HDPE Canal boat

[agg221]

It's an interesting concept. A couple of comments.

 

Welding is very easy with HDPE. It's much easier, safer and less energy intensive than welding steel. As has been commented on, adhesives stick very poorly to it, but it is simple to weld angled braces and lugs on so it should be straightforward to create a stiff structure with mounting points which can be screwed in to.

 

It should be sufficiently tough and abrasion resistant to give a good service life. I think a design for canals would need suitably placed rubbing strips, in the normal places and probably along the chine. There is no risk of corrosion so these need not be sealed welds, but I think they would be needed as wear plates.

 

The shift away from fossil fuels is leading to oil companies revisiting what they can do with their reserves. Replacing other construction materials with oil-based plastics is an attractive option for them so expect plastics to be developed for such purposes and to be priced attractively. HDPE is reasonably environmentally friendly in that it can be recycled several times in a cradle to cradle process, although it does eventually degrade.

 

Overall, it will be interesting to see how this goes - ballasting will be necessary so there will be a compromise to be made to achieve draft without excessive height to allow headroom over the ballast. I'm not sure how much ballast it will take in practice - more than a standard boat but perhaps not that much - you only need to add the difference in weight between the steel and the HDPE. It should have a nice low centre of gravity though which should make it pretty stable.

 

I particularly like the idea of no blacking. The cabin could also be made self-coloured, as has been done with 'plastic vans' recently https://arrival.com/uk/en/topic/van so no painting at all!

 

Alec

Edited January 31, 2023 by agg221

[David Mack]

6 minutes ago, agg221 said:

The cabin could also be made self-coloured, as has been done with 'plastic vans' recently https://arrival.com/uk/en/topic/van so no painting at all!

Do you have any choice? If adhesives don't stick to HDPE does paint? Or vinyl wrap?

[agg221]

Just now, David Mack said:

Do you have any choice? If adhesives don't stick to HDPE does paint? Or vinyl wrap?

Vinyl wrap does. Other things can stick well enough for a coating, just not well enough to carry a load. The Arrival vans needed a solution to provide signwriting, which works satisfactorily it appears.

 

Alec

[blackrose]

8 hours ago, David Mack said:

In a canal environment there will be frequent rubbing against the sides at locks and bridges, and some (unplanned) impacts with fixed infrastructure and other craft, as well as rubbing of the chine angle in shallow water, and contact with underwater items such as shopping trolleys and lumps of masonry.  How robust is HDPE against abrasion and impact? Would a canal craft need metal rubbing strips in the most vulnerable areas?

 

I also think abrasion resistance will be a big problem. You've only got to look at the bottom of a used HDPE kayak to see why. Look at all the gouges and scrapes and and then think about how much deeper that damage would be when a boat weighing tens of tonnes scrapes along a lock wall against some uneven concrete or brickwork or protruding steel bolthead on a lock gate.

Edited January 31, 2023 by blackrose

[peterboat]

1 hour ago, blackrose said:

 

I also think abrasion resistance will be a big problem. You've only got to look at the bottom of a used HDPE kayak to see why. Look at all the gouges and scrapes and and then think about how much deeper that damage would be when a boat weighing tens of tonnes scrapes along a lock wall against some uneven concrete or brickwork or protruding steel bolthead on a lock gate.

I said the same earlier 

[PeterF]

How about when the whole boat lifts up as it goes over the obligatory washing machine on the Rochdale creating a significant point load.

[Bee]

Interesting ideas. Of course back in the early days of leisure boating there were plenty of plywood cruisers that didn't have a particularly long life but worked OK for a few years and there were plenty of terrible old wooden narrowboats around that were not especially strong or watertight.. To be honest steel is pretty good stuff but it hasn't got a particularly long life either unless its kept well painted, electrically isolated and constantly worked on.  GRP is a good material but large flat areas need reinforcing or framing  too and HDPE could be just as successful with luck.

[IanD]

11 hours ago, magnetman said:

The Turkish boat is designed to do 32 knots. For this you want something light and buoyant. For canals you actually want boats to be as heavy as possible. 

 

I still think the basic problem is going to be getting it down in the water. 

 

What are you thinking of using to do this? 

The reason steel canal boats have to be heavy and low in the water -- if we ignore air draft -- is stability, because they have a heavy steel cabin. Boats built out of aluminium drew less and were still stable because of having a much lighter superstructure, but cost would be a problem nowadays. Maybe HDPE can provide a lower cost solution that's still robust enough?

[PD1964]

 If the draft/stability works out and they could keep the weight down, these boats could be the ideal solution for a trailer/weekend canal boat, offering a cheap go anywhere holiday boat, powered by a small electric motor and solar. Obviously would all be dependent on workable dimensions, interior design and functional equipment, but may work? The HDPE concept certainly gets the mind thinking.

  

Edited February 1, 2023 by PD1964

[booke23]

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. It’s late so feel free to check and correct my calculations!

[Jon57]

5 hours ago, PD1964 said:

 If the draft/stability works out and they could keep the weight down, these boats could be the ideal solution for a trailer/weekend canal boat, offering a cheap go anywhere holiday boat, powered by a small electric motor and solar. Obviously would all be dependent on workable dimensions, interior design and functional equipment, but may work? The HDPE concept certainly gets the mind thinking.

  

It could work maybe. I think it's a bit of a pipe dream atm. 🤔😂

[Tony Brooks]

9 hours ago, Bee said:

Interesting ideas. Of course back in the early days of leisure boating there were plenty of plywood cruisers that didn't have a particularly long life but worked OK for a few years and there were plenty of terrible old wooden narrowboats around that were not especially strong or watertight.. To be honest steel is pretty good stuff but it hasn't got a particularly long life either unless its kept well painted, electrically isolated and constantly worked on.  GRP is a good material but large flat areas need reinforcing or framing  too and HDPE could be just as successful with luck.

 

The thing with GRP is that the framing can be/is installed as part of the laying up, so the framing is actually part of the hull. It is admitted that HDPE does not bond sell with glue and it tends to flex. So I ask myself how are the RSJs mentioned above, bonded to the hull in a way that makes them part of the hull.

[shaun15124]

 

weight is roughly 20t, as nothing is in it ( i know this needs a lot more weight we are looking at many ideas ) 

 

in regards to internally, we put ribs in every 600 so you can screw panels, etc ( again this is still ongoing and we have looked at better ways for this not to flex ) 

 

 to painting you can actually paint HDPE if you wished ( or you can have many colors of hdpe ), vinyl wrap is actually a great idea as well thank you for that thought

 

we put the steel frame for support and rigid in terms of balance we are in the process of this and looking at many options one that has been suggested is 

pouring concrete in this ( I'm not really sure if that is a good way or not to be honest ) 

 

 

[Momac]

2 minutes ago, shaun15124 said:

 

weight is roughly 20t, as nothing is in it ( i know this needs a lot more weight we are looking at many ideas ) 

 

in regards to internally, we put ribs in every 600 so you can screw panels, etc ( again this is still ongoing and we have looked at better ways for this not to flex ) 

 

 to painting you can actually paint HDPE if you wished ( or you can have many colors of hdpe ), vinyl wrap is actually a great idea as well thank you for that thought

 

we put the steel frame for support and rigid in terms of balance we are in the process of this and looking at many options one that has been suggested is 

pouring concrete in this ( I'm not really sure if that is a good way or not to be honest ) 

 

 

Not exactly light weight 

Concrete would add weight but not really likely  to add structural integrity. 

[shaun15124]

[magnetman]

8 hours ago, IanD said:

The reason steel canal boats have to be heavy and low in the water -- if we ignore air draft -- is stability, because they have a heavy steel cabin. Boats built out of aluminium drew less and were still stable because of having a much lighter superstructure, but cost would be a problem nowadays. Maybe HDPE can provide a lower cost solution that's still robust enough?

The reason a canal boat with a conventional swim needs to be heavy is you have to get the uxter plate under water in order that the propeller doesn't ventilate. 

 

The boat being discussed has a conventional swim so will need to be ballasted down to about 2ft draught. 

 

Another reason is so you can get lower air draft and still have internal headroom. Also handling will be bad in wind with a very shallow boat with a tall cabin. 

[magnetman]

10 minutes ago, MartynG said:

Not exactly light weight 

Concrete would add weight but not really likely  to add structural integrity. 

 

I think he meant 2 tonnes not 20. If it is already 20 tonnes it won't need much ballasting. How could it be 20 tonnes? 

 

 

Concrete is apparently 2500kg/cu.m so 8 cubic metres needed to add 20 tonnes. Doable perhaps ? It would add rigidity which may be helpful. 

[magnetman]

If the space to pour the ballast was say 11m x 3m that would be 33 square metres so the ballast would need to be poured to a depth of 8/33m which is about 25cm above base level. 

 

So if you did need to add 20 tonnes then ballasting and flooring would take out around 1ft if the interior headroom. 

 

I reckon. 

 

 

[matty40s]

22 hours ago, shaun15124 said:

 

HDPE Boats are comfortable: HDPE is not a rigid material. Therefore HDPE boats are very comfortable especially in strong weather conditions, sailing on choppy seas in comparison to rigid conventional boats. 

 

This bit concerns me, how much flex, and how is your interior supposed to stay together, showers sealed, pipes connected, splashbacks leak free if you have lots of movement through the structure?

[Tony Brooks]

I am wondering if it needs a keelson to resist hogging, otherwise any tendency to flex along its length will put a lot of strain in the side to baseplate joints. It may also stretch and bow the cabin sides between the upright stiffeners.

[Tracy D'arth]

So many negative vibes!

 

Its an interesting proposition, I am willing to give it a go.

If you produce a 57' by 6' 10" hull, that is the most popular size, I would love to help with the logistic problems of fitting it out.

I would consider double bottoming the base panel and using a heavy metal ballast rather than concrete which has a lower mass and too many problems. This large mass could be a rigid fabrication and carry the stern gear and propulsion unit, spreading the load into the whole structure. The RSJ is part way there but is too subject to twist and creates point loads into the HDPE.

[agg221]

36 minutes ago, Tony Brooks said:

I am wondering if it needs a keelson to resist hogging, otherwise any tendency to flex along its length will put a lot of strain in the side to baseplate joints. It may also stretch and bow the cabin sides between the upright stiffeners.

 

That might be useful. Actually, borrowing quite a lot from wooden canal boat design might be a good idea in general (the ribs already are for example) as there are some similarities in properties between wood and HDPE. Other potentially useful things to borrow would be  the use of a thin, sacrificial steel shoe plate where the sides and base meet and possibly steel rubbing strips and ice plates at the bow.

 

With regard to the question of how to attach ribs/frames - that one is relatively straightforward. HDPE does weld easily so you can add either a full HDPE rib or a low attachment rib/series of lugs to which you can mechanically fasten a steel rib.

 

One direction which has been alluded to above which might be a useful halfway house is the use of HDPE for cabins. Wooden cabins do have quite a few advantages, e.g. keeping the centre of gravity lower and reducing condensation. They are also better for sound deadening. However, they are quite difficult to keep sealed between the boards, fairly high maintenance and do rot through easily if damage goes unnoticed or is not rapidly repaired. HDPE might add the advantages of wood without the drawbacks. It does need a proper upstand lip all the way around just inside the gunwhales for attachment but if that was done I can imagine this could be quite a useful approach. It might, for example, have been a good option for Oates if it was reasonably cost-effective. Oates had its wooden cabin replaced with steel, but to keep it stable the weight had to be kept down. That has meant thin steel and I can't add any high level storage. I would have had more options with welded HDPE panels. There are still a few 1970s boats about with wooden tops which now need replacement so I can imagine there are some good opportunities to try this if it is reasonably cost-effective.

 

Alec

Edited February 1, 2023 by agg221

[rusty69]

45 minutes ago, magnetman said:

 

I think he meant 2 tonnes not 20. If it is already 20 tonnes it won't need much ballasting. How could it be 20 tonnes? 

 

 

Concrete is apparently 2500kg/cu.m so 8 cubic metres needed to add 20 tonnes. Doable perhaps ? It would add rigidity which may be helpful. 

I thought I read somewhere that it weighed 6 Tonne (metric, not imperial). 20 Tonne seems an awful lot for an empty boat, and 2 tonne too light.

Edited February 1, 2023 by rusty69

[Tracy D'arth]

4 minutes ago, agg221 said:

 

That might be useful. Actually, borrowing quite a lot from wooden canal boat design might be a good idea in general (the ribs already are for example) as there are some similarities in properties (e.g. the use of a thin, sacrificial steel shoe plate where the sides and base meet).

 

With regard to the question of how to attach ribs/frames - that one is relatively straightforward. HDPE does weld easily so you can add either a full HDPE rib or a low attachment rib/series of lugs to which you can mechanically fasten a steel rib.

 

One direction which has been alluded to above which might be a useful halfway house is the use of HDPE for cabins. Wooden cabins do have quite a few advantages, e.g. keeping the centre of gravity low and reducing condensation. They are also better for sound deadening. However, they are quite difficult to keep sealed between the boards, fairly high maintenance and do rot through easily if damage goes unnoticed or is not rapidly repaired. HDPE might add the advantages of wood without the drawbacks. It does need a proper upstand lip all the way around just inside the gunwhales for attachment but if that was done I can imagine this could be quite a useful approach. It might, for example, have been a good option for Oates if it was reasonably cost-effective. Oates had its wooden cabin replaced with steel, but to keep it stable the weight had to be kept down. That has meant thin steel and I can't add any high level storage. I would have had more options with welded HDPE panels. There are still a few 1970s boats about with wooden tops which now need replacement so I can imagine there are some good opportunities to try this if it is reasonably cost-effective.

 

Alec

I would doubt that there are sufficient 1970s timber top hulls remaining  in good enough condition to warrant spending this sort of money and time on. 

[magnetman]

The cost is an interesting question.

 

How does finished product price compare with the equivalent in steel? 

 

I presume it must be quite a bit cheaper but interesting to know what the actual ratio is. 

 

I personally think there is more opportunity with this sort of material to make small static houseboats rather than cruising canal boats but the market is smaller. 

 

I haven't seen any negative vibes on this thread just genuine interest and concerns about things like rigidity in use.