quorneng
Trying to get a conventional 3D printed powered plane of a reasonable size (say 1000 mm span) below 250 g is hard so I wondered if it would be lighter to 'print' a conventional stick and tissue type structure.
I can print wing ribs with a strength and weight that is pretty close to balsa but the real test would be the spar given that most printers (including mine!) have a limited bed size. The maximum possible item length is 280 mm and only then by printing across the bed's diagonal.
After much experimentation this is the final result.
25Aug20a.jpg 
1000 mm span it weighs 220g with an 850 mAh 3s with a AX 1806 2100 kV motor driving a 6x4.
Using three 3.7 g servos it is flown 3 channel bank and yank as the V tail is elevator only. 
Apart from the glass fibre (fishing pole) tail boom it is all just printed PLA components (all 42 of them!) glued together with UHU POR.
To keep the weight of the printed parts to a minimum the battery sets the cross section of the fuselage. 
FuseMotor.jpg
The printed nose cowling provides cooling air for the motor and for the 10A ESC.
NoseCone.jpg
I would not claim it is any better than a conventional balsa stick & tissue plane but it is very cheap to make, in fact just the dope costs more than the PLA required to print the air frame. 😮
Still waiting for some suitable calm weather to make a video!
Quote 4 0
JettaManDan
wow...crazy that you went that far in weight savings. looks like it has paid off. hope we get to see a flight video!
My YouTube Channel - 250+ Video's! http://www.youtube.com/jettamandan09

I'm an R/C Junkie! 40+ planes - 12 Heli's - 6 multirotors - and ground vehicles galore! I've got issues.
Quote 0 0
solentlife
Bit concerned about using UHU por to join PLA ??? 

Usual recc'd I see is for CA .... 

I have to admit that online are various Wing Rib STL files .... so maybe not a bad idea to have a go for all sorts of designs.
I'll fly anything if I can launch it ! Youtube : solentlifeuk
Quote 0 0
quorneng
The trouble with CA is after a day or two it makes the joint rather brittle as it actually effects the PLA, particularly on very thin sections.
I did ensure the design of each joint gave as much glue area as possible and preferably in shear rather than direct tension.
I was surprised just how effective POR is indeed after a few days I found it was difficult to separate the joint without damaging the joint itself which is about as strong as is likely to ever be required.
The sub 250 g plane was actually a development of print techniques I evolved for a replacement test wing for a heavier plane.  
Wing1.jpg   
Same 1000 mm span but carrying over twice the weight.
SilverWing1.jpg 
No balsa or carbon just printed PLA bits glued together. The printed/tissue wing ended up some 45 g heavier than the Depron/Balsa original.
There is a video of it doing loops and rolls.
Quote 1 0
Dodgy Crasher
Gorilla glue clear gives a pretty strong joint too, I just bought some and it's pretty good, stick it on one section and apply water to the connecting piece.
I also put a smear of it over a small piece of paper onto depron, wiped it with water and it set clear but like a rubberised coating, still trialing it on different stuff,
I'm building a Bae Hawk and it's going to feature a lot in the build, but yeah UHU por is hard to look past,
Nice build that, all light and delicate 👍
Quote 0 0
quorneng
The fact the print/tissue wing was heavier than the Depron original bothered me so I went through the design to see where I could save some weight.
The final result was a tapered wing with a tapered spar as it better matches the bending load on the wing.
Ailerons1.jpg
Of course the printing is rather more involved as there are no 'common' parts, everything is different. 😄
It was made to be directly interchangeable, held on with 3 nylon M4 bolts, with the other wing sets. 
TaperWing.jpg 
The taper wing weighs exactly the same as the Depron wing although to be fair it does have slightly less area.
Overall this exercise has not really proved anything as a Depron wing has better aerodynamics and is certainly more resistant to both handling and hanger rash.
It is just a pity that the 2 mm thick Depron sheet is no longer available. 😠
Quote 1 0
JTiger
1000mm span < 250g sounds like it would be pretty floaty!
Quote 0 0
quorneng
JTiger
It actually flies surprisingly fast as the wing section is quite thin.
25Aug20a.jpg 
I now have a video of it flying.

Of course with only 220 g of inertia the ground slide on grass is virtually non existent. 😄 
Quote 2 0
JTiger
Very nice! Looks like a fun plane
Quote 0 0
mastermalpass086
Very nice concept, and surprisingly scale in its characteristics - I guess it has a similar relative density and power-weight ratio to a full size aircraft. I was expecting it to be as floaty as your An-2, what with being sub-250 with a metre wing span. Considering the thin wings, are the speeds we are seeing the minimum it can go at and be stable, or can it be floaty if you lower the throttle?
BRB - Building another nosecone.
Quote 0 0
quorneng
mastermalpass086
With thin (10% t/c root, 6.5% tip) and narrow chord (130 mm) wing its slow speed characteristics are limited. It stalls at a relative low angle of attack so limiting its slow speed flight.
The video is really only showing its 'cruising' speed. Full power was not used at any time as I simply did not want to risk breaking the printed wing on its second flight. 😉
Notice that when in the ground effect on landing it can and does slow right down.

The AN2 although 3.5 times heavier does have 4 times the wing area and a thicker 12% t/c wing section. In addition biplanes tend to have better slow speed characteristics due to the 'slot' effect of the wings.  Even then the AN2 only really 'floats' when the flaps are down.      
Quote 1 0