Rc plane thrust calculator
Estimate Propeller's Static Thrust updated: December 14, Ambient Temperature :.RC Jet Engine Thrust Test
Altitude :. Barometer Pressure :. Prop Diameter :. Prop Pitch :. Prop Static RPM :. Estimated Static Thrust :. Supplied Power :.
Horse Power. Prop's Absorbed Power :. Static Efficiency :. Static Pitch Speed :. Level Flight Speed :. Max recommended. Some notes: A tachometer is needed in order to measure the prop's RPM. The propeller converts the engine's torque force into thrust force. It's rather difficult to predict the thrust produced by a propeller with accuracy, since props with the same diameter and pitch often have different blade shapes and areas and also may be more or less flexible depending on the brand and on the type.
So, the results here are therefore only approximate. The thrust produced depends on the density of the air, on the propeller's RPM, on its diameter, on the shape and area of the blades and on its pitch. Geometric Pitch is the distance an element of a prop should advance in one revolution if there was no slip. Mean Geometric Pitch is the mean of the geometric pitches of the several elements of the prop's blade. Slip is the difference between the prop's Mean Geometric Pitch and the actual pitch, which is called Effective Pitch.
Virtual Pitch is the distance a prop would have to advance in one revolution in order that might be no thrust.
During constant level flight speed, the thrust force is equal and opposite to drag. A static thrust to weight ratio greater than 0. However, thrust alone is not enough to guarantee the plane to fly, since other factors, such as the prop's Pitch Speed must also to be taken into account.
Unless it's a glider, the adequate Static Pitch Speed should be greater than 2. To produce the same thrust, a 6x4 prop needs about W at RPM. You may estimate the power needed if you know the static pitch speed and the thrust you need. Whereas a propeller designed for greatest efficiency at take-off and climbing with small pitch and large diameter will accelerate the plane very quickly from standstill, but will give less top speed.
The plane reaches max level flight speed when the Thrust becomes equal to Drag. To Main Page.Sorry, it's not that simple, and I don't think it scales linearly with blade. Honestly I don't have the answer right now for how to get this calculation to work for a 3-bladed prop. I'd need a bunch of data points so that I could tweak the correction factor for this equation in order to make it applicable to a 3-bladed prop.
Thinqer, since it's very good questions like yours that drive me to learn and think and explorer more, let me give a more lengthy explanation. Since a propeller blade is like a wing, it is nice to think of them as wings. This is a very good analogy, and is correct to think of them as such. One way of analyzing a propeller blade even involves slicing the blade into many many cross-sectional elements of a small, but finite depth, then analyzing them each individually as 2-D airfoils, multiplying the results by the depth to get 3-D lift forces, and summing the results of all segments to get the thrust summed lift of the entire propeller.
This is called Blade Element Theory. Now, it may seem logical to extend this comparison of propeller blades to wings in an incorrect manner as well.
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For example, if you have a wing of a given size, at a given angle of attack, and at a given airspeed, it will produce a certain amount of lift, L. If you have two of these wings separated by enough distance that they are each getting clean airflow, you will get a lift equal to 2L. Three wings will produce 3L units of lift, etc. However, this linear scaling does NOT apply to propeller blades. Five blades of a given size, pitch, and angular velocity DO produce more than 4 blades, which DO produce more than 3 blades, which DO produce more than 2 blades, etc, but the scaling is not linear.
The reason thrust or lift scaling is nonlinear is because the blades must occupy a finite amount of space, equal to the frontal, circular area of the spinning propeller, and the more area the blades occupy, the less area that air has to pass through the blades. At some point, adding more blades will produce LESS thrust, not more though this would have to be many many blades, blocking much of the frontal area. I derived my equation knowing that thrust is a factor of this disc area, as well as the velocity of the air moving through this area.
Note that the air moves from the front of the airplane, perpendicularly through the propeller disc, and towards the tail of the airplane. It can only approach it asymptotically. A 2-bladed prop with the same pitch and diameter and at the same RPM might produce an exit velocity of 0.
Now, to complicate matters, static thrust is proportional to the exit velocity squared, so in this example, the 2-bladed prop would produce 1. See how non-linear this is? If it were linear, a 3-bladed prop would produce 3x as much thrust as a 1-bladed prop, and a 4-bladed prop would produce 4x as much, etc. Now, in actuality, I do not know these exact relations, and I made up the numbers in this example to make my point. I need more data to get real numbers.
If you, or anyone else has a thrust stand and wants to take data on 3 or 4-bladed props, please do! You can click the link in my document above to add your results to my spreadsheet.As experienced modelers know, many aircraft fly better with the motor angled a few degrees down and a few degrees to the right.
These are two different axes of rotation. Torque roll is primarily countered by trimming the ailerons with some right trim, or adding a little extra weight to the right side of the plane, not by angling the motor to the right.
Relatively simple explanations of the primary factors requiring the right and down motor angles are:. P-factor, or Propeller-factor, is a relatively simple concept when understood, which states that for a clockwise-rotating propeller when viewed from the cockpitas airplane angle of attack increases, a LEFT yaw is produced due to a thrust differential the propeller creates.
Imagine looking at the airplane from the left side looking directly down the left wingwith the motor to your left when viewing the plane this way. This creates extra thrust on the right side of the plane. This creates less thrust on the left side of the plane. The right thrust angle counters this left yaw due to P-factor, for an upright, positive angle of attack.
Note: A Right-thrust angle would make the P-factor yaw worse not better if the plane were flying upside-down. Down-thrust angle:. The down-thrust angle is required primarily to offset the climb response of higher-speed airflow over the wings.
As throttle is increased, airspeed over the wings due to prop-wash alone tries to almost instantaneously make the airplane climb.
Down-angle counters this climb for increased throttle. Also, the aircraft will actually speed up, causing additional lift trying to make the plane climb. Again, down-angle counters this climb effect. Therefore, the down-thrust angle counters both the climbing effect, and some of the yaw due to P-factor! Torque is not why motors are often angled slightly down and to the right. Rather, the thrust angles are to counter the tendency to climb with increased throttle, as well as the tendency to yaw left due to P-factor being induced at positive angles of attack.
Skip to content. RC engines thrust angles, down and to the right, why? Dimitrios Katsoulis. January 14, RC Calculators. The RC airplane design calculator has been created in order to provide an approximation of specific airframe parameters.
Use this airplane design calculator to help you determine key airframe dimensions along with an approximate target weight and power for your radio control aircraft. The recommended build material when using the design parameters for the RC airplane design calculator is foam board. Building with foam board allows a lightweight, inexpensive and easy to build airplane. This airplane design calculator assumes that the shape of the wing is of a constant cross sectional area.
This requires the main airplane wing to be rectangular in shape when viewed from above and as pictured below. Each calculated parameter can be reviewed in the image below to better understand where the dimensions are measured from.
To use the calculator simply select the type of airframe that you are building. Next, enter the wingspan of the airplane you plan to design and make. The wingspan of the airplane is entered in imperial inches units. Airplane Design Calculator — Use this airplane design calculator to help determine specific dimensions of your design.
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Here is what happens when you don't store LiPo bat. Load More… Follow on Instagram. Trainer Sport Glider.Unfortunately most of them are not correct. P factor is short for propeller factor. Your plane is traveling forward. You pull up on the elevator, and now your plane is traveling forward with an increased angle of attack.
Therefore we point the engine to the right to counteract this force. So, why is right thrust needed? The propeller creates a spiral slipstream that surrounds the fuselage. Most planes have the vertical stabilizer on top of the fuselage.
The slipstream hits the fin on the left side, pushing it to the right, which causes the plane to yaw left. The engine is angled to the right to counteract this effect. But why do different planes have differing amounts of right thrust? The two main factors are the location of the tail fin and the ratio of airspeed to slipstream strength. High airspeed causes a straightening of the slipstream and thus less yaw, whereas low airspeed combined with lots of engine effort will have more side forces in the slipstream and create more yaw.
For examples of the two extremes, imagine a pylon racer vs a big, draggy biplane with a long, low pitch propeller. This explains why biplane designs sometimes call for as much as 5 or 6 degrees of right thrust, whereas very fast planes typically have little right thrust or even none.
Airfoil selection and wing location relative to the engine are the key factors determining the proper vertical orientation of the thrust line. For example, a typical balsa trainer needs a lot of down thrust. This causes a rotational tendency with the center of drag as the axis. The result is that the airplane pitches upward when the throttle is advanced, as if you were pushing forward on an object hanging from the ceiling by a string.
The high angle of attack slows the plane down, and the plane will stall or at least wallow around, or if the engine is very powerful the plane will go slow and climb like crazy. Pitching up and climbing can be mitigated by trimming the elevator down, but then you have a twitchy plane with a bunch of lift in the rear, and the nose drops when you cut the throttle and try to land.
If I trimmed the elevator down for speed it would drop like a rock when the throttle was lowered. The reason is because the floats added drag on the bottom, which brought the center of drag down closer to the thrust line projected from the back of the engine. Different airfoils behave differently as the angle of attack changes. For instance, the center of lift of a flat bottom wing moves as speed and angle of attack change.
Undercambered airfoils, depending on the exact profile, can be more affected by angle of attack and airspeed than flat bottom airfoils, but they also tend to produce less drag in general.
Symmetrical airfoils maintain the same center of lift at different angles of attack and therefore do not react much to changes in trim or throttle. Skip to primary content.Thrust-to-weight ratio is a dimensionless ratio of thrust to weight of a rocket, jet engine, propeller engine, or a vehicle propelled by such an engine that indicates the performance of the engine or vehicle.
The thrust-to-weight ratio and wing loading are the two most important parameters in determining the performance of an aircraft. For example, the thrust-to-weight ratio of a combat aircraft is a good indicator of the manoeuvrability of the aircraft.
The thrust-to-weight ratio varies continually during a flight. Thrust varies with throttle setting, airspeed, altitude and air temperature. Weight varies with fuel burn and changes of payload.
For aircraft, the quoted thrust-to-weight ratio is often the maximum static thrust at sea-level divided by the maximum takeoff weight. In cruising flight, the thrust-to-weight ratio of an aircraft is the inverse of the lift-to-drag ratio because thrust is equal to drag, and weight is equal to lift. Aerospace Engineering Dynamics. External links wikipedia. Solver Browse formulas Create formulas new Sign in.
Thrust-to-Weight Ratio. Solve Add to Solver. Description Thrust-to-weight ratio is a dimensionless ratio of thrust to weight of a rocket, jet engine, propeller engine, or a vehicle propelled by such an engine that indicates the performance of the engine or vehicle.
Related formulas. Categories Aerospace Engineering Dynamics External links wikipedia. Recently viewed formulas.New to RC flying? Get my popular ebook today, to help you on your way! More of a 'rule of thumb' than a hard and fast rule, the Watts per pound rule is one that lets you determine the power output needed for your electric rc airplane, to give it the performance that you desire.
Here are some Watts per pound values that should put you in the right ballpark for your particular plane By working around those categories you should be able to decide how much power your rc airplane needs to perform well, but it has to be said that those values aren't set in stone. They are very good starting points though. Over-propping an electric rc airplane is one sure way to burn out the ESC because the motor is forced to work harder than it's designed for, and so it tries to draw more current than you calculated the ESC to handle.
Incidentally, a Watt is the correct unit to measure electrical power and Watts are calculated by multiplying the voltage V by current in amps, for which the proper symbol is 'I' but you'll also likely see it written as 'A'. If you're looking for the IC internal combustion equivalent, 1hp horsepower is equal to W. The only sure-fire way to determine how much power your particular setup is producing is to use a Watt meter.
This useful little tool actually essential if you do want to start experimenting with different EP setups connects between the flight pack and ESC, and will give you various readings throughout the power range.
Simply connect it up and power up your plane, and read off how many Watts are being produced. Above: an RC Watt meter is essential once you get in to doing your own electric power setups. It's worth noting that although the Watts per pound rule works on the actual flying weight of the airplane, the more realistic and accurate reference to a plane's performance in relation to its flying weight is called the wing loading.
The larger the wing area and lighter the plane, then the lower the wing loading will be and vice versa. A lower wing loading means slower take off capability and better flying performance in many ways.
But for the purpose of calculating power requirements for your model, in terms of the Watts per pound rule, work with the actual weight of it and don't worry about wing area or loading. If you're a complete beginner to the hobby with your first RTF rc planethen you won't need to worry about Watts per pound or wing loadings just yet. But as you get more in to the hobby, do take the time to understand and know how to use these important calculations.
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