Megna 25 (oz12876)

About this Plan

Megna 25. Radio control sport/pattern model. Wingspan 78 in, wing area 1,000 sq in. For Super Tigre 2500 engine.

Quote: "It's big, it's beautiful, and it's hot! The large sport/pattern ship you've been waiting for. Megna 25, by Alex Bouknight.

The Megna 25 is a mid-wing aerobatic type plane designed around the Super Tigre 2500. Super Tigre has long been a favorite of mine and their large 2000 series glow-type engines are excellent in terms of performance and price. The engine offers a nice power-weight ratio for an engine of this size and was a perfect base for the project. The model, although not large by today's standards, offers good visibility in the air and will just barely fit into a mini-van. Some of us do not have unlimited shop or storage space, and have to limit the size to some reasonable compromise. My niece, Megan, might have had something to do with the name?

The two wing panels supported by a wing tube is an excellent approach to a mid-wing design and the tube/sockets can be purchased from Gator R/C Products, 3713 Pompano Dr, Pensacola, Florida 32514 (904) 476-8639. The large hatch gives easy access to the radio/tank area and makes the wing attachment very workable. The radio requirement will be a four channel/six servo layout. I would recommend the use of coreless or larger servos on the flight surfaces, as the flight loads of this size model would be a bit too great for standard servos. I used a coreless servo for each aileron and one for each elevator-half, driven by a Y-chord. The rudder used one high output servo driving a pull/pull cable arrangement and a standard servo on the throttle.

The use of balsa/ply laminate on many of the sub-structures, was used to reduce weight while still retaining vibration dampening qualities. There are numerous lightening holes throughout the assembly. Choose your wood very carefully. Most of the strength comes from the glue layer between the ply and balsa, and does not require heavy wood. Make the parts carefully and spread the epoxy very thin. The model will balance very nicely if you take care with the wood, especially in the tail area. Light airplanes fly better.

The finish is something that you might want to consider carefully. The model has a lot of surface area, especially fuselage side area. The choice of finish can vary the final weight considerably. A little difference in weight spread over a large area has a multiplying effect. I have seen a number of models that looked nice, but never flew as well as they would have with a lower wing loading. The obvious lightest choice is to MonoKote the whole aircraft, or at least the wing panels and tail area. I normally paint the fuselage which helps with the compound curves and gives a little more flexibility on the color scheme lay-out. It will produce the best finish, but takes more time and work to complete. In any event, build the model as light as you can, not compromising strength.

Construction: Wing: The wing panels would be a good place to start the construction process. I recommend the use of a wing jig, like the A-justo-jig (see https://rclibrary.co.uk/title_details.asp?ID=1044) to build as accurately as possible. Due to the span of the panels, each one will have to be built separately to provide enough length on the jig for the rib guides. If you can live with a slightly higher wing loading and want to build both panels at the same time, shorten the span of each side just enough to fit both on the jig.

Prepare all the ribs by cutting to the correct size and shape. Notice that the inboard section which supports the wing tube uses 3/16 balsa ribs while the outboard section uses 3/32 balsa. Choose light wood for the larger ribs as most of the ply strength comes from the ply doublers..."

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