Props vs Jet drives.....

[c c]

The Royal Navy are doing it with their latest all electric ships....but whether you'll get much use out of electric aircraft lifts or railguns on a nb I'm not so sure

A LIFT - now theres something I hadn't thought of to extend boating into our old age. Drive on mobility scooter? You've added a whjole new train of thought.

[~ HD ~]

one site i was looking at regarding diesel electric

 

~ http://www.ossapowerlite.com/index.htm ~

 

fairly expensive i imagine ..

 

can't get my head around .. electronics and water ..

'specially salt water .. i.e. the potential corrosion problems ..

 

but the again .. the combination has been around since at least WW1

 

i quite like the idea of a variable pitch prop ..

although don't know if they are useful on canal boats ..

saw one system by a well known scandinavian company ..

prop blades could be replaced independently in the case of damage

[WotEver]

Shameless bit of self-promotion follows:

 

GBJetski2010

Hmmm... "Blog has been removed"

[mykaskin]

i quite like the idea of a variable pitch prop ..

although don't know if they are useful on canal boats ..

saw one system by a well known scandinavian company ..

prop blades could be replaced independently in the case of damage

 

Must admit to been interested in variable pitch, but reducing something this size:

 

 

to the size of a canal boat prop will have it's own inherent problems. There are some "auto feathering" props which use shaft speed and centrifugal force to control pitch. They give a higher engine loading at lower revs thus maximising engine effeciency, but stills allows for full power output at high revs.

 

What I would really want is a fully controlable fowards and backwards prop to allow the engine to stay full power but be instantly reversable since it takes so long for the engine to slow down and speed up. Also would be really cool to be on tickover yet still making a really good speed!

 

Cheers,

 

Mike

[~ HD ~]

i was looking at these ..

 

~ http://www.hundestedpropeller.dk/ ~

 

looks like 150 hp engines on up :-/

 

must be smaller ones though ..

 

( this computer doesn't do youtube unfortunately )

 

my interest is continental canals and sea travel ..

and figuring fuel consumption .. plus back up propulsion power ..

i fancy either a ketch rig or junk rig .. on a small clipper style barge ..

( mast and rigging would need to fold down somehow

( don't know if a small clipper would be possible given the bow shape

( yet to research that :-)

haven't quite figured lateral resistance regarding draft and keel potentials ..

motor-sailers generally go by 1ft draft for every 10ft length ..

i've only seen one pic of a dutch clipper on the 'dry' ..

was shallow 'v bottom with skinny bilge keels ..

figured a variable pitch prop could be feathered to reduce drag when using sails ..

 

don't know if i've got it right .. but fuel consuption seems on par with HGV vehicles

but i might have got my sums wrong ..

i used to drive 350/400 cummins .. and similar cats 325/425 ..

fuel consumption was about 3.5mpg ( usa ) .. sometimes more .. depending

Edited August 3, 2010 by ~ HD ~

[bargemast]

Must admit to been interested in variable pitch, but reducing something this size:

 

 

to the size of a canal boat prop will have it's own inherent problems. There are some "auto feathering" props which use shaft speed and centrifugal force to control pitch. They give a higher engine loading at lower revs thus maximising engine effeciency, but stills allows for full power output at high revs.

 

What I would really want is a fully controlable fowards and backwards prop to allow the engine to stay full power but be instantly reversable since it takes so long for the engine to slow down and speed up. Also would be really cool to be on tickover yet still making a really good speed!

 

Cheers,

 

Mike

 

 

A variable pitch prop is ideal as you can adapt the pitch exactly to the revs and so power output of the engine, normally in combination with a pyrometer to avoid overload. A big part of the Scandinavian fishing fleet used to have slow-rev engines and a variable pitch prop "HUNDESTED" was and probably still is the best known, they had lovely glow-bulb engines of their own make too in the past.

 

Those props wouldn't have an easy live on the canals with a great lack of water under the keel stirring up and going through mud, old matresses and other crap.

 

The repair bills of a prop like that would surely become the most expensive part of your yearly cruising out-goings.

 

Peter.

 

For sea, and plenty of deep enoug water, I would want one, but for the majority of the U.K. cannals NEVER !

[bargemast]

i was looking at these ..

 

~ http://www.hundestedpropeller.dk/ ~

 

looks like 150 hp engines on up :-/

 

must be smaller ones though ..

 

( this computer doesn't do youtube unfortunately )

 

my interest is continental canals and sea travel ..

and figuring fuel consumption .. plus back up propulsion power ..

i fancy either a ketch rig or junk rig .. on a small clipper style barge ..

( mast and rigging would need to fold down somehow

( don't know if a small clipper would be possible given the bow shape

( yet to research that :-)

haven't quite figured lateral resistance regarding draft and keel potentials ..

motor-sailers generally go by 1ft draft for every 10ft length ..

i've only seen one pic of a dutch clipper on the 'dry' ..

was shallow 'v bottom with skinny bilge keels ..

figured a variable pitch prop could be feathered to reduce drag when using sails ..

 

don't know if i've got it right .. but fuel consuption seems on par with HGV vehicles

but i might have got my sums wrong ..

i used to drive 350/400 cummins .. and similar cats 325/425 ..

fuel consumption was about 3.5mpg ( usa ) .. sometimes more .. depending

 

 

You were just a bit quicker then me with the Hundested and as a bonus you came up with their web-site, which I hadn't looked at. I remembered them having looked at a couple of Danish fishing boats with those engines and props that were for sale about 35 years ago for peanuts.

 

In your case for your Clipper, you should maybe study the possibilities of a drop-keel to have an acceptable draft for the canals and inland waterways, but also when anchored at sea you can come much closer to shore and dry out on a fairly flat bottom.

 

Peter.

[~ HD ~]

In your case for your Clipper, you should maybe study the possibilities of a drop-keel to have an acceptable draft for the canals and inland waterways, but also when anchored at sea you can come much closer to shore and dry out on a fairly flat bottom.

 

i took a look at these .. one version has a drop keel ..

~ http://www.steelboats.com/huffler_yachts.htm ~

 

saw another .. but have lost the site link ..

it lifted up into a coffee table enclosure ..

and the steel base had eliptical shaped 'pads' for grounding on ..

i think it was meant as an option for grp hulls ..

[Derek R.]

Mike won't be happy 'til he gets Victoria doing this: Fireboat Sea Trials (Handy water pistols for bridge louts!) Fitted with four Hundested props apparently.

 

Derek

[Rick-n-Jo]

I have been playing with the idea of building a boat without a diesel engine or tiller but with a one of the modern quiet watercoled diesel generators powering every electric demand you could wish for plus a 240v electric motor to drive the prop with steering by bow/stern thruster. Has anyone tried this? There must be problems or we would have seen it already.

 

Yes, I have, exept that it's a 48V DC generator and motor, and traction battery, with oodles of domestic power via inverters. John (Barge Sara) has a similar set up. Forum search for his posts and mine (nb Pleiades) to save me repeating what's already been written.

 

So we've done the propulsion bit of your idea, but not the steering bit. I'm not sure why you'd want to do that. I've seen some folk who try to steer by bow thruster, and it's usually pretty horrible to watch!

 

For a better CWDF search tool go here

 

Rick

Edited August 3, 2010 by Rick-n-Jo

[bargemast]

Mike won't be happy 'til he gets Victoria doing this: Fireboat Sea Trials (Handy water pistols for bridge louts!) Fitted with four Hundested props apparently.

 

Derek

 

 

Most impressive with her 4- 70" variable-pitch props and 4 very powerful engines MTU 12V4000 (2000 Hp@2000n), I don't think somehow that you have to make way for this boat in the near future on the G.U.

 

To see her 4 props watch this video : http://www.youtube.com/watch?v=XF2LPd2QVuc

 

I don't think that Mike's JP 2 (great engine for his boat !) would be powerful enough (not even on full throttle) to power one of those handy water-pistols for the bridge louts.

 

Peter.

[c c]

Yes, I have, exept that it's a 48V DC generator and motor, and traction battery, with oodles of domestic power via inverters. John (Barge Sara) has a similar set up. Forum search for his posts and mine (nb Pleiades) to save me repeating what's already been written.

 

So we've done the propulsion bit of your idea, but not the steering bit. I'm not sure why you'd want to do that. I've seen some folk who try to steer by bow thruster, and it's usually pretty horrible to watch!

 

For a better CWDF search tool go here

 

Rick

 

Thanks for that - I found some very interesting links.

Edited August 3, 2010 by canalchef

[Derek R.]

For a better CWDF search tool go here

 

Rick

 

That link has flagged a Trojan Horse blocked by Avast webshield. No go.

 

Derek

[carlt]

That link has flagged a Trojan Horse blocked by Avast webshield. No go.

 

Derek

That's surprising, considering it was set up by Gary Peacock.

[mykaskin]

I don't think that Mike's JP 2 (great engine for his boat !) would be powerful enough (not even on full throttle) to power one of those handy water-pistols for the bridge louts.

 

Peter.

 

The JP2 shifts a hell of a lot of water, and you don't actually need much on them water hoses as they are high pressure.

 

Mike

 

That link has flagged a Trojan Horse blocked by Avast webshield. No go.

 

Derek

 

Nothing wrong with the website as far as I can see. Ignore it, it probably just thinks that because it's a form that is posting to another website.

 

Mike

[blueprince]

Why pump water at bridge louts? Not when you can save the price of a pump out!

 

Also I thought about a jet propulsion system when I was having my hull built, I thought a diffuse enough intake would eliminate the problems of jetsam and flotsam, something like two parallel intakes built in either side of the hull. Not having seen it done anywhere before, and not wanting to discover a really good reason why it wouldn't work after I made the hull modifications i shelved it, but it still seems the only way you could run one without it fouling all the time.

[Trilby Tim]

I think a jet drive wouldn't make a great deal of sense on a canal boat. The efficiency would be extremely poor. To move a boat forwards you accelerate a body of water backwards. To generate a certain amount of thrust you can either move a large body of water slowly or a small body of water quickly. However efficiency is maximised when the difference in speed between the body of water you're accelerating and the speed of the boat is small. So for a canal boat going slowly the most efficient way to move is to to push a lot of water slowly. So for a jet drive to be efficient in a canal boat you'd need a very large diameter duct and impeller moving water relatively slowly, which wouldn't really be practical. A typical jet drive moves a small volume of water at high speed, and that's good for high speed craft, but not canal boats. And that's without problems with fouling. you'd need a fairly fine grill over the inlet to stop rubbish from lunching the impeller, and that would cut the efficiency even more, not to mention needing clearing all the time.

The photo in #18 looks like a steerable Kort nozzle, similar to a kitchen rudder locked in the open position. I do get some prop fouling, but I'm not really sure if it's more or less that with a with a conventional rudder. The types of things I've pulled out have been like weed and plastic sheeting. The clamshells don't really get in the way of clearing debris. I think the clamshells actually partially protect the prop from larger things like shopping trolleys and mattresses. I've had some fairly chunky pieces of wood go through there which have made an awful noise (one even stalled the engine ), but haven't done any damage. What has caused damage has been bumping it against things like lock gates. I've just had the boat out the water to fit an improved MkII version which gets round that problem, I need to get round to updating the blog.

[bargemast]

The JP2 shifts a hell of a lot of water, and you don't actually need much on them water hoses as they are high pressure.

 

Mike

 

 

To get the water in a big long reaching powerful jet you need lots of Hp's, in the discription of the "Fire Fighting Boat 343" they say that with the 4 engines of 2000Hp each they can deliver 50.000USgpm, if they use 2 engines they can still provide 20.000USgpm.

 

With your Lister JP2 you can probably drive a pump that will give you a reasonable jet that would be strong enough to reach the bows of Victoria and the bridge you're going through, but I can't see it going much further.

 

Peter.

[Mikeonb4c]

I think a jet drive wouldn't make a great deal of sense on a canal boat. The efficiency would be extremely poor. To move a boat forwards you accelerate a body of water backwards. To generate a certain amount of thrust you can either move a large body of water slowly or a small body of water quickly. However efficiency is maximised when the difference in speed between the body of water you're accelerating and the speed of the boat is small. So for a canal boat going slowly the most efficient way to move is to to push a lot of water slowly. So for a jet drive to be efficient in a canal boat you'd need a very large diameter duct and impeller moving water relatively slowly, which wouldn't really be practical. A typical jet drive moves a small volume of water at high speed, and that's good for high speed craft, but not canal boats. And that's without problems with fouling. you'd need a fairly fine grill over the inlet to stop rubbish from lunching the impeller, and that would cut the efficiency even more, not to mention needing clearing all the time.

The photo in #18 looks like a steerable Kort nozzle, similar to a kitchen rudder locked in the open position. I do get some prop fouling, but I'm not really sure if it's more or less that with a with a conventional rudder. The types of things I've pulled out have been like weed and plastic sheeting. The clamshells don't really get in the way of clearing debris. I think the clamshells actually partially protect the prop from larger things like shopping trolleys and mattresses. I've had some fairly chunky pieces of wood go through there which have made an awful noise (one even stalled the engine ), but haven't done any damage. What has caused damage has been bumping it against things like lock gates. I've just had the boat out the water to fit an improved MkII version which gets round that problem, I need to get round to updating the blog.

 

Well put. I had wondered about exactly that with jet propulsion. Worm drives anyone?

[mykaskin]

22hp engine seems to be able to provide 800 litres a minute at 7 bar with a standard centrifugal pump, which I would have thought would be enough with a suitable nozzle. Obviously it wouldn't be the same volume of water shifted by the 343.

 

Mike

Edited August 4, 2010 by mykaskin

[bargemast]

22hp engine seems to be able to provide 800 litres a minute at 7 bar with a standard centrifugal pump, which I would have thought would be enough with a suitable nozzle. Obviously it wouldn't be the same volume of water shifted by the 343.

 

Mike

 

 

That works out at 13.3 litres a second, which will make it very quick to fill a couple of buckets in no time at all.

 

The volume shifted by the fire fighting boat works out at 3125 litres a second, so only a bit more.

 

My personal choice of engine would be de Lister JP2 anytime, as I would be financially unable to even just start up the others.

 

Peter.