How wide is a canal?

[Guest]

Slide of topic, but meantime we are awaiting professors answer, but to keep us on track or close to the center of tha canal, or deepest part, other string length question, how long and tall is a "normal" NB rudder plate?

 

Usually the height that's available under the counter stern, most likely measured and considered after completion of the hull structure. The historical boat plans that I have pinned to the wall, 2'6" square would be a good ball park estimation...

[Tony Brooks]

 

Why? The squat is an interaction between the channel (below and to the side) and the hull itself. A designer can change the hull, the shape of the hull and thus the interaction between the channel and the hull - the Cb no? So yes, you want to know the values...

 

From the squat perspective, is a flat bottom superior to V-bottom? Traditional aft swim, clone craft aft swim, XR&D "slipper stern" profile - which one would minimise the squat from that part of the hull profile? Spoon bow? Racked bow? Eco-bow?

 

Its seems to me that the way the water level drops alongside the boat and the way the stern drops is to do with water being unable to get past the boat fast enough. If that is so the the greater the "gap" between hull and bottom must allow more water past the hull. This would suggest a V bottom would be better than any other form and if a slipper stern can be built in with the minimum of deadwood in front of the props so much the better. This would tend to indicate the use of P or A brackets but I have doubts about their longevity on canals. I have seen what can happen to P brackets on 27ft GRP cruises on the Thames.

 

An advantage of a V bottom is you can more easily get alongside in many places.

[Dalslandia]

 

Usually the height that's available under the counter stern, most likely measured and considered after completion of the hull structure. The historical boat plans that I have pinned to the wall, 2'6" square would be a good ball park estimation...

 

They seems to be rectangular, but that might be because "modern" NB is shallower below the counter

[Guest]

.... and if a slipper stern can be built in with the minimum of deadwood in front of the props so much the better. An advantage of a V bottom is you can more easily get alongside in many places.

 

Well I followed that thinking until I thought about the squat.

 

Imagine a hull with a spoon bow (shaped like the back of a spoon, used throughout Europe on barges) and the side cut-a-way of the XR&D slipper stern... OK, take the side view - consider that the water line is the base of an inverted aerofoil / hydrofoil section. (I wish I could draw!)

 

You have a section that has a large radius leading edge but a fine trailing edge... and that's exactly the type of profile you use on a slow aeroplane to create maximum lift at low speed - so when inverted you have the perfect section for maximum squat at low speed.... by accident, and despite best intentions!

 

(I suspect that Peter Nichols is one of the few UK builders that get it, he builds his hulls shallow, minimum displacement = minimum squat effect - unfortunately I didn't find the guy easy to communicate with, and the lines of his hulls never seduce me - but technically his designs are, hydro-dynamically at least, a small step ahead of the vast majority)

Edited February 24, 2016 by dpaws

[Dalslandia]

 

Its seems to me that the way the water level drops alongside the boat and the way the stern drops is to do with water being unable to get past the boat fast enough. If that is so the the greater the "gap" between hull and bottom must allow more water past the hull. This would suggest a V bottom would be better than any other form and if a slipper stern can be built in with the minimum of deadwood in front of the props so much the better. This would tend to indicate the use of P or A brackets but I have doubts about their longevity on canals. I have seen what can happen to P brackets on 27ft GRP cruises on the Thames.

 

An advantage of a V bottom is you can more easily get alongside in many places.

Thats my thoughts too Tony, and experience from 60000 locks.

What dpaws have is a "modern" NB down to the chine then a V bottom, with the question how deep what goes under the water to make it better in every way .

[Tony Brooks]

Thats my thoughts too Tony, and experience from 60000 locks.

What dpaws have is a "modern" NB down to the chine then a V bottom, with the question how deep what goes under the water to make it better in every way .

 

From his CAD development of the hull form I thought it looked more like Noah's arc than a narrow boat hull. The hull sides looked far too tall to me. A typical modern narrowboat has its air draft set by bridge and tunnel heights and its draft set by the need to accommodate 6ft tall people. Those constraints leave little room for much of a V bottom unless parts of the V extend above the floor line however something is better than nothing.

 

I do not understand this spoon bow business. However fine the bow entry is there is still the bulk of the hull preventing water flowing easily past the boat and as I noted before its the stern that drops, not the bow, on typical canal craft. The on-line illustrations of spoon bows don't look so different to my Colecraft bow but its underwater shape as opposed to what is visible is just bowed up flat plate.

 

It sounds to me as if the proposal is for a very bluff bow that has the underwater shaped so it pushes water ahead of it to generate some lift to counteract the squat. That would make the stern squat even more.

 

This makes my head hurt - build it along the lines of a horse draw butty and proper Josher hull. They were developed over years and years by experience of what worked and what did not.

[Guest]

 

From his CAD development of the hull form I thought it looked more like Noah's arc than a narrow boat hull.

 

The trolls they came in two by two - hurrah! hurrah!

[RLWP]

 

The trolls they came in two by two - hurrah! hurrah!

 

Excellent. I have been in two minds about how to respond to this thread. Now I'm decided

 

Richard

[Troyboy]

Does a pump out or cassette affect the squat in any way ?

 

I seem to remember from my school days that the heat of the beat is equal to the throb of the knob when the angle of the dangle is constant . Thought I'd just throw that in.

[Guest]

Does a pump out or cassette affect the squat in any way ?

 

I wasn't sure - but we'll be compositing, just in case...

[Tony Dunkley]

 

I wasn't sure - but we'll be compositing, just in case...

 

Definition of COMPOSITING:~

Compositing is the creative process of assembling and combining filmed or rendered elements from multiple sources, to create a final lifelike illusion or fantastical visual effect, delivered as a set of still or moving pictures.

__________________________________________

 

Is this really what you intend to do with the contents of the bog ?

[Guest]

Haha - ruddy spell checkers!!!

[Tony Brooks]

 

The trolls they came in two by two - hurrah! hurrah!

 

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.

 

Canal boat hulls have been developed by people for who economy of operation and load capacity was vital. I would think that after over 200 years the hull designs would have been refined to a point that would be very difficult to improve upon. I am not talking about modern leisure boats because they have been developed against different criteria. My view is that if you think that you and your Prof can come up with a hull design that is measurably more satisfactory that the horse drawn wooden butty boats and the true Joshers you will spend a lot of time, effort and money for little return. Still its what floats you boat I suppose.

 

You have studied the true Josher lines I assume because you seem to have made a fair attempt of describing the front end. I also wonder if Mr Nichols is not the one who is difficult to talk to. Its a bit unfair to expect long technical discussions until you are ready to pay your slot deposit.

 

I am still wondering how you square the small displacement you seem to want with a low air draft and the need for about 6ft of internal headroom. Then there is the question of if you did manage to square that circle would you be able to swing a prop that is both efficient and large enough to absorb the 30 odd BHP of the DV 36 plus your extra power from the electric motors.

 

PS If you are not that chap with the BV 36 plus electric motors idea I apologise, but I think you are.

[Guest]

I asked for, and kindly received information about the dimensions of canals - sometimes forums are simple, ask a question, get an answer, say thank you

 

Ignorance is never an excuse for bad manners...

[Gwydion]

Does a pump out or cassette affect the squat in any way ?

 

Well, my cassette bog is too tiny for me to fully sit down on it, so I have to sort of half squat and hover about a foot above it, all the while keeping my aim. It's not easy at all.

[Paul C]

 

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.

 

Canal boat hulls have been developed by people for who economy of operation and load capacity was vital. I would think that after over 200 years the hull designs would have been refined to a point that would be very difficult to improve upon. I am not talking about modern leisure boats because they have been developed against different criteria. My view is that if you think that you and your Prof can come up with a hull design that is measurably more satisfactory that the horse drawn wooden butty boats and the true Joshers you will spend a lot of time, effort and money for little return. Still its what floats you boat I suppose.

 

You have studied the true Josher lines I assume because you seem to have made a fair attempt of describing the front end. I also wonder if Mr Nichols is not the one who is difficult to talk to. Its a bit unfair to expect long technical discussions until you are ready to pay your slot deposit.

 

I am still wondering how you square the small displacement you seem to want with a low air draft and the need for about 6ft of internal headroom. Then there is the question of if you did manage to square that circle would you be able to swing a prop that is both efficient and large enough to absorb the 30 odd BHP of the DV 36 plus your extra power from the electric motors.

 

PS If you are not that chap with the BV 36 plus electric motors idea I apologise, but I think you are.

 

 

I'd say if they do the sums, propose different hull designs, make tweaks, rerun the model over and over etc and they come up with a hull shape the same as existing boats, the project has been as successful as if they come up with a variation on today's hulls. The trick is going to be getting the maths right, and being able to KNOW its right either by sanity checks, or very careful checking/review (possibly including modelling it against other known/available models).

 

The fun part comes when they are able to enhance the model with more and more fine grained variations, for example:

 

1) traversing a "lump" on the canal bed which comes close to the hull

2) traversing a "lump" on the canal bed which can be considered "rigid" and raises or tilts the boat out the water. Then the way the boat sits in the water becomes a 2 point model (the lump and the bouyancy), etc

3) traversing a "lump" on the canal bed which can be considered "elastic" - see above for similar calcs

4) traversing a bridge hole where the available depth is (for example) 2" too little. ie "How much speed does the boat need to allow its momentum to successfully make it through".

5) as 4 but the requirement to cut the motor

 

etc etc

 

I am sure we could all think of more.

[dave moore]

Who might build this paragon of design, I wonder.....most of the builders I know, traditionalists largely, would probably give it short shrift. To me the whole thing seems to be a sledgehammer to crack a nut...theoretical overkill compared to hard won practical experience....but it's the OP's choice.....

 

Dave

[RLWP]

Who might build this paragon of design, I wonder.....most of the builders I know, traditionalists largely, would probably give it short shrift. To me the whole thing seems to be a sledgehammer to crack a nut...theoretical overkill compared to hard won practical experience....but it's the OP's choice.....

Dave

Ahhh, another troll

 

 

Richard

[Guest]

Who might build this paragon of design, I wonder.....most of the builders I know, traditionalists largely, would probably give it short shrift. To me the whole thing seems to be a sledgehammer to crack a nut...theoretical overkill compared to hard won practical experience....but it's the OP's choice.....

 

Dave

 

I wholeheartedly support that opinion, but it's got little to do with centre channel dimensions - I don't want a fan club, but I'd like a fine hull for my canal boat, thank you

[dave moore]

In my experience, centre channel dimensions vary widely along every length of every canal I've boated on. It doesn't always follow a parallel course to the towpath either, as an inexperienced steerer found when they tried steering our boat on the BCN main line some years ago. I hope your efforts produce the finest swimming craft on the cut....have you thought of looking at fly boat lines from working days? They were built for speed, though the bottom is much nearer the top in most waterways today.

 

Dave

[Guest]

Thanks Dave, sincerely - she will be the fish's favourite, I'm sure!

 

Yes, I've studied a fair few prototypes, to the extent of replicating bespoke sculptured hulls like nb Beech in three dimensions.

 

You've hit the nail on the head "...though the bottom is much nearer the top in most waterways today."

 

Canals have changed. British Waterways refined their earlier designs in the 50's to accommodate changes to the canals back in those days; they haven't stopped changing. We now have the computing power readily available to continue the BW work further and I also have the distinct advantage that I can carry just one custom shaped cargo.

 

The deeper drafted working boats had gone out of fashion as far as new builds were concerned with the clone-craft brigade, but now they're making a come back with the various "traders" on the market, all slightly tweaked for today's environment afloat - much to the loud distain of many vultural flat-earthers!

 

Well, I'm going to give one a big underwater tweak and we'll see what happens - if now't else it'll keep the fish amused.

Edited February 24, 2016 by dpaws

[Hairy Animal]

Was the boat actually being lowered in the water or was the water level itself being lowered?

I'm fairly sure it was the boat getting lower in the water, as I don't remember the canal being particularly narrow and we never got going fast enough to generate much of a disturbance in the canal to lower the surface level.

 

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.

[Keeping Up]

It all reminds me of the attempts to create a more efficient bow shape, akin to those on ships, several years ago. On paper, and in test tanks, the new shape worked far better, and several Alvechurch hireboats were fitted with them. In practice it was generally rather different and on almost every canal we found that our conventionally-shaped boat could travel faster with less wash. On one occasion we caught up with such a hireboat on the Llangollen and he immediately pulled over and waved us by; as we passed he called out that he'd been letting boats past all week because he couldn't travel as fast as them without causing excessive wash.

[Guest]

Now I'll need probably need Laurence in on this one - but I recall talk about one of the BW designs from the 50's taking two days longer to reach it's destination than it's older counterparts...

 

Then again, whilst maybe not the most elegant design, the Admiral class seems well regarded for it's handling characteristics....

 

With so many fixed parameters any result will be a compromise, with gains in some areas and losses in others. I recall the Eco-bow research aimed to minimise forward hull resistance. If squat is a significant factor in the total canal boat drag, then a hull that has been designed to minimise squat will no doubt have a worse performance in other areas.

 

Once all the results are in then you can chose what you can and what you can't live without. Jump in without seeing all of the results first and the opinion is truly worthless. Everybody is entitled to their own opinion, even if it is wrong!

 

Professors tend to be more reliable in their opinions than pundits, and that's why I enjoy discussing concepts with them.

Edited February 24, 2016 by dpaws

[Hairy Animal]

Another example of similar problems was some time ago when the Ownerships boat share management company (long since demised) commissioned a narrow beam Dutch barge design boat from a boat builder they thought had a good record.

 

They sold quite a few shares in it but when the new part owners started using it on narrow canals, found that it became unmanageable in narrow bridge holes. So much so that several owners wrote off multiple wheelhouses. OS presumed it was just pilot error (the customer was always wrong in most cases) until the MD tried it himself and wrote off another wheelhouse!

 

When OS tried to sue the boatbuilder for producing an unusable boat, he basically said, no problem, I'm bankrupt, or something like that.

 

So the design of a narrowboat, especially below the waterline, can be very wrong if you don't know what you're doing.