Loki
28.05.2021 14:59:10
Expanded Area Ratio (EAR)
Similar to Developed Area Ratio with sections "unwrapped" from hub.
Largest area ratio. here
See full version: Propeller; Propulsion Terminology
Expanded Area Ratio (EAR)
Similar to Developed Area Ratio with sections "unwrapped" from hub.
Largest area ratio. here
Anti-singing Edge
The singing is a result of propeller diameter and R .P.M. , Boat speed and Trailing-edge thickness and shape or roundness. In most of the cases not much can be done on Diameter, Rpm's or speed, but we can modify the Edge Geometry. This has been the Strategy for all efforts to eliminate singing.
Most Propeller professionals (and others) are familiar with the Anti-singing Edge � a Chamfering of the Trailing edge, typically on the Suction side. This shape avoids the creation of curving flow eddies by cleanly separating the water flow off the blade.
The following graphic shows the Chamfering that goes from 0.5 or 0.4 Radius to the tip of Suction Side.
Cup
Small radius or curvature located at the trailing edge of blade.
Cupping, helps to reduce or delay cavitation.
Helps to reduce slip, thus increasing actual pitch and usable thrust.
Track
Measurement of axial position of all blades with respect to each other.
Blade Sections
Referred to as Cylindrical Sections.
Hub & fillet area account for about the first 20-30% of the sections. more
Maneuvering a Sailboat Under Power Course
Most sailboats are right-hand screw. So why then does the aft of the boat move to the port when reverse is applied? It is not what you expect. Some people think that the turn of the prop is pulling the boat sideways. But that is not the case because the pull in one direction balances the pull in the opposite direction. Turns out the action is a combination of what is experienced on airplanes called the p-factor as well as another phenomenon which was fully defined by one of the world’s most experienced prop engineers, Dave Geer of Geer Marine, Inc. Dave has written a full paper on what makes your boat go sideways which he has given NauticEd permission to publish inside our Maneuvering Under Power course. here
The terms right-hand screw and left-hand screw are defined as such: When viewing from aft, if the propeller turns to the right at the top of the sweep then it is deemed a right-hand screw. Named “right-hand” because the natural rotation of your right hand is pinky down and thumb up (clockwise). Conversely, the left-hand screw is counterclockwise when viewed from aft.
Take the NauticEd Maneuvering Under Power online course. Learn how to easily handle propwalk, back your boat into a slip on a windy day, and generally look like a professional in the marina. [links]
See the animation below which makes it clear. Tap on the Forward and Reverse buttons. here
Online, at home, in your own time multimedia theory learning integrates perfectly with on-the-water practical teaching to make you a confident and competent sailor. Read more about NauticEd
Left-hand Impeller [links]
What is an easy way to identify the difference between a left-hand and right-hand impeller? The table below gives a quick summary:
It is useful to know that any left-hand impeller can mix as a right-hand impeller if the rotation direction is reversed to counter-clockwise. The corollary is also true for right-hand impellers. here
Right-hand Impeller
An additional difference is availability – the vast majority of stirring impellers offered on the market are left-hand. If it is not specified, the general assumption is the impeller is left-hand. Suppliers usually identify right-hand impellers, but with the tips provided here you can identify the hand of most impellers from the image. more
Caframo offers one of the widest varieties of impellers at the laboratory scale, and provides the left-hand configuration for propellers and the pitched blade turbine. To achieve the versatility of both hands from an impeller, the Reversing Digital 2010 is able to rotate in either clockwise or counter-clockwise direction continually, or in both directions in an easy-to-program timed sequence. Contact us to identify the stirrer and impeller best suited for your application.
Yeah, Its not stamped (thanks oj) but Im pretty sure the newer models are LH just by looking at the pointy part or the cutting part of the blade and then the wider pushing part.[links]
Whats the easiest way to tell which prop I have. Need to know if I have a left or right hand prop.
"Never underestimate a man that Overestimates himself." here
Why did they go LH on newer models and RH on older??
2004 launch direct drive if that helps. more
Acme 913 prop, WS 420, Kicker L5 sub, JL/Kicker amps, Kicker in boats, Polk mm in roswell bar, 3000# ballast.