HDPE canal barge (UK)

I'm exploring the possibility of commissioning the construction of a live-aboard canal (UK) barge, 'wide beam' approx. 50ft(15m) x 12.5ft(3.5m) from HDPE as a cost-effective, low maintenance alternative to steel but I know next to nothing about boats/boat building. I've already approached a couple of plastics fabricators who seem to think it could be feasible, and there are certainly HDPE boats out there being subjected to infinitely more punishable conditions than a canal barge ever would be, tidemanboats.com for example. However my initial idea of sourcing some plans and drawings for a regular steel hull boat (or even a plywood one which I believe exist), chucking them at a fabricator and saying "Build that with HDPE" are undoubtedly rather naive, the rigidity of steel v. HDPE being one possible issue. I'm also aware that using a fabricator without any marine knowledge could be an issue. Any advice, comments, thoughts, observations, sympathy, witty remarks regarding this would be very much appreciated!

 

Any material can be used, but most won't be ideal. HDPE will make a very heavy boat at that size. You will need some very clever engineering solutions for point loads like cleats, engine mounts, etc. Another problem is the high rate of expansion/contraction of the material. It will make doors and windows jam or get too loose. Soft polymers, like HDPE, will have a considerable amount of creep deformation under constant load. What it means, is that the boat will significantly deform with time. In short, it is not a very good material for the purpose. Canal boats live is fresh water, which makes steel a good material. With a modicum of maintenance, the boat will outlive your grandchildren.

 

Rigidity is an obvious concern. Presumably a barge could be built with enough frames, girders, etc to stiff enough. You may want to consult an engineer with experience designing in both HDPE and steel. The engineer's time will cost something but the potential is to save you from spending much more money on a build which will not be satisfactory.

Building the shell (hull an cabin) is only part of the cost of building a boat. Then there is fitting out. Attachments can be made to a steel shell by welding or with epoxy or other adhesives can also be used to bond to steel. With HDPE attachments will be limited to mechanical fasteners. This is likely to increase the time and cost of fitting out an HDPE shell compared to a steel shell. Also builders of canal boats are experience in fitting out steel shells and know how to be efficient. Anyone fitting out an HDPE shell will probably be learning as they work whick will also increase cost.

Another concern may be weight. I assume you will want standing head room. Many canals in the UK have restricted overhead clearance, sometimes refered to as "air draft" limits. This means that if you start with the maximum height of the boat above water which can navigate the waterways you plan to visit, and then subtract the thickness of the top of the boat including framing and interior ceiling and add the desired interior head clearance you arrive at the maximum height of the cabin sole/floor relative to the water. Usually the cabin sole/floor will be below the waterline. Next continue to work down with the thickness of the cabin sole/floor, height of frames and bottom thickness to arrive at the minimum draft of the boat. This along with the width and length of the boat will establish the volume of the hole the boat must occu;y. Multiply by the density of water to obtain the weight of the displaced water, apply Archimede's principle, and you have the minimum weight of the boat. Steel canal boats frequently have concrete ballast under the floor to achieve sufficient weight, and I assume an HDPE boat may be lighter and require more ballast.

 

Another issue with an HDPE boat may be hauling for maintenance. Yards used to hauling steel boats may be reluctant to haul an HDPE boat. Any design of an HDPE boat needs to include analysis with the loads imposed when hauling. These may be one of the worst case situations.

 

Are there any good books or other resources about boat building in HDPE ? I get the feeling that gonzo is being a touch alarmist, there are a few small boats around made of it that cop a pounding, and I have yet to hear too much negative reportage, but maybe it just hasn't reached my ears.

 

Anti-fouling allegedly not required, which might circumvent a lot of that.

 

HDPE boats to 40 feet built by these people, so seems feasible. I wonder how many sales the stipulation of black only, as the colour, costs them. I have never seen a roto-moulded black HDPE boat, so obviously the prejudice against colours other than black ( Maximum UV resistance) is not universal. Black in a tropical climate would be "untouchable".

Tideman Boats BV | Indestructible HDPE Workboats

 

Thanks for the input. As Gonzo suggests the creep deformation definitely sounds like a potential headache for a build where steel is simply substituted with HDPE, however I suppose this could be mitigated to a large degree if frames/girders etc. employed as per DCockey. HDPE can be welded I'm given to believe so not sure the attachments issue would be too much of a concern. On balance though, whilst I'm sure there is an interesting and practical boat of this type to be had using HDPE it's probably something best undertaken by someone with the resources to experiment, trial and error, which isn't me alas, so I'll probably be looking at steel for which, as Gonzo points out, the maintenance needn't be too burdensome

 

I'm sure you're aware, too, of the limits to navigation that width imposes. Many key uk navigations are 'narrow' canals, at 6'10" wide.



The red navigations are narrow. No guarantee this is definitive!

 

Hi. Thanks for this, yes am aware of the width issue, there are a lot of widebeams out there, just need to use their common sense and look at maps like this Cheers

 

Correctly designed, HDPE would do fine, in fact it might do better than fine, because bumps and scrapes would not matter, no paint to scratch and expose steel or other materials to rust and decay. Just a matter of the specs being right for the material. And no anti-fouling problems !

 

Hi everyone,
I work for a plastic fabrication and manufacturing company and we have built this all out of hdpe the size is 40ft by 10ft if any one would like to see this or even hear more details,
please get in touch. I'm more than happy to show pictures of the process

 

Some interesting plastic builds..

https://polyline.com.au/poly-commercial-workboats/

Used Alumarine 6.5 Punt for Sale | Boats For Sale | Yachthub https://yachthub.com/list/boats-for-sale/used/power-boats/alumarine-6-5-punt/264783

https://pfg-group.com.au/aquatruck/

New Work Punt 5.5m Hdpe: Commercial Vessel | Boats Online for Sale | Polyethylene/plastic Heavy Duty Fully Welded High Density Polyethelene Plate | Western Australia (WA) - Perth WA https://www.boatsonline.com.au/boats-for-sale/new/commercial-vessel/work-punt-5-5m-hdpe/267384

https://polyline.com.au/tuff-punt-dinghies/ ..with the horseshoe bow!

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