Propulsion problems

[dmr]

Any boat (with motor/engine) will do more then a knot in gear at idle, most do 2-2.5-3 knots, I can't think it is ventilating at so low powers, in forward gear. and hardly not is reverse at idle/tickover.

 

Cavitating can happen as said if the propeller is put on backward, the blades is shaped for being efficient in forward gear, a slight cavitating in the short moments it is in reverse gear don't harm the propeller. but if was constant. I seen propellers on RC planes put on backward. so it can happen.

A narrowboat that does 2.5 knots at idle will be about as much use as a chocolate teapot!

 

...............Dave

[Dalslandia]

A narrowboat that does 2.5 knots at idle will be about as much use as a chocolate teapot!

 

...............Dave

It is good it come to use..

 

Dalslandia does go 2.5 -2.8 kts when I enter the lock, in gear. it is less then walking speed.

[Murflynn]

.............. but following another boat travelling at 1knot can be a right pain in the wotsit.

[sbillis]

Any updates on what the problem is? I understand that the OP was going to lift the boat and check things out.

 

Simon

[sjc]

Any updates on what the problem is? I understand that the OP was going to lift the boat and check things out.

 

Simon

 

Quite right, well remembered !

I never got to see it in the end but some other friends did, and they took a few pictures. Once I obtain copies ( with the boat owner's consent ) I'll post them on here. However, from the images I've seen we were all very very wrong. There is no simple solution, the stern design is out of this world and needs serious metalwork to fix it :-

 

The rounded stern continues below the water line, so there is no swim whatsoever. Looking from the rear the prop and rudder are mounted within a "box" chamber cut into the rounded stern. Each side of the box chamber has a small rectangular channel that goes forward and out to the side of the boat. So, these rectangular channels supply the water to the pop, they are quite small ( hard to estimate dimensions from the image I saw ) so severely limit the water reaching the prop. This is why the boat never picks up speed, no idea about the vibration though.

 

So the next step is to get some quotes to correct it, and decide if it is worthwhile, the boat remains out of the water this week for blacking.

[RLWP]

Wow! I don't think anyone of us would have guessed that

 

I'd love to see some photos if you get permission

 

Richard

[Paul C]

 

Quite right, well remembered !

I never got to see it in the end but some other friends did, and they took a few pictures. Once I obtain copies ( with the boat owner's consent ) I'll post them on here. However, from the images I've seen we were all very very wrong. There is no simple solution, the stern design is out of this world and needs serious metalwork to fix it :-

 

The rounded stern continues below the water line, so there is no swim whatsoever. Looking from the rear the prop and rudder are mounted within a "box" chamber cut into the rounded stern. Each side of the box chamber has a small rectangular channel that goes forward and out to the side of the boat. So, these rectangular channels supply the water to the pop, they are quite small ( hard to estimate dimensions from the image I saw ) so severely limit the water reaching the prop. This is why the boat never picks up speed, no idea about the vibration though.

 

So the next step is to get some quotes to correct it, and decide if it is worthwhile, the boat remains out of the water this week for blacking.

 

Wow, that's bonkers and thank you for returning to update the thread. How does your friend feel about it? Did they buy the boat simply as accommodation or with a plan to go cruising? Did the price reflect that basically this boat was only suitable for the former?? It seems bizarre that a shell builder would do this, and someone would buy it without realising but I guess weirder things have happened etc....

[MtB]

Wow! I don't think anyone of us would have guessed that

 

I'd love to see some photos if you get permission

 

Richard

 

 

You're overlooking posts 58 and 65, guessing this!

 

[Murflynn]

who was the shell builder?

 

sounds like it must have been a backyard bodger who is not familiar with narrowboats.

[sjc]

I am reluctant to name shell builders, but from my research they do still seem to be in business. I really am limited by what the boat owner authorises, like many posters on here, if it were my boat I would tell the world !

[Murflynn]

perhaps their real expertise is in the building of the canal version of land based 'mobile homes' - which of course are not really mobile at all, but have to have the ability to move to be classified as such.

Edited October 8, 2015 by Murflynn

[tidal]

It sounds like an abortive (or aborted) attempt to create a ducted propeller.