Foamy Factory 40" version
A fantastic 3D Park-Flyer that can do it all!
So you want to build a 3D Electric? Keep on reading!
Airframe Material: 6mm Extruded Poly-Styrene (XPS) Isoboard
Brush-less Motor: Model Motors Mini AC 1215/16
Batteries: 3Series Etec Lipo 1200mAh (3S1P)
Gearbox: GWS 300 - C ratio [5.33:1] *(The D ratio [6.60:1] will work better but I can't find any currently)
Prop: GWS 10x8 Slow fly *(The 12x6 will work better with the D ratio gearbox)
Servos: GWS Narrow series x 4
Receiver: JR R600 6 channel
Amp Draw Static: With the C box and 10x8 prop it is 9Amps
All Up Weight (AUW): 350g without landing gear and 370g/13oz with landing gear.
This plane can also be flown in a 36" version with normal GWS 300 brushed motor and Nicad batteries.
What material do I use?
The ideal material to use is Depron (www.depronusa.com), but we don't get it in South Africa!
Depron specification says for the 6mm sheets it weighs 200 g/m2
So I started to experimented with various foams:
EPS (Expanded Poly-Styrene)
I tried all the available densities in 16, 20, 26 & 32 KG/m3
It is easily available from SAGEX and other foam manufactures.
I found the 32 KG/m3 the best, in 6mm sheets it weighs +/- 200 g/m2 close to Depron, but it is too brittle.
Foam Board
It is available in art supply stores like Herbert Evans, and you get 3mm and 5mm,and being "Art supplies" it is expensive.
It is covered by a paper card board on both sides.
To use it one first have to get rid of the paper by leaving it overnight in your swimming pool and then removing the paper.
It has a nice finish and is stiff
I found the 3mm too thin for THIS model and the 5mm to heavy at almost 370 g/m2.
XPS (Extruded Poly-Styrene)
This is what I have found to work the best.
The source I have found in South Africa is Isoboard www.isoboard.co.za
They manufacturer it in 20mm and bigger sheets, for insulation purposes.
It is too thick and needs to be ripped into sheets with a foam cutter, see diagram below.
Make sure you take the skin of first, since it is denser than the rest of the foam and the skin sheets tend to bend.
The inner foam pieces come out nice and straight & stiff in 6mm thickness and weighs close to Depron at 200 g/m2.
When you cut it make sure the wire is set to hot and keep moving at a constant speed otherwise it will form waves.
Once it is cut it might form what looks like fibre glass strands on the surface.
This is easily "polished" away with a dry cloth and the finish is smooth.
XPS cuts very easily with a very sharp hobby knife, as can be seen by the ailerons in the pictures below.
The bottom line is until we can find depron in SA the only stuff worth-while is XPS.
OK, how do I build it then?
Go to www.foamyfactory.com they have free plans available like the 3DFX and some commercial ones.(This plane is from a commercial plan)
Or go to www.rcgroups.com join the electric forum and search in the 3D electric and foamy forums for plans, there are many designs freely available.
Get some 6mm foam sheets as discussed above, or cut your own or get it cut by a CNC wing cutter.
Get some 4 or 5mm hollow carbon fibre tubes for the wing spar from the kite shop, try www.kitesgalore.co.za or www.hiflykites.co.za
Get some RC electric kit from your local hobby shop, I have found www.madmodels.co.za the best and close by me.
For glue one can use epoxy (heavy), or specific contact foam glue like 'UHU Por' from crafts-shops.
What follows below are my construction pictures with some notes:
The pieces marked out and some cut out.
The puzzle start to come together. I painted the surface before taping the hinges.
One can use any acrylic paint available from craft shops, I thin it out with 50% water.
The bottom with the carbon fiber tube spar installed.
My engine mount is thin ply onto two sides of a hardwood stick.
An easy Pull-Pull System. 15LB Strength Nylon coated Stainless steel wire from the fishing tackle shop.
Twist the ends together and put over an open lighter flame, the nylon melts and burns together.
The pin is thin piano wire in a Dubro quick link for easy tension adjustment.
Control Horns are thin ply wood cut too shape.
350grams AUW without the landing gear
