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| Cavitation
Bubble |
PROPELLER TERMINOLOGY
CAVITATION
Cavitation is a general term used to describe the behavior
of voids or bubbles in a liquid.
Cavitation is usually divided into two classes of behavior: inertial
(or transient) cavitation and non-inertial cavitation. Inertial cavitation
is the process where a void or bubble in a liquid rapidly collapses,
producing a shock wave. Such cavitation often occurs in pumps, propellers
and impellers.
D.A.R. Disc Area Ratio
D.A.R is the ratio of the projected blade area to the area of the
circle described by the diameter of the blades. Normally, this is
expressed as a percentage. 3-bladed propellers are normally about
50% or 0.50 D.A.R. 4-bladed around 0.7., and 5-bladed around 0.9 or
90%.
Obviously the size of individual blades influences the D.A.R.. On
propellers with overlapping blades it is not impossible to have a
D.A.R. in excess of 100%
E.A.R. Expanded Area Ratio
This is a ratio of the actual area of the propeller blades to the
area of the circle described by the diameter of the blades. This is
sometimes referred to as B.A.R. Blade Area Ratio. Normally E.A.R is
a higher percentage than D.A.R.
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| WildCat
Propellers |
Screw Propeller Definitions
- Diameter(D): distance from tip to tip
- Hub: the connection between propeller and shaft
- Blade Tip: the furthest point on the blade
- Blade Root: the point where the blade meets the hub
- Pitch(P): Theoretical distance a propeller would move
in one revolution
- Pitch Angle: Angle of the blade with respect to incoming
flow. It usually varies from root to tip.
- Fixed Pitch:
- The pitch is constant all the way from the blade root
to the blade tip.
- Blade is fixed to the hub and cannot be altered.
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Contact WildCat Props!
Custom propeller configurations are also available on request. Should you
require assistance in selection of a new propeller suited to your vessel,
restoration-repair of your existing propellers or prop tuning-maintenance
please contact WildCat Props. |
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Read How WildCat Props Exceeds the
Expectations of Our Customers!
A quick note to thank you for your excellent work over the last 5 years
(those being years Wildcat worked on Backlash wheels), we have placed in
the top three (first, second, third) for six tournaments. The smaller three
blade wheels allow us to go slow for winter rockfish trips. And we like
the economy of 20 knots/20 gallon/hr (combined). But I really get excited
with the 24x27 ZF 4 blades. Your recommendations were right on: 30 knot
cruise, 35 knot top end, zero cavitation, super smooth and (best of all)
fuel economy!!! Right after we put the 4 blades on in Hatteras, we won the
2007 Hatteras Village Open with a 613# Blue Marlin and another release.
If someone thinks you are too high - don't forget -you are saving them money
on fuel. And that fuel expense is not likely to change!!!
Thanks again, Troy and Team,
Capt Steve Richardson owner/operator "Backlash"
Read more customer testimonials here |
Also read customer propeller case studies |
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