Just when you thought all Australian General Aviation manufacturers had gone to the same place as the Tasmanian Tiger, along comes Gippsland Aeronautics with their Airvan. As the name suggests this is a utility machine designed for no nonsense hard work in the less developed parts of the world where a payload may include all manner of hardware, from 200 litre drums to a fridge and, it's all made in Australia.
Gippsland Aeronautics already have a successful agricultural design to their credit and rumour has it that Cessna have expressed serious interest in acquiring the Airvan design lock stock and barrel. A not insignificant endorsement of the design although it would be a shame to see it go overseas.
I saw the prototype about two years ago at the Avalon airshow and mused over the possibility of constructing an R/C model. Nothing further happened until Airborne offered me an opportunity to build the prototype from their newly prepared plan. The chance to build what is probably the world's first R/C version of this interesting all Australian general aviation design was too good to pass up.
Airborne's Airvan is a sport scale model which I found a delight to build and fly. The construction is quite straightforward with nothing of particular complexity. Nevertheless a fuselage jig was very handy.
Commence by preparing a kit of parts and pieces. I photocopied the parts I wished to fabricate and then used spray adhesive to glue them to the wood. I then cut everything out using a powered jigsaw. Tip - leave a cm of paper all round when cutting out the photo copy, the paper tend to lift with the up stroke of the jigsaw.
Make a survey of required hardware. Obtain the necessary items either from your own stocks or your hobby shop and place everything into a plastic bag so it is all together and available as you need it.
The wing consists of a centre section, left and right panels. Build the centre section first.
Start by cutting out from 1.5mm balsa, the bottom sheeting for the centre section. From this cut out the recess for the servo and mark out the positions of the ribs. Glue dihedral brace D-2 in position on this sheeting ensuring it is square to the base. Fit the aft sections of ribs W-1 in place and glue up against the back of the dihedral brace D-2. Glue the centre section spars to the front of D-2 one upper, one lower. Fit the forward halves of ribs W-1 in place so the tags fit between the spars. Sheet the top of the centre section. Now, wedge up the lower sheeting at the leading edge until it is in contact with the underside of the ribs and glue. Glue the 6.5mm rear spar in place. Sheet the top of the centre section. You now have a complete centre section with the ends of the dihedral brace protruding from each side.
To achieve the necessary dihedral you should now construct a building board which allows the centre section to sit flat and an adjoining wing panel to be built at the correct angle. One wing only needs to be supported since you can complete one wing and then turn the whole job around to build on the other wing at the correct dihedral. The jig can be built from 19mm ply or similar. Mark the position of ribs spars etc. directly onto the building board and protect with grease proof paper.
Once the centre section is positioned on the board commence the wing panel by cutting out and positioning the bottom sheeting, pin it down. Position and glue the lower spar and glue it securely to the front of the dihedral brace, use weights to hold it flat on the building board. Glue in place the aft section of ribs W1, W2 and W3. Glue in the upper spar. Fit the forward sections of ribs W1, W2 and W3. Glue in the reinforcing pieces designated S4a. Now glue in the spar securing hard points S1. Wedge up the lower wing sheet until it is in contact with the ribs and glue. Fit and glue the upper wing sheeting.
Install the dihedral brace D1, followed by leading edge strip and trailing edge spars. Repeat this process for the other wing panel. Once both wing panels have been completed the wing can be removed from the building board.
Install the aileron torque rods in position on the back of the rear spar and construct the trailing edge pieces that fit between the inboard ends of the ailerons. Cut a slot in the back of this trailing edge piece to accommodate the torque rods, cut it into three sections, one for the centre and one for each wing and then glue it in place on the rear spar.
Apply the cap strips to the ribs and cut the ailerons and plane them to profile.
The wing tips on this model are a little different, the aim being to have the trailing edge of the wing tip piece rising all the way to the tip. It is a good idea to have a look at a picture of the real Airvan or those of a Britten Norman Islander which has an identical design to get a feel for the concept. Start the tip by making up a suitable block of balsa for each tip to a thickness equal to the depth of the wing ribs at the spar (deepest point). Mark out the wing tip shape in plan view and cut out. Now, offer the tip up to the end of the wing so that the bottom edge of the block is flush with the bottom of the wing. Mark the shape of the wing tip rib onto the tip block. Now carve and sand the wing tip block so as to follow the outline of the tip rib as marked, while retaining the high outboard trailing edge corner on the extreme end. You'll get the idea as you do it so you can't really go wrong. Complete both tips and glue in place on the ends of the wings.
Leave the wing here and build the fuselage to the point when it is time to build in the windshield area.
After you have completed the fuselage to the point of installing the windshield piece, position the wing and using F3a as a template drill the wing dowel holes through F3 and insert the dowels into the wing leading edge. You can now glue the wing dowels in place with the wing in position but be careful no to glue the dowels in the wing leading edge to F3.
While the wing is on the fuselage drill holes for the wing bolts, around these holes install the reinforcing disks as shown on the plan and then build up the over wing fairing from balsa.
Install your aileron servo and the wing is ready to cover.
Cut out the fuselage sides from 3mm balsa sheets. Standard stock sheets will need to be joined to make up the required depth. To get the sheets to fit against each other neatly use the same technique as is used to get balsa sheeting for foam wings to fit nicely, that is, overlap them and cut them both with a sharp knife. Cut out the fuselage sides. Mark on the insides of the fuselage side the positions of the formers and the internal fittings. On each side glue in place the 9.5mm triangular section balsa around the inside edges and notch behind F6 to permit a later bending of the fuselage sides. Glue in place the wing seating pieces designated WS.
Now get your fuselage jig out and dust it off. Set the fuselage side in the jig and trial fit the formers F3 through F6. Also trial fit parts FS1 and FS2. When satisfied, glue formers in place with everything held square by the jig. Once dry, set in place and glue FS2 (2 off). Insert parts FS1 (4 off) through F2 into F3 and glue.
When pulling the sides together start at the front. Set your jig to bring the sides evenly together with F1 in position. The Airvan needs a fair amount of downthrust, 5¡ in fact and also 2¡ of right thrust set by F1. Once happy, glue in place with epoxy and leave in jig to set. The pieces called FS1 are also glued (CA).
Before pulling the rear end sides together, first make up the block which fits between the sides (I made mine hollow for lightness). Now paint a 50/50 mixture of ammonia and water onto the outside of the fuselage sides at the point were you want them to bend, this expands the fibres on the outside, facilitating the bending process. Using your jig, slowly bring the sides together using the rear block as a guide to indicate when sufficient bending has been applied. The aim is to get a sharp bend at F6 with the sides straight as they run back to the tail. Finally install formers F7 and F8.
Next install the 6.5mm square spine top and bottom followed by F5. Install the undercarriage mounting block. Sheet fuselage top and bottom but do not build up windshield area. Now is the time to position the wing and drill the wing dowel holes as described in the wing building section.
Making up the windshield area is a bit of sculpture's job. Glue in place some balsa block and sand them to shape. Again a picture of the real thing helps to get the shape right.
Make up the engine cowl from balsa as shown on the plan and install hardened areas to take the securing screws. Cut holes as necessary to get the cowl around the engine.
Make up the undercarriage as per plan or you can do as I did and make it out of 3mm aluminium strip from the hardware shop. The axles are turned down high tensile bolts.
Finally, don't forget to fit the strake under the tail.
Make up wing structure from a combination of hardwood and aluminium strip. I have the struts permanently screwed to the wing and use PK screws as drop through pins to secure the inboard ends during rigging.
I used and OS 25FP and required custom muffler to clear the firewall.
The tail surfaces are straight forward and easy to construct over the plans on a flat surface. Sand to shape then fit hinges, control horns, and elevator joiner.
Once final installation is complete cover in your favourite film. I used one of the two flying prototypes as a guide for the colour scheme, which was overall white with red and dark blue trim. The colour markings are made up in solar trim as are the windows. Use Windex sprayed on to allow you to slide the pieces of trim sheet into position on the model, when you are happy squeegee out the water, working away from the centre for adhesion and removing any bubbles. The Gippsland Aeronautics motif is cut from a pamphlet and sealed under a piece of clear contact. The word AIRVAN on the tail is done the same way after AIRVAN was typed up on computer and printed out.
Some of my colleagues expressed scepticism at the use of an OS 25FP as a power plant. As it transpired however this was adequate power but not so much as to desperately and unrealistically overpower the machine. Anyway I like sport scale models to have a realistic power to weight ratio.
After a few taxi runs I opened the throttle for take off. The model tracked straight as an arrow. I allowed plenty of ground run to build up speed and then rotated gently. The model lifted off and climbed very realistically to a safe height. In flight the model proved to be highly manoeuvrable and great for low flying were it can best be seen. Aerobatics are not an issue since the full size machine is not aerobatic.
Time for a landing. I cut the power to descend to circuit height and noticed the model lost height fairly rapidly - lots of drag from struts and wide fuselage don't you know. I flew a fairly tight race track circuit and closed the throttle as I turned onto finals. The model tracked to the threshold and rounded out nicely for a touch down on the main wheels - very satisfying.
The landing approach is relatively steep and it's nice to have some throttle in hand to stretch the glide when necessary. Be wary if the engine fails, this model will drop a wing if stalled.
The Airvan is just the thing for the modeller who is looking for a sport scale type that is economical in construction time, flies nicely and looks good in the air.
SPECIFICATIONS Air Van
Type: R/C Sport Scale Model Wingspan: 1.5 metre Length: 1 metre Engine: .25 - .40 Radio: 4 function R/C required
Plan No. 647
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This page was last modified on the 15 January 1999