Foamboard Spitfire Build

 
The full size SZD-30 Pirat is a single-seat multipurpose glider aircraft from the Polish firm PZL Bielsko which first flew in 1966, and started production in 1967.

This RC scale version of the SZD-30 Pirat is 3.2 metre wingspan or 21% scale.

Wing area:  62sq/dm, 960 sq ins

Weight: 2.6/3kg

CoG: 76 to 80mm from leading edge

Servos: 2x Aileron min 5kg, 1x Elevator min 2.2kg, 1x Rudder 4kg, 2x Airbrake 2.2 kg, Tow Release 4kg (based on deflection at 70kph) 

This kit  includes:

*Fuselage – CNC Foam cores ready for 2mm balsa planking. $50

*Wings –Built up, kit includes ribs, leading and trailing edges, main spars and shear webs. $60 

or

EPS foam version cores, jackets and end ribs $50

*Tailplane – EPS foam core ready to be laminated with 1.0mm balsa– $10 

*Fin – EPS foam core ready to be laminated with 1.5mm balsa $10

*3d Printed canopy frame $10

*PVC Clear Canopy $10

*12mmx10mm Ali Joiner Bar $5

This kit does not contain electric/electronic components, balsa planking, wing skins, covering or glue.

Planning the fuselage construction:

The foam fuselage consists of 4 pieces, front and back left side and front and back right side.

The first action is to:

•  Glue the fronts and backs shells together using Titebond Original, PVA or 5min Epoxy.  Leave overnight if possible...Care should be taken to ensure the pieces are aligned. The top of the fuselage should be a straight line. Use pins at an angle across the join to hold the parts inplace.
• Planking is best started with Fuz half shell flat on the bench. Start  planking using 10mm wide 2mm thick balsa strip down the middle.(King Plank). As you work out from the middle the strips should get thinner. Maybe down to about 5mm toward the bottom and the top. Each plank needs to be sanded to shape and the bottom edge of the strip is slightly sanded to ensure no gaps are formed. Put pins at opposing angles every appox. 60mm. That should hold the balsa planks inplace until the glue dries.
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• Once the fuselage is planked then you need to cut in the wing and bottom keels. Start by tracing around the ply and then either with a router or knive make a 3mm recess. 
• Glue the ply plates inplace both side.
• Good time to make the wing joiner box using good quality wood glue not CA

Glue the ply 

Next prepare for radio gear and the option of a brushless motor up-front.

As a guideline only remove the foam needed to accomodate the servos, battery and RX.

The battery needs to at the front to help with balance.

A tow release system also needs to included. See picture as a suggested way to incorporate the tow release.

Also note how to include bracing and firewall if a brushless is to be installed. Note 2deg down thrust is required.

Setting up the fin.

Rudder servo in the back

Once the servo/ radio gear and battery access have been sorted it is ready to join...we used epoxy slow cure mixed with Qcells...... 

Fin

Rudder Construction

Start by gluing the leading edge and ribs onto the 2mm balsa middle silhouette.

Now turnover and do the other side


The tabs are removed and the 1/8" tube is tacked in place with CA.

Next the 6mm balsa false leading edge is glued in place.

Round off the false leading edge, sand all the edges flush

The 3mm balsa hinge tube support is then glued on the front with tabs in place.

The Wing

Wing sheeting : 1.5mm balsa top and bottom with 1.5mm caps on the trailing edge.

The same format for the wing tip. Note 1.5mm ply airbrake. The Leading edge can be formed from balsa stock or a harder material like obechi.

Foam Wing Planform

Built up wing getting started:

Titebond original is recommend for gluing the wing.

You may need to put a 6.5mm drill through the anti rotation holes to accept the 90mm 1/4" tubes.

It is good practice to put the panel together dry, before gluing.

Glue the leading and trailing edges in place. Good practice is to tack some of the tabs in place onto the building board with medium CA to stop movement. A small right angle set square should be used to ensure the ribs are vertical.

 Glue the two face ribs to Rib 1 and 2 making sure the 1/4" aluminum tube is in place to align the four rib pieces.

You can now glue the spars, joiner box, end ribs and false leading edge in place. Use clamps to hold the structure together while glue sets.

  The square Carbon joiner tube at rib 13 and 14 can be glue in. Note you need to make some packers to sit on top and bottom and connect the top and bottom spars. Hard balsa is fine......

The shears webs can now be glued in place.

The top drag spars (3x3 and 8x3) can now be glued in place...... 

Make sure to glue the lower square joiner in place and then glue the drag spare on top of the joiner.

Glue a 3mm balsa false leading edge to the 1.5mm leading edge. This give a better glue join to the 1.5mm balsa sheeting.

Long board sand the trailing edge in preparation on the 1,5mm trailing edge capping.

Glue a 1.5mm by 15mm balsa trailing edge cap to the the trailing edge.

 

The top sheeting, I used 1.5mm by 100mm starting trailing drag spar and finishing half way on main spar.

Next the trailing 8mm by 1.5mm balsa edge caps

Once the top is sheeted you can break the wing off the plan. Knock/Cut off the rib tabs, sand the false leading edge and lightly sand the underneath to ensure all parts are flush.

Now is the time to glue in 8x3 and 1/4" sub spars.

You can now cut out the airbrake cavity from the underside. Bay 9 to 13 on the spar line.

We can now fit the servo tray for the airbrake and sort out a wiring harness.

next leading edge

Foam Tail :0.75mm balsa skins pressed on to the eps foam cores with epoxy. Carbon strips are optional

You can mount a low profile servo in the tailplane, this is KST 08

We left the JR plug sticking out to mate with the JR plug in the fin.

Trailing edge is 35mm trailing edge balsa stock
Note the centre section has a combination of end grain/balsa 3mm ply and end grain balsa.

Elevator top hinged with covering

Airbrakes