HDPE canal boat

[IanD]

https://www.thetelegraphandargus.co.uk/news/24606407.bradford-firm-launches-innovative-new-canal-boat-water/

 

Not a narrowboat, but they hope to have one it time for Crick.

 

Knowing how flexible (low Young's modulus) HDPE is, I expect there is an internal steel frame to keep the boat rigid, which would make it a bit less eco-friendly than claimed ("weight reduction"). I also wonder how thick the various sections are to get enough strength and rigidity, they'd have to be many times thicker than steel which will reduce any weight/cost saving...

 

Getting rid of corrosion/blacking/painting would be a big advantage though 🙂 

 

Found some more details -- steel frame inside thick plastic panels, as expected...

 

https://www.towpathtalk.co.uk/plastic-fantastic-revolutionary-new-boat/

 

"With a base thickness of 20mm, sides of 15mm and a roof thickness of 12mm..."

Edited September 25 by IanD
more details added

[Hudds Lad]

3 minutes ago, IanD said:

https://www.thetelegraphandargus.co.uk/news/24606407.bradford-firm-launches-innovative-new-canal-boat-water/

 

Not a narrowboat, but they hope to have one it time for Crick.

 

Knowing how flexible (low Young's modulus) HDPE is, I expect there is an internal steel frame to keep the boat rigid, which would make it a bit less eco-friendly than claimed ("weight reduction"). I also wonder how thick the various sections are to get enough strength and rigidity, they'd have to be many times thicker than steel which will reduce any weight/cost saving...

Is this the same one that was doing the rounds a few months back?

I note it still has no windows, assuming chopping holes in the sides also not good for rigidity.

[IanD]

13 minutes ago, Hudds Lad said:

Is this the same one that was doing the rounds a few months back?

I note it still has no windows, assuming chopping holes in the sides also not good for rigidity.

From the photos it looks like it relies on an internal steel frame for overall rigidity, at least for the hull -- whether this extends up to the cabin isn't clear. If it doesn't then cutting holes for windows will make the cabin a lot more flexible than a solid tube, this really screws up torsional rigidity... 😞 

 

It would be interesting to see a proper analysis of the design from a structural engineer, preferably not one employed by the company... 😉 

 

For comparison, HDPE is 7x lower density than steel (1g/cm3 vs 7) but steel is 250x stiffer (200GPa vs 0.8). With panels 2x the thickness of steel (what they're using) HDPE weight will only be about 30% of steel, but steel panels will be 60x stiffer (stiffness=thickness^2). For the same weight HDPE would have to be 7x thicker than steel (70mm/42mm/28mm) but steel would still be 5x stiffer.

 

Unreinforced plastics are not good structural materials... 😞 

Edited September 25 by IanD

[David Mack]

I think this is he same boat as discussed before.

 

A load of eco bullshit in the article though:

 

“When the time comes, the material can be recycled, making it an eco-friendly option in a world increasingly conscious of environmental impacts."

Have they never heard of steel, as used in conventional narrowboats, being recycled?

 

“It's a lighter material than steel, which makes it more fuel-efficient—a major plus for those looking to reduce their carbon footprint."

Since conventional steel narrowboats are ballasted to get them down in the water, for reasons of achieving sufficient draft for the propeller, reducing airdraft and providing some resistance to being blown about by the wind, a lighter HDPE boat will just need more ballast.

 

7 minutes ago, Hudds Lad said:

I note it still has no windows, assuming chopping holes in the sides also not good for rigidity.

But the pieces cut out would make good kitchen chopping boards!

[Bee]

First there was wood, then iron, steel, aluminium, grp, concrete now plastic.  All with plus points and some minus points as well.  My  guess is that steel is still going to be the best material but we need to view it as high maintanence and not just fit and forget but modern coatings can make the stuff last for years longer than before.  Good luck to them anyway.

[IanD]

15 minutes ago, David Mack said:

I think this is he same boat as discussed before.

 

A load of eco bullshit in the article though:

 

“When the time comes, the material can be recycled, making it an eco-friendly option in a world increasingly conscious of environmental impacts."

Have they never heard of steel, as used in conventional narrowboats, being recycled?

 

“It's a lighter material than steel, which makes it more fuel-efficient—a major plus for those looking to reduce their carbon footprint."

Since conventional steel narrowboats are ballasted to get them down in the water, for reasons of achieving sufficient draft for the propeller, reducing airdraft and providing some resistance to being blown about by the wind, a lighter HDPE boat will just need more ballast.

 

But the pieces cut out would make good kitchen chopping boards!

 

Given that the cabin is much lighter, you could still have a stable boat with a considerably smaller draft than a steel one -- air draft would be correspondingly bigger, but this is rarely a problem. It would still need ballast to stabilise it, but in theory you could reduce draft to maybe as low as a foot or so, great for shallow badly dredged canals and would drop the power needed to propel it to maybe a third of a conventional steel boat. You'd have to use a much smaller prop -- or maybe two of them powered by electric motors? Should work since the power needed per prop would then be so much lower (about 1/6) so small diameter is fine, you could genuinely cruise along at normal speed on 1kW instead of 3kW, so either 3x the range (a week?) or much smaller/cheaper batteries.

 

However the key to make all this work is not to try and copy a conventional steel boat, but to completely rethink the design to take advantage of lighter weight and new materials/drive methods.

 

Wouldn't half move around in crosswinds though -- which could of course be fixed with (quiet!) bow/stern thrusters... 😉 

Edited September 25 by IanD

[booke23]

Isn't this the boat that the builder posted about a while back? An extensive discussion ensued. 

 

I posted the following back then:

 

However the design looks conventional, so I think the boat would have to draw about 26 Inches to get the uxter plate in the water. With that much hull in the water it would displace just under 20 tonnes, so a lot of ballast required. A heavy old lump if you scrape it against some protruding stone work.

 

It's an interesting concept, with some big advantages. (total lack of corrosion and hull maintenance). However I'm not sure it will have the required abrasion resistance for canals.

 

 

Edited September 25 by booke23

[IanD]

17 minutes ago, booke23 said:

Isn't this the boat that the builder posted about a while back? An extensive discussion ensued. 

 

I posted the following back then:

 

Very interesting. I just watched the time lapse video on YT and see it has RSJ’s on the base plate internally, presumably to stiffen it.  

 

I’ve made some (very) rough calculations. Assuming HDPE density of 0.97g/cm3 I reckon the shell weighs 2.5 tonnes. There looks to be about a tonne of RSJ, so 3.5 tonnes in total. These calculations are a little speculative so could be out a bit.

 

However the design looks conventional, so I think the boat would have to draw about 26 Inches to get the uxter plate in the water. With that much hull in the water it would displace just under 20 tonnes, so around 16 tonnes of ballast required. A heavy old lump if you scrape it against some protruding stone work.

 

 

 

 

Yes, I'm sure its the same one -- and I agree with your estimates and conclusions.

 

Using HDPE to try and make what is basically a rust-free copy of a conventional narrowboat (with the same draft and therefore weight, mostly ballast and steel frame) doesn't look sensible to me, it's fighting against the disadvantages of HDPE (soft and floppy compared to steel) and not making any real use of the advantages (light weight) -- yes there's no hull corrosion, but that's not a killer advantage.

 

It's a bit like inventing carbon fibre and using it to make a biplane instead of a sleek monoplane -- yes I know the material properties are very different, but the concept is similar.

 

They could have rethought the idea completely and come up with a boat the same length/width but half the weight/draft and needing a third the power on the canals, and taken advantage of this to go hybrid/electric but with a much smaller/cheaper/lower-power/longer-range propulsion system -- then they'd have something with some major advantages over conventional boats.

 

To bring something new and different to the market you sometimes need to be bold/radical and take advantage of what you're good at, instead of fighting a conventional battle on a field of your enemy's choice where they are strong -- literally, in this case... 😉 

Edited September 25 by IanD

[booke23]

17 minutes ago, IanD said:

 

Yes, I'm sure its the same one -- and I agree with your estimates and conclusions.

 

Using HDPE to try and make what is basically a rust-free copy of a conventional narrowboat (with the same draft and therefore weight, mostly ballast and steel frame) doesn't look sensible to me, it's fighting against the disadvantages of HDPE (soft and floppy compared to steel) and not making any real use of the advantages (light weight) -- yes there's no hull corrosion, but that's not a killer advantage.

 

It's a bit like inventing carbon fibre and using it to make a biplane instead of a sleek monoplane -- yes I know the material properties are very different, but the concept is similar.

 

They could have rethought the idea completely and come up with a boat the same length/width but half the weight/draft and needing a third the power, and taken advantage of this to go hybrid/electric but with a much smaller/cheaper/lower-power/longer-range propulsion system -- then they'd have something with some major advantages over conventional boats.

 

To bring something new and different to the market you sometimes need to be bold/radical and take advantage of what you're good at, instead of fighting a conventional battle on a field of your enemy's choice where they are strong -- literally, in this case... 😉 

 

Absolutely.

 

There are some excellent HDPE boats....mostly smaller planing hull designs that are great. 

 

I'm not certain about my calculations as a later photo of the boat in the original thread showed a lot more steel work than I anticipated, so I've deleted them. The basic principle remains....As you say it would have been better to redesign the boat to take advantage of the material rather than copy a steel widebeam design and ballast it extensively. 

 

 

Edited September 25 by booke23

[IanD]

3 hours ago, booke23 said:

 

Absolutely.

 

There are some excellent HDPE boats....mostly smaller planing hull designs that are great. 

 

 

They didn't even rethink how the steel frame was done -- ribs and stringers (like they seem to have used) work in steel ships when they're attached to steel hull plates and made into a U or box, the combination of the two is much more rigid than the frame alone. When attached to flexible HDPE the frame itself has to provide all the stiffness, and what they've used is poor for that, it's like the bendy chassis that vintage cars (or more modern trucks) use that you can see twist over bumps.

 

They could have come up with something using a lot less steel with much better stiffness -- especially torsional -- using box sections, maybe fabricated instead of I/C/H/Z sections -- it's the same problem Telford faced with the Menai Straits bridge, and he understood how to solve this in Victorian times without even the aid of CAD... 😉 

 

To quote J E Gordon, this boat is like the roofs of Greek temples -- intellectually squalid... 😞 

Edited September 25 by IanD
Telford, not Brunel!

[ditchcrawler]

 

[booke23]

Here's another couple of videos from their YT channel. Looks like a Canal line engine fitted. It'd be very interesting to know what it weighs.

 

Launching the boat: - 

 

 

 

 

Some pictures of it on the water:-

 

 

 

 

 

Edited September 25 by booke23

[IanD]

31 minutes ago, booke23 said:

 

Absolutely.

 

There are some excellent HDPE boats....mostly smaller planing hull designs that are great. 

 

 

Some quick calculations -- based on measured speed/power for hybrid boats, plus Vicprop analysis -- suggest that an HDPE boat with half the weight/draft would need about a third of the power on normal canals, for example 1kW for cruising instead of 3kW to maintain the same speed. Anyone who hates maths, look away now... 😉 

 

The reason is that on canals -- as opposed to deep/open water which is what Vicprop analyses -- for a given power level measurements show you typically only get about 80% of the open-water speed, which due to the cube law means you need 2x the power for the same 100% speed, which means drag is doubled. This is due to the relative size of the boat compared to the channel, in both cross-sectional area and depth.

 

If you halve the draft (and therefore the cross-sectional area, and the weight, and the amount of water displaced) then you'd expect to get at least 90% of the open-water speed at half the power compared to the boat above, which means 68% of power for 100% speed, so drag is 3x lower -- as is power required, and fuel (energy) consumption, which it would make it a natural for hybrid/electric propulsion, it could run on solar power alone for most of the year.

 

Having only a 1' draft would also probably mean rethinking the hull design at both bow and stern, which was traditionally done for boats drawing up to 4' but wasn't really changed for modern boats where this was halved -- more like an airboat bow/slipper stern is probably the way to go, and multiple props (at least 2) to allow small diameter without high speed and noise.

 

The end result could be something with big advantages over both traditional steel boats and the mess they've come up with. No doubt it would be too radical for some though, who would mutter into their beards about it not having a Josher bow or a trad engine room... 😉 

Edited September 25 by IanD

[Peugeot 106]

I believe HDPE can be reinforced with conventional fibres (Glass, Carbon, Kevlar, Rockwool eg Basalt). This could add quite a lot of Rigidity depending on fibre distribution and length. I don’t suppose extruding it with long fibres is economical

 

I’m not sure what the price advantages over conventional thermoset composites will be. Resin infusion is a pretty advanced and known technology for large structures as long as your not planning to visit the Titanic with titanium bow and stern “attached”

 

Steel does have advantages for hulls.  Even under massive punishment it just dents

 

i  agree that there are some pretty good small boat hulls out there that withstand all sorts of punishment especially as club dinghies, canoes, rescue boats etc but I’m not sure how that will translate into something 70 ft long. We should remember how a lot of us hated grp boat hulls when they first came out. I have one that’s 60 years old. It looks pretty retro these days and is much admired but many of its wooden brothers and sisters have fallen apart as the resourcinal glue has passed its 50 year old design life. Grp has eclipsed wood.

 

i agree with Ian that they need to think out of the box a bit and not slavishly copy a steel Narrowboat ( anyway the glue on rivets will probably fall off)

[booke23]

Regarding the weight - Watching those videos and looking at the approximate draft, it must weigh between 10 and 15 tonnes. 

[IanD]

19 minutes ago, Peugeot 106 said:

I believe HDPE can be reinforced with conventional fibres (Glass, Carbon, Kevlar, Rockwool eg Basalt). This could add quite a lot of Rigidity depending on fibre distribution and length. I don’t suppose extruding it with long fibres is economical

 

I’m not sure what the price advantages over conventional thermoset composites will be. Resin infusion is a pretty advanced and known technology for large structures as long as your not planning to visit the Titanic with titanium bow and stern “attached”

 

Steel does have advantages for hulls.  Even under massive punishment it just dents

 

i  agree that there are some pretty good small boat hulls out there that withstand all sorts of punishment especially as club dinghies, canoes, rescue boats etc but I’m not sure how that will translate into something 70 ft long. We should remember how a lot of us hated grp boat hulls when they first came out. I have one that’s 60 years old. It looks pretty retro these days and is much admired but many of its wooden brothers and sisters have fallen apart as the resourcinal glue has passed its 50 year old design life. Grp has eclipsed wood.

 

i agree with Ian that they need to think out of the box a bit and not slavishly copy a steel Narrowboat ( anyway the glue on rivets will probably fall off)

 

Reinforced HDPE (usually with fillers) has maybe 2x-3x the stiffness, but also considerably higher cost -- and it's still much *much* less stiff than steel, terrible for anything that needs to be stiff and rigid. If you're going to add strong long fibres like glass to stiffen/strengthen it then HDPE is a waste of time, conventional GRP (resin-based) is what you want.

 

The problem is that when you have a hammer everything looks like a nail -- they have HDPE and are trying to do something with it that it's fundamentally not very good at, and then using it in such a way as to make its disadvantages worse and to largely nullify any advantages it might have.

 

For crying out loud, starting out with something light and then ballasting it down like a steel hull and sticking a Canaline engine in  -- are they insane?

 

Anyone interested in this sort of thing should really read "The New Science of Strong Materials (or why we don't fall through the floor)" and "Structures (or why things don't fall down)" by J E Gordon -- two of the best popular science books ever written, covering metals and wood and composites and buildings and ships and bridges and rivets and bias-cut dresses and balloons and why you can't put a crease in a worm and many other fascinating things... 😉 

Edited September 25 by IanD

[peterboat]

4 hours ago, IanD said:

 

Given that the cabin is much lighter, you could still have a stable boat with a considerably smaller draft than a steel one -- air draft would be correspondingly bigger, but this is rarely a problem. It would still need ballast to stabilise it, but in theory you could reduce draft to maybe as low as a foot or so, great for shallow badly dredged canals and would drop the power needed to propel it to maybe a third of a conventional steel boat. You'd have to use a much smaller prop -- or maybe two of them powered by electric motors? Should work since the power needed per prop would then be so much lower (about 1/6) so small diameter is fine, you could genuinely cruise along at normal speed on 1kW instead of 3kW, so either 3x the range (a week?) or much smaller/cheaper batteries.

 

However the key to make all this work is not to try and copy a conventional steel boat, but to completely rethink the design to take advantage of lighter weight and new materials/drive methods.

 

Wouldn't half move around in crosswinds though -- which could of course be fixed with (quiet!) bow/stern thrusters... 😉 

Could give it a keel? That would help keep it going straight.

[Peugeot 106]

53 minutes ago, IanD said:

 

Reinforced HDPE (usually with fillers) has maybe 2x-3x the stiffness, but also considerably higher cost -- and it's still much *much* less stiff than steel, terrible for anything that needs to be stiff and rigid. If you're going to add strong long fibres like glass to stiffen/strengthen it then HDPE is a waste of time, conventional GRP (resin-based) is what you want.

 

The problem is that when you have a hammer everything looks like a nail -- they have HDPE and are trying to do something with it that it's fundamentally not very good at, and then using it in such a way as to make its disadvantages worse and to largely nullify any advantages it might have.

 

For crying out loud, starting out with something light and then ballasting it down like a steel hull and sticking a Canaline engine in  -- are they insane?

 

Anyone interested in this sort of thing should really read "The New Science of Strong Materials (or why we don't fall through the floor)" and "Structures (or why things don't fall down)" by J E Gordon -- two of the best popular science books ever written, covering metals and wood and composites and buildings and ships and bridges and rivets and bias-cut dresses and balloons and why you can't put a crease in a worm and many other fascinating things... 😉 

I agree with this and I have read new science of strong materials though my copy is an ancient Penguin . I’ll have to look out for your others recommendation

 

My only comment is that although to me  this doesn’t seem to be an appropriate use for HDPE I may be wrong. If it doesn’t work at least it will give more knowledge of the design envelope 

 

A faint heart never won a fat woman so good luck to them. I just hope they don’t loose a shed load of money. I suspect they may be slightly insane but hey a lot of people reckon I am too!

 

[IanD]

5 minutes ago, peterboat said:

Could give it a keel? That would help keep it going straight.

Maybe, don't know how much that would help unless it was pretty deep -- which could then present a problem if water levels drop and the boat tips over instead of sitting flat on the bottom...

[peterboat]

Just now, IanD said:

Maybe, don't know how much that would help unless it was pretty deep -- which could then present a problem if water levels drop and the boat tips over instead of sitting flat on the bottom...

As you said earlier maybe they need to design a better boat, the issue is I suppose our boats are high on space for the design.

[IanD]

1 minute ago, Peugeot 106 said:

I agree with this and I have read new science of strong materials though my copy is an ancient Penguin . I’ll have to look out for your others recommendation

 

My only comment is that although to me  this doesn’t seem to be an appropriate use for HDPE I may be wrong. If it doesn’t work at least it will give more knowledge of the design envelope 

 

A faint heart never won a fat woman so good luck to them. I just hope they don’t loose a shed load of money. I suspect they may be slightly insane but hey a lot of people reckon I am too!

 

Both my copies are old (1991) Penguins, still great books though.

 

I hope that was intended to be a fair woman (or even lady...) and autocorrect got you... 😉

[Peugeot 106]

In one of Uffa Fox’s books there’s a photo of him starkers captioned “modesty is only a sense of physical imperfection” 

 

Apologies I thought the fat woman was another of Uffa’s sayings. He was after all best mates with Prince Philip!

[agg221]

1 hour ago, IanD said:

Maybe, don't know how much that would help unless it was pretty deep -- which could then present a problem if water levels drop and the boat tips over instead of sitting flat on the bottom...

This is not a problem I regularly find myself worrying about in my round bottomed boat.

 

What is the relative stiffness of HDPE cf. pitch pine? I wonder whether steel is the wrong frame of reference and actually HDPE should be considered with reference to wooden boat construction, which seems to have worked well enough for a couple of centuries.

 

Alec

 

[IanD]

1 minute ago, agg221 said:

This is not a problem I regularly find myself worrying about in my round bottomed boat.

 

What is the relative stiffness of HDPE cf. pitch pine? I wonder whether steel is the wrong frame of reference and actually HDPE should be considered with reference to wooden boat construction, which seems to have worked well enough for a couple of centuries.

 

Alec

 

HDPE is far less stiff than wood, even pine is about 15x stiffer -- which is why wood is an excellent construction material for boats (or buildings, or aircraft), and plastics aren't...

 

(a thick wooden panel or hull the same weight as a thin steel one is about 3x stiffer)

[Momac]

https://www.bulldogboats.co.uk/#:~:text=Bulldog Boats are designers and,in an almost indestructible workboat.

These are work boats and not canal boats of course but they do demonstrate the possibilities.