Canopus and Sculptor

[FadeToScarlet]

Just a thought- have you ever steered a deep drafted boat before?

 

I'm assuming Canopus has something like 2'10" to 3' draft. Steering a deep drafted boat is very different to a modern, shallow drafted boat; for example, you need to be in the channel, and if you're not, the boat will not steer and will do its own thing, such as not being able to get around a corner.

 

In what way does it "handle like a pig"? And have you any experience of steering deep drafted boats?

[Guest]

Just a thought- have you ever steered a deep drafted boat before?

 

I'm assuming Canopus has something like 2'10" to 3' draft. Steering a deep drafted boat is very different to a modern, shallow drafted boat; for example, you need to be in the channel, and if you're not, the boat will not steer and will do its own thing, such as not being able to get around a corner.

 

In what way does it "handle like a pig"? And have you any experience of steering deep drafted boats?

 

The published build draft is 2'6", so I wouldn't say she's particularly deep. The majority of the time was spent on the Grand Union south of Braunston going up and down and up and down, so not a particularly narrow or shallow canal.

 

I don't have experience of original deep drafted working boats on the canal, no. My previous handling experience is not relevant here (Suezmax etc)

[alan_fincher]

The sales advert and brochure is still available here.

[alan_fincher]

It seems to me that Canopus is over-propped. Cobbett at 62' had a 20" square prop on her and I had absolutely no issues whatsoever.

 

Well Canopus is recorded as having a Lister JP3, both powerful and slow revving so should normally need a pretty big blade.

 

However, if the sales brochure is correct, this only has a 2:1 Blackstone box on it, which will dramatically reduce the required prop sizing over what it would need if on a 3:1 reduction.

 

So without knowing what reduction box Cobbett had, it is perhaps difficult to comment on how comparable the two situations are.

 

What I can say is that "Sickle's" HA3 manages to swing a 26" x 19.4" blade, and also only has a 2:1 reduction. However the characteristics of an HA3 will differ substantially from a JP3 despite a similar power output, and I'm not sure what the JP3 can cope with. I'm staggered anybody thought an Axiom was a good idea on a JP though!

nb Canopus is indeed now in my custody, she is mine, fully paid for and my comments about her handling are based on my own experiences so far.

 

I'm trying to remember exactly where, but it must have been you we passed somewhere, almost certainly on Thursday, I think, travelling North up the GU, somewhere North of Weedon.

 

At least she looks and sounds alright!

[GUMPY]

Idleness had/has a Crowther big bladed 80% 23x19 on its JP3 and it worked just fine.

[Laurence Hogg]

Can't find a decent photo of the completed boat, instead you'll have to imagine the boat in the first photo with the paint job in the second....

 

 

 

Why is a fake GUCCCo boat carrying the number of one which is still extant, Dorado is 36.

[alan_fincher]

The vertical post isn't good, but it makes no sense that Dave Harris would continue with a design if it had proved troublesome, and as others have posted, they've had good experiences with the same layout.

 

Ex FMC Empress is according to this Norbury Wharf web-site page "reputed to be the oldest surviving purpose built motor narrow boat in this country, she dates from 1887"

 

This photo linked to the same Norbury Wharf page, clearly shows a vertical post in front of the rudder.

 

 

This suggests to me that such arrangements were not uncommon on this kind of craft.

 

I think it is a non-issue.

 

Why is a fake GUCCCo boat carrying the number of one which is still extant, Dorado is 36.

 

This is not uncommon, I think.

 

There are two Theophilus, for example - the original, and an excellent Steve Priest built "Northwich remake".

 

I'm guessing many of the "GUCCCo remakes" share numbers with extant GUCCCo motors, as so many of the real thing still survive.

[davidg]

_{The original owners chose 36 as it was the 36th boat Dave Harris had built.}

[matty40s]

The previous owner didn't even realise it had a curved swim until pointed out to him.

He was also advised against changing the prop (at his own expense even though having sold the boat) as we said let the new owner make their own mind up. He showed us lots of detailed graphs as to why the new prop would do the job.....we just nodded and continued to drink tea.

The Axiom is made by the same people who made the present and previous prop....Clements, I reckon they just knew that they had a captive victim to test props.☺

Edited December 26, 2016 by matty40s

[Guest]

I'm trying to remember exactly where, but it must have been you we passed somewhere, almost certainly on Thursday, I think, travelling North up the GU, somewhere North of Weedon.

 

At least she looks and sounds alright!

 

Yes Alan, guilty as charged! With time I'll get to know faces, my apologies for not acknowledging you at the time.

 

I can confirm the 36 was Dave's 36th, renumbered by the last owners to 06, though I can't remember for why.

 

The sales specs were correct, at present a JP3M with a Blackstone 2:1. Present prop is 26" dia 24.5" pitch, area ratio unknown, I'll dig the manual out, it's noted somewhere.

 

After some work has been done I intend to revert immediately to a three bladed prop. For now you've all convinced me to leave the vertical strut in place and sort out just one thing at a time (well two, because the weed hatch leaking may have a strange influence?).

 

Whilst the vertical strut is a poor design choice in our opinion, it does seem that what I've experienced so far is unique to my set-up alone and not commonplace across all strutted designs.

[DHutch]

From the above it seams hard to know where the issues lies.

 

However certainly I would expect very different characteristics from a deep-ish full length boat with a vintage engine, than a lighter smaller propped hire boat with a isuzu. Chalk and cheese. If no one better than the other.

 

I don't think many powered narrowboats stear well out of gear, if some better than others.

 

EmilyAnne is about 2ft8 with a 26 inch dia prop. Three blades, but a DAR about as close to one as you can get.

 

Certainly if you have never steered a genuine historic working boat it seems unfair to compare a replica to said original.

 

 

 

Daniel

[matty40s]

It's OK being an anorak if you know what you are talking about, not just repeat what others are talking about.

 

Edited to add...should be added to previous post, not a response to Dan.

Edited December 25, 2016 by matty40s

[Guest]

The previous owner didn't even realise it had a curved swim until pointed out to him.

He was also advised against changing the prop (at his own expense even though having sold the boat) as we said let the new owner make their own mind up. He showed us lots of detailed graphs as to why the new prop would do the job.....we just nodded and continued to drink tea.

The Crowther is made by the same people who made the present and previous prop, I reckon they just knew that they had a captive victim to test props.☺

 

Wise people these prop guys! Nice to meet you!

[alan_fincher]

So far Canopus has handled like a pig. This may have something to do with the 26" dia 4 blade prop, it may be the consequence of the skeg support post being so close to the leading edge of the rudder. It maybe also be due to the weed hatch that doesn't seal correctly.

 

Has the pitch of the 26" 4 blade prop been stated?

 

It has previously been suggested that the VicProp calculator is not a million miles out when used for narrow boats, (it proved not to be far out for ours, at least).

 

I can't see where I have entered bad data here, but I'm surprised how large it suggests, even for a 4 blade prop.....

 

3 Blade 27.7" x 23.6"

4 Blade 26.0" x 23.2"

 

So that actually suggest 26"

 

Have I used incorrect data? (I don't believe your boat can be as much as 25 tons, if genuinely only 30" draft.....)

 

[EDIT: Sorry, it looked like it would retain the formatting of the report - It hasn't unfortunately!]

Data Input Waterline length in feet: 65 feet Beam at the waterline in feet: 7 feet Hull draft in feet (excluding keel): 2.5 feet Vessel weight in pounds: 50000 lbs Engine Horsepower: 35 HP Number of engines: 1 Total Engine Horsepower: 35 HP Engine R.P.M. (max): 1200 RPM Gear Ratio: 2:1 Shaft R.P.M. (max): 600 RPM Number of shaft bearings (per shaft): 1 Desired speed in Knots: 5 knots Horsepower Calculations This will calculate the maximum horsepower and torque available at the prop(s). Total available horsepower at the engine(s): 35 HP Total available torque ft/lbs at the engine(s): 153 ft/lbs Horsepower loss of 3% per gearbox: - 1.1 HP Horsepower loss of 1.5% per shaft bearing: - 0.5 HP Total horsepower available at the propeller(s): 33.4 HP Total torque ft/lbs available at the propeller(s): 293 ft/lbs Speed & Power Calculations Basic displacement speed and horsepower required Displacement hull speed (1.34 X sqrt of waterline length): 10.80 Knots Minimum horsepower required at propeller(s) for Hull speed: 109.1 HP Calculations based on desired speed and available HP HP required at propeller(s) for desired 5 knots speed: 10 HP Estimated maximum speed with existing 35 horsepower:

This is the speed we will use for the propeller size. 7.48 Knots At this point it is important to note that all of the calculations above are based on full RPM and HP. Most engines are rated to run at a percentage of thier full RPM. This is what will determine your maximum cruising speed. The propeller sizing calculations below are based on 90% of full RPM. This gives the engine some reserve power to allow for variable loading in the vessel.

 

Propeller Size Number of blades Diameter (inches) Pitch (inches) 2 Blade 29.0 X 23.9 3 Blade 27.7 X 23.6 4 Blade 26.0 X 23.2 The propeller sizes shown above do not contain calculations for cavitation or blade loading.

If you find that the recommended propeller is too large to fit your vessel, you can try increasing the shaft speed. Failing this, you can reduce the diameter and increase the pitch at the expense of your propeller efficiency. The rule of thumb is 1 inch of diameter is equal to 1 1/2 to 2 inches of pitch.

Edited December 25, 2016 by alan_fincher

[ditchcrawler]

 

Has the pitch of the 26" 4 blade prop been stated?

 

It has previously been suggested that the VicProp calculator is not a million miles out when used for narrow boats, (it proved not to be far out for ours, at least).

 

I can't see where I have entered bad data here, but I'm surprised how large it suggests, even for a 4 blade prop.....

 

3 Blade 27.7" x 23.6"

4 Blade 26.0" x 23.2"

 

So that actually suggest 26"

 

Have I used incorrect data? (I don't believe your boat can be as much as 25 tons, if genuinely only 30" draft.....)

 

 

I make it 25 tons ish

[matty40s]

I will see if I can lay my hands on the New prop data sheet. DPAWS probably has it in his encyclopedia somewhere ...

[alan_fincher]

I make it 25 tons ish

 

From my experience the number you enter doesn't radically change the calculated prop size, (provided the number you use is not a million miles out).

 

I used 22 tons and got

 

3 Blade 27.7" x 23.6"

4 Blade 26.0" x 23.2"

 

but increasing to 25 tons doesn't actually change radius, just pitch

 

3 Blade 27.7" x 22.9"

4 Blade 26.0" x 22.5"

 

Actually, looking at how relatively level it sits in the water, it might be getting towards the 25 ton mark, but the difference is only 0.7" of pitch - it still indicates 26" diameter for a 4 bat prop.

Edited December 25, 2016 by alan_fincher

[wrigglefingers]

Well Canopus is recorded as having a Lister JP3, both powerful and slow revving so should normally need a pretty big blade.

 

However, if the sales brochure is correct, this only has a 2:1 Blackstone box on it, which will dramatically reduce the required prop sizing over what it would need if on a 3:1 reduction.

 

So without knowing what reduction box Cobbett had, it is perhaps difficult to comment on how comparable the two situations are.

 

What I can say is that "Sickle's" HA3 manages to swing a 26" x 19.4" blade, and also only has a 2:1 reduction. However the characteristics of an HA3 will differ substantially from a JP3 despite a similar power output, and I'm not sure what the JP3 can cope with. I'm staggered anybody thought an Axiom was a good idea on a JP though!

 

I'm trying to remember exactly where, but it must have been you we passed somewhere, almost certainly on Thursday, I think, travelling North up the GU, somewhere North of Weedon.

 

At least she looks and sounds alright!

Corbett had a PRM260 on a near as dammit 3:1 reduction. What I do know about Cobbett (62' curvy swims and planked double curved front Josher bow, absolutely no rivets) drew 2'7" at build but once people and stuff were loaded on her, was gauged at far closer to 3'. She liked to get into the channel and sit chuntering along. I found her very responsive even after she was fully loaded. She did, however, steer very differently to my previous boat which drew less than 1'10". Learning to steer her was a long learning curve but worth it. Boating with her was quite the best thing and I deeply regret not being able to keep her because my bloody knee made boating so difficult.

[alan_fincher]

I will see if I can lay my hands on the New prop data sheet. DPAWS probably has it in his encyclopedia somewhere ...

 

I think prop sizing is very critical to how well the boat gets away from a standing start, cruises at a speed, and ultimately stops. If all that is "as expected", then the prop sizing is probably not far off. If the boat is slow off the mark, needs what feels like excessive RPM to maintain a good cruising speed, and will not stop when you want it to, the prop is almost certainly undersized. If the engine nearly stalls, (or actually stalls), as you engage gear, and will not run up to anything like full RPM, it is almost certainly oversized.

 

I'm wondering on what basis we are being told a 26" 4 bat prop is unsuitable. We do however need to know the pitch of that prop. I have just had a prop repitched from something between 15" or 16" to 21", with the diameter unchanged - the difference this has made to normal cruising revs and ability to stop is impressive. However none of what we have changed stops it being a big heavy old boat, and handling like you might expect a big heavy old boat to handle. The more accurately you copy the features of an old working boat, the more you end up steering something that feels like an old working boat(!)

[David Mack]

 

Has the pitch of the 26" 4 blade prop been stated?

 

It has previously been suggested that the VicProp calculator is not a million miles out when used for narrow boats, (it proved not to be far out for ours, at least).

 

I can't see where I have entered bad data here, but I'm surprised how large it suggests, even for a 4 blade prop.....

 

3 Blade 27.7" x 23.6"

4 Blade 26.0" x 23.2"

 

So that actually suggest 26"

 

Have I used incorrect data? (I don't believe your boat can be as much as 25 tons, if genuinely only 30" draft.....)

 

[EDIT: Sorry, it looked like it would retain the formatting of the report - It hasn't unfortunately!]

 

Data Input Waterline length in feet: 65 feet Beam at the waterline in feet: 7 feet Hull draft in feet (excluding keel): 2.5 feet Vessel weight in pounds: 50000 lbs Engine Horsepower: 35 HP Number of engines: 1 Total Engine Horsepower: 35 HP Engine R.P.M. (max): 1200 RPM Gear Ratio: 2:1 Shaft R.P.M. (max): 600 RPM Number of shaft bearings (per shaft): 1 Desired speed in Knots: 5 knots Horsepower Calculations This will calculate the maximum horsepower and torque available at the prop(s). Total available horsepower at the engine(s): 35 HP Total available torque ft/lbs at the engine(s): 153 ft/lbs Horsepower loss of 3% per gearbox: - 1.1 HP Horsepower loss of 1.5% per shaft bearing: - 0.5 HP Total horsepower available at the propeller(s): 33.4 HP Total torque ft/lbs available at the propeller(s): 293 ft/lbs Speed & Power Calculations Basic displacement speed and horsepower required Displacement hull speed (1.34 X sqrt of waterline length): 10.80 Knots Minimum horsepower required at propeller(s) for Hull speed: 109.1 HP Calculations based on desired speed and available HP HP required at propeller(s) for desired 5 knots speed: 10 HP Estimated maximum speed with existing 35 horsepower:

This is the speed we will use for the propeller size. 7.48 Knots At this point it is important to note that all of the calculations above are based on full RPM and HP. Most engines are rated to run at a percentage of thier full RPM. This is what will determine your maximum cruising speed. The propeller sizing calculations below are based on 90% of full RPM. This gives the engine some reserve power to allow for variable loading in the vessel.

 

Propeller Size Number of blades Diameter (inches) Pitch (inches) 2 Blade 29.0 X 23.9 3 Blade 27.7 X 23.6 4 Blade 26.0 X 23.2 The propeller sizes shown above do not contain calculations for cavitation or blade loading.

If you find that the recommended propeller is too large to fit your vessel, you can try increasing the shaft speed. Failing this, you can reduce the diameter and increase the pitch at the expense of your propeller efficiency. The rule of thumb is 1 inch of diameter is equal to 1 1/2 to 2 inches of pitch.

If this hull can carry a 26" blade with appropriate clearance to skeg and uxter, then the hull depth has got to be more than the 2'6" used in that calculation.

[mark99]

 

Ex FMC Empress is according to this Norbury Wharf web-site page "reputed to be the oldest surviving purpose built motor narrow boat in this country, she dates from 1887"

 

This suggests to me that such arrangements were not uncommon on this kind of craft.

 

 

The anode is in the slipstream too - like most rear-most anodes. (Although I'm not sure if anodes were used on early carrying working boats).

Edited December 26, 2016 by mark99

[koukouvagia]

 

Another picture of the skeg and rudder brace. This one is ex-FMC Owl.

Two things to note:

(1) at some time in the past there was an attempt to make the steering a bit lighter by chopping out a half moon hole in the rudder and by adding a small balance plate. This latter modification meant having to cut a chunk off the skeg brace.

(2) the skeg was paper thin when we bought the boat. You can see the weld line where a new piece was added.

 

I fully agree with FTS's remarks about having to learn a new technique for steering deep drafted boats. On shallow and twisty canals it's very easy to let your attention wander. One moment all is well, the next moment you are out of the channel and beginning to stem up.

 

 

[alan_fincher]

To see a Dave Harris stern with this offending vertical post before the rudder there is another photo here (that I daren't copy but you can see for yourselves):

 

http://walkerstug.blogspot.co.uk/2012/04/rudder-and-skeg.html

 

and here is the one from Canopus which, to the best of my understanding from the person who owned the camera I am able to use freely without copyright restriction:

 

P1090409.JPG

 

 

 

 

The original prop was indeed as above 24" 3 blade but with a minute imbalance on one blade that lead the previous owner to change it out.

 

 

 

The published build draft is 2'6", so I wouldn't say she's particularly deep. The majority of the time was spent on the Grand Union south of Braunston going up and down and up and down, so not a particularly narrow or shallow canal.

 

Well from the pictures, if the original blade was 24", then the draught under the uxter seems more than 2' 6".

[bargemast]

 

Thank you Peter, that's very kind of you - best wishes to you and yours too.

 

I still fully intend to have my curvy hull design built, but have realised that I need to be in the UK and close to the build workshop whilst it's in progress because it's so different to the norm.

 

nb Canopus will provide that UK base for me, and will also be our family cruiser for many years to come, I am sure.

 

She's a beauty but with some teething problems, but that's all part of the fun and provides valuable experience on the canals. I suspect the new 26" prop which was fitted before I collected her is responsible for some of the present woes. The vertical post isn't good, but it makes no sense that Dave Harris would continue with a design if it had proved troublesome, and as others have posted, they've had good experiences with the same layout.

 

Slowly slowly we'll change things around until my expectations are either met or until I've lowered them, as Jan said, my expectations may simply be unrealistic.

 

Rudder forces aren't consistent and change with speed. Typically the right arm aches a lot more than the left on an evening after cruising. At close to 90kg I'm not lightly built and it takes my full strength and full rudder deflection at times with very little effect.

 

The bow thruster that was fitted later is excellent, very very impressive indeed. At slow speed we rounded a small island marina in a howling gale without touching another object. It's when the revs increase that it all feels very strange indeed, both forward and aft.

 

I'll be inviting experienced hands to take her out in April and from their feedback I'll no doubt have a better idea of where any issues may lie.

 

For now the prop is No.1 suspect, but I'll remove the vertical post and modify the skeg when she's next out of the water.

The fat line sounds like the best idea to start with, and could work out to save you a lot of money too, unless these experienced hands will encounter the same problems as you have.

 

Don't do anything that's not really necessary, but if you decide (one day) to cut this strenghtening bar, you could add a compensation plate on the rudder, which will make the steering a lot lighter.

 

Peter.

[alan_fincher]

If this hull can carry a 26" blade with appropriate clearance to skeg and uxter, then the hull depth has got to be more than the 2'6" used in that calculation.

 

Yes, something doesn't quite add up here, does it?

 

Of course an original GU boat would have a very significant upward dishing of thwe uxter plate, increasing the gap between uxter and skeg, without increasing the static draught with the uxter sitting on the surface of the water, at the exge of the counter.

 

It is not obvious whether Dave Harris has gone tothat level of sophistication, but I rather suspect not.

The sales specs were correct, at present a JP3M with a Blackstone 2:1. Present prop is 26" dia 24.5" pitch, area ratio unknown, I'll dig the manual out, it's noted somewhere.

 

Well that to me seems a bit over-propped, but not necessarily massively.

 

Maybe take a couple of inches off the pitch, or an inch of the diameter, based on that prop calculator that I posted. IMO, the 4 blade thing should be a non issue, if the sizing is right - there is at least one Small Woolwich out there that flies with a 4 blade prop, and a similar sized engine.

Edited December 26, 2016 by alan_fincher