How wide is a canal?

[Giant]

Quite a good example of 'squat' was back in 1992 (7th August) when the QE2 hit some underwater rocks in open water off Martha's Vineyard (Dukes County, Massachusetts) which should have been below the QE2's hull but, due to her speed and consequent 'squat', caused quite a lot of damage.

 

A more notorious example would be the Herald of Free Enterprise. It was worked out in the investigation that her squat increased suddenly beyond a particular speed, and had she been travelling a couple of knots slower she might never have sunk.

[Guest]

 

A more notorious example would be the Herald of Free Enterprise. It was worked out in the investigation that her squat increased suddenly beyond a particular speed, and had she been travelling a couple of knots slower she might never have sunk.

 

You're right, and the shallow water was cited as being a contributing factor.

[Tony Brooks]

If the idea is to stop squat then how about being really radical.

 

If,as I believe, a moving boat's vertical position relative to a datum drops because water is being pushed in front of it while the prop is pumping water away from the stern causing the local water level to drop how about putting the prop at the front working like an aircraft prop. This would allow the engine to be positioned with plenty of room for the electric motors. Water that is being pushed up in front of the boat will be "pumped" backwards by the prop and the prop flow might even lift the boat a little. In fact there would be a very free entry for water into the prop so this could well improve efficiency as well.

 

There is a little mater of debris and prop fouling to consider though.

[Hairy Animal]

 

A more notorious example would be the Herald of Free Enterprise. It was worked out in the investigation that her squat increased suddenly beyond a particular speed, and had she been travelling a couple of knots slower she might never have sunk.

That's interesting, I'd not heard that. I see from the wikipedia article that a sister ship crossed the Channel with its bow doors open without sinking, so the squat effect was in that case a very significant factor.

Edited February 25, 2016 by Hairy Animal

[hughc]

The finest and fastest swimming hulls were probably those of the Potteries boats working down the Chesire locks. thinking back to when we had the Avon it was amazing how much faster she was than any of the Fellows Mortons or Union boats we used to meet. A close look at the design of the Knobstick horse boats might help your design process.Regards, HughC.

[Tony Brooks]

The finest and fastest swimming hulls were probably those of the Potteries boats working down the Chesire locks. thinking back to when we had the Avon it was amazing how much faster she was than any of the Fellows Mortons or Union boats we used to meet. A close look at the design of the Knobstick horse boats might help your design process.Regards, HughC.

 

And that more or less sums up my concerns. It must be more productive to study the lines of hulls that are known to swim well and then see how and if they can be modified to suit today's shallower canals than to ask a question that is truly impossible to answer and then use such answers as you are given to do calculations. I find professors or not old style experience over 100s of years usually beats maths - but not always.

[Tam & Di]

 

I see, just because your favourite project has received what you consider an an adverse opinion the person voicing it must be a troll. I think that the same could be said of a person who seems intent of over complicating a fairly simple project and the tries to involve others into his machinations.

 

 

All this nonsense is simply displacement activity, in lieu of actually doing some boating.

[Tony Dunkley]

After the partial capsize and sinking of 'Herald of Free Enterprise', the engine controls were found set to full astern, and that was taken as reliable evidence that the flooding via the open bow doors was brought about by 'squat' in it's most severe and dangerous form when, after straying a little too far into the shallower water on the edge of the dredged channel at relatively high speed, the ship 'dived' and put the forard part of the car deck under sufficiently to instigate the flooding.

The loss of buoyancy from the initial flooding was sufficient for the flooding to continue after the ship recovered from the 'dive', and the loss of stability [reduction in GM] from the free surface effect of the water on the car deck then led to the partial capsize.

 

'Diving' is something which occurs when flat bottomed vessels, from narrowboats to barges to ships, and trimmed either level or by the head, stray from relatively deeper water into shallows at a greater speed than they would normally achieve in the shallower water. The sudden extreme pressure drop beneath the hull, caused by more rapid than normal flows of water resulting from the higher than normal speed [in the shallower water], is sufficient to literally suck the vessel rapidly downwards, usually until it contacts the sea/river/canal bed. The loss of speed which always accompanies the dive usually results in the vessel rising again almost immediately, but if the sea/river/canal bed is silty or muddy, they can be held down by the suction created by the mud or silt. If that happens, then normal procedure is a short burst of full astern to break the suction; hence, the setting the controls of the 'Herald of Free Enterprise' were found in following the incident.

[Guest]

 

And that more or less sums up my concerns. It must be more productive to study the lines of hulls that are known to swim well and then see how and if they can be modified to suit today's shallower canals than to ask a question that is truly impossible to answer and then use such answers as you are given to do calculations. I find professors or not old style experience over 100s of years usually beats maths - but not always.

 

The poster proposes to take something that works well, and then compromise the very part that is responsible for the good performance but without knowing, understanding or barely comprehending the mathematics of why it performed well in the first place...

Edited February 25, 2016 by dpaws

[valrene9600]

If your not happy with someone's contribution why not ignore it. Having a go at people just makes you look pathetic.

[Tony Dunkley]

As a footnote to my post #83 above:

 

Loaded barges operating in the restricted, meandering and muddy deepwater channels of the upper Mersey, lower Trent and Ouse, and the upper Humber are/were apt to dive if straying slightly out the channel whilst underway with a tide under them at normal operating speeds, and if loaded to capacity, can put the decks a good way under in the process.

There were, however, marked differences in their propensity for diving between individual barges from the same yards and built to the same design. Certain of them were notorious for doing it, with others not so; theoretically and on paper, identical vessels, but all behaving differently and not only with regard to any tendency to dive. Some were markedly faster than others despite having the same engine and sterngear installations, and some handled noticeably easier and better than their theoretically identical sister ships.

Perhaps something for dpaws to think about before indulging in any more pointlessly minute and inefficacious aspects of hull design.

Edited February 25, 2016 by Tony Dunkley

[Giant]

Thank you for your contribution - the hack and hope brigade! Bravo! FFS don't let hard evidence and research papers deter you, what do they know eh?

 

I looked back - in all the associated threads your behaviour is utterly and consistently clueless. I'm not aware of your agenda, but equally I'm not aware of your legendary technical success in the field of hull design and confined channel hydrodynamics.

 

Yes Tam, the process is called design, it's usually in lieu of the activity that the project concerns, a common sequence of events which has been repeated throughout history. Unless you have a positive contribution then I'm sure more amusement could be had elsewhere - maybe ask one of the grandchildren to download an app for you - crosswords should be well suited.

 

I was finding the threads on your project interesting, despite some lack of practicality in your approach. After that outburst however, I think you may find people less inclined to help you.

 

Not only is your post rude as all hell and completely unnecessary, it's directed at some of the most experienced and helpful people on the forum, and they are telling you the truth.

 

Hull design is not my field, but anyone who has worked with computer modelling of any kind will tell you that it will only get you so far. That goes even for things where the equations are much simpler, let alone trying to solve Navier-Stokes in a muddy ditch full of rubbish.

 

 

[RLWP]

I'm not aware of your legendary technical success in the field of hull design and confined channel hydrodynamics.

 

Would you care to parade you experience and qualifications? As far as I'm aware from your posts, you've never even been on a canal boat

 

Richard

[steamcompound]

 

There were, however, marked differences in their propensity for diving between individual barges from the same yards and built to the same design. Certain of them were notorious for doing it, with others not so; theoretically and on paper, identical vessels, but all behaving differently and not only with regard to any tendency to dive. Some were markedly faster than others despite having the same engine and sterngear installations, and some handled noticeably easier and better than their theoretically identical sister ships.

 

And the vessels that were built almost always deviated from the drawings, even at the highest levels of shipbuilding, thus the performance differed one from another. With naval vessels fine tuning of propellers to vessel was necessary and when visiting dockyards or Stone Manganese sets of props differing a few inches in pitch could be seen, marked up with the vessel name and number.

[Guest]

 

I was finding the threads on your project interesting, despite some lack of practicality in your approach. After that outburst however, I think you may find people less inclined to help you.

 

Not only is your post rude as all hell and completely unnecessary, it's directed at some of the most experienced and helpful people on the forum, and they are telling you the truth.

 

Giant, thank you for your advice, I have taken it. I respect and appreciate your positive and patient contributions to our project. Our understandings of "helpful people" however may differ...

[Giant]

Giant, thank you for your advice, I have taken it. I respect and appreciate your positive and patient contributions to our project. Our understandings of "helpful people" however may differ...

 

Clearly so. My understanding is "people who give their time to help you", yours seems to be "people who tell me what I want to hear". Your reaction to very reasonable concerns about your approach says far more about you than it does about the people whose help you are rejecting and criticising.

 

I think that you may find your interests in calculation and modelling of hull performance better served by the boatdesign.net forums than here. But I expect you will still find people telling you to research what is done in practice and known to work well from experience.

 

Calculations and simulation results are only as good as the simplifications and assumptions they are based on. And for anything involving fluid dynamics the results can be highly nonlinear, so targeting nominal and average conditions can be misleading.

 

I used to work in research at a university. One of the thing I did was write simulation software. And I am telling you that your faith in modelling is far too high. The system you are trying to model is very tricky and anyone seriously tackling it would be looking to have as much real world data and experience as possible.

[Tony Brooks]

 

The poster proposes to take something that works well, and then compromise the very part that is responsible for the good performance but without knowing, understanding or barely comprehending the mathematics of why it performed well in the first place...

 

Thank you for your contribution - the hack and hope brigade! Bravo! FFS don't let hard evidence and research papers deter you, what do they know eh?

 

I looked back - in all the associated threads your behaviour is utterly and consistently clueless. I'm not aware of your agenda, but equally I'm not aware of your legendary technical success in the field of hull design and confined channel hydrodynamics.

 

Yes Tam, the process is called design, it's usually in lieu of the activity that the project concerns, a common sequence of events which has been repeated throughout history. Unless you have a positive contribution then I'm sure more amusement could be had elsewhere - maybe ask one of the grandchildren to download an app for you - crosswords should be well suited.

 

 

My agenda as I hope most of my 6500 posts show is to try to use what technical expertise I have to help peoples' problems. I do not have and do not claim to have any success or experience of hull design but what I do have is over 50 years of personal experience and experience in inland boating. My observations tell me that a moving inland boat lowers itself when compared with a fixed datum because the water level local to the boat drops. I have also given two reasons why that happens. I note that you have neither countered my explanations or explained why it happens. Knowing my limitations I also suggested that you look at the lines of past and existing hull forms as starting point but you have given no indication that you did much of this at all.

 

You also do not appear to have grasped the fact that the dimensions of inland boats are fixed by the height and profile of tunnels and bridges, the depth of water, and the height of the accommodation. This then leads through into the design of the interior because if you use much more that a very shallow a V hull form the hull bottom plates are likely to protrude above the floor level. That may well be fine for a centre walk way boat but not for one with any walkways on the side. It may also have implications for tankage.

 

Your first question seems completely off the wall to me and needlessly complex because you imposed limitations and seemed unwilling to compromise or alter your design. I am particularly referring to you refusal to consider belt drives when they have been used on some hire boats for years. The next question you ask is absolutely impossible to answer and a few walks alongside canals for observation and thought would tell you that. In fact other posters told you that but you persist in thinking using maths and CAD will do something that others have been trying to do with varying success since the 18th century. In computers we used to have a saying garbage in = garbage out and unless you can model every inch of every canal you are very likely to get garbage out of the maths for most of the time. Others have tried to explain this to you. It does not matter if the sums are worked correctly if the initial values are wrong.

 

The CAD drawing you posted on the 18th has no dimensions and looks to me to be very high on the side and more of a wide beam. It also looks as if part of the hull just over half way forward is very much the shape of a conventional modern narrowboat except your hull curves slightly in towards the chine where as a modern boat's hull sides slope in. If anything the modern boat is narrower at this point than your drawing is. That should help water flow past the hull or to reverse that you design might hinder it. I do agree however that the stern part should provide a much less restriction to the water flow to the prop than almost all modern boats.

 

To have that hull built will be expensive although if you are willing to use thinner plates it MIGHT be a little easier. I am thinking about all the odd shaped plates that will be needed to get those compound curves and in all probability the extra welding. Then you really should be thinking about the resale value even if you have no intention of selling it at present. A poster has already given you a name for one particularly "unfortunate novel design that cost the original owner over twice as much as a conventional boat and then was very difficult to control. I do not think your design will be difficult to control but judging by that CAD drawing may well be difficult to sell if needed.

 

I suppose that what I am trying to say is that I have been trying to persuade you that your time, research and money can almost certainly, in my view, be spent elsewhere for better overall results in the end. However if this is just something like a student project then it is interesting but not, again in my view, very practical. Time will tell.

[valrene9600]

Tony why are you bothering. His rudeness should be the key that locks him out of any more discussion.

[Paul C]

When I did research as a student I used many sources of information, and there was a "rank" of suitability - for example good quality research papers, reputable text books were top; trade body publications next. Then it was lesser-quality papers, lecture notes, personal opinion, general quotes off the internet (including forums), Wikipedia. The lecturers really hated people quoting off Wikipedia and referencing it, and often an assignment using it would end up in the bin!

 

If you're doing some research and have come to the forum for help/suggestions, then you're already scraping the barrel, IMHO......or you are actually well advanced and are simply doing it for amusement - I was always too busy to discuss on a relevant forum, something I'd established a long time ago.

 

Realistically what are you going to do - quote this forum thread as a reference? If not, then how are you validating the value for "canal width" as an appropriate real-world measurement?

[Tony Brooks]

Tony why are you bothering. His rudeness should be the key that locks him out of any more discussion.

 

I have been hauled over the coals for telling a poster my opinion of their ability to wire a boat without help so there is no way I can explain why I have been trying to give him other things to look at. I formed my opinion with the first post in the other thread and had it reinforced by that CAD drawing. I know that some people (me included) can be reluctant let go their pet conceptions however "way out" they appear to others so I have just been trying to save him a lot of time and money, if indeed this is a real project, which I now doubt. If it is a student project then I think his Prof needs hauling over the coals for allowing him to collect virtually meaningless data, in the overall schemes of things, for further processing, let alone encouraging him by offering to do the calculations. However, maybe he will only find out when the project is marked. As you say, I don't think I will boater with him any more except to point out any concerns so his ideas do not have undue influence on others who mat well not have the experience to sort the good and poor.

[Guest]

 

Clearly so. My understanding is "people who give their time to help you", yours seems to be "people who tell me what I want to hear".

 

I think that you may find your interests in calculation and modelling of hull performance better served by the boatdesign.net forums than here.

 

Thanks Giant - as I eluded to earlier, the question posted was regarding the width of a canal, so I'm always pleased when people respond accordingly with data that I want to hear. Absolutely nowhere have I invited people's opinions regarding the viability this project, or indeed regarding my approach to the project, so yes, I find it both rude and ignorant when members decide to voice theirs in my direction in a derogatory manner.

 

Thanks for the forum suggestion, yes, the technical discussion with some members there goes on privately and in great depth. Importantly all of our empiracle equations under consideration have associated model data, acquired in accordance with ITTC recommendations regarding data repeatability etc. so error margins of the theory at least are known. Whilst the accuracy of computing simulations increase with processor power, the far greater issue seems to be the accurate full scale replication of a design; each ship is naturally only an approximation of the design itself.

 

The large majority of my co-conspirators are retired lecturers (three ex-department heads and counting...) and published industry consultants with impressive backgrounds, to me at least. So far we can conclude that squat is very sensitive to the Cb value, and this sensitivity increases with Froude number. That's an interesting thing to know, because both can be altered sympathetically at the design stage.

[Dalslandia]

If the idea is to stop squat then how about being really radical.

 

If,as I believe, a moving boat's vertical position relative to a datum drops because water is being pushed in front of it while the prop is pumping water away from the stern causing the local water level to drop how about putting the prop at the front working like an aircraft prop. This would allow the engine to be positioned with plenty of room for the electric motors. Water that is being pushed up in front of the boat will be "pumped" backwards by the prop and the prop flow might even lift the boat a little. In fact there would be a very free entry for water into the prop so this could well improve efficiency as well.

 

There is a little mater of debris and prop fouling to consider though.

 

In the photo section there is boat like that with a built in propeller in a tunnel in the centre of the bow, water outlet under the boat.

 

http://www.canalworld.net/forums/index.php?app=galleryℑ=7185&size=large

 

Seems to be from 1871, note the article about Sweden railroad idea. ​

​

Edited February 25, 2016 by Dalslandia

[Guest]

Author Richard Barker (1987):

 

An analysis of 59 boats that were very closely of a size with the Trial, and some of which had been in service for up to 23 years when gauged, reveals that the average wooden boat had the following characteristics:

 

Average length: 69 feet 10 inches (68'4" to 74'6")

Average breadth amidships: 6 feet 8.4 inches (6'2" to 7'1")

Average unladen draught: 9.8 inches (8-1/16" to 12-3/4")

Maximum gauged capacity: 26.73 ton (24 to 30 tons)

Maximum draught: 38.9 inches (36.34" to 42.62")

Plan prismatic coefficient at light draught: 0.80 (0.745 to 0.872)

Plan prismatic coefficient at laden draught: 0.847 (0.79 to 0.922)

Within these averages there were considerable variations. Some clearly had vertical sides throughout, other must have flared considerably, with up to 18% changes in plan area from light to laden. Despite the variations, and the variety of different routes and builders among so many boats with nothing but the Trent in common, it is conspicuous that the majority fall within quite a small range of dimensions.

Of the 59:

Length & Bread - 50 are between 69'0" and 70'0" 29 are between 6'8" and 6'9"

Only 5 exceed 71'0" Only 4 exceed 6'10"

Only 2 exceed 72'0" Only 2 exceed 7'0"

[Guest]

 

In the photo section there is boat like that with a built in propeller in a tunnel in the centre of the bow, water outlet under the boat.

 

This is pretty much as we were discussing before, which would offer a platform for the twin Schilling arrangement. The Torque-jet rim drive motor may offer part of the solution to the problem with debris.

[bargemast]

Hi dpaws,

 

I have no idea about your age, but the only useful thing to say that I can think of (which doesn't help your design of the ideal narrowboat) is : "Wouldn't it be much nicer to be exploring the canals now (or very soon) on a less than perfect boat but enjoying life on the water, instead of endless studies that will slow your chances down of ever being able to do so much more then neccesary by a long long time ?

 

If I had to make that choice, the answer would be crystal clear, and without the need for endless calculations, with or without the help of computer programms.

 

Good luck anyway.

 

Peter.