Fly Electric!

'Bounce'


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'Bounce' is my best aeroplane! It is a 3D model designed for EPP foam. It flies really well with a CD-Rom motor and Lithium cells. The main advantage of using EPP is that it is much more resilient than Depron, hence the model's name. Being flexible it survives most crashes although does tear occasionally. EPP is almost half the weight of Depron although you tend to use more because it is less rigid.

The plane is designed for flat sheet EPP from Flying Foam in the USA. You need one 3mm sheet and half a 6mm sheet per plane. They have minimun order quantities so plan to build at least two and share the rest with your mates. Thin sheets are now also available from FlyingWings in the UK although they don't currently list 6mm (but do have two colours!). Other sources of EPP are on my Links page but I don't think any others sell thin enough flat sheets.

With a small brushless motor the plane will prop hang with ease, knife-edge and performs extremely well indoors and out. To make a rigid enough wing using 3mm EPP it needs to be dual skin. A single piece folded over yields a blunt leading edge which I think provides a nice transition from forward flight through 'high alpha' to full vertical hovering. The wing is 605mm (24") in span and 200 sq in area.

The plane weighs 167g (5.9oz) with three 4.4g servos and three 340mAh Lipols (heavier with 9g and larger batteries obviously). I use cells ranging from 340-830mAh with 450-600 being the best. 6g servos are OK for indoor use but tend to suffer from blow-back on rudder in the knife edge and flutter on elevator in wind. 9g servos, particularly on rudder and elevator, are recommended for outdoor 3D flying.

The wing has six 6mm EPP ribs. A hollow 3mm carbon spar provides strength with 3mm EPP vertical 'webbing' between the ribs. This spar must be placed inside the wing at the top (not bottom) so that internal bits of the wing can be cut away to accommodate the battery. All components are glued to each other with contact adhesive (I use 'EvoStick' or UHU POR allowed to dry 10mins to make joins instant). After gluing all the bits to the one skin I roll the bottom onto the top surface with a sheet of ply underneath to help fold the entire wing in one go (don't pull too much or it will stretch and distort). A sheet 300x600mm will make one wing. The ailerons are 6mm EPP hinged with five or six Mylar strips on each aileron glued with UHU Por or epoxy.

The fuz has evolved a bit. I started with the box structure used on similar Depron models (Ultimate and Mumbo Minor). However this was not rigid enough for EPP. The plans show the latest design which is a 'diamond' shape at the back. To make the fuz rigid enough it has 2mm carbon rods stuck inside each side. Flat carbon would be easier. A 6mm EPP 'spine' is sandwiched between these carbon rods (similar to a the sheer webs in a wing). If you use round rods you need to cut a recess in both edges of the EPP spine for the carbon to fit into (so that the EPP spine can reach the sides).

The sequence is to glue the EPP doublers and carbon spars to each side with contact adhesive. Glue the two sides together along the length of the spine, obviously with the spine between them. Allow to dry. Pinch the top and bottom of the fuz together to form the diamond shape. Glue these joins with a bead of Evostick or UHU POR. On the bottom you should only join the rear half because the front half will be 'zipped' closed with velcro. The top transitions from a diamond shape to a square at the firewall.

You should now have a fuz which is glued the full length of the top and only the rear half of the bottom. Push the wing through the opening and glue it in place. Mount the stab and rudder. The tail rotates on a 2 or 3mm carbon spar through an appropriately sized tube. Place the motor, battery and servos in roughly the right places to determine where the CG is and whether you want the servos moved forwards or back. I suggest a fairly rearward CG on the plans (30-33%); you might like to start with 25-30% until you are used to the model.

Hopefully the pictures will help illustrate the construction I have tried to describe but send me an email if something is not clear. As usual you may build the model but may not profit from the design. Plans in various formats follow. On the PDF's you probably don't want to 'fit to paper' as this may distort the size. Page 1 should print a reference line to check. Email me if you are having problems.

Format Free Plans
'PDF' A4 paper 37kb
'PDF' Letter paper 36kb
CAD 'DXF' version 119kb

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