Frequently Asked Questions

1.   Do I need to order spare blades?
    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.
2.   How much do extra blades cost?
    Extra blade sets (5 blades) are approximately 1/3rd the price of a new propeller.
3.   How do Contur® props react to impact injury?
    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.
    Example:
Damaged carbon fiber propeller 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.
 

These broken blades will get you home without shaking your boat apart!

4.   What is cavitation burn?
    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. Cavitation Burn
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.
5.   Absorbing the Energy of Cavitation
   

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

   
Get Windows Media Player 10 Get Microsoft Power Point Viewer

Get Windows Media Player to view the video above.

Get Power Point to view the Cavitation Presentation above.

6.   What kind of blade injury can be repaired?
   

Carbon Fiber Propeller Blades

Superficial injury that does not involve the carbon fiber. The special epoxy coating is impact resistant.

 

7.   What other advantages of impact injury over metal?
    The blades are light weight and elastic. They take the impact force usually sparing the shaft and transmission.
8.   How do Carbon Fiber Props result in better fuel efficiency?
   
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. Fuel Efficiency Graph
9.   How large can a composite prop be?
    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.
10.   Why are the small size props so expensive?
    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.
11.   Do I need to put antifouling paint or prop-speed on the props?
    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.
12.   After ordering, how long will it take to get my props?
    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.
13.   What if I can't get all my measurements?
    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.
14.   Can the blades be changed underwater?
    Yes

Click on this photo for an enlarged view.

Composite Carbon Fiber Prop
 
 
 
 
 
15.   Will I still be able to use my boat if I damage a blade?
    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.
16.   Can I use my present metal props as spares?
    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).

Annapolis Prop

Click on the photo for an enlarged view.

   
17.   Industry Competition?  
    Many companies are working to develop Composite Propellers. To the best of our knowledge, Contur Props are the only inboards with replaceable blades. Contur is the only one certified by Lloyds Shipping, ISO 9002 and in use on civilian yachts and large military vessels including submarines.
18.   How does the shaft and strut position affect water flow?
   
19.   Characteristic Comparison Table
    Bronze vs. Carbon Fiber Propellers
20.   WHAT ABOUT PROP SPEED?
    Unlike metal these props can be painted with whatever bottom paint you normally use. Prop Speed is designed for use on metal and is appropriate for the hub only.
   

Carbon Fiber Prop Bottom Paint On Carbon Fiber Prop

   

Click on the photos for an enlarged view

A Volonte' Ltd.
Shipping Address: Email A Volonte' Ltd. Punta Gorda (941) 815-1988
3155 Harbor Blvd. Ft. Lauderdale (954) 323-2898
Punta Gorda, Florida Ft. Lauderdale (954) 380-PROP 
33952 Fax (888) 298-4036
Email: sales@conturprops.com

For Our European Clients Email: sales@fleetwatermarine.com

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