nb Beech

[Pluto]

Bow waves. Well they can be observed, and horse drawn packet boats rode them, blessed if I know the calculations required to measure one!

Try looking for a soliton, first investigated on the Union Canal in Scotland.

[Derek R.]

(snipped)

 

This is the same force as felt when you hold the back of a spoon against the stream of water from a tap, it's lift, like a spoiler on a car boot, it's a lift force that happens to be downwards.

 

Same as happens on an aerofoil which creates lift. The faster stream of air across the top of the wing creates low pressure, the higher beneath creates high pressure - hence lift. Is this not Bernoulli's effect.

 

Try looking for a soliton, first investigated on the Union Canal in Scotland.

 

Excellent - thanks Mike.

 

https://en.wikipedia.org/wiki/Soliton

[mark99]

Hang on a mo. Perhaps think about the difference between lift and momentum transfer.

 

Lift (pressure difference) I don't think, is the force you are feeling on a spoon in water; it's more momentum transfer.

[Guest]

Hmm, it will be the resultant of various forces, but for sure the squat is caused by "lift" - when you pass another boat on the canal you feel this force as it pulls you in towards the other boat. The other boat is simply acting as a surface, the same as the bottom of the canal is doing as we pass it...

 

The study of barge bow shapes that I attached before shows data from two depths of water, the results are different, and the shallower the water the more significant becomes the forces other than the bow wave resistance - and in the same way, the closer you pass the other boat, the harder it is to control that pull into the other boat... **

 

If you're really bored you can calculate it

 

THE EFFECT OF PASSING SHIPS ON MOORED SHIPS

 

** ...without a sneaky blast of a bow thruster, heaven forbid

Edited January 13, 2016 by dpaws

[ChimneyChain]

Take a deep breath and breatheeeeeee

 

Darren

[Derek R.]

Let's go back to looking at BEECH . . . . It's a far nicer view.

[Guest]

Oh I agree Once the lads have been to measure I'm hoping that I can feed those dimensions into a 3D CAD program and render the result, so we can all see the bow profile from different angles - in fact I'm surprised that someone hasn't done a 3D model of each of the classic boats, I'd be so interested to see how they really differ side by side, and also apply fluid flow simulations to see how efficient their shape really is...

 

I guess that no one so far has really cared about hull profiles because canal diesel engine kWs are cheap (and without obvious penalty) and potential efficiency gains are small but the inevitable increase of electrical propulsion systems will bring more attention to this area as the cost per KW in an electrical system is very expensive in comparison.

[mark99]

I've skimmed a few sources re Bernoulli and ships squat. Interesting facts are:

 

Squat varies directly with breadth (doubling breadth doubles squat)

Squat varies by the square of speed (doubling speed quadruples squat)

Squat can be doubled when meeting another ship (> speed = > Bernoulli)

 

Also modified my opinion - Bernoulli effect is a significant source of forces on a moving boat.

Edited January 13, 2016 by mark99

[Laurence Hogg]

I think whats being forgotten here is that you don't need all this B-Shit to produce a good efficient hull. The Shropshire Union boats were highly efficient and then there came the "engines" which gave the design then used by the motors. All these craft did millions of miles on the waterways without any major problems. The largere GU boats became popular because you could load more in them, hence the boatmen preferred them. Only in the dying days with badly maintained canals did any design technology come into play.

 

God look what Hitler had to say about arse heavy "Joshers":

 

[FadeToScarlet]

Hydrodynamics is one thing, the other is load capacity.

 

A Josher motor might be fine and efficient at moving through the water, but it can't take a huge weight of cargo- which wasn't a big problem for FMC as they were merchandise carriers mostly. At the other extreme, you've got motors like the "tree class" Severners, boxy and slab-like (Rolt called them "biscuit tins", but could carry 33 tons on a 3'6" draught, which is nearly a Josher pair!

[Guest]

Oh Laurence that's brilliant, I've tears streaming - thank you for sharing

[Guest]

Hydrodynamics is one thing, the other is load capacity.

 

A Josher motor might be fine and efficient at moving through the water, but it can't take a huge weight of cargo- which wasn't a big problem for FMC as they were merchandise carriers mostly. At the other extreme, you've got motors like the "tree class" Severners, boxy and slab-like (Rolt called them "biscuit tins", but could carry 33 tons on a 3'6" draught, which is nearly a Josher pair!

 

I think that's why the design process holds the interest for me, capacity vs efficiency, the internal requirements of a CC pleasure boat will dictate the efficiency of the hull, the same as the cargo carried before dictated the class of boat used.

 

I'm quite surprised that I'm looking at only a 61' LOA hull - I've got everything I think we'll need and more in the space, and we can still fine the swims down quite a bit. The advantage of the 3D CAD work is that you can see how the space inside "feels"; there's been quite a few changes as a result.

[AMModels]

Greenie for Laurence, even though Hitler bad mouthed Kangaroo! That was brilliant.

[Pluto]

I still think this is one of the best traditional-style hulls to have been built, with more useful space for its length than any traditional narrow boat shape. It handles well, despite, or perhaps because of, having a single cylinder engine, and has been over much of the system, including tidal sections. The prop is easy to get at without a weed hatch, and the bow shape allows that area to be used as a bed, maximising space usage. Alan Holden, who had it built by Roger Lorenz, tells me that he will be selling next year, after he has taken part in the L&LC 200 anniversary, though he wants to sell someone who would appreciate the boat.

 

 

[Guest]

That's a classic bow shape for the cargo barges on the continent, the "spoon" bow, well proven, stable in a swell and, like you mentioned, it offers excellent space on the inside.

 

Looks like he could do with just a little more ballast...

[Pluto]

That's a classic bow shape for the cargo barges on the continent, the "spoon" bow, well proven, stable in a swell and, like you mentioned, it offers excellent space on the inside.

 

Looks like he could do with just a little more ballast...

It is actually based on a steel Leeds & Liverpool Canal boat, their design coming from those built from wood, and the first photo was taken just after being put into the water for the first time.

[Derek R.]

Here's another shot taken in the mid to late eighties:

 

 

[Tony Dunkley]

I still think this is one of the best traditional-style hulls to have been built, with more useful space for its length than any traditional narrow boat shape. It handles well, despite, or perhaps because of, having a single cylinder engine, and has been over much of the system, including tidal sections. The prop is easy to get at without a weed hatch, and the bow shape allows that area to be used as a bed, maximising space usage. Alan Holden, who had it built by Roger Lorenz, tells me that he will be selling next year, after he has taken part in the L&LC 200 anniversary, though he wants to sell someone who would appreciate the boat.

 

 

I like that a lot, . . . the fore-end shows just what can be done with some flat plate, a good helping of know-how, and a bit of ingenuity, but it looks from the top photo as though they've departed from the lines of the run and under the counter on the later Yarwoods built boats, and 'Everton', 'Farnworth' and 'Darwen'.

 

In fact, it's reminded me about something which rather puts the more fanciful theorizing in this topic about hull shape, and it's minimal effect on the speed and performance of canalboats, into some sort of perspective. The matching of hull operational displacement and speed with engine, gearbox reduction ratio and propeller blade design, diameter and pitch have far more effect on performance than any amount of fiddling about with hull lines, and 'hydrodynamics'.

'Everton' and 'Farnworth' were to all intents and purposes identical vessels, only differing in that one had a 3 x cylinder Armstrong and the other a 3 x cylinder Lister with roughly the same power output.

The really noticeable and big difference was in the loaded and empty performance of them both. Fully loaded with the same tonnage, Everton would rapidly leave 'Farnworth' behind, but with both boats light, 'Farnworth' would easily outrun 'Everton'.

The difference in performance was the same in any depth of water, or size of waterway, from the relatively restricted width and depth of the Bridgewater to the Ship Canal and Manchester Docks in depths of around 30'. The only significant difference between the two boats were the propellers, which were both very different in design and blade form.

[Guest]

Well Tony, I'm hoping one day to find the answers...

 

The shape above is used in the Polish article attached earlier, it's performance deteriorates as the water gets shallower, it's profile is very similar to a high lift wing section, so a strong low pressure area, so lots of pull into other boats. However, I would expect it to be very manoeuvrable, the high lift profile will pull a lot of extra water along with it making the rudder very responsive. You'll need more power to push it along than you would for nb Beech for example, assuming they are more of less the same length, but of course you have a longer accommodation space inside too, which was the design motive.

 

Not a case of re-inventing the wheel, but of choosing the most suitable wheel.

 

I'm not sure how the two cases compare if we took the accommodation length as the primary dimension. So, for the same length of accommodation, the boat posted above would be shorter than Beech, but the displaced volume could work out to be very similar.

Edited January 15, 2016 by dpaws

[Guest]

I've got the three plans from a Josher, a large Northwick and a large Woolwich all laid out in the lounge (thanks Laurence!) - it's fascinating to see how the shape has evolved in that order, from an almost symmetrical cigar shaped Josher to the buffer bows of the Town Class, and even a hint of an s-shaped stern profile into the propellor.

 

In fact, for me the Josher has the worst stern profile, most similar to the typical clone craft in profile, looking from above. The large Northwick is sort of in the middle, with a buffer bow than the Josher but a straight taper into the propellor, like a stereotypical sharpened colour pencil I suppose.

 

I'd never realised that a Josher was so tall, 6" more than the Town Class yet with less hold depth - no wonder their bow can look a little "snooty"...

 

Gawd - am I starting to become anoracky? I was counting rivets earlier, literally!

[MtB]

What sort of anorak do you have??

 

[Guest]

Ahhh... I hadn't realised their were distinct classifications in these circles... Can you suggest some categories that I could consider? Do any involve special handshakes or jolly dancing with jingle bells? I think they scare me the most! haha

[MtB]

Ahhh... I hadn't realised their were distinct classifications in these circles... Can you suggest some categories that I could consider? Do any involve special handshakes or jolly dancing with jingle bells? I think they scare me the most! haha

 

 

OMG I'm gonna have to do the Morris dancing joke now.

 

Why do Morris dancers wear bells?

 

So they can annoy blind people too!

 

 

 

Sorry. Dpaws MADE me tell it :D

[Guest]

Haha like it Mike, happy to shoulder the blame!

 

Looking again at Beech I can imagine a tall bow because the shearline carries that shape forward, but of course it's a wooden hull. I wonder when they switched over to the composite construction with iron sides if they kept the original sternpost dimension but lost the shearline in the metal because it's harder to reproduce, and consequently ended up with a steeper angled foredeck than it's wooden counterpart.

Edited January 15, 2016 by dpaws

[MtB]

I reckon it is because riveted iron gets a boat designer a far more sophistimacated and efficient stern design. Look at the upwardly dished uxter plate and delicious swim shape on most iron hulls...