Canopus and Sculptor

[ditchcrawler]

In my parallel world the flatter a boat is the better it handles.

If you look at loaded boats on the continent they are loaded to be bow down for a very goid reason.

I have always ballasted my boats to be as flat as I can, even the deep, 2ft9, drafted ones.

Not as deep as you guy but I run flat as well, 2' 4" static

[Guest]

In my parallel world the flatter a boat is the better it handles.

If you look at loaded boats on the continent they are loaded to be bow down for a very goid reason.

I have always ballasted my boats to be as flat as I can, even the deep, 2ft9, drafted ones.

 

Yes, I'd agree, but the hydrodynamics win here. The lower she is the greater the curvature of the bow in the water, (the centre of lift moves forward in conjunction with a longer moment) so the pull into the bank effect will increase dramatically. The guys cruising on the continent aren't experiencing the same lateral forces on the hull as the channels are much wider.

 

Alan - re the trim thoughts, I've just had a bingo moment - I fully filled the forward water tank Braunston before leaving the G.U.; that will have decreased my trim and made her more sensitive to the channel. This, combined with the narrowing of the channel northbound was why she felt a different beast altogether which really shook my confidence.

 

Previous to that I'd spent days going up and down the G.U. getting a feel for her, after which I'd felt relatively comfortable, well, going forwards that is...

Edited December 29, 2016 by dpaws

[GUMPY]

Not as deep as you guy but I run flat as well, 2' 4" static

That was Idleness, JP3 flatter than flat.

Here it is 10 years after I sold it.

https://www.dropbox.com/s/33xwxxyaat6xjae/2013-09-20%2015.51.42.jpg?dl=0

[GUMPY]

Thev reason some boats struggle with the channel is that the owners are trying to make them go to fast..........

No other reason.

Oh and before anyone says anything I will push on harder than most but have learnt when to back off the throttle.

Edited December 29, 2016 by Loddon

[Guest]

Thev reason some boats struggle with the channel is that the owners are trying to make them go to fast..........

No other reason.

 

Oh believe me, in this case it was the owner not being able to slow the beast down!! It was like trying to walk a Springer Spaniel pup... with me hanging off the gear lever handle for dear life! The 26" prop had just been fined by about 2" pitch in an attempt to improve the braking performance, so going forward she's very hot off the mark.

Edited December 29, 2016 by dpaws

[alan_fincher]

In my parallel world the flatter a boat is the better it handles.

I see where you are coming from, and can see some of the theory behind it.

 

However, taken to its full conclusion, you could then argue that a fully laden working boat with its draught at over 3 feet throughout will be easier to handle than a completely unloaded one with its back end at that kind of draught, but the front towering out of the water, and drawing almost nowt.

 

This is simply not my personal experience particularly if you factor in the "how well can it be made to stop".

 

The reality is that if you had say 18 tons of cargo in addition to the weight of the boat, whilst it may handle OK when under way, even with a well matched prop, it is going to be far harder, and take a much greater distance to stop it.

 

The experts are telling me that we have probably now got Flamingo about as good as it is going to get, given it has a heavy conversion, but repeatedly I am hearing "it is a big heavy boat - it's never going to handle like an empty one". It is much improved, but stopping in a hurry is still not a strong point.

 

We have also had Sickle, (admittedly only 40 feet) with quite different degrees of ballasting at the front end at different times, as it was suggested it would be an even better boat if made to sit more level. I have no idea if that might be true when using it as a tug, (it may be), but my honest opinion is it makes little difference when in normal use on its own.

[GUMPY]

Its a different style of boating. Try Parglena on the GU at 36ton 60x12x3 that was a handfull until I learnt to slow down,mind you it would still stop in its own length. Talking of stopping I have changed the prop on every canal boat I have owned except Loddon in order to get the best forward/reverse performance.

[FadeToScarlet]

In my parallel world the flatter a boat is the better it handles.

 

Similarly to the barges on the continent, you want to load a narrowboat slightly foreend-down, as by all accounts it's significantly easier to steer- and less likely to slide up a mud bank, inexorably pushed on by the momentum of the load, getting well and truly stuck or "stemmed up".

[BEngo]

It aint just the modern boat owners that find bows up to be worse than flat. Tom Foxon, in Number 1, notes that New Hope loaded fairly lightly was 'hard to steer like all narrowboats in that condition".

 

Dolphin the josher is ballasted pretty flat and is a heavy bugger like all Joshers of that vintage but it swims very well and is fairly easy to steer. Stopping it wants plenty of welly tho.

 

Colin did once tell me that it swam even better down by the head a bit so as to level out when pulled down but the draft in that state meant he couldn't go anywhere!

 

N

[matty40s]

I loaded Old Friends up at the nose with 25 sacks of coal and brimmed the water tank before coming round the Leicester ring at the start of the month. The gunnels were almost level for the first time.

It swam remarkably well , even on the shallow Coventry sections and went like a dream on the river.

[bargemast]

 

Yes, I'd agree, but the hydrodynamics win here. The lower she is the greater the curvature of the bow in the water, (the centre of lift moves forward in conjunction with a longer moment) so the pull into the bank effect will increase dramatically. The guys cruising on the continent aren't experiencing the same lateral forces on the hull as the channels are much wider.

 

Alan - re the trim thoughts, I've just had a bingo moment - I fully filled the forward water tank Braunston before leaving the G.U.; that will have decreased my trim and made her more sensitive to the channel. This, combined with the narrowing of the channel northbound was why she felt a different beast altogether which really shook my confidence.

 

Previous to that I'd spent days going up and down the G.U. getting a feel for her, after which I'd felt relatively comfortable, well, going forwards that is...

Just one question dpaws, "Have you ever been on a barge on the canals in France ?"

 

Myself I've spend many of my working life years on barges overthere, and I think that they are comparable to the UK canals.

 

They make look wider from a narrowboat point of view, but they were made for "Freycinet" size barges (originally 38m50 x 5m05), and if 2 laden barges meet there on the narrower sections you can run into problems that can make you lose many hours.

 

On this photo you can see 2 laden barges that are glued together because of a lack of depht in the canal, and turning their props would make it worse as they'll pull all the water from underneath their barges which will make the problem even worse.

 

The only way they managed to get very slowly past each other was to raise the water in the pound as much as possible, and then pull with their car cranes and ropes to win centimeter by centimeter to get finally out of this nasty position.

 

photo by KVM

 

Peter.

[Guest]

No Peter, I've never had the pleasure, but look's to be a fascinating scene.

 

I wasn't commenting about the UKC, but the lateral forces between the "vertical" channel sides and the parallel slab hull side, so "sideways" squat rather than getting sucked into the mud beneath.

 

Looks like the French object to dredging costs as much as our lot do, have they classed their sludge as toxic too? I assume that hazardous waste legislation is preventing our volunteers from being able to dredge their local stretches - in the end that's the only way the whole system will get gradually get cleared out

[MtB]

 

On this photo you can see 2 laden barges that are glued together because of a lack of depht in the canal, and turning their props would make it worse as they'll pull all the water from underneath their barges which will make the problem even worse.

 

The only way they managed to get very slowly past each other was to raise the water in the pound as much as possible, and then pull with their car cranes and ropes to win centimeter by centimeter to get finally out of this nasty position.

 

 

 

Ok the UK canals putting the engine into astern generally pushes an inch or two of water under the boat and helps it float off shallow water. Presumably that wouldn't have worked in this situation, but why not?

[bargemast]

No Peter, I've never had the pleasure, but look's to be a fascinating scene.

 

I wasn't commenting about the UKC, but the lateral forces between the "vertical" channel sides and the parallel slab hull side, so "sideways" squat rather than getting sucked into the mud beneath.

 

Looks like the French object to dredging costs as much as our lot do, have they classed their sludge as toxic too? I assume that hazardous waste legislation is preventing our volunteers from being able to dredge their local stretches - in the end that's the only way the whole system will get gradually get cleared out

 

Dredging in France has the same problems as in the UK, they have to find land where the dredged mud can be dumped, and left for many years.

 

Peter.

[bargemast]

 

 

Ok the UK canals putting the engine into astern generally pushes an inch or two of water under the boat and helps it float off shallow water. Presumably that wouldn't have worked in this situation, but why not?

 

That won't work, to start with because you don't lift up 300 + Tonnes that are several inches deep in the mud by reversing, the only, and best working way is using ropes, and they will work even better if there's a field with a helpful farmer with a tractor giving a pull in the right direction.

 

Nowadays barges are equipped with an most useful electronic gadget named A.I.S. on which you can see the position and name of other barges, and if you're familiar with the canal you're on, you can talk to the other barge through the VHF to decide on the best place to pass each other to avoid the running both aground missery, as it's much better to wait somewhere where it's wide and deep enough to let another barge pass.

 

Peter.

[Tonka]

Posted 24 October 2015 - 03:15 PM

With reference to a much earlier post of mine back in the summer . Yep Canopus is a lovely looking boat , but not when it smacks into you without slowing , rips your cratch cover , puts a dent your hull and the steerer utters those immortal words , 'CONTACT SPORT'. Even his wife had to hold onto something in the bow ( whilst yelling at him to slow down) he hit us with such force . Luckily I was hard in reverse when I saw his speed as he missed the corner , or it could of been worse , a possible insurance claim . As it is I can use a needle and thread and you only notice the dent when the curtains are up ( not often if it's a wet summer) . Still Canopus nice looking boat but don't want to see her that close too again . Bunny

Found this from 2015 which proves Dpaws is not the only owner who had problems with Canopus

[IanD]

There seems to be a lot of argument on this thread between the two conflicting views of "lots of narrowboat hulls are badly designed hydrodynamically" and "that's the way it was done in the past (or still is) so there can't be much wrong with it". In their way, they're both right...

 

Lots of work -- both theoretical and backed up by experiments -- has been done over the last couple of hundred years on how to optimise hull design, even for unusual cases like narrowboats in a relatively shallow canal, though most of the effort has been deep sea ships for obvious reasons, and most of this work has been to minimise drag because this maximises speed or minimises fuel consumption. A lot of this work (bow bulges etc) isn't relevant to narrowboats, but a lot almost certainly is (propellor clearances etc) and is either ignored or directly contradicted by most hull designs -- for example the prop is almost always too close to the deadwood and too far from the rudder to give smoothest water flow and best rudder response, and vertical skeg bars are almost certainly a bad idea. Note that I say "almost" because no tests have been done, even though it's *almost* certain what the outcome would be ;-)

 

Instead the hulls are built the way they are because of other reasons -- a "proper" stern design would need a long sturdy prop shaft extension tube and a very strong skeg, it's much easier to build it the "traditional" way or even add vertical bars for added strength. Properly shaped double-curved swims at both ends would almost certainly give better handling, less wash and lower fuel use, but are much more difficult and expensive to both build and maintain and eat into the boat interior space. A big slow-turning prop gives better efficiency and stopping power than an "egg-whisk", but means the draught must be deeper making for a heavier boat with more tendency to plough the bottom -- and the additional drag from this completely swamps any lower drag from a better hull form.

 

So many of the things which in an ideal world would make for a "better" hull design don't really work on today's under-dredged canals -- having a beautifully designed big-prop deep-draught long-swim streamlined hull is great on a river or deep canal, but on many canals and for many people a small-prop shallow-draught box with rounded ends (like a Springer) is actually a better bet even though a hydrodynamicist would choke when shown the hull design. Most of the drag and wash in a narrow shallow (most!) canal is due to the amount of water which has to be pushed back past the boat (displacement, length*draft) not the fineness of the bow and stern forms -- these do have an effect, but this is much smaller proportionally than in any deep-sea hull.

 

Which basically sums up as the people pushing for better hull shapes (or that many traditional practices are bad) are right, but the differences are smaller than they think -- though they're probably more correct about how to get the best water flow over prop and rudder than some other things, and this could easily be improved without being too difficult/expensive to build. This probably makes a much bigger difference to boat handling and wash than the prettiness of the bow shape, but overall draft and the way the boat is trimmed (bow up/level) makes the biggest difference of all. Many of the ways that hulls were traditionally (and still) built are distinctly dodgy (e.g. vertical skeg bars) but make little difference in real life, which is why they carried on doing it.

 

Is that fair to both sides?

Edited December 30, 2016 by IanD

[Guest]

I agree with almost every word Ian, that's a fair summary. The finer the forward and aft swims are then the lower the "suck" to the nearest channel side. As you mentioned, the water is squeezed and has to rush from one end of the hull to the other, so as the water velocity increases so does the lift. The faster the curve transition from bow to side (ie the more buff the bow) then the higher lift forces that will be generated. All things being equal, the finer "Josher" bow should pull less than the "buffest" Woolwich bow, making her easier to track the channel.

 

a "proper" stern design would need a long sturdy prop shaft extension tube and a very strong skeg,

 

I had a quick sketch. The lower foto on the first image is the one I posted previously - not perfectly side on but it's close enough to illustrate the difference.

 

25" prop fitted (blades are a bit too fat) clearances: rudder to aft prop 70mm, fwd prop to deadwood 210mm, top tip 112.5mm, lower tip 38mm. Rudder leading edge extended to give a 20% balance and central flat blade encased in a Schilling "camshell" arrangement:

 

 

 

Structural interface between skeg web and tube extension not optimised for stress dissipation - have to protect it from an upward skeg deflection distorting the tube.

Edited December 30, 2016 by dpaws

[JohnO]

Yes what they all say #199 to #210 ^^^
to add,
bear in mind the bow sits up out water so not an "equal displacement”?. When boats were gauged they took multiple free board measurements of the the hull to gauge the total load.
You say the weed hatch is 1 or 2” into the water? There is probably removable ballast around the stern anything aft of engine. You could move this ballast forward thus raising the stern and bringing down the bow, you could try getting the counter out the water at rest. You maybe surprised how much it takes to get the fore end down. I have had to design the interior of my boat around getting that “tug” style look. I prefer the way my boat performs and it “looks” right. I think that prop is not ideal and the original sounds much more like i would expect, but i know f… all about that black art.
"but the lateral forces between the "vertical" channel sides and the parallel slab hull side, so "sideways" squat rather than getting sucked into the mud beneath”
The forces you need to worry about are the ones which keep the boat glued to the side if steering tight on the approach to a bend, Charity Dock bend on the Coventry Canal is a good one. Steerers can’t see oncoming traffic round the bend so hung the inside, see a dozen GRP cruisers facing them, worry some more, hug a little more, then carry on straight into the boats they were trying so hard to avoid, also driving hard into the corner then backin off leaving little steerage rather than coasting into corner then driving round and out. The Oxfords, Coventry and Ashby should provide a learning curve.

 

 

 

Canopus Built by D Harris & D Gunby - Length : 19.812 metres ( 65 feet ) - Beam : 2.083 metres ( 6 feet 10 inches ) - Draft : 0.61 metres ( 2 feet ). Metal hull N/A power of 27 HP. Registered with Canal & River Trust number 509849 as a Powered Motor Boat. ( Last updated on Wednesday 22nd May 2013 )

 

edit: to to on

Edited December 30, 2016 by JohnO

[Guest]

You say the weed hatch is 1 or 2” into the water? ....You maybe surprised how much it takes to get the fore end down.... The Oxfords, Coventry and Ashby should provide a learning curve.

 

Canopus Built by D Harris & D Gunby - Length : 19.812 metres ( 65 feet ) - Beam : 2.083 metres ( 6 feet 10 inches ) - Draft : 0.61 metres ( 2 feet ). Metal hull N/A power of 27 HP. Registered with Canal & River Trust number 509849 as a Powered Motor Boat. ( Last updated on Wednesday 22nd May 2013 )

 

Interesting points John. We're about 1cm into the water at present, I'd be reluctant for much less when static only to avoid wavelets slapping the uxter plate which I've been warned is quite annoying after a while apparently.

 

I should be able to get the bow down by using the maximum moment available; the forward gas locker will one day be converted into a fore-peak water/ballast tank, so extra weight at the optimal position, it's the best chance I have.

 

Must admit I'm rather looking forward to the Ashby for training runs

 

Thanks for the reminder, I'll get her details on the central database updated after April.

Edited December 30, 2016 by dpaws

[Guest]

 

Posted 24 October 2015 - 03:15 PM

With reference to a much earlier post of mine back in the summer . Yep Canopus is a lovely looking boat , but not when it smacks into you without slowing , rips your cratch cover , puts a dent your hull and the steerer utters those immortal words , 'CONTACT SPORT'. Even his wife had to hold onto something in the bow ( whilst yelling at him to slow down) he hit us with such force . Luckily I was hard in reverse when I saw his speed as he missed the corner , or it could of been worse , a possible insurance claim . As it is I can use a needle and thread and you only notice the dent when the curtains are up ( not often if it's a wet summer) . Still Canopus nice looking boat but don't want to see her that close too again . Bunny

Found this from 2015 which proves Dpaws is not the only owner who had problems with Canopus

 

 

I'd spotted that before and drew the same conclusions. The previous owner had a wide range of experience of boat handling including wide-beams on the continent; not a careless or complacent type of chap by any means. He'd have had good experience on 'Pus at that time too, having toured extensively for a few years before that event.

 

The timing of the remark would seem to coincide with the Axiom being fitted. By his account there was no reversing effect below 500rpm (accentuated by a nervous-with-the-speedwheel issue?)

 

Naturally I feel for poor Bunny - but I can sympathise with the previous owner too...

Edited December 30, 2016 by dpaws

[JohnO]

 

I'd be reluctant for much less when static only to avoid wavelets slapping the uxter plate which I've been warned is quite annoying after a while apparently.

Thanks for the reminder, I'll get her details on the central database updated after April.

 

tis true, not a problem if you sleep on the butty. Good luck updating those details maybe easier said than done. I went into an office and gave details but nothing ever happened, hope you have a better experience.

[Guest]

The forces you need to worry about are the ones which keep the boat glued to the side if steering tight on the approach to a bend, Charity Dock bend on the Coventry Canal is a good one. Steerers can’t see oncoming traffic round the bend so hung the inside, see a dozen GRP cruisers facing them, worry some more, hug a little more, then carry on straight into the boats they were trying so hard to avoid, also driving hard into the corner then backin off leaving little steerage rather than coasting into corner then driving round and out.

 

Ahh, so in practice you actually prefer these lateral forces, that explains the favourable comments about a fully loaded boat. You allow the bow to hunt the channel but counteract at the tiller to keep her off the near bank.

[IanM]

I still think you're concentrating too much on the theory of how a boat 'should' behave and trying to get your boat to perform 'perfectly' when in practice the changes you suggest making will probably make no noticeable difference in reality.

 

Just get out there and use the boat and enjoy learning its characteristics

[Guest]

I still think you're concentrating too much on the theory of how a boat 'should' behave and trying to get your boat to perform 'perfectly' when in practice the changes you suggest making will probably make no noticeable difference in reality.

 

Just get out there and use the boat and enjoy learning its characteristics

 

It's all part of understanding, there are so many conflicting answers and experiences, and none of them are wrong per-say - it's a challenge to understand each and the reasons why in each case.

 

I hope to have a noticeable improvement for the crash stop and I've illustrated quite clearly all the potential for improvement and why.

 

We'll see - it's the learning that's the fun part