Controlable Pitch Prop

Also known as VPP(Variable Pitch Prop). While still self debating it, I still haven't given up on this system for my motorsailer build. My friend John owns a 28ft. Albin Vega equipped with a two cyl. Volvo diesel coupled to a CPP system as installed day one from the factory. One of the common responses on a previous thread on this topic was that the CPP system is rarely used on low powered engines. However this seems to contradict that general statement. In this age of extremely high cost fuel I would think that CPP systems would come into their own being the most controllable and efficient set up in prop drive. I more or less direct this request toward the European/Asian forum members as historically the small CPP systems, from all indications were more popular there. Question, Is there to anyone's knowledge a company still manufacturing, gearing up or coming on stream with a system compatible with say a 30hp. diesel. With Tnx. Geo.

A yacht is not defined by the vessel but by the care and love of her owner

 

To lower costs a CPP was frequently used with a reduction gear , but no clutch/gearbox.

Worked fine for fisherman , but today folks that visit a marina may have a grand time docking , as they crank a wheel to spin from Fwd to Rev.

A CPP requires a thrust bearing to be mounted , which means the engine can be on softer mounts and dance more.Which is good.

A CPP is great for fuel consumption BUT , lets say its 25% more efficient.(doubtful)

A 28 ft boat will frequently cruise on one quart/liter an hour at LRC.

With the usual pleasure boat running 200 hours a year it takes a lot of running for 5 hours and paying for 4 hours to make up the initial CPP purchase price.

Bigger engine , bigger boat , bigger savings , tho even at 100HP perhaps 5GPH it will be a long time.

Now at 800hp , 40-50GPH the pay back becomes realistic.

 

From my experience, there are still manufacturers of the smaller CPP systems in Sweden and Norway. I could not find the information on a small company that I knew of near Alesund, Norway that still made both the CPP gear and small marine diesel engines, but I did find this...

http://www.frydenbosabb.no/index.php?mapping=16

I'm pretty sure that Endressen and Co. (ServoGear) only make their superbly engineered CPP systems for larger vessels...but they would be a good place to ask about who is still manufacturing the smaller systems.

 

Fred, I guess I'll just have to install a big mother engine in my build . Seriously, it's possibly wishful thinking on my part but I was hoping some of the bigger European manufactures possibly introduced or re introduced a smaller unit. My choices are limited to a; (1) fixed blade and put up with the drag and engine carbon build up which motorsailers are subject to if one is not really careful. (2) A feathering prop which are extremely expensive and subject to just as much if not more wear and maintenance than a CPP system, less the feature of being able to match the prop pitch to engine rpm. This of course obtaining max. drive efficiency and motorsailing without the worry of carbon. (3) Use a two blade prop and the old vertical behind the keel trick to reduce drag. However there is still a lot of drag plus the fact loss of drive torque when compared to a three blade. The CPP seems to be the winner barring the cost issue. I more or less just threw it out there again, hoping some wise company seen the market potential and are or about to mass produce driving the demand by reasonable pricing. Ya I know i'm dreaming but what the heck else is there to do .

 

Thanks BMcF, I did scout out Saab some time ago and did e mail them but no response. They are one possibility, another being Jurjens in Holland (B.V.Mogema)of which I am attempting communications. We had a guest at our B&B from Holland that was going to check out this company for me but I haven't heard back as of yet. I was more or less shaking the bushes to see if there were any new guys on the block. --

 

See this thread for possible hints

http://www.boatdesign.net/forums/propulsion/cpp-desapear-recreational-boats-who-gets-benefit-crime-26778.html

And this one

http://www.boatdesign.net/forums/props/controllable-pitch-propeller-summary-30695.html

Check with a company called Servogear AS, in Norway.

 

Cpp/vpp System

I thought I'd throw this brochure out there with the possibility that someone might pass on some info on this company. This is an old brochure I picked up at a boat show many yrs. ago.I have been unsuccessful in contacting them. Possibly they have been bought out or changed their name. Certainly a well engineered and good looking system. Thanks for any help ---Geo.

 

Thanks TAD, I seem to recall reading these threads before but i'll re read to refresh. I've had always has a liking of the unit in my prev. post but never quite made it financially to seriously look at a purchase. Certainly looks well engineered.

 

Up Date --I have located an E mail address for the brochure company info@mogema.nl and sent off an e mail re their old brochure. I will update as soon as get a reply for anyone interested in their units.

 

VN,
Good day.
I'm sorry to say I am not the geographically gifted respondent you are seeking but thought this may be an appropriate time for me to chime in.
I'm sorry I'm not completely up to speed on your thread as I am having vision issues this morning but believe I have the gist of it.
IMO, you are on the right track.
I think if you can find an attractive, simple, sound design and manufacturer and you can justify the cost that it will fit into a more versatile propulsion system.
If it's not cost effective then you are better off without.
Although not as versatile, there is nothing "wrong" with a well designed, fixed pitch prop.
Cheers

 

I cast a look about and realized that what might be termed "almost working" VPPs for smaller boats aren't that expensive on eBay, which brought up the question: why not more expensive?

On this web page: http://www.submarineboat.com/casting_boat_props.htm I may have come across a possible answer with these words "And we needed a replacement for the hydraulic distributor ring that is missing from our Hundrsted controllable pitch propeller, control box. Hundrsted wants $2200 for the part ..." so a hundred to a few hundred dollars for a fixer upper is looking less of a good deal ... unless you know your way around a lathe as those fellows did. Now, those guys on that page are also casting their own props which may be a bit more involved than most might want to get, but it does point out that if you have, or have a friend who has, some skills those good deals on old equipment may actually be an option.

 

I said in another thread that CPP were no longer available for small (less than 50HP) engines and I would *love* to be wrong.

Sabb in Norway (note the spelling it is NOT Saab) used to make units as small as 10HP but AFAIK no longer do so. If I can ever find one used, near me, I'll buy it. If I could get my hands on a decent set of drawings I'd consider making one.

Hundested I think still make CPP gear but start at 50HP. And as noted, not cheap.

My solution FWIW was to buy a Bukh diesel engine with a 3:1 reduction g/box and a 22" Autostream feathering prop with settable pitch stops for both forward and reverse. As the boat hasn't hit the water yet I can't comment on how well it's all going to work but I can say with certainty that it won't work as well as a CPP.

However I can't *get* a CPP setup so.......

PDW

 

What are the reason(s) for wanting variable pitch on a motor-sailer, particularly ?

 

I think the better question is, why *wouldn't* you want one?

Fixed pitch props are only really efficient at one shaft speed. You can get a lot better endurance and thrust by altering the pitch of the prop in line with speed through water and engine RPM. Also you can go from forward to reverse without any dramas at all, or have the prop set to minimise drag under sail.

The Autostream prop I have allows me to set the pitch for forward & reverse separately and to tune both to the hull/engine combination but still only really for one speed in forward and a different one in reverse. I also get the low drag under sail, but it's still a poor second best to a CPP.

There are a few drawbacks to a CPP. They're more complex and therefore expensive and generally require a bigger (hollow) shaft, bigger hub and therefore bigger prop tube. This isn't an issue if they're fitted as part of the original build, but - mass production boatbuilders care far more about first cost and profit margin than lifetime efficiency, so - shrug.

PDW

 

So, what is the comparison between the variable pitch prop, and a folding design, in the motor-sailer ? Under sail only I assume the folding model is best, but maybe inferior under power ? Is the controllable pitch mainly useful under a combination of sail and engine ?