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1. |
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Do I
need to order spare blades? |
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You can
order a full set of spare blades (10) for a remarkable low
price, if they are ordered at the same time you order your
prop.
This program gives the yacht owner the equivalent of four
props at a competitive price to the best metal. Imagine
traveling with your spare props in a sac or box. Blades
weigh around 5 lbs. each for a 80' yacht. |
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2. |
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How
much do extra blades cost? |
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Extra
blade sets (5 blades) are approximately 1/3rd the price of
a new propeller. |
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3. |
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How
do Contur®
props react to impact injury? |
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Whether you run aground or hit a submerged object the
Contur props do not bend. Portions of a blade make break
off and leave the remaining blade to propel you safely
home. |
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Example:
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This vessel accidentally ran aground, but
continued to operate for a further 1800 miles
without realizing that the propeller blades had been
damaged - the Skipper only wondered why the speed
had dropped
off.
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These
broken blades will get you
home without shaking your boat apart! |
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4. |
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What is
cavitation burn? |
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Cavitation is caused by turbulent water impacting
the prop hub and leading edge. This
photo demonstrates the deteriorating effect of
Cavitation Burn eating away at the bronze base of
the prop blade.
Carbon fiber props can be designed to minimize
this effect, however analysis of the boats
bottom and the cause of turbulent flow is
equally important. Boats cruising at 25+ knots
should be especially aware of their bottom
configuration as blades have been known to
separate from their hub as a result of
Cavitation Burn. |
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5. |
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Absorbing
the Energy of Cavitation |
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Numerous
methods of handling the energy of disintegrating
cavitation bubbles - "Here is a method of absorbing the
energy ideally suited to Contur props since it can be
applied in the mold." (See video and power point)
Cavitation Video
Cavitation Power Point Presentation |
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6. |
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What
kind of blade injury can be repaired? |
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Superficial injury that does not involve
the carbon fiber. The special epoxy
coating is impact resistant. |
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7. |
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What
other advantages of impact injury over metal? |
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The
blades are light weight and elastic. They take the impact
force usually sparing the shaft and transmission. |
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8. |
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How do
Carbon Fiber Props result in better fuel efficiency? |
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This
chart demonstrates carbon fiber props. Because
carbon fiber props are flexible and custom designed
for your boat, they approach the ideal load for each
RPM. Note on the graph the difference in height
between the red & green graph. That difference is
the increased fuel efficiency. i.e. Greater torque
using less fuel. |
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9. |
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How
large can a composite prop be? |
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The
largest propeller ever made is one of Carbon Fiber
Composite. The 2.9m diameter
composite propeller is on the RV Triton triple hull
warship. |
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10. |
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Why
are the small size props so expensive? |
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These
are custom made props and the set up costs for a small
prop is virtually the same as a large one. Multiple
identical props do reduce the costs. Several owners with
identical hulls and power could combine to purchase
several sets thereby reducing set up costs. |
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11. |
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Do I
need to put antifouling paint or prop-speed on the props? |
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We do
not recommend any other coating. The polyurethane paint is
not conducive to barnacle attachment and marine growth can
usually be wiped off with a gloved hand. Light sanding and
repaint, brush, roller or spray is recommended at the time
of hauling for a bottom job. |
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12. |
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After
ordering, how long will it take to get my props? |
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Our
standard delivery is approximately 8-10 weeks. Please note
that propellers are manufactured in Germany and we have a
great relationship with customs, but cannot control their
time frame. |
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13. |
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What
if I can't get all my measurements? |
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We
are here to assist in any way that we can and if at all
possible we can assist you with the measurements and
accompany you on a sea trial to help you gather your
performance information. |
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14. |
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Can
the blades be changed underwater? |
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Yes |
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Click on this photo for an enlarged view. |
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15. |
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Will
I still be able to
use my boat
if I damage a blade? |
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Yes,
you will be able to get home or to a convenient place for
a diver to remove the prop for repair or blade
replacement.
Running with
damaged blades will not extend the damage. |
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16. |
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Can I use my
present metal props as spares? |
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Yes, but if
you change one, be prepared to notice a tendency to turn
away from that side because of increased efficiency of the
Contur propeller. (US Naval Academy project - two
identical props, one Carbon, one Bronze, had trouble
keeping a straight course). |
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Click
on the photo for an enlarged view. |
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17. |
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Industry
Competition? |
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Many
companies are working to develop Composite Propellers. To
the best of our knowledge, Contur Props are the only
inboards with replaceable blades. Contour is the only one
certified by Lloyds Shipping, ISO 9002 and in use on
civilian yachts and large military vessels including
submarines. |
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18. |
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How does the
shaft and strut position affect water flow? |
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19. |
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Characteristic Comparison Table |
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Bronze vs. Carbon
Fiber Propellers |
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