Designing a Kite for a Truck Adventure

[WhatmoughG]

Hey,

I am embarking on a drive to the arctic circle. I have spent a bit of time googling looking for a kite to pull behind my truck to film the adventure and can't find much useful information.

Is there anyone that could design or point me in the direction of a place to design a decent kite to pull behind( and above) my truck with a ~2kg camera lens. Maybe a little extra payload to accommodate a gimbal.

 

[strive]

Well 2 kg is actually quite a decent payload for a (relatively) small kite, but the main problem here would be stability, because the towing vehicle generates considerable vortices. Thus the kite will have to fly quite high above and far behind the car, which means every gust of wind will move it so far sideways that it might be difficult to keep the camera on the car (if you want to film the car).

If you just want to film the surrounding scenery, sideways movement is not problematic, but you’ll still need automatic stabilization of the camera, because there will be a lot of shaking.


Another problem is getting the kite in the air. You will need someone to help you with that when there will not be enough wind.


The last problem is landing the kite safely – without breaking the kite or the camera, and without it hitting the car.

So preferably you would need some means to control the kite, thus my bet would be to go with a more rigid structure – a glider (with rc). This would also eliminate the takeoff and landing problems.


If you give more specific demands (video quality, size, weight, complexity, price), you can get better answers.

 

[WhatmoughG]

Flying high above the vehicle is what I am looking for. I guess, how high above should be determined by vortices perhaps as you say they are a considerable problem. This will help determine the lens and camera that I use.

I never considered vortices so that is valuable information to think about while flying whatever I finally end up with. On the ice road there should be semi trucks that will be coming from the other direction that will have an even larger effect than my own truck.

The idea of the kite is to get a wide angle video of the truck with the surroundings as it is driving.

I will mount a gimble on the kite which will allow the camera to stay level and properly oriented even if the kite pitches and rolls. It will also have rc to alow to control of the camera orientation

A glider is probably more what I was thinking too. I imagine a wing with skis on it for takeoff and landing. Pulled by 2 (or more) cables that are on either side of the wing to help keep it centered behind the truck.

One Idea that I have that may help stability is if the towing cables actually continue past the glider to a sled that stays on the ground underneath and behind the truck. This might allow me to control the height of the glider by changing my vehicles speed.

I would probably like to be traveling around 40km/h to 60 or 80.

 

[strive]

When you said 'polar circle' i thought it would be a desolate road, not a two way road…

You will be traveling at 10 to 20 m/s and so will be the aircraft… if it hits an oncoming car it will do quite some damage. In worst case scenario it can be deadly; not to mention it’s probably illegal.

 

[WhatmoughG]

There will be lots of driving on desloate roads. It probably would be wise to not use it anywhere where there's a chance of other vehicles

 

[rcgldr]

Why not use a radio controlled model (electric motor so cold isn't a problem)? For 40 to 80 kph, some type of aircraft as opposed to a multi-rotor would probably be better. To make it simpler to fly, you could also consider using a 3 axis gyro so that the model is self stabilizing.

 

[WhatmoughG]

I was thinking something that is pulled with cables from the truck would be better because it would only require one operator, just for controlling the camera Gimbal. Also I thought it should be a little cheaper...

 

[rcgldr]

One issue is trying to make a glider that is stable while being towed at 40 to 80 kph, and you'll need an operator and/or 3 axis gyro to keep the glider stable and an operator for the camera.

 

[WhatmoughG]

What would the the person operating the glider be doing? Are you saying that it wouldn't be possible to have a glider that stays on course by itself? Thanks

 

[rcgldr]

Are you saying that it wouldn't be possible to have a glider that stays on course by itself?

The closest example to this is a free flight model, but those fly at two speeds, one setting for climbing and a second setting for gliding (this is handled by a one shot timer). In this case you have a tethered model operating at 40 to 80 kph. It's going to wander about among all three axis, roll, yaw, and pitch. I'm thinking pitch stability is going to be the main issue.

For a normal glider, the pitch stability is trimmed to result in level flight at a specific speed. Going slower results in the glider pitching down, which increases it's speed back to its trimmed speed, going faster results in the glider pitching up, which decreases its speed down back to it's trimmed speed.

To deal with a range of speeds and to deal with the tension of a tethered model, somone or something will need to adjust the elevator to maintain level flight and avoid pitching up or down. Turbublence and crosswind components will affect all 3 axis, which is why I mentioned a 3 axis gyro. There would still need to be an initial trimming setup to coordinate the gyro with the response rate of the control surfaces. The yaw axis would have to allow the model to yaw in order to follow the truck if the truck turns or if there's a crosswind.

 

[strive]

This problem is somewhat similar to the problem of controlling the fuel line during mid-air refueling.

Also, we could look at our aircraft as a pendulum (since it will naturally sway in a similar manner).

If the camera is self stabilized, the sideways and the vertical movement will not bother us much, thus we only need to limit the swaying motion, not prevent it completely.

As the car will accelerate and the planes altitude increases, the downward force (due to the tether) will increase, thus limit the max altitude. As long as the horizontal and vertical stabilizers are effective enough the swaying should not be a problem. And sufficient roll stability could be achieved by a high wing back-sweep.

What needs to be done is something like the Argo (row), or a towed sonar, except that we want it to fly.
http://www.naval-technology.com/contractor_images/6831/images/99900/large/1.jpg

It’s doable without the need for an operator (provided ±10° sway is permisable), the only problem is with the landing.

 

[WhatmoughG]

10° of sway should be fine, the gimbal will be able to handle that much.

Do you know of a platform that could be modified or a kit that would be suiting or do you think this is something that could be built from scratch easily enough?

 

[WhatmoughG]

Researching my trip I have found that the speed limit on lots of the ice roads is actually only 25km/h

 

[strive]

I don't know of a suitable existing aircraft, but it’s worth checking around.

With 25 km/h you’ll be hard pressed to make anything fly, it’s not impossible, but it would be far easier to have a powered rc plane that is not tethered to the car.

Before rc transmitters were widely available, people used to fly powered airplanes that had several tethers by which they were controlled much as kites are. The default mode of such a plane was to circle above the person controlling it (it could circle stably without any input from the controller). This could be adapted for when you are traveling at low speeds, however achieving stabile circling might be difficult due to the forward motion. Check the history of model planes, perhaps it yields something useful to you.

Most available rc aircrafts don’t have a high enough payload capability, thus it will probably have to be built from scratch. The plane itself should be quite cheap and easy to build, however I don’t think it’s design is that straightforward, it would require a few calculations and a test or two.

 

[rcgldr]

This problem is somewhat similar to the problem of controlling the fuel line during mid-air refueling.

For a probe and droque system, the drag from the drogue (like a shuttlecock) keeps the end of the flexible line near horizontal. The receiving aircraft intercepts the line and attaches to it. For a flying boom, there are movable airfoils near the end of the boom and an operator on the sending aircraft has to control the boom.

... sufficient roll stability could be achieved by a high wing back-sweep.

any passive geometry for roll stability will be affected by a cross wind component, causing the aircraft to lean away from the cross wind (roll downwind), just the opposite of what would be wanted.

As the car will accelerate and the planes altitude increases, the downward force (due to the tether) will increase

Tension in the line will be proportional to the lift minus the weight of the aircraft (in the direction of tension). I'm not sure what the ideal location for the tow connector on the model should be. For a tow where the glider follows behind and slightly above the towing aircraft the tow hook is in the nose. For a hi-start type launch (similar to a kite being launched), the tow hook is in front of the center of lift, usually close to the center of mass.

With 25 km/h you’ll be hard pressed to make anything fly ...

That's fast enough for a model aircraft with a light wing loading. To carry a load, it's probably going to need to be a larger model, with a wing span in the range of 2.5 to 3 meters.

Before rc transmitters were widely available, people used to fly powered airplanes that had several tethers by which they were controlled much as kites are.

I'm not aware of such models. There were/are "U" control models, where the pilot controls the elevator on the model via a pair of lines that feed through guides on the innner wing. Sometimes there's a third line in the middle, usually for throttle control. The rudder is slightly offset so that the model yaws a bit outwards to keep the lines taught. The lines provide roll stability. There are also free flight models that are completely passive. For roll stability they use dihedral in the wings. For pitch stability, the center of weight is in front of the center of lift, and the "elevator" is trimmed so that the model flies level at a certain speed. For yaw stability, weathervane effect from the vertical tail surfaces are used, but the rudder is slightly offset since the goal is to have the model make large circles in the air. The models aren't always completely passive, as there's usually a timer device that sets the trim for the powered or launched climb, then when the timer expires, the trim is switched to glide mode. For the completely passive models, the motor is just strong enough to produce the speed needed for a climb and not too fast which would result in looping.

 

[strive]

For a flying boom, there are movable airfoils near the end of the boom and an operator on the sending aircraft has to control the boom.

Exactly, and as we do not have to hit a small target, only keep the plane within a desired ‘’window’’, a mechanism could be made which would turn the control surfaces in the direction to turn the plane towards the center of that ‘’window’’. This is not a solution by itself, but it limits the extent of the planes movement, thus it also limits design problems.

any passive geometry for roll stability will be affected by a cross wind component, causing the aircraft to lean away from the cross wind (roll downwind), just the opposite of what would be wanted.

True, but an effective vertical stabilizer would turn the plane into the wind and counter that. As the tether also pulls downwards (and as long as the tow connector is below the center of lift), the plane should orient itself into a relatively stable position (after a period of time). Also, the flight will never be ‘’smooth’’, rather it will adopt a flight mode similar to a Dutch roll.

That's fast enough for a model aircraft with a light wing loading. To carry a load, it's probably going to need to be a larger model, with a wing span in the range of 2.5 to 3 meters.

The construction has to be very durable (since landings will probably be rough) and it’s always beneficial to keep it cheap. Thus the plane + payload would weigh somewhere around 5 kg.
For this a 2 m˄2 wing area is wise, it can be done with 1 m˄2, but due to structural and logistical problems (landings and transport), high aspect ratio wings are problematic, thus I would start with a tapered delta. A 2.5 m span is probably a good tradeoff between structural/logistic problems and aerodynamics.

I'm not aware of such models. There were/are "U" control models, where the pilot controls the elevator on the model via a pair of lines that feed through guides on the innner wing. Sometimes there's a third line in the middle, usually for throttle control.

I was referring to the U-control models, but didn’t know the name. Some of them had additional controls like flaps and rudder, although I’m not sure of what benefit the letter was.

 

[rcgldr]

I was referring to the U-control models, but didn’t know the name. Some of them had additional controls like flaps and rudder, although I’m not sure of what benefit the letter was.

The rudder is fixed to produce outwards yaw to keep the lines tight. Flaps could be used to shorten takeoff and landing distances. One of the contest types for U control models is called carrier deck, emulated with a limited length take off and landing zone.

Researching my trip I have found that the speed limit on lots of the ice roads is actually only 25km/h

At 25km/h, you might want to consider a multi-rotor model. You could probably attach a light tether, such as mono-filament fishing line to the "nose" of the multi-rotor to get it to follow the truck. You'd want a multi-rotor that can self stabilize, but disable the heading (yaw) axis to allow it to follow the pull of the tether.

 

[WhatmoughG]

We have a multirotor but I'm not sure if we want to use it with a tether behind the truck..

I think a tapered delta design with a couple of skis for take off and landing is what I should go with. I'll try for a 2.5m^2 Like you're saying strive. I should be able to get something like that built pretty quickly.

 

[strive]

The necessary wing surface area depends on the wing geometry and the chosen airfoil.
Which airfoil have you chosen?

You will need a very effective tail section.
Which geometry and airfoil have you chosen for it?

 

[WhatmoughG]

I'm searching the internet for plans for somthing that fits your criteria that I can use or scale up. I'm not an engineer or anything so I pretty much need to copy a design 100%

 

[rcgldr]

We have a multirotor but I'm not sure if we want to use it with a tether behind the truck.

You could do a trial run, first with just the tether connected and the truck not moving, then try moving the truck slowly to see of the multi-rotor remains stable. The multirotor already has a 3 axis gryo, and if it can compensate for the external load, it will end up very stable. Again you'd want to set it up so that it remains level, but allow it to yaw and transverse to follow the tether.

 

[jthiede1]

The camera kite...did you find anything that worked WhatmoughG?