The Controllable Pitch Propeller, a summary.

Every time we have the term CPP coming up here, there is at least one self proclaimed “expert” popping up, with the idiotic statement: “nice but expensive” and / or “yes but that does´nt suit here”

Nonsense!


CPP RATIONALE

Why a CPP?
There are several advantages provided by Controllable Pitch Propellers, here named CPP. This summary has the intention to outline several of the reasons why CPP should be favoured for motor vessels, as for sailing vessels, and motor sailers.
While of course it is true that a Fixed Pitch Propeller (FPP) can be more efficient than a CPP, it is never given that opportunity... The FPP can only be maximally efficient at one rpm with one amount of power input and at one load condition: those, in example, for which it was designed. At that one rpm and load, the FPP is capable to absorb all the power that the engine can produce. At any other rpm, or any other engine or vessel load, the FPP can not operate efficiently, that’s being either over - or under pitched.
A properly sized CPP on the other hand is able to be efficient over a wide rpm range, and over a wide range of engine loading. This is so because the propeller's pitch can be adjusted as needed in order to absorb all the power that the engine is capable of producing at any rpm.
With a CPP, you make pitch adjustments under-way to suit the complete variety of conditions. It is very easy to choose the appropriate pitch setting with a CPP. Though it needs some exercise.

At highly variable loads on a long range power yacht, if fitted with a CPP, the pitch can be increased when the vessel is light, and decreased when loaded without having to vary the engine rpm, and it will provide maximum load on the engine.

CPP installations do´nt have a reversing gearbox, only a reduction gear. Instead of changing the direction of rotation, the blades articulate clear around until they bite in the water in the other direction.

Than there will be no doubt as with a FPP whether the correct pitch has been choosen for the boat. Too many boaters have discovered, that calculating the ideal propeller pitch sometimes is not really a exact science...! But with the wrong FPP, efficiency is not as expected and your cost spiral begins to turn the wrong way.

Is a CPP more expensive than a FPP installation?

NO it is´nt!
When comparing the same quality of components (and a shaft tube as part of the stern gear), the purchase price is about the same as for a FPP arrangement.

BUT……..
Lengthening the service life of your engine by the factor 4 at least, saving fuel on every single mile you operate outside the narrow window of max. efficiency, being able to operate a “beefy” Diesel as economical (or better), than a small toy at “handgrenade” setting, that all makes perfect sense!
And it comes for free once you got rid of the idiotic statement that a CPP is expensive.

The entire commercial fleet in Scandinavia is using exclusively CPP´s since about 100 years now!
There is ice in the Baltic and North sea ports almost every Winter, the CPP is still the choice, why?
The single blade is the weakest point in such arrangement! When it hits heavy ice or a log, it brakes. That is pretty easy to repair and does not affect the rest of the drivetrain. Have a spare one aboard, as every fisherboat there has.

Fisherman are not Yachties, they do´nt have money to waste, nor time for servicing coked engines. (and replacing them every other year)
But there is no fisherboat around up there with a FPP installation. So, whats cheaper?

I hope this short summary made some points clear enough, that we must NOT discuss them again when the CPP is coming up next time!

Regards
Richard

edit:
some links:
http://www.hundestedpropeller.dk/?id=4172
http://www.cp-propeller.com/
http://www.helseth.no/eng/products.htm
http://www.frydenbosabb.no/index.php?mapping=16
http://www.servogear.no/pages/product.aspx?nr=33
http://www.nogva.no/?CatID=1191
ZF CPP´s
http://www.grmo.dk/default.aspx?pageID=10002&lang=da
http://www.bergpropulsion.com/
http://www.bukh.dk/uk/mainframe.htm
http://www.westmekan.com/index.php?option=com_content&task=view&id=9&Itemid=11
http://www.masson-marine.com/de/pro...marine-verstellpropeller/mms300_03_01_01.html
http://www.piening-propeller.de/de/verstellpropeller.htm
http://www.wartsila.com/,en,product...7667EE8-340B-4D80-BF44-64B1EAF44ED4,,8007.htm

 

Richard, I'm just wondering: Do you have stock shares in CPP technology?

I'm all for CPP but the complexity is a consideration for me.

You've raised good points, thanks for that.

-Tom

 

Yes of course I have stock shares in all of the manufacturers above, why would I make this effort if not!

The complexity of a common gearbox is equal to a CPP setup!

 

Hi Richard,

I have an ineterest in CPP's. Post me some information / link(s), and some pricing please. All sizes.

Thanks

 

Fanie's in rare form today! Richard, why do you suppose CPPs havn't caught on over here? They seem perfect for some fisheries.

 

I've been looking for CPP's for a while, I have an app for them.

Funny thing about them is seems the moment you are interested in them the 'suppliers' seems to disappear...

Can't use something you cannot get.

 

Join the queue....................

Mark, they are! US builders just do´nt know them! (as French and Italian too)
Trolling whith a fully laden engine at 2kn is just nothing but perfect and you can do that for centuries if you like! Then having your catch aboard WOT homeward, and never even thinking about economy, or killing the engine!
Trolling gearbox...what a nonsense.

Fanie,
there have never before been so many manufacturers of CPP´s on the market as today! None of the better ones disappeared recently.
I added some links to the opening post!!!

Regards
Richard

 

Okay, show me one that will work on small engines like those that drive the majority of sailing yachts in this country. These are typically 20 HP or less, often gas engines. The initial outlay for usual products are high, from my research (several years old now) and no small units, just big, costly ones. Find me one that I can use as a substitute for a 10 - 15 HP gear box, that doesn't cost as much as a small diesel and I'll buy a few of them this year alone.

Yes, you can go on about improving engine life, matching load to pitch, to RPM, etc., etc., etc., but you can't sell this to a small boat owner looking for a repower at twice or three times the cost of a direct replacement unit.

 

It may happen they hear you at Bukh Marine in Denmark!

But you are right Paul, there is actually no proper CPP installation available in the low power range! They start to make sense from about 50hp up.

Regards
Richard

 

I can't answer with the knoweldge of Richard. I just used them time to time in some boat. And yes it make a lot of sense.
The probleme here in the US we have the "Status quo"
Nobody realy knows why but they don't sell CPP, so they don't exist period. They sale for a huge amount of money complicate transmission, but try to find a CPP. No way.
Only one naval architect in the US to my knoweldge talk at length and realy tried to explain and impliment in the US the CPP is Karsten.
It's true in Europe they have the CPP on great a majority of the motor vessel.
On small Hp, since the demise of the old Sabb, the CPP is gone.
By the way I am mounting a Sabb with CPP in the aluminum schooner for a customer who found one in second hand. We are very glad.
The customer is a US merchant engineer, he wanted from the beginning a CPP on the 30 hp range. So he went thru the second market to find a Sabb.
Cheers
Daniel

 

Westmekan has something for smaller engines with standard gearboxes starting from 25mm shaft diam.. Not as neat solution as with cpp gearbox but anyways..

 

Beside outboard you have NO inboard gas engine of 20hp or less in this country. NO one. Beside the one off built by the owner and killed by the insurance. Sorry. Only diesel one.
Cheers
Daniel

 

Outboard you can change another pitch propeller in a minute or two

 

A ZF transmission with a 9Hp Yanmar cost more than $10,000.
Who are we kidding here? This is an insult to sailors.
A good small diesel of 9 hp for agricultur pump (Yanmar) cost $1,200 brand new retail price with taxes.
Can we be a little less sucker here?
You put a reduction gear with thrust bearing ($450) and a CPP you can sell it for $4000 with a beffy profit
And the "Very High Price To Marinize" is pure B.S.
But we have some who cornered the market, and are happy with that.
ZF is happy and Yanmar is happy. Why bother with what realy work, why going to the drafting board when we can suck up money from suckers?
They decide the price in the US, and stick with it.
By the way the CPP will be the end of marine low hp transmission market.
And it is the most juicy market for yards and the like.
Cheers
Daniel

 

Okay, Richard. You have seen my boat and have an idea of how I like to do things - that is why I have an interest in CPPs. I am speaking from complete ignorance here as I HAVE NEVER SEEN A CPP. My thought always was that they were "clunky" and a compromise. When you relate the positives, it has made me think again.
The part that I perceived "clunky" was the hub. I always thought that they had to be less than perfect at the 15 -20 knots I spend a majority of my time but in actuallity, the hub area on a fixed prop is in dirty water anyway and it is difficult to achieve correct pitch at the hub and the working area of the blade simultaneously.
Can we use my boat as a "what if"?
Last year I spent $21,000 dollars on transmission, shaft, and cutless bearing. Would I have been within reach of one of these setups? My power is D9-500 Volvo (transmission 305A ZF 2 to 1 reduction) electronically regulated at 2675 RPM (full rack, they say, is 2600 RPM). I usually run at 2250 RPM but hurry at 2400 RPM and conserve at about 1100 RPM. Thanks