Canopus and Sculptor

[mark99]

My boat has a bar and fake rivets and handles ok. Go figure.

[FadeToScarlet]

The only bar my boat has is full of bottles of single malt, rum, Port, and wine. This probably has an effect on the steering.......

[Ray T]

No idea where I got this photo but found it among my files:

 

[ditchcrawler]

No idea where I got this photo but found it among my files:

 

229363_10150911978877824_2134321663_n.jpg

Thats What I did to my rudder

[WotEver]

Thats What I did to my rudder

Did you employ the services of a respected and experienced naval architect to add those 4 inches?

[ditchcrawler]

Did you employ the services of a respected and experienced naval architect to add those 4 inches?

No, but I made a bolt on extension first a bit bigger than required and spent a summer taking it off and trimming until I got near the result I wanted, I would like what it better but I am not spending 2 grand.

[Dalslandia]

The canal I trafic, most often same length every day, up or down, have some sharp bends, just after or before locks and narrow canals, most is a shallow 6 feet, plus some between the locks, I can tell by the water level in the pond between the locks how well Dalslandia will turn that day, (also depending on load) before I remade the plane plate rudder to a Schilling rudder, some turns was very marginal, will it go well or not was the question, with or without using the BT. but with the Schilling there is always a marginal if i make the turn or not, so saying that a boat can't be improved is just a way to say "I am jealous on those that have the insight"

[Chertsey]

The canal I trafic, most often same length every day, up or down, have some sharp bends, just after or before locks and narrow canals, most is a shallow 6 feet, plus some between the locks, I can tell by the water level in the pond between the locks how well Dalslandia will turn that day, (also depending on load) before I remade the plane plate rudder to a Schilling rudder, some turns was very marginal, will it go well or not was the question, with or without using the BT. but with the Schilling there is always a marginal if i make the turn or not, so saying that a boat can't be improved is just a way to say "I am jealous on those that have the insight"

We dream of six feet! (Well, maybe not that much, we might drown).

[ditchcrawler]

I think it was Matt who posted a picture of a wide beam with an eyebrow over the bow thruster tube so that it didn't suck air. Some Narrowboats are not very deep at the bows.

Saw this today

I think it was Matt who posted a picture of a wide beam with an eyebrow over the bow thruster tube so that it didn't suck air. Some Narrowboats are not very deep at the bows.

Saw this today

[stegra]

Saw this today

 

That looks to me like it might force the thrust downward and lift the bow, thus exaggerating the very problem it's intended to solve.

Edited February 3, 2017 by stegra

[MtB]

 

That looks to me like it might force the thrust downward and lift the bow, thus exaggerating the very problem it's intended to solve.

 

 

 

I doubt more than a few kg of 'lift' would be generated, and probably an equivalent downforce on the inlet on the opposite side.

 

10 or 20 kg of lift won't make any discernable difference to bow height in the water. Especially not on a widebeam.

[Joe Bourke]

I would say the eyebrow design in this instance will have a detrimental effect on the efficiency of the bowthruster. Eyebrows or fairings are usually in front of the bowthruster tube to aid through water performance and steering. My own boat has a fairing forward of the tube for that reason. For optimum performance any grill should be as fine as possible to aid flow through the tube, with as little obstruction as possible.

[Guest]

UPDATE: Canopus was recently moved for me by Phill Abbott (Wharfhouse Narrowboats).

He reported that she didn't seem to handle to badly for a boat of her size, but the acceleration was far too strong and stopping was almost impossible, even at full reverse (he's an experienced boater and very familiar with speed-wheel control).

The work will now begin... 

[Dalslandia]

So, you just need to mount the propeller the other way, it will go better in reverse then forward, the cone on the shaft need to taper the other way though. :-)

[alan_fincher]

2 hours ago, dpaws said:

UPDATE: Canopus was recently moved for me by Phill Abbott (Wharfhouse Narrowboats).

He reported that she didn't seem to handle to badly for a boat of her size, but the acceleration was far too strong and stopping was almost impossible, even at full reverse (he's an experienced boater and very familiar with speed-wheel control).

The work will now begin... 

 

How can you have acceleration that is "far too strong"?  I would have though that was a good thing.  If you want to accellerate less, then wind it on less.

(Passed it at Wharf House this morning by the way.....)

 

[IanM]

6 minutes ago, alan_fincher said:

 

How can you have acceleration that is "far too strong"?  I would have though that was a good thing.  If you want to accellerate less, then wind it on less.

(Passed it at Wharf House this morning by the way.....)

 

I suspect that whatever the boat handled like, the OP would still find fault with it to justify their planned modifications.

[Guest]

2 hours ago, alan_fincher said:

 

How can you have acceleration that is "far too strong"?  I would have though that was a good thing.  If you want to accellerate less, then wind it on less.

(Passed it at Wharf House this morning by the way.....)

 

I assume it's a prop issue, anything above tick-over (to quote Phill, please feel free to ask him yourself) and she accelerates away like a puppy stung by a wasp... 

I've every confidence that Phill knows how to handle a speed wheel delicately, and to "wind it on less", it's not rocket science, only the throttle is very very sensitive at present - the speedwheel linkage was done at Brinklows to the best of my knowledge, so there's no mickey mouse ratios involved. 

The prop could be way too fine, but then that doesn't tie in with the complete lack of reversing bite...

 

Bored Ian?

[MtB]

I'd say there is something odd going on like a slipping clutch in astern. A blade that makes the boat too fast at anything above tickover is too coarse in pitch - but one would expect a blade like that to bite well in astern too. 

However, on my boat the blade Crowther specified worked ok-ish in ahead but the brakes in astern were virtually non-existent. I changed the blade to one with a much higher DAR and the brakes came back. What blade spec is on yours? (And what engine? I've forgotten.)

 

 

Speeling edit. 

Edited March 17, 2017 by Mike the Boilerman

[matty40s]

The blade is pushing the water so  fast backwards, it has nothing to dig into when it revolves the other way.

[Guest]

4 minutes ago, Mike the Boilerman said:

I'd say there is something odd going on like a slipping clutch in astern. A blade that makes the boat too fast at anything above tickover is too coarse in pitch - but one would expect a blade like that to bite well in astern too. 

It's a three blade with about a 55% DAR from memory - mean pitch is 24.5”, diameter as 26” - JP3M motor. No strange transmission sounds when in reverse, Blackstone box...

I'd always associated fast acceleration with a fine pitch, but I guess there's so much torque on hand from the JP3 that it can still accelerate a coarse blade... 

I suspect the prop positioning and the deadwood under the stern will be sufficiently disruptive to compromise the braking performance, but that doesn't sufficiently describe how she feels - forward and reverse are absolutely chalk and cheese in performance.

[Guest]

4 minutes ago, matty40s said:

The blade is pushing the water so  fast backwards, it has nothing to dig into when it revolves the other way.

I see where you're coming from Matty, but at "normal" forward cruise speeds? Setting aside my own naivety, I've every confidence in Phill's cruise speed control.

She prop-walks quite strongly in reverse, so something's happening. I suspect that when the rudder blade is inevitably moved across to control the traverse, it's then (in combination with the vertical post) obstructing the clean water flow to the prop, so the prop is trying to grip turbulent water, reducing it's effectiveness?

[MtB]

3 minutes ago, dpaws said:

It's a three blade with about a 55% DAR from memory - mean pitch is 24.5”, diameter as 26” - JP3M motor. No strange transmission sounds when in reverse, Blackstone box...

 

Bluddy hell. That blade is, I suspect, specified to soak up all the power available on a JP3, M or otherwise! An almost square prop. 

For that diameter I'd have expected something like 18" pitch (or even less) to get some finesse into the forward speed, and a DAR of perhaps 70% 

But I'm no expert. Daslandia will no doubt have something worthwhile to say! 

[Guest]

7 minutes ago, Mike the Boilerman said:

 

Bluddy hell. That blade is, I suspect, specified to soak up all the power available on a JP3, M or otherwise! An almost square prop. 

For that diameter I'd have expected something like 18" pitch (or even less) to get some finesse into the forward speed, and a DAR of perhaps 70% 

But I'm no expert. Daslandia will no doubt have something worthwhile to say! 

I think you're right Mike, it's the type of prop calc'd to suit a JP3 very well indeed... on the Humber Estuary!

Still can't work out why it does so very little in reverse - and I mean frighteningly little... like Austin Minis back in the 70's on a wet morning sort of non existent braking...

[MtB]

6 minutes ago, dpaws said:

I think you're right Mike, it's the type of prop calc'd to suit a JP3 very well indeed... on the Humber Estuary!

Still can't work out why it does so very little in reverse - and I mean frighteningly little... like Austin Minis back in the 70's on a wet morning sort of non existent braking...

 

You never had an Austin A35 then did you?!!

Matty might be on the right track, the 'turbine effect' of an almost square blade could be why there is no 'grip' on the water. Are you sure the shaft is rotating properly in astern? Can you see it with some boards lifted, say?

[Guest]

1 minute ago, Mike the Boilerman said:

 

You never had an Austin A35 then did you?!! Can you see it with some boards lifted, say?

Ahhh... A35 no, Fiat 500 yes, probably equally as useless! At least with the Fiat you could stick your feet out, that helped....

Yes, I lifted the cabin floorboards to see the shaft as the neutral point was not obvious to me through the gear change mechanism. The shaft's definitely turning in the opposite direction too, I even checked that!

It's not a square blade, but the blades are quite "fat" (apologies, can't place the photo at present).

I'm convinced it's a hydrodynamic issue as I'd suspected originally and Matty has suggested too - the prop in reverse simply can't get hold of the water...