# Tag Info

15

Aircraft do not scale linearly, for a number of reasons. Most aerodynamic equations include a speed squared term. If you halve the speed, you only get a quarter of the lift and drag, so models tend to be lighter and less powerful than you'd expect. If you make a plane with half the wing span, it only has a quarter of the wing area. So now a half size model ...

12

TLDR; Aft CG means stalls are unrecoverable! Why is CG relevant? The plane's elevator is the control surface for pitch angle. The elevator is its own proper wing, and as such only has a certain amount of force it can develop before it stalls. Once it stalls, then pitch control is lost. Not a happy day. The force that the elevator must develop is the lever ...

10

You might be able to write custom flight control software for a multi-copter that would simulate this. You might get close just by radically limiting the pitch and roll rates and being gentle on the throttle. In either case it wouldn't be intrinsic to the design. If you want smooth, soaring flight, you'd be best to build a fixed wing model with a fairly ...

9

(Edit: The original version of this question asked about "drones" in general. This answer was based on the question pre-edit, hence the clarification of drones vs. quadcopters.) First, a word of clarification. A drone is just any unmanned aircraft. The specific type of drone you described in your first paragraph is called a quadcopter. Now, if you ...

8

Elaborating on @Robin's answer with the full effects of the cube-square law. If we were to construct a model aircraft at half the length of a full aircraft, the model would: Have half of the wingspan as the full aircaft Have a quarter of the wing area Have an eighth of the mass Counter intuitively, this means that the model has more surface area per ...

7

The decision between CW (clockwise) and CCW (counterclockwise) propellers has to do with the direction your motor/engine will spin, not really in regard to where you're putting the engine on the plane. CW props will create thrust behind them when spun in a clockwise direction, and CCW props will create thrust behind them when spun in a counterclockwise ...

7

So many different issues, I study a lot of the FAA regulations closely but have contemplated this same question a few times. The power and weight of gear is heavy, so to make it all the way around is not going to happen without a lot of hacking. (solar proof of concept or similar notwithstanding) Efficiency of solar (power and weight) is a problem. The ...

7

In case you would prefer an answer with citations (as different regulators have different views on this), at the following link is CASA web page regarding "Recreational unmanned aircraft (including models)". There is a link on this page to the "... rules for flying model aircraft and drones." - this phrasing demonstrates CASA consider ...

6

Technically, you could connect 2 motors if they're exactly the same and it will probably work. However, there is a good possibility of various weird things happening due to this. The problem with connecting more than one motor to a single ESC stems from how these motors are driven. An electric motor works by using electromagnetic coils to pull permanent ...

6

Maybe! Let's take a look at what parts from the RC car we might be able to reuse for an RC plane. You haven't shared any specific details about the RC car you're looking to salvage parts from or the RC plane you're trying to build, so I'm not able to make a specific analysis. RC Transmitter and Receiver One major concern is how many analog channels the RC ...

6

Strictly speaking, "Drone" refers to any unmanned aircraft that can fly autonomously. Usually, however, a drone is classified as any unmanned aircraft even if it requires a remote pilot's control. By this definition, yes, a fixed wing would be classified as a drone because it is an unmanned aircraft.

6

The main things you need are a motor, battery, electronic speed controller (ESC) and servos. The ESC sits between the battery and motor, and it also has a thinner cable that goes to the receiver. The wires from ESCs are often labelled, but if not, there will be two big wires on one end that are the input from the battery (red for positive, black for negative)...

5

Back in the early days of RC, people only had single channel radios, and vintage models were designed to be flown with only the rudder (and a small amount of fuel in the tank to limit the maximum height). Vintage models were typically high-wing with lots of dihedral and a forward CG to make them very stable. Car RC gear should be fine in this sort of model, ...

5

From a technical standpoint it is possible, but there are a number of considerations: Only need one ESC so lighter ESC needs to have a higher current rating to fully power the motors Motors must be identical (more of a problem if home-building with what's on the bench) Loss of redundancy (if a prop jams or motor fails, you have no thrust) Cannot use ...

4

Most forces in aerodynamics are proportional to area, speed squared, air density and a 'coefficient' that describes how efficient your object is. There's also usually a 1/2 for obscure theoretical reasons. If you work in metric, the density of air at sea level is basically 1, which takes that out of the equation. The maximum lift coefficient of an average ...

4

This paper (AE-74-1054-1) from the University of Tennessee has a graph on page 15 showing the best they managed was 1:17 with the step on top and 1:8 with the step on the bottom but these were at a very specific angle of attack, and about half that was more typical. The wind tunnel results show that for this new airfoil the lift/drag ratio is lower than ...

4

You can, but it's not recommended. First of, you will need an ESC that can handle twice the current of what one motor consumes. The motors will also be seen as one single motor by the ESC, so of one of them has an error or becomes out of sync, both of them will stop.

4

The largest difference is that in Reynolds number, which is the same issue that wind tunnel models have. The Reynolds number is linear in length, which for the wing is the chord length. So for example, a quarter-scale model will have a Reynolds number equal to one-forth that of the full-scale aircraft (in the same atmospheric conditions). The reason this ...

4

If a plane has a preference, it's probably for a clockwise prop. This dates back to before electric motors, when people hand-started glow motors. You'd kneel next to the plane, hold the fuselage with your left hand and flick the nearest blade of the prop down with your right hand (or a short piece of wood, if you valued your fingers!). That resulted in a ...

4

I'm afraid it's not that simple. As you mention, planes can fly with a fairly low thrust to weight ratio. Obviously gliders can fly with no power at all, so there's no critical lower-limit. The other issue is that pitch-speed is important - the prop needs to be producing thrust when the plane is moving, not stationary. Measuring static thrust only tells you ...

3

The premise of your question is based on fairly limited observation of aviation. First there are many fixed wing "drones". They just haven't been as prevalent in the consumer market as in the segments of the hobby market that grew out of the longstanding R/C aircraft hobby, and in the professional market. Next, in terms of rotary wing flight, it's ...

3

The key here is to understand pitch speed. The pitch of a prop is how far it will advance in one rotation if there's no slip, so a 5" pitch prop spinning at 15,000rpm will advance 75,000 inches per minute, or about 70mph. That means that when your plane reaches 70mph, the prop cannot produce any thrust. Now, exactly how much thrust is required to reach ...

3

This is an interesting idea and I think it could work. There are, however, a few things that are worth considering. First of all, a controller for an rc car will usually have only 2 or 3 channels. This is only a problem if you want more controls such as rudder, elevator, elevons, etc but if you only want to control pitch you will have enough channels. ...

3

Yes, it would! A YouTuber, Thomas Stanton, has actually built a helicopter controlled with reaction wheels in this video! However, for a fixed wing aircraft, you would also have to consider the location of the reaction wheels relative to the centre of mass, and you would most likely want to house the reaction wheels internally to avoid adding extra drag. ...

3

I've enjoyed the Great Planes RealFlight simulator for a number of years. It has lasted well and I like the included transmitter controller. It is not free nor cheap, but it will save you a lot more in RC models that you can bring home from the flying field ready to fly again (i.e. it will save you many crashes).

3

While I'm far from knowledgeable enough to give you a chart like you requested, I can do a general overview of the methods commonly used in RC modelling for airframe fabrication. I must begin with this: Almost all of these are applicable to an aircraft of about any size. It's even hard to tell which is better, they're all just different. So, without further ...

3

According to this page you don't need to register your drone "you’re only flying for sport or recreation, including model aircraft flown at CASA-approved model airfields". Since you're only intending to fly your drone in recreational purposes it seems like you don't need to register your drone even if it weighs over 250 grams. I am no legal expert ...

3

The image below shows a fairly basic fixed wing electronic configuration. Depending on your design you might not need it all, and for more complicated builds with flaps and retractable gear you would want more, but I think it is a good overview. For the most part, you should not need to solder; most hobby electronics comes with common connectors pre-fitted ...

3

Summary The necessary electronic components: Transmitter & receiver, ESC, motor, servos. (yes, it really is that simple) How they are linked together: basically; battery plugs into ESC input, ESC plugs into receiver, servos plug into receiver, and motor plugs into the ESC output. Detailed explanation The construction of a fixed wing can be fairly ...

2

Typically the motor will point down and to the right. There can be various reasons for this. I've included a plans excerpt from https://aerofred.com/details.php?image_id=91062 Downward angle Sometimes it's to align the motor with the true flight direction, because the wings need some AOA (Angle Of AttacK) greater than 0. In the excerpt above, you can see ...

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