Fixed-wing VTOL Tadem-wing

[rekklesna]

Hello,

I wanted some advice on a project I'm working on. I'm studying mechanical engineering and doing a senior capstone project in university. I am working on designing and building a VTOL fixed-wing drone for search and rescue applications. I'm restricting drone to fit within 0.5m x 0.5x so that the product is small enough to manuever through tight spaces. Additionally, I want to go with a quad motor set up so I don't need to worry about using the tilting mechanism for stability during hover. Because of this, I'm planning on doing a tandem-wing design where the motors are mounted on each wingtip and capable of tilting for forward flight and hovering. I have included some pictures of concept sketches.

I had some concerns about the design. Will there be any issues with having the tandem-wings on the same level? I'm wondering if I should include some vertical separation between the wings so that the airflow affected by the first wing is not going over the second wing, but I'm not certain how that will affect the hovering. I'm also not sure how I should deal with the CG. A tandem-wing aircraft needs a CG that is closer to the front so that the front wing stalls first, but a quadcopter needs a CG centered between the rotors. It seems difficult to balance both of these. Putting the CG forward will be really important for stability in forward flight, so I will probably do that, but I wonder how that will affect the hover control. If anyone has any advice on this configuration, that wold be much appreciated.

 

[Piotrsko]

Umm nope. Most tandems have the CG halfway between the two wings. Think "Dragonfly". If the wings are at least two chord widths apart, interactions tend to be minimal for most low speed flight but I can't see a reason you have to have them on the same horizontal plain. Also think of tandem as a really large surface horizontal stabilizer that has lifting capacity on the aft surface. None of this would hinder hover mode except draggy as heck on high G lift off. If youre using motors for vertical, stall is a non concern, you just add power to the stalled surface pair and use thrust for recovery.

 

[Scotto]

Hello,

I wanted some advice on a project I'm working on. I'm studying mechanical engineering and doing a senior capstone project in university. I am working on designing and building a VTOL fixed-wing drone for search and rescue applications. I'm restricting drone to fit within 0.5m x 0.5x so that the product is small enough to manuever through tight spaces. Additionally, I want to go with a quad motor set up so I don't need to worry about using the tilting mechanism for stability during hover. Because of this, I'm planning on doing a tandem-wing design where the motors are mounted on each wingtip and capable of tilting for forward flight and hovering. I have included some pictures of concept sketches.

I had some concerns about the design. Will there be any issues with having the tandem-wings on the same level? I'm wondering if I should include some vertical separation between the wings so that the airflow affected by the first wing is not going over the second wing, but I'm not certain how that will affect the hovering. I'm also not sure how I should deal with the CG. A tandem-wing aircraft needs a CG that is closer to the front so that the front wing stalls first, but a quadcopter needs a CG centered between the rotors. It seems difficult to balance both of these. Putting the CG forward will be really important for stability in forward flight, so I will probably do that, but I wonder how that will affect the hover control. If anyone has any advice on this configuration, that wold be much appreciated.

Hello and welcome. Your design change ideas all sound logical to me but I am no expert. A couple other things I notice is there is no vertical stabilizer and the wingtip is obstructing the flow of a big chunk of your propellers/rotors in hover mode.
Your post caught my attention because I started making something kind of similar based on the Blackfly. Its a tandem wing vtol but the motors dont tilt. Its more like a tail-sitter but a belly-sitter.
Im going to be trying to figure out Nick Rehm's dRehmFlight system to control mine. What is your plan for control?

 

[Scotto]

For a search and rescue drone I think a hot air blimp would be awesome because it could stay up for hours not minutes and with propane I think it would be cheaper to operate than helium. It just would not like wind. And people would be scared of it starting a fire, but gas and lithium are fine. nevermind

 

[rekklesna]

Hello and welcome. Your design change ideas all sound logical to me but I am no expert. A couple other things I notice is there is no vertical stabilizer and the wingtip is obstructing the flow of a big chunk of your propellers/rotors in hover mode.
Your post caught my attention because I started making something kind of similar based on the Blackfly. Its a tandem wing vtol but the motors dont tilt. Its more like a tail-sitter but a belly-sitter.
Im going to be trying to figure out Nick Rehm's dRehmFlight system to control mine. What is your plan for control?

Yeah I've thought more about the tandem wing design and I'm not entirely convinved it's worth it. If the two wings are too close it seems like the rear propellors won't be very efficient in forward flight since they are behind the front propellors. And having 4 tilt mechanisms would be a lot of additional weight. If I don't tilt the rear propellors, then that's extra drag as well. I might try a tricopter design with the rear rotor embedded in the tail surface.

I'm planning on using Ardupilot which has some VTOL capabilties (https://ardupilot.org/plane/docs/quadplane-building.html). Will be running it on a Navio2 flight controller.

 

[Scotto]

Hey, I made some progress on the BlackFly style plane. I tried flying it with no gyro just an 8ch receiver, and I managed to vertically take off and fly for maybe 45 seconds before crashing. It actually felt pretty close to stable flying, but the rates were too high and maybe a little tailheavy. Not too bad though, really. I was surprised it made it over the fence.

The fuselage aerodynamics were pretty crude, but I think I know where to put the battery now.