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Old 22-02-2009, 08:20   #1
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Question Controllable-Pitch Drive

Our British built 31' sloop came with a controllable pitch drive on a Perkins 4.107 engine. It is a 2 blade prop with a rod inside shaft. Have not found any manufacturer's mark.

I would like to know if anyone has experience with this system pro or con.

Have considered replacing with a conventional Hurth hydraulic transmission.
As I am concerned about the reliability of the system.

Thank you for any information on this subject.

Tim
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Old 22-02-2009, 09:49   #2
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I'd give it a once over and if the system is good keep it.
If its working properly and you can do maintenance on it its a BIG plus in my opinion.
The only one I'm familiar with is the Hundested and its exceptional.
BUT they absolutely require proper maintenance.
I wish I had one.
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Old 22-02-2009, 10:32   #3
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Thanks for responding. i will give it a try and hope for the best.
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Old 22-02-2009, 13:10   #4
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I've always liked the concept. Saab did it for years....
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Old 22-02-2009, 13:49   #5
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If its reliable then excellent. Be careful not to lug the engine though...diesels will not last long if they are run at low RPM's with over pitched props. If you can reach the engines maximum RPM with the controllable pitch prop at its maximum pitch, then you are okay. If not, then don't go past the pitch at which the engine can reach its maximum RPM, especially at lower RPM's. There are some who feel it is fine to lug a diesel but I believe what Cummins recommends, that you don't.
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Old 11-03-2009, 13:27   #6
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I have also sailed with Hundested installations and they are excellent and reliable....I had a 48' aluminum ketch with a Hundested CP prop. The engine was a Perkins 4-108.I bought the boat in Michigan and made the trip from there to Mobile Al via Macinaw (mostly under sail), to Chicago where we unrigged her and then south on the river system.

In my installation, the Perkins was coupled to the Hundested unit through a Hurth transmission with as I recall, approximately a 2.2-1 reduction.

I also have a little experience with CP props from many years go when I was in the Merchant Marine in offshore tugs.

CP props allow you to make the best use of HP for given sea conditions and (at least in my history with them) when properly used, increase fuel economy. One big plus (in the case of my Hundested installation) is the ability to feather the prop when sailing to reduce drag to a fraction of what you get with a fixed pitch prop with the shaft brake on.

The back side of this is that its reportedly easy to destroy a diesel by overpitching. In my ketch I set the pitch fairly shallow when manovering in close quarters and used the transmission for ahead/astern (although it was possible with the Hundested, just much slower response time..... lots of turns on the pitch control). Under way I would, again depending on wind and sea conditions, increase the engine RPM to where it was in the middle or upper end of the torque curve and add pitch. When the exhaust dirties up and when coolant temperature starts to increase then its too much.

In large vessels pitch is set with an eye to a pyrometer i.e. a thermometer to measure exhaust gas temperature, to avoid loading the engine past its rated HP. That having been said, I dont know what a not to exceed pyrometer temperature would be i.e. at what temperature the engine was putting out its maximum rated HP. I would imagine that it would vary from engine to engine.

Before I sold her I went back over the logs. In the time that I owned her I averaged .8 GPH. That figure was reached by dividing the number of hours on the Hobbs by the number of gallons burned. Eight tenths of a gallon per hour is pretty respectable consumption for 48'. She did not have a generator.

One additional note. I considered her very underpowered. In my opinion a boat should have a minimum of 1.5 HP per foot of LOD.

Hope this helps

I totally agree with David's recommendation and support of the Cummins recommendations.
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Old 11-03-2009, 14:45   #7
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I agree with Carr that measuring exhaust gas temperature is the key. What engine manufacturers recommend is wide margin safety which is wise without measuring. I know that pyrometers are available with easily mounted temp sensors, Dashew uses them with Hundested with great success.

Also, the trick is in combination with motor-sailing. You can increase the pitch a lot when the sails provide part of the power requirement.

cheers,
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Old 11-03-2009, 15:17   #8
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variable pitch

thanks for the info, have been warned about the overheating. The boat is 4.5 ton, 31' w/ Perkins 4-107 power. Can't finder any maker id on transmission gear or manufacturer of CP unit. The pitch control controller is missing, but seems to have been a lever connected to the slide bearing that moves a rod inside the shaft to a twin blade prop. Hope it works.

Quote:
Originally Posted by carr View Post
I have also sailed with Hundested installations and they are excellent and reliable....I had a 48' aluminum ketch with a Hundested CP prop. The engine was a Perkins 4-108.I bought the boat in Michigan and made the trip from there to Mobile Al via Macinaw (mostly under sail), to Chicago where we unrigged her and then south on the river system.

In my installation, the Perkins was coupled to the Hundested unit through a Hurth transmission with as I recall, approximately a 2.2-1 reduction.

I also have a little experience with CP props from many years go when I was in the Merchant Marine in offshore tugs.

CP props allow you to make the best use of HP for given sea conditions and (at least in my history with them) when properly used, increase fuel economy. One big plus (in the case of my Hundested installation) is the ability to feather the prop when sailing to reduce drag to a fraction of what you get with a fixed pitch prop with the shaft brake on.

The back side of this is that its reportedly easy to destroy a diesel by overpitching. In my ketch I set the pitch fairly shallow when manovering in close quarters and used the transmission for ahead/astern (although it was possible with the Hundested, just much slower response time..... lots of turns on the pitch control). Under way I would, again depending on wind and sea conditions, increase the engine RPM to where it was in the middle or upper end of the torque curve and add pitch. When the exhaust dirties up and when coolant temperature starts to increase then its too much.

In large vessels pitch is set with an eye to a pyrometer i.e. a thermometer to measure exhaust gas temperature, to avoid loading the engine past its rated HP. That having been said, I dont know what a not to exceed pyrometer temperature would be i.e. at what temperature the engine was putting out its maximum rated HP. I would imagine that it would vary from engine to engine.

Before I sold her I went back over the logs. In the time that I owned her I averaged .8 GPH. That figure was reached by dividing the number of hours on the Hobbs by the number of gallons burned. Eight tenths of a gallon per hour is pretty respectable consumption for 48'. She did not have a generator.

One additional note. I considered her very underpowered. In my opinion a boat should have a minimum of 1.5 HP per foot of LOD.

Hope this helps

I totally agree with David's recommendation and support of the Cummins recommendations.
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Old 11-03-2009, 15:54   #9
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Might try contacting the yard and/or designer from whose board she sprang. Additionally I would bet that Perkins or the builder....would possibly have somewhere in their archives information about possibly whose transmission and drive it is.

One other suggestion. Contact Perkins, explain the situation and ask them about installation of a pyrometer in the exhaust manifold or the elbow before you go into the seawater riser...... I considered this in my last boat but never did it. I feel sure that Perkins can give you a pretty good idea of a not to exceed temperature for exhaust gas. Additionally if the engine is under the cockpit, a mechanical pyrometer ie. one with a capillary tube could possibly be used in lieu of a more expensive electrical unit because the distance from the sensor to the gauge could be somewhat short. The dial could be mounted somewhere in the cockpit to be able to keep an eye on when you are pitching the prop and occasionally thereafter when under power. The installation of the actual probe I dont think would be that difficult....after purchasing the pyro find a machine shop to put the mounting hardware in the elbow (or the Perkins recommended position....they might recommend somewhere on the exhaust manifold) insert the probe and tighten the lock bolt down. It should be pretty straight forward.

One thing that you might note is this...and I would want to talk to Perkins about this as well.....I personally would not push the maximum temperature i.e. maximum loading. I would run shy of that somewhat. I also would discuss with Perkins the fact that the mounting point for the pyrometer sensor might be (depending on whether or not they recommend placement) a little remote from the actual exhaust manifold. Where this goes of course is that the exhaust gas may cool somewhat in passing through an uninsulated exhaust manifold and loose heat in the act of part of it being absorbed by the manifold. Actually this all sounds a lot more complex than it actually is.... were she mine I would have a pyrometer in conjunction with using the temp guage on the engine and I think you should be pretty safe.

There are probably some folks here on the forum who are a lot more knowledgeable than am I with this. I remember in some of the tugs I worked in that on the main engines each cylinder had a pyrometer. Additionally as I recall there was one at master control as well that whatever engineer that was currently on watch would monitor along with the myriad of other stuff that needed checking in a vessel of that size and complexity.....

Hope this helps. On the other hand I would watch the water temp closely and the exhaust as well and not necessarily let it stop me from sailing. Carefully. Thats the method I used in my ketch, in the river trip and afterwards until I sold her and never a problem with the engine or drive train. I woud err if it were though on the side of a pyro provided it was not terribly expensive.

Carr

Additionally I just spied Nick in Jedi's post and Im in accord with him.

As an afterthought- I have close voyaging friends who migrated to Australia from England. They know quite a bit of the history of yachting and sailing in the UK. If you have problems with this I would be happy to e mail them for suggestions on how to run down the origins of your ship and her equipment....
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Old 20-09-2011, 02:49   #10
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Re: controllable pitch drive

Hello all,

could someone tell me a bit more about the practical maintenance of a Hundested VP4? I have one installed and ofcourse will follow the manual. But just wanted some practical advise. Also any ideas about using water emulsifying grease against normal grease?

All the best

Hein
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Old 20-09-2011, 06:40   #11
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Re: controllable pitch drive

This attached pdf may help you understand your prop.
Attached Files
File Type: pdf Variable Pitch and sailing Propellers.pdf (443.9 KB, 157 views)
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Old 20-09-2011, 06:58   #12
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Re: controllable pitch drive

Imulsifying grease must be used....not regukar grease.....

I have experience with them.

A pyrometer is the key here.

The biggest problem with them is "overfutzing"

These systems have been in use in Europe for years esp on fishing noats.
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Old 20-09-2011, 07:32   #13
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Re: controllable pitch drive

Thanks for the advice. There is some kind of temperature sensor in the exhaust, right before it is mixed with colder water. How should I set up a pyrometer? Also exhaust temperature?

And why not regular grease? Is it because emulsifying grease forms a sludge and keeps the water out? Will regular grease not keep the water out?
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