This plane was intended to be a high efficiency's slope soaring aircraft and because of such does not have mounts for a motor, but a conversion for one would not be to difficult to come up with if someone is interested in that. The idea behind it was to come up with a lighter way to manufacture 3D printed aircraft (as the existing ones on the market are remarkably heavy) and the logical way to do this is to reduce printed material. The final product (though still a bit heavy) should be within the acceptable wing loading for a slope soarer. Because of this the aircraft uses a traditional spar and rib technique. The plane was intended to use a V-tail system but that is an area that still needs some work and I will update if I get a chance to work on it. Otherwise someone would come up with a design themselves or maybe use balsa wood to make one.
The choice for the elliptical wing (besides looking awesome) was for efficiency sake as an elliptical wing has the lowest theoretical Induced drag (more information about it here https://www.grc.nasa.gov/www/k-12/airplane/induced.html). This wing shape comes at a cost and that happens to be stall characteristics. Too try and not bore you to much, basically, an elliptical wing stalls the whole wing simultaneously meaning no control suddenly and wing drop. Normally this is counted with wing tip twist, where the tips of the wings are twisted down so they have a lower angle of attack, but who wants to waste efficiency on safety... just don't stall it right?
As far as assembly goes it is fairly self explanatory, all parts only fit in one spot. Some parts need doubling up like the joiners of the fuselage. Also something to note is that when you wish to print the second wing some parts need to be mirrored in order to work. The wingtip, back plates and ribs with servos all need to be mirrored in order to work. The groves on the front of the ribs are intended for a 2mm solid round carbon fibre rod and the hinges for the control surfaces are all made from 4mm hollow round carbon fibre. A good tip when working with carbon fibre is to epoxy the ends to try and stop splitting which occurs relatively easily.
Airfoil: Eppler 193 (http://airfoiltools.com/airfoil/details?airfoil=e193-il)
Weight (Theoretical) : 800g
Lift Distribution: Elliptical
Root Chord: 0.2m
Control Surfaces: Flaps, ailerons, V tail (or traditional empennage)
2x 6mm hollow box section carbon fibre
1x 10mm hollow round carbon fibre
4x 4mm hollow round carbon fibre
2x 2mm solid round carbon fibre
6x 9g Servos
and your own Battery and ESC combination.
This plane uses a covering film and though I have not yet gotten up to this stage of construction Kraga has a good tutorial on it that I would recommend looking at.
Any questions about anything to do with the aircraft or potential ways to improve the design feel free to contact me.
Design has been changed so that the main wings now have a set angle of incidence. The angle of incidence is 5 degrees, chosen because it is the max lift to drag of the eppler 193 (http://airfoiltools.com/airfoil/details?airfoil=e193-il) airfoil. I have not printed out the new fuselage myself so if any issues can be found please tell me and I will fix them.
Also I have now altered the wingtip because it was a surface (which my printer read fine, but others might not) so I have redone it so that it is now a solid object instead.
I have not flown this plane myself yet because I have been busy with uni. There may be issues with this design that I not found yet, build at you own risk. I am planning on finishing my own one during the next uni holidays and I will update the files if i make any design alterations. Otherwise have fun with the parts, love to see if anyone can get it to fly!
WANHAO Duplicator i3 Plus
All parts where printed with a single wall thickness (0.4mm for me). I printed bottom and top layer height so that about 3 layers occurred (0.6mm for a 0.2mm layer height) and found this to work quite well. As for infill I normally used about 10% for most fuselage and wingtips, but I did print the back fuselage higher as all of the forces from the wings and tail transfer into that one piece. One weird thing with the printing that I found (But this could just occur on my dodgy Chinese printer) was z axis shrinkage. I found about a 1.5% to 2% shrinkage in the z axis and when you are printing of 180mm high parts that can cause a significant difference. I noticed it most in the control surfaces so if you are noticing all your control surfaces are 20mm short maybe try multiplying the z axis (and only z axis) by 1.5%.