Need to lift 20 pounds of aircraft in the air

[kevparang]

I am doing a competition with my friends can anyone help me make a plane the is 20 pounds. I am an intermediate pilot. I have tools and a 3D Printer.

 

[wilmracer]

Are you talking about a plane to lift 20lbs, or a plane that is over 20lbs? 20lbs is actually not THAT heavy when you get to larger planes.

What are the rules for your competition?

 

[kevparang]

Okay, so the weight of the plane is 20 LB it is not lifting anything. I will probably use a heavy battery and some weights. They rules are the plane has to fly for 20 minutes, does not need to do acrobatics. If needs to be at least 5 feet wingspan, and 1 foot height. Max 7 feet wingspan and 5 feet high. The Plane must be at least 20 LB it cannot be more than 30 LB. It has to glide for 30 seconds.

 

[kevparang]

I need to make it for $50, that is one rule too.

 

[mybad]

I need to make it for $50, that is one rule too.

... for the airframe, I assume.

Is the object of the competition to simply BUILD something within those specs, or are you competing for time, distance, or whatever?

Well, as a starting point, I plugged some numbers into WEBOCALC and came up with the following.


20 lb total weight
7 foot wingspan
20 inch chord
Gentle scale flight of 20 minutes

here is one solution ...

Exceptional Outrunner motor 180 kv
10S 8000 battery
47 amp used (use 60 amp ESC)
21/14 prop

84 watts/lb
27.4 oz/ft2

gives 250 oz thrust for gentle scale flight
stall speed 26mph
cruise speed 64 mph
15-26 minute flight depending on throttle use

Good Luck!

 

[kevparang]

We will do a race, but you have 2 years to build. Well thanks.

 

[Fluburtur]

You would probably be better making a competition of making the smallest plane with standard size stuff (35mm motor and 1300mah battery and 9g servos)
Now, that would be interesting because it would get a pretty high wing loading.

 

[kevparang]

Well then I would have to tell my friends to change the rules with me. Now this is some thinking because of the wind shape....

 

[Hai-Lee]

You do not state if the $50 is to include any electrics or if it is just for the bare aircraft.

Given the information you have provided though I would lean towards a multi-wing Aircraft perhaps even a Sopwith Triplane.

Plenty of available wing area for the span and given that a nice slow glide and sink rate. Dihedral for a little additional stability
and a simple box type fuselage construction. With the lower per wing load you can also make the wing structure a little less complicated and heavy. You could also fit functional wing bracing to enhance its realism or scale appearance as well as reducing the wing inner complexity.

Because of the triplane layout another benefit would be a large cavernous fuselage with tons of room for balancing weights FPV or just plain old flight video recording.

You even have enough cord to play with undercamber wing construction to further enhance its low speed handling characteristics.

I will watch to see what solutions you and your friends come up with.

LAND SLOWLY and SWING A BIG PROP!

 

[kevparang]

It is for the bare airplane or airframe.

 

[Hai-Lee]

Sounds doable. Should be enough margin to allow for the wings to be removable for transport.

Let us know what you decide.

"Coming down in one piece is not the problem. Being in one piece after the landing is".

 

[kevparang]

Okay.

 

[mybad]

Since you have two years to design and build, you might want to try something the old-timers did in the day of free-flight. They actually designed an airfoil in the oversized elevator, thus further decreasing wing loading. Not sure how you determine ideal CG in such a case.

A classic example was the Lanzo Recordbreaker.

https://www.youtube.com/watch?v=vwqGTDHuWCA

http://www.rcgroups.com/forums/showthread.php?t=1197784

http://www.rcgroups.com/forums/showthread.php?t=2635040

 

[Ketchup]

Ideas

Massive guinea pig! Build a giant guinea pig and put a HUGE battery in it for weight and flight time, use 6 channels and make the cargo bay working (like peter did) for more weight and cool factor, also, with the last channel, flaps, because the plane might not fly without them (you should also try fixed leading edge slats)