Construction Guide

Part I


The ZN Line Synergy is the latest in a long line of models designed by current F3a World and European champion Christophe Paysant Le Roux.  The Synergy is a development of Christophe’s Alliance; it incorporates a slight change in fuselage profile bringing the cockpit forward to increase side area and a change in wing span to improve snapping capabilities.


The kit is available from Probuild Aircraft or direct from ZN Line of France and is available at many different stages of construction.  For the modeller with a bottomless pocket it can be purchased finished and ready to fly, but be prepared to be on a long waiting list.  The quality of finish from Probuild and ZN Line has to be seen to be believed.  Unfortunately my Dads pocket isn’t that deep so I opted for the standard carbon kevlar fuselage with formers, sheeted wing panels joined with carbon, sheeted tail plane and rudder.  A lot of the hard work has been done but there is a lot more to do!


This model is being built with competition solely in mind and no expense or time is spared to make the bare airframe as light as possible.  The choice of materials and adhesives is all part of the process and I shall detail the strongest and lightest to use in each stage of construction.  The trimming of servo horns, cutting of unwanted material and using small amounts of glue all go to making sure everything is as light as possible.  Why does the model need to be so light?  Well, the lighter the model the easier it will be to fly.  For example in spins or snap rolls the lighter model will stop with the sticks as there is less inertia in the airframe.  At the top level over spinning by 15° can be the difference between second and first place.


My original ZN Line Synergy flown with great success to win the 2003 GBRCAA Masters League Title.


As this will be the second Synergy I have built in as many years, I hope to put everything I have learnt from the first build to make this model better in terms of flight performance and flying accuracy. Although the original did win the 2003 Great Britain Radio Control Aerobatic Association masters national league championship.  I am hoping to make the model lighter; at just over 10.5lbs the first model was heavy and really should have been lighter, so I hope to make improvements in weight, specifically on the wing and around the mounting of the tail plane.  I would also like to improve the finish of the fuselage; although the colour scheme was attractive I felt the surface finish could have been better, specifically the edges of the paint left by the masking tape.  I also believe the paint added unnecessary weight on the first build so I hope to use less paint to achieve a better finish.  The preparation of the surface to a large extent determines how good the final finish is, I will detail how I have tried to accomplish this and how to use as little paint as possible in a later article.  The layout of the radio gear on the servo tray could also have been better planned as the receiver installation was a little tight and didn’t leave much room for packing.  I hope to be able to make the installation neater, more durable and hopefully a little lighter.  With the increased power of the YS140DZ being used in my second Synergy and the plans to make the airframe lighter, it should give me the best possible chance in my first year in FAI; the premiership of F3a aerobatics.


The fuselage is moulded in Belgium by ZN Line and is a combination of carbon, Kevlar, and glass cloth along with foam inserts for rigidity.  Pascal Nowik moulds the fuselages; he works for Mudry Aviation who mould the cowls for the full size Cap 232.  The fuselage is received finished in white gel coat and is ready for the insertion of the formers and mounting of the wings, tail plane and rudder.


I always like to ease myself into the construction of a new model and I usually start with the cockpit.  The cockpit floor is first sanded ready for painting.  Numerous other methods can be used for covering the cockpit floor, felt for example or dolls house floor carpet, which can be obtained from your local Hobbycraft shop.  I prefer to paint, but it is a matter of personal preference as it is only aesthetics and adds very little weight.  Once the cockpit floor has been covered the pilot and cockpit panel can be added.  The control panel seen here is created in Corel Draw using numerous instruments from a flight simulator and printed onto Inkjet Vinyl which can be obtained from Overlander.  The control panel is then simply stuck into place.  Normal photo paper can be used and I have found that Pacer Slo-Zap works very well.  The scale pilot is a work of art in itself and very light and can be obtained from Probuild Aircraft Limited.  He can be glued in using five minute epoxy, the vibrations of the YS140L meant that my last pilot looked as though it may become unstuck, so two aluminium dowels are glued through the cockpit floor into the pilot. The cockpit itself is moulded from very thin tinted plastic.  This needs cutting to shape and is fixed using five minute epoxy.  A smooth finish is achieved with filler and then sanding.  To make sure the cockpit is not scratched while sanding the cockpit fuselage join, masking tape, the type from DIY shops is placed over the cockpit.  The filler is epoxy based laminating resin with very light fairing compound from Cherbourg or Fibretech.  Thixotropic agent can be added to thicken the filler so it doesn’t run.  After sanding the first stage of construction is complete.


Cockpit, panel, and pilot installed and ready for painting. The cockpit panel adds to the realism and is easily created on Corel Draw.


This is a good time to go round with the Dremel to trim of any excess material around the wing saddle, the belly pan and the nose of the fuselage.  All edges are cut to an overlap of 10mm and tidied up with some emery paper.


Before all the formers are inserted it is a good time to fix the belly pan as access becomes difficult with all the formers installed.  Trying to find 2mm bolts in the long dew soaked grass at 8.30 on Sunday morning preparing for a comp is not the best of starts so the belly pan bolts have to be retained.  The belly pan is fixed with five 2mm cap screws, these cap screws are made so they cannot fall out, this is done with two diameters of carbon tube, the smaller tube allows the Allen key to pass through but not the bolt head, and the second wider tube is just big enough for the bolt head to pass through.  An aluminium cup is placed on the bottom of the larger tube with a clearance hole for the 2mm cap screw.


Each assembly is then fixed into the belly pan with laminating resin and cotton fibres, two behind the wing, two just in front of the undercarriage and one right at the nose.  This provides a very secure mount for the belly pan.  The hole positions are marked onto the fuselage using engineers blue, this liquid is painted onto the fuselage and allowed to dry.  The belly pan is then manoeuvred into place and the bolts turned, this will scratch the engineers blue and leave a clear mark.  These can then be simply drilled and captive nuts inserted.  Other methods are available to mount the belly pan; MK magic boxes for example make a neat installation.


Retained belly pan bolts shown installed into the belly pan and a cross section of their construction.


The undercarriage is the next stage to be addressed.  The current fashion in aerobatics is for a fixed undercarriage, there are many pros and cons to fixed or retracts but the swept carbon fibre legs from ZN Line fit the Synergy perfectly.  The first job is to drill three holes in each mounting plate of the leg.  Three 4BA bolts will hold each leg in place.  Once the six holes have been drilled in the undercarriage the legs can be placed onto the fuselage and drilled through.  The undercarriage plate is from ¼” ply, and needs to reinforce the fuselage.  The ply needs sanding to the contours of the fuselage until it fits the inside bottom of the fuselage with as close a fit as possible to ensure the minimum amount of adhesive is used to fix in position.  The six holes are then marked onto the plate, drilled and six aluminium blind nuts were manufactured and secured into place.  Fitting the blind nuts before fixing the plate means I can bolt the undercarriage in place while the glue dries to ensure a perfect location is achieved.  The plate is fixed into place with laminating epoxy mixed with cotton fibres.  With the undercarriage plate secured a carbon/nomex saddle is added vertically into the fuselage for extra rigidity.


Undercarriage plate installed into the inside bottom of the fuselage, with captive nuts inserted and vertical saddle installed for strength.

Carbon ZN Line legs bolted to the undercarriage plate.  Domed Aluminium washers not only look good but spread the load of the three retaining bolts over a large area.


The kit also includes a set of spats which transform the look of the model; I do most of my flying off grass and have yet to crack a set of spats.  Carbon cloth and carbon tows are fixed inside the spat to help with durability.    The MK 55mm wheels and spats are attached to the undercarriage legs using MK wheel axles available from Probuild.


This concludes the first article in the Synergy build, in the next issue we shall deal with the installation of the firewall and engine.


Click here for Part II


The Original Series of Articles was published in RC Model Flyer

It is published here with the kind permission of Ken Sheppard. Editor - Model Flyer