Strong Light Weight Filament and Design Help For Designing RC Airplane

[Kevparang 10]

I need to find an material that is lightweight and very strong. I also need to bee able to smooth the layers out so it is like an injection molded part, because I am designing an RC Airplane that can hold 50KG/110 LB of weight. I need to find a material that matches my requirements of this project, help with designing the plane. Anyone who is an expert in electronic for the controller or who have flown RC Airplane/Drones/Helicopters are appreciated. Aerospace Engineers are also needed. This is for an event or contest between my friends.

Any help or ideas are appreciated.

Other Information:

The two printers I can print on are

RoBo3D R1+Plus

robo3d.com

Build Volume

10*9*8 inches with a heated bed of 8.4*8.4 inches

Monoprice MP Select Mini

monoprice.com

Build volume:

4.7*4.7*4.7 inches

[Kevparang 10]

My printer temperature can go to 290C hotend and 90C heated bed. It is glass.

[gr5 962]

I have a few thoughts. First of 100 pounds is - wow - a very heavy plane. Where are you going to store and build such a thing? I guess a garage because you will probably need a big door.

Anyway, stay away from CF (carbon fill) filaments as they are no stronger and no more stiff (and stiff is bad for filaments usually). Nylon is amazingly strong due to it's flexibility but not my favorite material for quadcopters because it's a bit too flexible. Still it's amazing - you can drive a car over pretty much anything made with nylon and it will flatten but bounce back to it's original shape.

Really I would stick with PLA for the strength as it's hard to beat. But I would mix it with CF rods that you can buy from places that sell RC kits. Those rods are really amazing and you can integrate them into your designs. For example when making the fuselage have many rods running the length of your fuselage such that they somehow attach or latch onto the PLA fuselage. You can use the CF rods for cross bracing as well.

Really it's hard to beat balsa wood (coated with soemthing to add strength) when it comes to light weight and strong.

As far as "injection mold" smooth - you could use PLA/PHA and completely submerge in acetone. There's a lot of discussion including helpful videos in this topic:

https://ultimaker.com/en/community/10412-acetone-finishing-on-pla

Or you can go the ABS route which is easier to process with acetone but ABS you will probably find has horrible layer adhesion unless you enclose your printer and turn the fan almost completely off. It takes a while to learn a new material. ABS is excellent for aircraft - it's a tiny bit more flexible than PLA (but same strength) and that tiny increase in flexibility means it is much much less brittle (think crashes).

[Kevparang 10]

Yes, It will either be displace on the wings or one on the plane, or in the plane. Pretty hard to take off. I still need to figure electronics to hand that, we might be lowering it to 20 pounds because you need a permit to fly and it is going to be expensive. I am just doing a competition with my friends.

[Project4558 4]

Did you have a design in mind? I printed and flew a small lightweight model about 4 years ago, Printed in sections on my UP! Plus printer. For both the wings and fuselage I printed the ribs, leading and trailing edges, as well as the nose and tail of the plane. Linked the fuselage with CF Tubes (as suggested above).

Then I covered it with solarfilm (a common RC plane wing skin material) which adhered to the ABS really well and shrinks when heated to form a tight skin over the wings and fuselage. Worked for me, printing the wings solid or hollow was too heavy for the size of model I had designed.

CJ

[Project4558 4]

Ah! I found some old pictures! Here is the tail, aft fuselage and part of the aft wing with the solarfilm covering.

Here's an exploded CAD view of the model from sketchup. Tandem wing. Flew well when I had it.

CJ