- The plan for Renaissance is one of the FREE pull-out plans with RCM&E's July 2018 issue.
Having created a plan, it is reasonable to expect some changes to occur. Although I’ve tried to think ahead, the practical build of the model will inevitably throw up unforeseen issues.
I should briefly touch on CNC or laser-cut parts. There are a number of companies that will take your drawings (even freehand) and produce a set. I regularly use this approach as it speeds up the build. I still make mistakes and then have to revert to transferring the shape from the revised plan onto the base material but, whichever way you choose, a set of parts is the first step in the construction process. Importantly, there’s nothing here that couldn’t be made by hand.
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A set of CNC parts was ordered for speed but there’s nothing here that can’t be cut with hand tools.
Where to start? Try to plan a logical sequence, the build process can get complex, so think it out ahead as far as you can. Since everything attaches to the fuselage then this seems to be the best starting point.
From the beginning this model was to be electric powered, however I now find myself fitting an ASP .52 four-stroke. This decision meant a redesign of the motor bulkhead (former F1) which needed to be sited further back in the fuselage and longer to reach the full fuselage depth.
Aligning the engine mount to F1 and drilling to suit fixings, fuel lines and throttle.
The forward fuselage showing balsa doublers to the wing seat that act as a base for the formers and assist in jigging the internal geometry.
FUSELAGE
Fuselage sides are 6mm balsa sheet with a 6mm square balsa lattice at the rear. This provides a light and strong structure with the lattice locating into cut-outs in the front sheet section. The top edge, being the datum line for the fuselage, allows for accurate alignment. The front section has a 3mm medium balsa doubler between F2 and F4 across the wing seat area and can be aligned and glued in place.
Starting to assemble formers to the fuselage. The wing seat doubler is an integral part of the structure to maintain alignment.
Former installation progression is straightforward as each jigs off the previous.
Triangular balsa reinforcement is glued into the corners at the rear of F1 and front of F2, F3 and F4. Two 6mm balsa wedges are used top and bottom at the rear of the fuselage to bring the sides together. These are glued and the fuselage ends clamped till dry. Remaining formers can then be slotted and glued into position down the fuselage aligned with the marks we made earlier.
The tail is brought together against a substantial wedge insert – top and bottom – giving a high contact area joint and clamped till dry.
Now 12mm wide strips of 6mm balsa are added between the longerons behind each former position top and bottom. To form the rebate glue joint for the top decking a length of 6mm square balsa is glued to the top datum edge of the fuselage leaving a 2mm depth for the sheeting to sit from F2 back to F7.
Each former, clamped till dry, ensures good tight joints and prevents movement resulting in a warped fuselage.
We can now fit the instrument panel and the 6mm sq. battens forward between the instrument panel and F2 and the 6mm sq. battens between F3 and F4. We can also add the 6 x 3mm batten in the top slot across each former including the top angled section to former F3.
We all make mistakes; former undersize was trimmed redrawn and a new top section attached with a bridging plate across the joint.
When dry we can cut and glue the 6mm balsa top strip extending from F4 to F9 then shave and sand the edges to align with the formers when dry. Next, I add the 6mm battens around the formers in preparation for the sheeting.
Moisten the outside face of sheeting helps it curve. Pin or tape in place and allow to dry before gluing will make life much easier with those difficult curves.
The rear top sheeting is from 2mm balsa with grain running along the length. Due to the curves a card template makes cutting the shape easier. Moisten the outer surface and tape or pin in place and leave to dry, this will help the sheet conform to the shape and make it easier to glue in place once dried.
Diagonal cross- bracing, measure carefully to keep joints tight to maximise strength.
We can now fit the 2mm sheeting that forms the cockpit area from F2 to front of F4, flush with the edges of the 6mm strips. Make a template and trim the opening to final shape.
Undercarriage next, a 6mm ply undercarriage mount using some triangular balsa section around the inside joints to strengthen.
Final sand of the cowl sat on the fuselage so the shape can be blended.
The fuel tank/battery hatch is made using a former to the rear of F1 and another to the front of F2 each spaced by a thickness card to give clearance. I use Sellotape on the top of the fuselage sides before cutting and gluing in place the 6mm square cross battens linking the formers together. When dry sheet with 2mm as per previous sections. The hatch should now be able to come away freely (Sellotape and card removed).
Temporary engine fit to work out clearances for the cylinder head, and needle.
A cowl is made in much the same way only forward of the front former we glue laminates of soft 6mm balsa to form the nose, 6mm battens between formers and then 2mm sheet around. The lower section of the cowl is made of two 6mm balsa sheet laminates on the inside face of the fuselage sides forward of F1 and then two 6mm balsa strips across the front edge internal sides and then a further 6mm strip to the front edge. Basically building up a thickness to be carved and sanded to shape. Then I’ve added 6mm soft balsa to the underside of the engine bay back to the undercarriage block before carving and sanding to shape.
Final fit is not too bad, a little excess to ensure cooling and access to fixing bolts to the mount.
Next a temporary fix of the engine and mount to trim the cowl and fuselage side for clearance around the cylinder head and needle valve as necessary. Both hatch and cowl are retained by self tapping screws into 2mm ply plates glued into the inside faces of cowl and hatch, these align with further 2mm ply plates on the inside of the fuselage sides.
Both engine and mount were removed and the internal areas given a coat of laminating epoxy to fuel proof.
Undercarriage plate and underside of cowl. A cooling slot needs to be cut but now sanded to shape.
The undercarriage is made from 3mm aluminium sheet, cut, folded and drilled to fix with self tapping screws. Two 4mm axle clearance holes allow a 4mm piano wire (bent to shape) and retained by a saddle clamp in the centre (see pic). The piano wire gives the undercarriage a degree of spring that aluminium on its own would not. This is a job for the hacksaw, vice and much patience. Measure twice and cut once as they say.
A simple wire joiner for the elevators, note ply facings to add strength.
TAIL
The tailplane is built over the plan using 6mm medium balsa throughout. I start by cutting and pinning a strip to form the trailing edge. Then add the centre sheet section and tips. The leading edge strip can then be added, followed by the horizontal and diagonal braces and left to dry. Trim the curves and round off the leading edge. Trim away the centre area to align with the top longerons on the fuselage for a snug fit, central and square to the fuselage. The elevators are made from a length of 6mm medium balsa leading edge with 2mm medium balsa centre sheet cores and then 2mm balsa strip ribs top and bottom, 1mm ply plates are then added to reinforce the wire joiner position and location of the control horn. The leading edge can be rounded and the elevators halves sanded to a general taper of 2mm at the trailing edge.
Bend up a U-shape 3mm piano wire joiner for the elevator and drill and recess into the leading edge at the centre section. Glue the wire joiner in place with epoxy and leave to dry.
A commercial tail wheel with the wire slotting into the rudder for directional control.
Fin and rudder follow the same basic construction process. Note the solid sheet lower part of the fin that will sit directly on top of the tailplane.
For additional support to the fin and tail we need to create a slot from scrap soft balsa block glued to the rear of F9. Use scraps of 6mm material covered with Sellotape to simulate both tail and fin before gluing the block in place. The Sellotape should stop parts sticking together so that, when dry, the scrap pieces can be removed with ease. Add a small 6mm balsa block at the rear so that we can now carve and sand to the fuselage shape. We can cut away the rear scrap later before covering.
A commercial wire tail wheel was added fixed to a 3mm ply plate on the underside of the fuselage, the wire extension being bent to slot into the rudder for control.
I chose to fit the control snakes for elevator and rudder, supported down the fuselage at various points, the open rear structure making access easy.
Well, every plane needs a pilot and this guy seems to fit quite nicely.
WASHOUT
Before the top wing sheet is added I’d suggest a little washout. What’s washout? Washout adds a slight front-to-back twist into the wing raising the trailing edge at the tips by a few degrees each side. This has a few effects, but the most useful for model aircraft is that it changes the angle of attack of the wing tip relative to the centre section so that, as we approach the stall with the nose of the model raised, the centre region of the wing should stall first so we avoid the dreaded tip stall. The secondary effect is that the reduced angle of attack of the tips in normal cruise flight effectively reduces drag.
In this case a simple block of 6mm balsa acting as a spacer under the trailing edge of the last ribs will create the twist needed once the sheeting is glued in place. Start with the trailing edge and then leading edge strips, centre regions and then cap strips between, wait till dry and then repeat for the other side.
WING
The wing was built in two halves before bringing together with main spar and rear spar braces. As usual the first step is to create the necessary parts, i.e. ribs, spars and braces.
To start the front a 6mm square spar is aligned with the wing centre line and pinned down over the plan. Use the wing ribs as a guide, position and pin in place the rear lower spar.
The first wing panel half pinned to the work surface. Ribs positioned onto the base spars and main spar brace glued at the centre line.
Glue the two 3mm ply plates for the aileron servo hatch to the spars and then glue the wing ribs down over the spars. The first two ribs are cut to give clearance for the main 3mm spar brace so these ribs can only be glued to the rear lower spar at this time.
Now add the 6mm square rear edge that butts to the end of the ribs and then add the two top balsa spars. We need to sand the angle at the centre section to the dihedral required. The 3mm main spar brace can now also be glued into position behind the main spar aligned with the centre line and clamped till dry.
Sheeting to the underside and front spar brace that incorporates rear fixing of the wing locating dowels.
The rear short spar brace can also be added in a similar fashion as this will assist when we bring the two panels together, but leave the thinner top brace till after the panels are joined. The leading edge is cut from 6mm sheet and can now be butt-glued to the front of the ribs having first added the front section ribblets for the first two rib positions.
Remove the wing panel and repeat the process with the exclusion of the wing spar braces. Take care with spacing of the first two ribs and alignment to the wing centre line.
Front dowel fixing plate that aligns with the fuselage, dowels locate into forward spar brace for maximum security.
When the wing structure is dry we can then marry the two halves together by securing the panel without the spar braces to the bench and then sliding the second panel with braces into position. Check spars, leading and trailing edges match the dihedral angle of the brace and, when happy, apply glue to all contact areas, support and clamp in place till dry. Finally add the forward 3mm ply spar brace that will support the twin wing locating dowels to the front of the main spars and the rear ply spar top brace.
The wing will remain quite flexible until we have all the sheeting in place so its time to shape the leading edge with a razor plane and sand to align with the profile of the ribs.
Wing bolt fixing plate and control snakes fitted and routed to avoid clashing with bolt holes.
To keep things straight start by sheeting the underside of the wing first, one panel at a time. 1.5mm medium density balsa is cut and glued flush with the trailing edge and leading edge of the rear spar. Use the same technique for the front sheet from leading edge to the rear of the main spar.
Further sheeting is then added spanning the front and rear from the wing centre line out to the 3rd rib and again at the wing tip inboard to the 2nd rib. Add 1.5mm x6mm wide caps strips between front and rear, the aileron servo hatch cap strips being positioned flush to the edge of the ribs such that a 1.5mm ply plate will sit flush onto the ply supports in the wing for screw fixing. When the underside is complete and dry we can repeat for the opposite panel then turn the wing over and fit the 9 x 38mm trailing edge section at the centre region.
Sheeting the top of the wing as per the underside but this time ensuring the wing panel is pinned flat to the building board as the wing will become quite rigid once the top sheeting is glued in place.
The leading edge can now sanded to a round form and we are ready to look at fixing the wing to the fuselage by means of two dowels and wing bolts.
So far so good I’d say.
Former F2 has wing dowel location holes pre-drilled. The wing front dowel plate from 3mm ply needs to sit inside the fuselage flush against F2 with aligned holes. Align with dowels and then tape in place such that the wing can be positioned onto the plate and sit in the correct position on the fuselage. Check that the wing sits central and square to the fuselage and then glue the wing to the wing dowel plate and leave to dry in position.
When dry the wing can be removed and 6mm balsa wedges shaped to match the leading edge added each side. The top sheeting can now be removed from behind the leading edge out to the edge of the first ribs and back to the main spar brace. Two dowels can then be cut such that they locate into the holes in the spar brace and extend 6mm through the front plate. Test fit and then glue in place. A little triangular balsa can be added for strengthening.
For the wing bolts fit a 6mm ply plate with balsa laminate glued in the fuselage relative to the trailing edge of the wing with the ply facing up. When dry, drill a clearance hole with the wing in position through the trailing edge and bolt plate. Captive nuts can then be glued with a small amount of epoxy into the balsa laminate and ply washers glued to the underside of the wing, assembly and left to dry.
Wing tips are from 3mm balsa glued onto the outer ribs centre line and then 6mm balsa wedges top and bottom aligned with the spars and leading and trailing edges.
Final details included 3mm balsa sheet added to the underside of the fuselage leaving a 1mm gap from the wing trailing edge and ending at Former F4. This was given a radius to the rear and then sanded to a taper flush with the underside. A similar balsa plate was added forward of the tail wheel ply plate. Final job is to sand off all the rough edges, assemble and stand back and take a look at our efforts.
In the July 2018 issue article I’ll take a look at covering, equipment installation, pre-flight checks and the maiden flight reports and thoughts. ✈
