Carbon fiber ship propeller

Claim of 9% reduction in required (presumably engine/shaft) power due to use of a carbon fiber propeller.
http://gcaptain.com/first-carbon-fiber-main-propeller-installed-merchant-ship/

 

Thanks - interesting reading.

Also liked this;-

http://gcaptain.com/dutch-naval-architects-come-cool-idea/

 

The increase in efficiency is tied to an increased diameter. This doesn't make a lot of sense, or at least is not clearly explained why they were able to make the CF prop larger but not the Ni-Al-Brz one.
CF is a very strong material, but I think that stiffness is an issue as well as the fatigue that a propeller experiences over its life.

 

Stiffness might be an issue, but a well designed CF structure has significant benefits in fatigue life. Very high modulus fibers might actually increase the basic material stiffness, but strength typically is reduced.
And by thinning the blade the blade stiffness is rapidly reduced even if the material is stiffer.
This is a very complex technical problem, you're not likely to really know if they succeeded for a long time in use.

Impact damage is a more significant issue for the practical life span of the blade.

If this was so good, why didn't they make the drive shaft from CF? Perhaps that's next

 

Ships are getting CF shafting, just not the outboard sections. I don't think that the regulatory bodies are ready to allow a hole that big in the ship filled with a hollow carbon tube.

The carbon inboard sections really help with bearing spacing and alignment, not to mention weight savings.

 

The increase in efficiency can be tied to both a larger diameter and a much lighter rotating weight, Less rotating weight has a lot of positive effects. The stiffness in carbon fiber can be tailored with the right matrix.

 

Propellers rotate. Propellers do not "reciprocate".

 

Less rotating weight only affects the acceleration. Once it gets turning at whatever rpm's , it makes no difference.

 

Most props nowadays are overhung from the end of the shaft. A lighter propeller means less weight on the strut bearing or the stern tube bearing and less wear over a given time period. A lighter propeller also means a better shaft alignment and lower shaft deflections, and different whirling critical speeds in the shaft.

 

Damn autocorrect, thanks for catching that