WHY YACHT RUDDERS BREAK

2021 ◽  
Vol 162 (A4) ◽  
Author(s):  
K Klaka
Keyword(s):  
Steady State ◽  
Design Calculation ◽  
Allowable Stress ◽  
Structural Failure ◽  
Force Coefficient ◽  
Calculation Process ◽  
Sailing Yacht ◽  
Is Design ◽  
Boat Speed

For most sailing yachts, losing a rudder is probably the most catastrophic structural failure other than losing the keel. Rudder failure happens with distressing regularity. This paper examines the hypothesis that the underlying reason is design failure. There are many qualitative decisions to be taken in the design calculation process. Example calculations are presented which show that the maximum rudder force generated in steady state conditions is easily underestimated. For a typical spade rudder of a typical modern production sailing yacht, the normal rudder force should be calculated using a boat speed of at least 125% hull speed, and a force coefficient of at least 1.3. Care must be taken in selecting an appropriate value for the allowable stress of the material used for the stock.

Why Yacht Rudders Break

2020 ◽  
Vol 162 (A4) ◽  
Author(s):  
K Klaka
Keyword(s):  
Steady State ◽  
Design Calculation ◽  
Allowable Stress ◽  
Structural Failure ◽  
Force Coefficient ◽  
Calculation Process ◽  
Sailing Yacht ◽  
Is Design ◽  
Boat Speed

For most sailing yachts, losing a rudder is probably the most catastrophic structural failure other than losing the keel. Rudder failure happens with distressing regularity. This paper examines the hypothesis that the underlying reason is design failure. There are many qualitative decisions to be taken in the design calculation process. Example calculations are presented which show that the maximum rudder force generated in steady state conditions is easily underestimated. For a typical spade rudder of a typical modern production sailing yacht, the normal rudder force should be calculated using a boat speed of at least 125% hull speed, and a force coefficient of at least 1.3. Care must be taken in selecting an appropriate value for the allowable stress of the material used for the stock.

Study on the Simulation of Temperature Field of Diesel Engine

2014 ◽  
Vol 971-973 ◽  
pp. 752-754
Author(s):  
Ya Nan Wang
Keyword(s):  
Heat Transfer ◽  
Temperature Field ◽  
Steady State ◽  
Diesel Engine ◽  
Simulation Method ◽  
Engine Piston ◽  
Calculation Process

In the case of each parameter Pistons have been basically provided ,to simulate the temperature field of Diesel Engine Piston, detailing the analysis of diesel engine piston transient heat steady state and heat transfer transient of the calculation process, providing a general simulation method of temperature field in general diesel engine piston.

Study on Basic Coal Consumption Characteristics in Dynamic Process of 660MW Ultra-Supercritical Coal-Fired Unit

2020 ◽  
Author(s):  
Junjie Yin ◽  
Ming Liu ◽  
Junjie Yan ◽  
Yongliang Zhao
Keyword(s):  
Steady State ◽  
Consumption Rate ◽  
Constant Load ◽  
Calculation Model ◽  
Dynamic Processes ◽  
Design Calculation ◽  
Coal Consumption ◽  
Steady State Condition ◽  
Load Cycling ◽  
Consumption Rates

Abstract With the spreading of intermittent renewable power, coal-fired power units should cycle frequently to balance the load between power supply side and demand side. Coal consumption of coal-fired units operating in dynamic processes is influenced by many factors, including thermal system, control system, heat storage variation, etc. Therefore, it is very difficult to evaluate the energy efficiency of coal-fired units operating in dynamic processes. It is important to ascertain the basic coal consumption rate in dynamic processes, which is the basis to evaluate the operation performance of coal-fired units. In this study, an off-design calculation model of 660MW ultra-supercritical coal-fired unit is developed and validated with design parameters. The developed model can be used to predict the coal consumption rates under steady-state off-design conditions. The basic coal consumption means the coal consumption of coal-fired units with operating parameters the same as target values. To calculate the basic coal consumption rate, a load cycling process is differentiated into lots of short time periods and every period is regarded as a steady-state condition with constant load, therefore the coal consumption rates in every period are equal to that of the corresponding steady-state condition. The calculation formula of basic coal consumption rates in is derived for load cycling processes. On the basis of the off-design calculation model and assumption of idealized condition, average coal consumption rates during different processes with constant load cycling rates can be calculated and analyzed. Results show that if the initial and final loads are both settled, the basic coal consumption rate remains unchanged and is independent of load cycling rate. If the load cycling amplitude remains unchanged, the basic coal consumption rate increases as the initial load decrease. The study aims to provide benchmark values for the energy consumption analysis in actual dynamic processes, and further study on coal consumption characteristics in dynamic processes will be developed based on it.

Aerodynamics, kinematics, and energetics of horizontal flapping flight in the long-eared bat Plecotus auritus

1976 ◽  
Vol 65 (1) ◽  
pp. 179-212 ◽  
Author(s):  
U. M. Norberg
Keyword(s):  
Steady State ◽  
Power Output ◽  
Lift Coefficient ◽  
Mechanical Efficiency ◽  
Flapping Flight ◽  
Mechanical Power ◽  
Power Stroke ◽  
Force Coefficient ◽  
Mechanical Power Output ◽  
Lift And Drag

The kinematics, aerodynamics, and energetics of Plecotus auritus in slow horizontal flight, 2–35 m s-1, are analysed. At this speed the inclination of the stroke path is ca. 58 degrees to the horizontal, the stroke angle ca. 91 degrees, and the stroke frequency ca. 11-9 Hz. A method, based on steady-state aerodynamic and momenthum theories, is derived to calculate the lift and drag coefficients as averaged over the whole wing the whole wing-stroke for horizontal flapping flight. This is a further development of Pennycuick's (1968) and Weis-Fogh's (1972) expressions for calculating the lift coefficient. The lift coefficient obtained varies between 1-4 and 1-6, the drag coefficient between 0-4 and 1-2, and the lift:drag ratio between 1-2 and 4-0. The corresponding, calculated, total specific mechanical power output of the wing muscles varies between 27-0 and 40-4 W kg-1 body mass. A maximum estimate of mechanical efficiency is 0–26. The aerodynamic efficiency varies between 0–07 and 0–10. The force coefficient, total mechanical power output, and mechanical and aerodynamic efficiencies are all plausible, demonstrating that the slow flapping flight of Plecotus is thus explicable by steady-state aerodynamics. The downstroke is the power stroke for the vertical upward forces and the upstroke for the horizontal forward forces.

scholarly journals The control of wing kinematics and flight forces in fruit flies (Drosophila spp.).

1998 ◽  
Vol 201 (3) ◽  
pp. 385-401
Author(s):  
F O Lehmann ◽  
M H Dickinson
Keyword(s):  
Steady State ◽  
Body Size ◽  
Force Production ◽  
Fruit Flies ◽  
Translational Velocity ◽  
Force Coefficient ◽  
Stroke Frequency ◽  
Force Coefficients ◽  
The Mean ◽  
Stroke Amplitude

By simultaneously measuring flight forces and stroke kinematics in several species of fruit flies in the genus Drosophila, we have investigated the relationship between wing motion and aerodynamic force production. We induced tethered flies to vary their production of total flight force by presenting them with a vertically oscillating visual background within a closed-loop flight arena. In response to the visual motion, flies modulated their flight force by changing the translational velocity of their wings, which they accomplished via changes in both stroke amplitude and stroke frequency. Changes in wing velocity could not, however, account for all the modulation in flight force, indicating that the mean force coefficient of the wings also increases with increasing force production. The mean force coefficients were always greater than those expected under steady-state conditions under a variety of assumptions, verifying that force production in Drosophila spp. must involve non-steady-state mechanisms. The subtle changes in kinematics and force production within individual flight sequences demonstrate that flies possess a flexible control system for flight maneuvers in which they can independently control the stroke amplitude, stroke frequency and force coefficient of their wings. By studying four different-sized species, we examined the effects of absolute body size on the production and control of aerodynamic forces. With decreasing body size, the mean angular wing velocity that is required to support the body weight increases. This change is due almost entirely to an increase in stroke frequency, whereas mean stroke amplitude was similar in all four species. Despite the elevated stroke frequency and angular wing velocity, the translational velocity of the wings in small flies decreases with the reduction in absolute wing length. To compensate for their small size, D. nikananu must use higher mean force coefficients than their larger relatives.

Paper 5: Vehicle Behaviour in Combined Cornering and Braking

1968 ◽  
Vol 183 (8) ◽  
pp. 19-34 ◽  
Author(s):  
A. J. Harris ◽  
B. S. Riley
Keyword(s):  
Steady State ◽  
Load Transfer ◽  
Equations Of Motion ◽  
Rear Wheel ◽  
Front Wheel ◽  
Slip Angle ◽  
Vehicle Model ◽  
Force Coefficient ◽  
Wheeled Vehicle ◽  
Non Linear

This paper considers first the steady-state motions of a simple two-wheeled vehicle model having non-linear sideway force relationships with respect to tyre slip angle. It is shown that any steady-state conditions may be represented and their solutions found by simple graphical means, using only the non-linear curves. The curves can be modified to take into account the influence of vehicle parameters such as compliance, roll steer, wheel camber, and load transfer. Stability boundaries are discussed and criteria are presented showing that stability of the motion depends only on the slopes of the curves and the speed of the manoeuvre at the cornering acceleration being considered. A more involved four-wheeled vehicle model is then considered when subjected to braking while cornering on a fixed radius path of 45·8 m on a wet Bridport macadam surface. Actual sideway force–slip angle curves for combined braking and cornering, as presented by Holmes and Stone (see reference (6))†, are used with the equations of motion derived for the quasi-steady state conditions of decelerating while cornering. The effects of front wheel steered angle and body slip angle on the forces necessary for the manoeuvre are also considered. An envelope of maximum cornering acceleration at various braking decelerations is presented. This shows that for those particular conditions up to about 70 per cent of maximum deceleration may be obtained before there is more than about 10 per cent loss in maximum cornering ability. Outside the envelope the vehicle fails to maintain the path. At the lower deceleration the car spins, and at higher values it continues tangentially to its original path without spinning. It is also shown that the total sideway force–slip angle curve for a pair of front or rear wheels, when one or both wheels have a high braking force coefficient, can have a sharp peak, such that for small increase in slip angle there is a rapid fall in sideway force. It is suggested that this is why a rear wheel skid which occurs while braking and cornering is more difficult to correct than one which occurs when only cornering.

scholarly journals Influence Analysis of Deck Equipment Positioning on Performances in Sailing

2016 ◽  
Vol Special edition (1) ◽  
pp. 101-109 ◽  
Author(s):  
Tin Matulja ◽  
Luka Jedretić ◽  
Marko Hadjina
Keyword(s):  
Influence Analysis ◽  
Light Wind ◽  
Data Collecting ◽  
Specialized Equipment ◽  
Field Measuring ◽  
Sailing Yacht ◽  
Boat Speed

Authors in this paper presented the analysis regarding influence of deck equipment positioning and trimming, which is directly connected with sails, on sailing yacht performance in sailing. The analysis is performed by on-field measuring during sailing using specialized equipment based on RaceQs application and GPS support. The analysis is related to light wind conditions without significant waves, then to moderate wind and waves and finally to storm wind and high waves. Data collecting was performed during 30 hours of measuring and monitoring where the relevant equipment was continuously repositioned and trimmed aiming to reach more boat speed for different sailing angles. The results are processed and presented. The research was enabled with help and support of Bavaria Yachts d.o.o. Further analysis is suggested for different wind conditions and sea states.

Computer-Aided Calculation of the Box Centroid of Linear Vibration Screener

2012 ◽  
Vol 580 ◽  
pp. 16-19
Author(s):  
Zhi Wei Wang ◽  
Ling Qin Meng
Keyword(s):  
Decomposition Method ◽  
Present Author ◽  
Design Calculation ◽  
Direct Impact ◽  
Linear Vibration ◽  
Accurate Calculation ◽  
C Language ◽  
Traditional Design ◽  
Computer Aided ◽  
Calculation Process

In the design of the vibration screener, the calculation of screen box centroid has direct impact on the performance of the vibration screening machine. In traditional design, calculation of the screen box centroid is carried out through repeated calculations and the adjustment of the vibrator installation, of which the calculation process is tedious with low accuracy. This thesis deduces the formula of calculating screen box centroid by the way of mass decomposition method, and programs for calculation of the box centroid of Linear vibration screener through C language. With the computer aid, the present author realizes the accurate calculation of screen box centroid and enhances the level of design for vibration screener.

Studies on Water in the Hydration Chamber of a Modified Electron Microscope

1970 ◽  
Vol 28 ◽  
pp. 544-545
Author(s):  
R. C. Moretz ◽  
G. G. Hausner ◽  
D. F. Parsons
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Electron Microscope ◽  
Steady State ◽  
Room Temperature ◽  
Small Mass ◽  
Equilibrium Pressure ◽  
Biological Objects ◽  
Mechanical Pump ◽  
Differential Pumping

Use of the electron microscope to examine wet objects is possible due to the small mass thickness of the equilibrium pressure of water vapor at room temperature. Previous attempts to examine hydrated biological objects and water itself used a chamber consisting of two small apertures sealed by two thin films. Extensive work in our laboratory showed that such films have an 80% failure rate when wet. Using the principle of differential pumping of the microscope column, we can use open apertures in place of thin film windows.Fig. 1 shows the modified Siemens la specimen chamber with the connections to the water supply and the auxiliary pumping station. A mechanical pump is connected to the vapor supply via a 100μ aperture to maintain steady-state conditions.

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