Controlable Pitch Prop

The problem is I can see the stars in the sky but not a dam CPP among them . Coffee break is over --back to the shop-working on the skeg --Have a good day Geo.

 

Treat a modern high speed diesel poorley (carbon it up) and you can shorten it's life by 50%. Do that a couple of times over a 10 year cruising (motorsailing)period and that 3 to 4 thousand dollar CCP looks like a good investment.

Many if properly maintained will run 6,000-10,000 hours . Underloading IS certainly a hassle , but the hours spent inshore under power will make up for a lot of underloading .

A head gasket and exhaust manifold gasket is far cheaper every 2000 hours , should the engine begin to carbon up.

To create proper engine loading all that is required is a cruising prop , and an EGT gauge and an understanding of how the engine should NOW be operated.

Remember many small diesels are simply yard equipment sourced and dont mind under loading any where near what an 800hp industrial sourced engine would find intolerable.

 

I have one of these...

http://www.seahawk.com.au/

Not cheap. I'd rather have a CPP, but I can't *buy* a CPP so I bought one of these. At least I get the benefit of low drag under sail and the ability to have a different pitch for forward & reverse. Against that the flat blades aren't a very efficient shape but edge-on, they do offer little drag, so.... pick your tradeoff. I have a couple other fixed blade props and I can see swapping over props if I was going to do a lot of motoring - say canals or inland waterways.

Sabb Norway undoubtedly have all the drawings still for their 10HP, 22HP and 30HP CPP systems. If you find a way of extracting a set of plans from them, please let me know. I have a comprehensive machine shop and access to professional casting people experienced in bronze & stainless steel as well as other metals.

However I doubt any company is going to release their drawings and the market is too small/cheap (on the buyer side) to justify making these small units, so we're all screwed. Unfortunately.

PDW

 

PDW -- I tend to agree on the old manufacturers not releasing their engineering info in kindness however if pestered enough possibly they will do so for a reasonable price or suddenly wake up and see this might be one way of keeping some their staff during the slow times on the big gear. Sort of a bread and butter income. OR as I mentioned before some Asian company might pick up on this thread thru the internet on one of their product demand marketing searches and presto-- obtain an old used unit, do a little reverse engineering and away we go. Not my choice but hey the new early bird gets the worm, thats capitalism. I have made this search sort of a come in from the shop hobby and actually i'm beginning to enjoy it.

 

If you read the submarine boat web site on their CPP, you'll see he did extract a fair bit of information from Hundedsted including some drawings of cross sections etc. So there is some hope.

I'd prefer not to use hydraulics personally but my interest stops at about the 30 HP continuous point. I have found an interesting master's thesis on CPP for ROVs, quite dated though it does have some engineering drawings for a prototype that was built. Problem is, it's too far off the other end of my interest WRT power.

So by all means - keep digging. There's at least one other person seriously interested. Probably for my *next* boat though - I'm not about to slice off the aft end of mine to install a bigger prop shaft tube, which would almost certainly be required.

PDW

 

The >problem< of under loading can simply be solved by using a bit more throttle .

Instead of say 1200rpm ,1400rpm would load the engine higher and assure a higher engine load .

The real hassle with under loading is not the carbon in the exhaust .

The rings on a diesel seal because compression pressure gets behind the rings and forces them hard against the cylinder walls.
Light loads mean less sealing pressure so blow by is increased.

The big problem is with no sealing load the rings will burnish the cylinder walls , polishing off those tiny scratches from the hone that are needed to hold lube oil.

After a while with less cylinder lubrication the cylinder wears and the engine begins to SLOBBER. Black slime coats the exhaust and engine vents.

Using a $100 EGT gauge would allow the engine to be worked hard enough to avoid all this at low load.

The choice is a bit more fuel burn when MS or finding and rebuilding an old CPP for your sized engine.

Thousands of outlay up front or an extra $50-$100 for every few thousand miles of MS operation under powered sail.

Your choice.

Dont let some ideal keep you from contemplating the math.

In your boat at probably under 2GPH a 10% reduction in the fuel burn will take a decade underway to see the just first thousand $$$ saved.

 

http://www.finn.no/finn/boat/parts/object?finnkode=47581678&searchclickthrough=true
A teaser bargain price $400

http://www.finn.no/finn/boat/motor/object?finnkode=47917626&searchclickthrough=true
With SABB engine

BR Teddy

 

If you are looking for a small diesel with variable belt transmission, this little car is made in France and can be driven without a licence.

500cc Kubota twin diesel with CVT belt drive:http://en.wikipedia.org/wiki/Aixam

My Sister has a caretaker who looks after her house, he's had one of these for 2 years and is very happy with the engine and gearbox.

 

If you thoroughly read through the entire thread, you can see how the connection evolved. No, venting is not changing pitch, that is quite obvious for anyone to see. However, the discussion included loading/unloading of the engine at various points, and vented propellers are one way of doing just that.

 

Hmmm - a bit less than $3000 AUD at current exchange rate.

Where's my friend Walter in Tromso these days......

PDW

 

I agree. Any engine life problems in a motor sailer can be solved with some combination of more rpm, periodic load increases and turning the engine off.

Anything to adjust propeller load will need to be inexpensive to be cost effective (in most small boat cases).

 

Very interesting TD, I translated most of the technical info however a little unsure of the 311mm dimension (I think inside measurement flange to flange ?) and the 1050mm which i think is overall total length??) Also I am not sure of the how this system operates. Some combination of electric/hydrolic set up. At $400 I would definitely be interested once I determine how the control mechanism worked. TD are you familiar with this set up ? Any help appreciated ---Geo.

 

FF and Jonr, I agree with both of you but that still doesn't solve the problem of prop drag when sailing. Think motorsailers and motorsailing not sailboats and motorsailing. Motorsailers and Heavy Cruising sailboats have poor windward capabilities thus usually motorsail to windward. Given the choice of the ultimate propulsion system for heavy crusing sailboats and motorsailers one would have to choose the CPP system. I might add the CPP set up also lends itself to gaining great efficiency under electric propulsion. Regarding the cost effective aspect you have to look at the total picture plus the wow factor. Any automobile having more than a small to med 4 cyl. engine with a max speed greater 75MPH is not cost effective but who really buys and drives such a machine. Personally I want to get the most out of my water machine and in my case a CPP will allow me to do it. This system is not for everyone but I bet if they were readily available many us would consider them a necessity for good performance and be so equipped cost effective or not.

 

311mm is the length outwards from the outer flange to the end of propeller hub. 1050mm is the stern tube length. Don't know the brand. It needs a hydraulic pump (original has been manual) to operate the pitch. Note this looks like a motor boat setup so most propably there's no possibility to feather the blades. Some handyman might make it thou but dunno?
BR Teddy

 

>... that still doesn't solve the problem of prop drag when sailing.

A large diameter two bladed prop stopped vertically sounds pretty good for most motorsailers (but evidently this isn't very common). PHRF rating indicate that cruising sailboats shouldn't worry about it.

I agree, if some company wants to make a low cost CPP, that would be great. I'd like to see someone run the numbers to show what it would be worth and how it compares to the alternatives.