Sierra Mk2 (oz15808)

About this Plan

Sierra Mk2. Radio control sport aerobatic slope soarer model. Wingspan 63 in.

Quote: "Sierra Ref: SM0014: The Sierra was a very popular sports aerobatic sloper, that for us, put the fun back into slope soaring. At the time we were flying models with a fully symetrical wing section. In poor lift conditions these models did not perform, yet the Sierra with an Eppler 374 semi-symmmetrical section could do almost everything a model with a fully symetrical section could do - but in much lighter lift conditions. Span 63in (1600mm).

The Sierra Mk2 is an attractive, no frills, second stage aileron trainer that has a wide following. Recently up-graded, construction now features a ply sided fuselage with foam veneer to wings make Sierra Mk2 even quicker and easier to build. Docile handling characteristics with the ability to stay up in light winds and a full aerobatic repertoire make the Sierra Mk2 a pleasure to fly and fly.

Specification:
Type: Sport Aerobatic
Span: 1590mm
Controls: Rudder/Elevator/Aileron
Av Wt. 1000gms
Section: Eppler 374 (Semi-sym)"

Direct submission to Outerzone.

Note this plan appears here on Outerzone thanks to the kind courtesy of the designer himself, Stan Yeo of Phoenix Model Products in Devon, UK. For more info and background, see the PMP website: www.phoenixmp.com

Update 26/3/2026: Added kit review from viation Modeller International, January 1998, thanks to RFJ.

Quote: "Phoenix Model Products have produced a value for money, practical and good looking slope soarer with excellent aerobatic performance. Mark Scott returns his verdict.

After returning to modelling after a short lay-off, my requirement was for a model to help me make a safe transition from a Rudder/Elevator slope/flat field trainer to an aileron slope soarer capable of performing most aerobatic manoeuvres and being able to operate under a range of conditions. I also wanted a model that would not require any specialist building skills since most of my models are made using very limited facilities on the kitchen table.

So why choose the Sierra? Having obtained brochures from several glider manufacturers, including Phoenix Model Products, my decision to buy the Sierra was made after a long telephone conversation with Stan Yeo of PMP. I was influenced by the practical application of his many years experience as a slope flier into sound features reflected in design and manufacture of the PMP range. I could have opted for the Stage 2 (oz15842) but didn't want to have to build yet another trainer before moving on to an aerobatic model - perhaps a bit ambitious, but I was determined to get slope flying cracked with the minimum of delay. The Sierra seemed the best compromise with its semi-symmetrical wing whilst maintaining simplicity in construction and radio equipment requirements - I liked the look of it too.

What's in the box: The Sierra follows the norm in terms of construction, as do the majority of the PMP range, using ply sided fuselages with balsa top and bottom, sheet tail surfaces and obechi veneered foam wings.

I was pleasantly surprised at just how comprehensive the kit was, ranging from the well finished wings with false TE fitted (under the veneer - a nice touch ) to a full accessories pack including wing bandages, torque rods and Mylar hinge strip. All the materials were of high quality and the fetish of machined components was very good. A full size plan and a 7 page leaflet giving suggestions for construction, finishing trimming and flying were also included. The plan gives handy construction and rigging tips and would also be useful should you be unfortunate enough to write off your fuselage; replacement wings are available from PMP, showing yet again their commitment to the beginner.

Fuselage Construction From the outset I decided to build the model for toughness so chose to use PVA throughout with the exception of Aliphatic for joining the wings and fitting the leading edges and tips. I used masking tape to hold the balsa components in place whilst drying.

The fuselage construction is 1.5mm ply sides and 5mm balsa bottom (10mm at the nose) and 6mm top decking. Care had to be taken when positioning the centre section formers but the decking and bottom presented no problems. I fitted additional structure in the tall section to support the control snakes and the fin base and also re-profiled the base of rudder to improve ground clearance altering the skid to suit. Additional fillets were added at the tailplane/rudder joints. Fitting the wing bolt nut plate as per the plan ensured sufficient clearance for the aileron torque rods.

Wings: As mentioned earlier, the false trailing edges are already fitted. The ailerons are controlled by torque rods and these were embedded in the centre section TE using the supplied hardware. The leading edges were pre-shaped and only required sanding to their final profile. Once the wings were joined, but not bandaged, the wing servo box was cut out and lined with sheet balsa epoxied in place. The wing bandages (supplied) were applied as per the instruction sheet - I have read conflicting reports about using a double bandage but it does make sure that the flying loads of the wing are more evenly distributed than using a single width bandage; rather like the function of a spar. I used a sandable resin and achieved a good finish across the centre section..."

Supplementary file notes

Review.

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