EVX-48
Construction of the top hatch started with a balsa and plywood frame (above left). Foam filler blocks (above right) were added to the plywood hatch frame. Once the foam was added to the plywood frame, it was sanded and shaped
(below left). Jim then used two layers of 3-ounce fiberglass cloth and glassed over to form the hatch (below right). The foam was removed just prior to painting.
nose blocks. Offset the motor mounting holes 1⁄16 inch to the left (when looking from the top). This will account for the motor off- set and center the prop shaft in the front opening. I cut the front nose block from two layers of 1
⁄4 -inch balsa sheet and laminated them together to form the 1⁄2-inch thick
block. Glue the nose block in place, add the 1⁄4-inch triangle corner supports, then add the top and bottom filler blocks. Rough shape the nose blocks before moving on to the top hatch.
3⁄8-inch plywood strips into a ladder frame that forms the hatch base. Add the center crutch and tack glue the assembly in place on the fuselage. Trim the sides of the ladder frame to match the sides of the fuselage and then add the hatch formers.
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The top hatch-canopy consists of a fiber- glass shell supported on a wooden frame. I use this type construction for most of the hatches I build because it produces a light and strong assembly that can easily take the abuse any hatch endures. While it may seem involved, the construction is actually much easier than it looks, and I find it the easiest way to form complex shapes such as the combined hatch and canopy on the EVX. Start building the frame by forming 1⁄32 ×
sure to use extruded foam board rather than the white beaded foam. The white beaded foam does not shape nearly as well. I buy mine at Lowes, but if you know any building contractors, they can probably give you enough scrap for the rest of your building days. I did the final shaping of the hatch and the nose block at the same time. This made it easier to keep the contours at the transi- tions smooth. When the final shaping of the hatch is completed, remove it from the fuse- lage and sand off slightly more than 1⁄64 inch to allow for the thickness of the fiberglass skin.
Before applying the glass cloth, attach the bottom of the hatch frame to small blocks making sure that the blocks do not protrude past the edges of the hatch frame. The blocks will keep the frame above the build- ing board and allow the glass cloth to prop- erly drape over the edges. I made my blocks from foam. I used two layers of 3-ounce cloth topped by an additional layer of 1.4-ounce cloth, together with Pacer’s Z-Poxy finishing resin to form the hatch skin. All three layers were put in place at the same time. When the Z-Poxy has cured, trim the
Fill in the spaces between the formers with extruded foam and start shaping. Be
edges, lightly sand the glass surface, and test fit the hatch on the fuselage. If your shaping was done accurately, very little filler will be necessary to get the final con-
tours. If there are any low spots that need to be filled, I recommend Superfil Epoxy Filler. Superfil is lightweight and sands very easi- ly. I also recommend that you leave the foam in place during the balance of construction, only removing it as the last step before final finishing.
To remove the foam, I simply picked it out with large tweezers. I secured the hatch with a 1⁄16-inch diameter dowel locating pin in the front and four 5⁄16-inch diameter mag- nets in the rear. The magnets were glued to the fuselage and 3⁄8-inch wide steel strips were glued to the hatch. I’ve had no issues with the hatch blowing off. Final shaping and sanding of the fuselage should be done with the hatch in place.
With the fuselage shaped, cut the bottom planking away between Formers F2 and F2A to make room for the 1⁄8-inch plywood landing gear mount. Epoxy the 1⁄4-inch filler block to the landing gear sub-mount, and then add the landing gear mount. Shape the edges to conform to the fuselage contours. Mount the landing gear with 4–40 bolts and blind nuts. Add the bottom filler block and sand to shape to complete the contours of the fuselage bottom. I added a 1⁄32-inch plywood plate under the bottom filler block and used the landing gear mounting bolts to hold the block in place.
JANUARY 2014
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