First Fixed wing scratch build

[SGrog]

Good day all!

I have had some experience with fixed wing aviation in the past, and am hoping to build a large bird that would be intricate in terms of capabilities, but simple in design, etc. The plan I am designing, for the full scale design will have a 12' wingspan based off of my figures and the fuselage will be around 6 inches or a little more wide.

Before I build the giant, I am going to develop a scale 4' wingspan of what I intend to develop, and not put any of the advanced components on, as I will develop those separately on the side. I will primarily build it out of balsa, and there is a place locally that you can rent a laser cutter, which is what I plan to do.

My questions are how do I make sure I have enough support to hold up the wings under large wing loads; Second, Im guessing here, but the whole assembly might be 25-30 lbs, how would I choose motors that can produce enough thrust? Im not looking for acrobatic type characteristics, but something that would fly like a C-130 or similar aircraft.

General Information about final design:

• 12' wingspan, likely a root chord of 12-14", wing up high similar to a Cessna 206
• Likely powered by two electric motors, but would like to fly with one if one fails.
• Fuselage between 6 and 8 inches wide, and equally tall, up to 9 inches tall
• Fuselage would be around 5' long, with a twin tail like a B-25
• Retractable landing gear similar to a PBY Catalina
• Central "bomb bay" underneath wings essentially
• Rear camera pod that would drop down like a B-24 bottom turret when in flight
• Front mounted camera in nose
• Hard points if possible.

Again, I would not start out designing the above, but a basic flying proof of concept, and designing the gear, bay, and pod seperately, and integrating in the final design.

Is this unrealistic, or what are peoples comments?

 

[rcspaceflight]

Maybe it's just me, but a 12 foot wingspan with a one foot chord sounds like a very long and narrow wing. Also a 12 foot wingspan with a 5 foot fuselage makes it sound like it'll be a stubby looking plane.

Or are you trying to build a Tupolev ANT-25? http://en.wikipedia.org/wiki/Tupolev_ANT-25

I don't know about figuring out how much support you'll need in the wings. But the more the better. You'd want to be able to at least pick up the plane by having a hand under the mid point of each wing. Preferable under each wing tip. (You might need two people's hands for a 12' wingspan.) You could certainly get away with complete overkill with wing spars.

I think you'd want to look at wing cube loading for the plane too. You don't want it too heavy or too light. http://www.flyrc.com/index.php/wing-load-calculator/

A static thrust calculator will help to determine what sized motor and prop you'll need. But that's trickier to figure out. http://personal.osi.hu/fuzesisz/strc_eng/ I like to aim for a 1:1 power to weight ratio. Technically you look at thrust vs. drag, but with RC planes, even big ones, it's a lot easier and good enough to look at thrust vs. weight.

 

[SGrog]

It would be similar to the Ant-25, and I just kinda threw out 5' , but would likely go larger to if needed 6-7? Part of the reason I was thinking of such a long and narrow wing was it should be rather stable, and Im looking for duration aloft, as well as usable surface area. Long term goals for that plane will be to cover the wings in enough solar panels that in theory, once I get to a cruise alt, I could almost indefinitely stay aloft, Just an idea.

The Wing loading and thrust calculators are very useful, thank you!

 

[rcspaceflight]

Makes sense. I don't know if you read much about the ANT-25, but...

Maximum speed: 246 km/h (153 mph; 133 kn)
Range: 7,200 km (4,474 mi; 3,888 nmi)
Endurance: 48 hours

A 4,500 mile range is rather ridiculous. Especially for a plane built in the 1930s.

 

[SGrog]

Yep, I read a little about it, and was kinda going with that design, or it would look similar to the U2, the wings would be more boxy so that I could make manufacturing easier, and would have fewer jigs. Im looking for something that I could get long duration, and minimal speed out of, I kinda want to use it for just a test bed, so the fuselage would be modular, and I could add or subtract components. Ill throw up a concept design of what Im thinking later today most likely.

Quick example: