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Rigger Building: Understanding Propeller, Turn Fin, and Aerodynamic Influences
Translated from German for everyone's convenience:
Author: Oliver Siess
hydro.jpg
Neutralizing the propeller influences
If the shaft of your Hydros exactly in the middle (in the longitudinal axis) fitted (top view), the boat will inevitably lead to a slight right turn. This phenomenon occurs because as already mentioned by Radeffekt and its propeller (about) torque ago. Especially large diameter propeller generate considerable torque, for this reason, at Hydro boats preferably relatively small screws at high speeds (= low torque) is preferred.
Basically, you can resolve this problem by gently moving the rudder to the left so that the boat is in neutral position of the stick straight. However, this is the worst way, since this "obstacle", that is, the rudder, provide valuable input power is not lost.
A better solution for balancing the propwalks to the shaft holder or the entire shaft slightly (up to 3 degrees) to rotate to the left (limit) is. It is also possible to complete the off-center shaft, so not exactly to install in the imaginary axis of the boat. Depending on the size of the boat propulsion system is then (as seen from above on the boat) by 2-5 mm parallel set right next to the longitudinal axis.
In both cases, is counteracted by the eccentrically acting now thrust of the PropeIlers Radeffekt, at best, raise the forces (= straight).
With a rigid shaft system, this must of course be provided already during installation.
If this measure is not sufficient, other solutions must be applied.
Although used by most manufacturers an isosceles V-angle in the hydraulic structures, it is common for some outriggers and Hydroplane models to compensate for the breaking of the model to the right with different float positions. Here, the left float (V-angle) is made flat, resulting in a greater wetted sliding surface of this float and thus to a pull to the left. Here, too, raise the forces, while a perfect straight line is the result.
But as already mentioned, will then trigger the (counter) torque of the propeller pulling the model right, because this is the right float a heavier burden. To compensate, you can either trim weights in or on the left float attach or change the weight distribution in the body so that both swimmers are charged while driving back the same. With outriggers can also set the left float closer to the fuselage.
It is important that the various measures to neutralize the propwalk and the propeller torque are always executed in mutual agreement!
But it goes further, because no action without reaction! If the propeller torque lifting the front left float data, it of course, the stern of the boat pushed down slightly. A small wedge, mounted on the rear right side of the fuselage, can help build a counter-torque to the lift effect on the front float. The use of wedges was (and still is) widely used as Outrigger were unknown with rear support floats.
Which method for balancing the torque or the propwalks for your boat is the best that can be generally said of course not, but they should not as far to move away from the suggestions of the manufacturer.
Turn Fin.jpg
Cornering
If the centrifugal force pushes the body in turns out, it is necessary to create a pivot point. Since Hydros more to move across the water as through, measures are needed to enable a better cornering ability. Hydro One has to almost downright somewhere "hook" to the extent possible to limit drift. This function takes as already mentioned the turn fin. It should be something placed before the focus on the right float. Turn the fin is mounted too far forward, there is a risk that the boat runs out of the course. The performance of these typical "Einkringeln" can often be seen in such boats.
If the turn fin mounted too far back on the other hand, very much rudder is needed to steer the boat, which of course leads to a loss of speed. Normally, the fin on the back of the right float is attached rather close to the fuselage. However, when the fin is too close to the center line, this can raise the right float. To prevent this, you can bend the fins turn towards the hull to keep the swimmers below.
For the bending of the fin, there are three possibilities: The turn fin extends fully in 90-degree angle into the water, what more should be the exception, is on some boats but certainly the only way. The second and most common way is to make it in the direction of the fuselage up to 7 °. Another variation is the turn fin to the beginning of the paper in 90 ° angle into the water-dip and curve, only 1 to 2 cm under water from 6 to 8 degrees.
The boat should have after the attachment of the fin a turbulent ride, check to see whether the fin is aligned straight! Make sure that the front edge of the turn fin is behind the fixing points, as it usually begins to flutter and the boat does not run smoothly with increasing speed. Some swimmers have a back, the reasons of production technology from the bottom front inclined to the rear. This offers a turn fin, which is (viewed from the side) in the fixed angle adjustable so that the above problems are excluded.
The rear swimmers have the task of the boat in turns to keep quiet. Some hulls, the height of the float to be adjusted. If the stern of your boat drifts in corners too much, it must lie deeper. Then set the float at a lower depth to bring the stern deeper.
If you set focus and turn right fin and the boat still in turns with the tail "is", you can also create a longer rudder problem. The goal is to take the smallest possible turning radius, without straining the engine by immersion of the hull so strong that he will lose much speed.
So it is not desirable to reduce the drift effect too much, as it ensures a clean and quiet curves and an efficient power delivery.
Aero.jpg
Aerodynamics
As mentioned above, is a hydro really a ship in the traditional sense. It is more a successful combination of a streamlined ship design with smaller contact surface on the water and many aerodynamic flight characteristics.
The current "great" Hydroplanes the Unlimited Hydroplane class developed by Hydro-and aerodynamics with doctor and professor. What is left at the end, is much theory, which in turn are "tested" at the object must practice. In the area of aerodynamics can be "let off steam" as an ambitious model builder actually. Now, not just any Schifflesbauer the mainframe computer of the Max-Planck-Institut at home, and so one can only think of what you yourself have tried and what one's colleagues of the "model-flying craft" communicate can do.
In short: Do not engage in too many experiments!
Many hydraulic models are equipped according to the original with spoilers and flaps, as they behave aerodynamically, mostly at all not up for debate. What is forgotten is that the originals are developed in a wind tunnel to the last detail and adjustable-board computer, the various front-and rear spoiler while driving. This is of course the model is difficult to understand or because of model-specific problems do not partially realized.
The Rumpfanstellwinkel is a very important parameter for the "dynamics". An airplane flies because of the negative pressure produced and the pressure under the wings of a boost. The same applies to our model Hydros: a hull with a positive angle of attack will take off at a certain speed at a negative angle of attack it is pressed down. Sharp edges cause air turbulence, which means resistance. Rounded corners and edges to reduce drag.
Author: Oliver Siess
hydro.jpg
Neutralizing the propeller influences
If the shaft of your Hydros exactly in the middle (in the longitudinal axis) fitted (top view), the boat will inevitably lead to a slight right turn. This phenomenon occurs because as already mentioned by Radeffekt and its propeller (about) torque ago. Especially large diameter propeller generate considerable torque, for this reason, at Hydro boats preferably relatively small screws at high speeds (= low torque) is preferred.
Basically, you can resolve this problem by gently moving the rudder to the left so that the boat is in neutral position of the stick straight. However, this is the worst way, since this "obstacle", that is, the rudder, provide valuable input power is not lost.
A better solution for balancing the propwalks to the shaft holder or the entire shaft slightly (up to 3 degrees) to rotate to the left (limit) is. It is also possible to complete the off-center shaft, so not exactly to install in the imaginary axis of the boat. Depending on the size of the boat propulsion system is then (as seen from above on the boat) by 2-5 mm parallel set right next to the longitudinal axis.
In both cases, is counteracted by the eccentrically acting now thrust of the PropeIlers Radeffekt, at best, raise the forces (= straight).
With a rigid shaft system, this must of course be provided already during installation.
If this measure is not sufficient, other solutions must be applied.
Although used by most manufacturers an isosceles V-angle in the hydraulic structures, it is common for some outriggers and Hydroplane models to compensate for the breaking of the model to the right with different float positions. Here, the left float (V-angle) is made flat, resulting in a greater wetted sliding surface of this float and thus to a pull to the left. Here, too, raise the forces, while a perfect straight line is the result.
But as already mentioned, will then trigger the (counter) torque of the propeller pulling the model right, because this is the right float a heavier burden. To compensate, you can either trim weights in or on the left float attach or change the weight distribution in the body so that both swimmers are charged while driving back the same. With outriggers can also set the left float closer to the fuselage.
It is important that the various measures to neutralize the propwalk and the propeller torque are always executed in mutual agreement!
But it goes further, because no action without reaction! If the propeller torque lifting the front left float data, it of course, the stern of the boat pushed down slightly. A small wedge, mounted on the rear right side of the fuselage, can help build a counter-torque to the lift effect on the front float. The use of wedges was (and still is) widely used as Outrigger were unknown with rear support floats.
Which method for balancing the torque or the propwalks for your boat is the best that can be generally said of course not, but they should not as far to move away from the suggestions of the manufacturer.
Turn Fin.jpg
Cornering
If the centrifugal force pushes the body in turns out, it is necessary to create a pivot point. Since Hydros more to move across the water as through, measures are needed to enable a better cornering ability. Hydro One has to almost downright somewhere "hook" to the extent possible to limit drift. This function takes as already mentioned the turn fin. It should be something placed before the focus on the right float. Turn the fin is mounted too far forward, there is a risk that the boat runs out of the course. The performance of these typical "Einkringeln" can often be seen in such boats.
If the turn fin mounted too far back on the other hand, very much rudder is needed to steer the boat, which of course leads to a loss of speed. Normally, the fin on the back of the right float is attached rather close to the fuselage. However, when the fin is too close to the center line, this can raise the right float. To prevent this, you can bend the fins turn towards the hull to keep the swimmers below.
For the bending of the fin, there are three possibilities: The turn fin extends fully in 90-degree angle into the water, what more should be the exception, is on some boats but certainly the only way. The second and most common way is to make it in the direction of the fuselage up to 7 °. Another variation is the turn fin to the beginning of the paper in 90 ° angle into the water-dip and curve, only 1 to 2 cm under water from 6 to 8 degrees.
The boat should have after the attachment of the fin a turbulent ride, check to see whether the fin is aligned straight! Make sure that the front edge of the turn fin is behind the fixing points, as it usually begins to flutter and the boat does not run smoothly with increasing speed. Some swimmers have a back, the reasons of production technology from the bottom front inclined to the rear. This offers a turn fin, which is (viewed from the side) in the fixed angle adjustable so that the above problems are excluded.
The rear swimmers have the task of the boat in turns to keep quiet. Some hulls, the height of the float to be adjusted. If the stern of your boat drifts in corners too much, it must lie deeper. Then set the float at a lower depth to bring the stern deeper.
If you set focus and turn right fin and the boat still in turns with the tail "is", you can also create a longer rudder problem. The goal is to take the smallest possible turning radius, without straining the engine by immersion of the hull so strong that he will lose much speed.
So it is not desirable to reduce the drift effect too much, as it ensures a clean and quiet curves and an efficient power delivery.
Aero.jpg
Aerodynamics
As mentioned above, is a hydro really a ship in the traditional sense. It is more a successful combination of a streamlined ship design with smaller contact surface on the water and many aerodynamic flight characteristics.
The current "great" Hydroplanes the Unlimited Hydroplane class developed by Hydro-and aerodynamics with doctor and professor. What is left at the end, is much theory, which in turn are "tested" at the object must practice. In the area of aerodynamics can be "let off steam" as an ambitious model builder actually. Now, not just any Schifflesbauer the mainframe computer of the Max-Planck-Institut at home, and so one can only think of what you yourself have tried and what one's colleagues of the "model-flying craft" communicate can do.
In short: Do not engage in too many experiments!
Many hydraulic models are equipped according to the original with spoilers and flaps, as they behave aerodynamically, mostly at all not up for debate. What is forgotten is that the originals are developed in a wind tunnel to the last detail and adjustable-board computer, the various front-and rear spoiler while driving. This is of course the model is difficult to understand or because of model-specific problems do not partially realized.
The Rumpfanstellwinkel is a very important parameter for the "dynamics". An airplane flies because of the negative pressure produced and the pressure under the wings of a boost. The same applies to our model Hydros: a hull with a positive angle of attack will take off at a certain speed at a negative angle of attack it is pressed down. Sharp edges cause air turbulence, which means resistance. Rounded corners and edges to reduce drag.
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