before it was glued into four 1/8″ holes I drilled in the cockpit floor.

The Wrap Up

Since I can be somewhat of a perfectionist, I added a silver 1/4″ automotive pinstripe to cover the seam between the blue and yellow covering. This added just the right ‘pop’ to the color scheme, and really added a finishing touch! Another piece of matte black vinyl was added to simulate the ‘step pad’ on the left wing. With the covering now complete, the World Models 1/6 scale Piper Pawnee is now essentially an ARF! Stay tuned to RCUniverse for Part Three – Final Assembly and the Flight Report!

Just remember – any imperfections in the wood WILL show through the covering. Take your time and get the airframe smooth! The smoother your surface, the better the Toughlon will look when stuck and shrunk! -GB

 

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