Fighter Face-Off PARK FLYER EDITION: Part 2

Written by Paul Kohlmann and Derek Micko
Scratch-building and flying opposing aircraft, Part 2
As seen in the October 2021 issue of Model Aviation.

In researching the process, inkjet printers have proven to be most commonly used for tissue printing. Most printers’ ink is water soluble, so before shrinking, the ink will need to be sealed—more on that in a bit. Most printers can print legal size (8.5 × 14 inches) and this will be needed for the print files provided. It’s also best to use a printer that has a form feed versus a tray feed. (Mine is a form feed at the back and goes down and through the printer.) I used light gray and white silkspan/tissue on the model. A word of warning: "Domestic tissue" (such as gift-wrap tissue paper) is typically not durable enough and it’s best to use modeling tissue. To feed it through the printer, the tissue needs to be temporarily attached to a sacrificial sheet of paper. Spray a light coat—and I mean a really light coat—onto the sheet of paper. Place the sheet of tissue over the paper and smooth it out by hand. The tissue can be carefully peeled back and reapplied if wrinkles form. Using a sharp blade, the tissue is trimmed along the bottom and sides of the paper. I usually leave approximately 1/4 to 3/8 of an inch of tissue overhang at the top of the sheet. This allows for easier separation of the tissue from the paper. Set the tissue/paper combo into the printer feed. Before printing, it’s best to set your printer preferences as borderless. After the sheet is printed, avoid touching any printed area and let it dry for roughly 10 or 15 minutes. When the ink is dry, it needs to be sealed/waterproofed. For this I used Krylon K01303007 Acrylic Spray Paint Crystal Clear in an 11-ounce aerosol can. You can get this at most craft and hardware stores. I applied several light misting coats. Don’t let it get too thick or wet. Let this dry, and then you a re ready for the application. When applying the tissue, I found that it’s best to cut the individual part free as opposed to peeling the full sheet of tissue o‘ then cutting out each part. To apply the tissue to the frame, I used a glue stick that goes on purple and dries clear. This is helpful in letting you know how much time you have before it’s too dry to work. Apply the glue stick on the "outside" frames of the section that you are covering, pulling it as taut as possible to remove any wrinkles. I’ve found that printed tissue will not shrink to the same extent that standard tissue does because of the light sealant coat. Seal the edges with thinned Eze Dope and let this dry for an hour or so. The tissue can then be shrunk using a fine mist of water. Holding the model above you, spray "up" at the part to avoid having any large water droplets hit it. Let the tissue fully dry, applying a thin coat of water to any stubborn areas. After this is complete, spray the section/part with several progressively heavier coats of Krylon. This is the final sealing coat, and it eliminates the need to seal the surface with Eze Dope.

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Whether you choose to cover with printed tissue or film, start by covering the tail sections first. If using tissue, you can cover the tail parts with the rudder/elevators hinged (but not glued) and attached. The whole section is covered with one piece, shrunk, and then the overhang is glued to the leading edge of the control surface. The rear of the fuselage is next. After this covering is applied, the exits for the 1/32-inch piano wire pushrods are opened up and the wire is fed through the fuselage and connected to the servos. Scrap stringers are used to "box in" the wires to keep them from flexing. The rest of the fuselage is covered in sections. The wing bottoms are covered next. One wing panel is then pinned to a board with 3/32-inch scrap material under W-8. Cover the top of the wing (outer panel/tip) with this in place before adding the rest of the top wing covering. When shrinking the wing tissue or film, keep the 3/32-inch scrap there to ensure that the washout remains. Find the canopy parts and paint them a dark gray and bend C-1 according to the plans. Glue C-1, F-3A, C-2, and F-4A to the hatch (see the plans detail). Using F4A a s a guide, mark the magnet location on the top of F-4 and drill it out, adding the magnets to F-4 and F-4A and ensuring that the polarity is correct. Add F-4B, C-3, and F-5A to the top of the rear fuselage according to the plans. The canopy framing is made from lightweight cardstock and templates are provided. Cut out the interior sections first then the outside edges. Glue these frames on top of thin, clear plastic sheeting. The prototype used 3 mil plastic. Bend and shape it to fit the formers before using canopy glue to attach it. Use canopy glue to also attach the cowling to the CR parts. Glue the tail sections and wheel pants/spats in place. Check the model’s suggested center of gravity on the plans and position the battery pack fore and aft as needed to get the correct location. The bottom hatch pack to be positioned far forward on the prototype. Set the control throws to be +/- 1/4 inch for the ailerons, +/- 3/8 to 1/4 inch for the elevator, and +/- 1/2 inch for the rudder. The model can be hand launched or can rise o‘ of the ground from a smooth surface. Because the Nate has a tail skid instead of a wheel, taxiing can be difficult. I set the model in the direction that I wanted to go, advanced the power, and it was in the air in roughly 10 feet. The prototype required little trimming and grooved nicely. The 2S 450 mAh battery pack setup is sufficient for most basic aerobatics; however, I recommend dual/higher rates for ailerons if you plan to perform more than slow rolls. Landings are a breeze. Set the model up on final approach and gradually reduce power. Flaring requires only a slight pull on the stick.

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The light, 7 to 9 ounces-per-foot wing loading keeps the model forgiving, and the stalls are easy to recover. Overall, this aircraft is fun to build and fly and can fit into smaller spaces. Give the Nate a try and check out printing on tissue. I think you will have a lot of fun with both! Infield Engineering 30-inch Brewster F2A-1 Buffalo: As Derek mentioned in the introduction to his Ki-27 Nate build in the September issue, this project is the second iteration of the Fighter Face-Off, in which Derek and I engaged in 2018. This time around, my subject is the Brewster F2A Buffalo. Few military aircraft have had as checkered a past as the full-scale Buffalo. Initially, the Buffalo was a star. In 1939, it beat out the Grumman Wildcat in testing to become the U.S. Navy’s primary fighter. Prewar pilots praised its maneuverability, although all variants were considered to be underpowered. But after a mauling by Japanese Zeros at Midway, the Buffalo was harshly criticized by surviving pilots as a flying coffin. The Buffalo was also pitted against the Japanese in the hands of both British and Dutch pilots. Neither group was particularly impressed with the stubby fighter, although admittedly, the Japanese had the upper hand in both pilot experience and ground support. The Buffalo fared reasonably well against early Japanese aircraft such as the Ki-27, but it was no match for the later Ki-43 Oscar. Soon, the British and Dutch found themselves in wars of attrition and retreat. It is this matchup between the Ki-27 and the Buffalo that is the subject of Fighter Face-Off, Part 2.

Tail Group Laminations

Begin the tail group by making forms for the laminated outlines. You can either print the tail group parts from the downloadable plans or trace the outline from your kit’s hard copy. Either way, use the inside line from the outline for the form’s template. Attach the template to the form material of your choice. I used 3M 77 spray adhesive to attach the plans paper to a 1/4-inch fiberboard panel. That seemed like a good choice until I realized that I couldn’t pin it down to my building board like the foam forms that I normally use. No worries—a pair of large spring clamps held the forms in place while I made the laminations. The edges of the form were covered with packing tape to prevent the laminations from sticking to the fiberboard. Soak 1/8-inch strips of 1/16-inch balsa in water overnight. Test that the strips are flexible before starting the laminations. This tail group is fairly small. Prebending the balsa over a small jar or steam can loosen it. Keep tension on the first strip to avoid kinks in the balsa as it bends around the form. Add pins as you go to keep the strip tight against the form and pushed against the surface of the building board. Put a thin, even layer of glue on one side of the next strip and repeat. Move the pins from the first strip to the second as you go. Do the same for a third strip then set the lamination aside to dry. Carpenter’s glue works great on wet wood and is easily sanded later, but make sure to let the outlines cure completely before unpinning them so that they hold their shape and don’t delaminate.

Framework

Now pin the outlines to the plans. Build up the inner framework by assembling the parts in numerical order. But don’t glue the parting lines for the rudder (parts V1 and V2) and elevators (H2 and H3). After the numbered parts are in place, the bracing can go in. I used a balsa stripper to cut the bracing stock from the edges of the balsa in my kit. Cut each brace slightly large and sand it to the perfect size and shape for its position. Start with the longer braces so that if you get a little overzealous with the sanding, you can take another shot at fitting it in a shorter position. After the last brace goes in and the assembly cures, unpin the tail group parts. Sand a radius in the leading edges (LEs) and a taper at the trailing edges with 60-grit sandpaper. Follow up with a light pass with 220-grit sandpaper. Separate the fin/rudder and horizontal stabilizer/elevators by cutting through the laminated outlines as shown on the plans. Bevel the LEs of the rudder and elevators and these parts are ready to hinge. I used 1/8-inch strips of CA hinge material on all of the control surfaces for my prototype.

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Fuselage

The left side of the fuselage is built over the plans in the old Guillow’s style. Start by gluing and pinning keel parts K1 through K4 to the building board. Formers F2L through F10L are next. Glue these to the keels so that the formers stand perpendicular to the board. The next steps will tie the formers together. Join the formers with side keel K5 then use the left side of the cockpit deck to join formers F5L through F7L. Now add the left wing saddle. Dampen the outer side first so that it curls slightly. Glue the wing saddle to keel F5 and formers F2L through F5L. Now add a few 1/16 × 3/32-inch balsa stringers to stiffen the assembly. Letting the assembly fully cure before unpinning it will help prevent warps in the fuselage. On the right side, unpin the left half of the fuselage and build the right half directly onto the left half. Start by adding the firewall. Preassemble this part by aligning and gluing balsa parts F1A and plywood part F1B. Now glue the firewall to the front keels of the fuselage’s left side. Note that the long motor mount slot goes on the left side of fuselage. Assemble the motor mount as shown in the detail drawing. Make sure that the side panels are in the correct positions. When assembled correctly, the motor will be positioned for the proper downthrust and sidethrust. Epoxy these parts together then fit the motor mount box into the well in the firewall. The belly hatch is next. Glue hatch formers F2H through F5H to keel K4 and the left wing saddle. Be careful not to glue hatch formers F2H or F5H to their respective fuselage formers or it will be difficult to free the hatch later. Now add formers F2R through F10R. Glue each of these parts to their left-hand mates. Use wing pin boss WP to strengthen former F2 and reinforce the wing pin hole. Slide in the battery tray from the hatch side and glue to the firewall and former F2. Preassemble the wing bolt boss from parts WB1 (plywood plate) and WB2 (balsa struts), and then attach it to former F5. Epoxy is a good adhesive for this critical assembly. Now that all of the inner parts are in place, join the right-hand formers with keel K5 and the cockpit deck. Dampen the right-wing saddle as before and attach it to its keel and formers. Complete the fuselage assembly by adding the rest of the stringers. Alternate from side to side and check for twisting as you go.

Cowling

The cowling is built up from a balsa and plywood frame that is planked with balsa. Begin by preassembling balsa cowling formers C2 and C3. Each is composed of three parts to manage the direction of the wood grain. Join these formers and plywood former C1 with cowling keels C4 through C7. Note that there are small alignment holes in parts C1 and C2. They mark the top of these formers. The square cutout in C3 is the top of that part. Use the plans sideview as a template for setting the angles of top and bottom cowling keels C4 and C7. Check that the angle of the sides of the cowling frame is the same from side to side as the assembly cures. Assemble the cowling opening ring from parts C8 through C10. Use the scoop openings to align these parts. Glue this stack to the front of C3. Note that the outside diameter of C3 is smaller than the cowling opening ring. This will make it easier to perch the planks on C3 in the next step.

Planking

Some builders shy away from planking because it looks tedious. It’s not that bad, especially on a small part such as the Buffalo’s cowling. It also helps that there isn’t much curvature in this cowling, meaning that the shapes of the planks will be simple. Plank the cowling between C1 and C3 with 1/16-inch balsa. Cut 1/2-inch-wide strips for this job. Add a plank to the top of the cowling that covers half of the cowling’s keel C4. Do the same with the bottom and keel C7. Tying the cowling rings and these keels together will make the cowling assembly much more rigid. As with the wing saddle, dampening the outside of the planks will make them curve slightly. Use this to your advantage as each plank is fitted. Place a plank in position to check for tight spots. Sand the plank lightly and fit it again. After a uniform parting line is achieved, glue the plank into position. I generally avoid using CA adhesive, but it works great for this application. A shot of accelerator helps to quickly cement it in place. Alternate the addition of planks from top to bottom and side to side to avoid warping the assembly. Sand the finished cowling with 120-grit sandpaper to knock off the high spots at the edges of the planks. The bottom of the cowling can be fiberglassed for more durability if desired. I expect that my Buffalo will be landing on soft grass, so I skipped this step. The final steps in the cowling assembly are the addition of the attachment hardware. Add two 1/8-inch diameter alignment pins to attach the firewall to the cowling. These can be made from doweling or barbecue skewers. Use two of the four attachment holes that are diagonal from one another. Use the other two holes for pairs of rare earth magnets. An easy way to deal with these is to put a small piece of waxed paper between each magnet pair then epoxy a magnet into each hole in the firewall so that the waxed paper is flush against the firewall’s surface and the second magnet is facing the cowling. After the firewall magnets are secure, fit the cowling over the two magnets. Adjust the cowling magnet hole openings if necessary.

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After the cowling drops over the magnets, put epoxy in the magnet holes and on top of the cowling magnets. Drop the cowling in place and wait for it to cure. When it does, remove the cowling and discard the waxed paper. The magnet pairs will be correctly oriented, and the gap set perfectly.

Wrapping It Up

That gets us roughly halfway through the build. Next time, we’ll frame the wing, rig the controls, and get some covering on this model. Until then, fly low and build light!

SOURCES:

Manzano Laser Works www.manzanolaser.com Park Flyer Plastics (817) 233-1215 www.parkflyerplastics.com Du-Bro (800) 848-9411 www.dubro.com Paul and Ralph Bradley’s Model Airplane Hangout www.parmodels.com FMS Printing on tissue Ki-27 Nate https://youtu.be/1980sL-UJC0 RCGroups Build Thread Park Flyer Fun Scale Ki-27 vs. I.E. Brewster Buffalo https://bitly/39zYm By Paul Kohlmann [email protected] | Derek Micko [email protected]
Photos by the authors and as noted