Syncat (oz16163)

About this Plan

Syncat. Radio control sport aerobatic model.

Quote: "Build this .40 powered sport aerobatic aircraft from this month's free pull-out plan, designed by Derek Martin.

Syncat was conceived some fifteen years ago with the object of providing an attractive, fast and agile aircraft of compact dimensions and with reasonable low speed hadling characteristics. My own model was completed and fitted with an HP40; other club members I think used the (then) current OS 40 engine. All the models met expectations and performed very well indeed. After several years and much flying and fun, mine was written off by a servo failure. We lost track of the other

models during various diversions into thermal soaring, large scale and so on. That was until a fellow club member purchased one of the original models, complete with an 0540, from a local model shop. He was very impressed with the model's performance and his comments convinced me that 1 should update the design to accept today's 40 size motors. Thus last winter I re-drew the plan and built the model with an Irvine 40 ABC up front.

This then is the current version of Syncat. As expected, it has gained speed and vertical performance, but lost none of its easy handling. Its flight envelope will be dictated more by pilot ability than model limitations. However, if you feel Syncat is for you, just be aware that, like most of its type, it will require careful and accurate building to ensure that its fast, vice free performance is realised.

Start with the wing: Begin by selecting a pile of balsa, noting that most of the wood should be of medium grade, but the wing main spars, leading edges and fin post must be good hard stuff, while the thicker material round the fuselage front should be much softer and lighter. Finally, check that your building board is flat and true and you're ready to go. Start with the wing; this has a fully symmetrical section and will require some form of jigging to the building board during construction to ensure a twist free structure. I use a trailing edge (TE) jig strip, cut from 1/4 sheet, and suitably shaped packing pieces under the leading edge (LE). The single ply template is used to cut the upper and lower outlines of all the wing ribs. This contributes to the wing design by progressively changing the thickness/chord ratio, root to tip.

It is recommended that the wing panels are first assembled the right way up, complete with sheeting and cap strips, and ignoring the ailerons at this stage. The panels should then be re-jigged to the building board inverted; the bottom spars, shear webs, front sheeting, rear spars/aileron bits and U/C rails, rear sheet etc, can all be added in that order. However, before commencing assembly, note the following details:

Part cut R1 ribs to facilitate later removal of cut outs for the servo well and front dowel. File torque rod holes in ribs R2 and R3. Don't glue TE top sheet to the ribs at rear spar positions; this will assist removal of the bits when the rear spars are fitted. Cut and leave out a small piece of sheet to allow fitting of the front dihedral braces. The ailerons can be cut free after the panels are assembled. Ensure exact alignment of the LE and TE's when joining the wing panels. Cut a small groove in the face of the rear spar to assist fitment of the torque rod and provide working clearance. File a flat on the inner end of the rods to key the horns. Finally, shape the LEs, glue on and shape the tips.

Fuselage next: Cut out the 1/8 sheet fuselage sides and the ply doublers. Now, using a few suitable bits of balsa strip and anything else to hand, pin down and pack the sides (as a pair!) to as near as possible the curve shown on the plan view. Glue on the doublers, corner strips and uprights and leave pinned together in the 'bent' position until set. In the meantime prepare your engine mounting and firewall (F2).

Ensure your engine mount rear face is flat and that the engine sits square on the beams, as far to the rear as possible. Mark, then drill and tap the engine bolt holes. Drill the mounting bolt holes, then cut and file away any excess metal, including a 3/4 in wide slot in the rear of the mount, parallel to the engine cylinder centre-line, to provide fuel and vent pipe egress..."

Syncat from RCM&E, December 1994.

Direct submission to Outerzone.

Supplementary file notes

Article pages, thanks to RFJ.

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