HDPE Canal boat

[agg221]

23 minutes ago, Tracy D'arth said:

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. 

 

I wasn't thinking of it so much as being a business opportunity, more a lower cost way to undertake the next stage of development to do a re-cabin than build a complete hull. Costs have not yet been mentioned, which would be interesting, but it might be viable.

 

Alec

 

Edited February 1, 2023 by agg221

[Tim Lewis]

 

[peterboat]

10 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?

When I was first playing with electric in the bathtub it was remarkable how little energy it required to move and stop it, especially in its stripped out state. It had 3 little keels on it so it so it didnt move sideways to much with wind either, so as you say a low cost solution and given it may draw very little it might not suffer the grounding problems I suffered last year?

[rusty69]

3 minutes ago, peterboat said:

When I was first playing with electric in the bathtub it was remarkable how little energy it required to move and stop it, especially in its stripped out state. It had 3 little keels on it so it so it didnt move sideways to much with wind either, so as you say a low cost solution and given it may draw very little it might not suffer the grounding problems I suffered last year?

Isn't playing with electric in a bath tub extremely dangerous? Or is it only if it has water and a person in at the time?

[peterboat]

Just now, rusty69 said:

Isn't playing with electric in a bath tub extremely dangerous? Or is it only if it has water and a person in at the time?

it was only 24 volts so no danger

[PD1964]

 As I said the HDPE concept gets the mind thinking, as with steel you can weld to it, use flexible high adhesives to secure wooden batons for lining out, drill and tap holes for fixings. A simple question will you be able to do these things with HDPE? Or will build fixings need to be special fixings/screws, heat bonding processes, purpose made adhesive’s? There’s lots of questions that could be asked.

 The 20T weight is not correct, as that’s roughly the same weight of a fitted out 60ft steel Narrowboat and when you look at the build Video they’re moving it around with hand pallet trucks.

Edited February 1, 2023 by PD1964

[IanD]

2 hours ago, magnetman said:

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. 

 

The draft under the uxter plate is only needed because of the propeller diameter that is conventionally used, and especially for a lighter-weight boat there's no need for such a big prop -- after all, outboards have *much* smaller ones.

 

Air draft could be an issue, but a lighter HDPE boat could maybe get away with less depth under the floor -- and to be honest we're not talking massively taller here, probably not much more than 8" or so higher out of the water. Compared to normal boats with all the crap you see on cabin roofs, I doubt that this is a real problem unless you want to venture through Froghall or Gosty Hill tunnels, rather unlikely for most boaters.

 

Moving a lot in crosswinds could be a problem, but many GRP boats seem to manage while being much lighter and shallower draft than narrowboats.

 

In the end it will come down to whether HDPE offers any overall advantages over steel, both have plus and minus points -- a steel hull is very robust but suffers from corrosion, is HDPE significantly cheaper by the time you've dealt with all the add-ons to make it rigid enough?

[magnetman]

3 hours ago, IanD said:

 

The draft under the uxter plate is only needed because of the propeller diameter that is conventionally used, and especially for a lighter-weight boat there's no need for such a big prop -- after all, outboards have *much* smaller ones.

 

Air draft could be an issue, but a lighter HDPE boat could maybe get away with less depth under the floor -- and to be honest we're not talking massively taller here, probably not much more than 8" or so higher out of the water. Compared to normal boats with all the crap you see on cabin roofs, I doubt that this is a real problem unless you want to venture through Froghall or Gosty Hill tunnels, rather unlikely for most boaters.

 

Moving a lot in crosswinds could be a problem, but many GRP boats seem to manage while being much lighter and shallower draft than narrowboats.

 

In the end it will come down to whether HDPE offers any overall advantages over steel, both have plus and minus points -- a steel hull is very robust but suffers from corrosion, is HDPE significantly cheaper by the time you've dealt with all the add-ons to make it rigid enough?

I was referring to the boat which has actually been constructed. 

 

As someone earlier pointed out this material would lend itself to the construction of punt style boats. Upswept bow and stern. Electric pod drives to propel it. 

 

I think that designing it the same way as a conventional canal boat is going to be problematic. 

Or cats. 

 

A pointy brick shape is too bouyant. 

[Tony Brooks]

35 minutes ago, magnetman said:

I was referring to the boat which has actually been constructed. 

 

As someone earlier pointed out this material would lend itself to the construction of punt style boats. Upswept bow and stern. Electric pod drives to propel it. 

 

I think that designing it the same way as a conventional canal boat is going to be problematic. 

Or cats. 

 

A pointy brick shape is too bouyant. 

 

If it is so light and easy to weld, I wondered why it was decided to make it brick shaped. If it were V bottomed, then it would sink further into the water, but it would probably preclude a side passage fit out.

 

Edited to add that it might also address my concerns over longitudinal hull flexing as well.

Edited February 1, 2023 by Tony Brooks

[PD1964]

8 minutes ago, Tony Brooks said:

 

If it is so light and easy to weld, I wondered why it was decided to make it brick shaped. If it were V bottomed, then it would sink further into the water, but it would probably preclude a side passage fit out.

 Maybe when they designed it on the computer a V design may of needed too much draught for their concept of a canal Narrowboat, or thought a flat baseplate would optimise more internal space then a V hull design?

 

  

Edited February 1, 2023 by PD1964

[Tony Brooks]

Just now, PD1964 said:

 Maybe when they designed it on the computer a V design may of needed too much draught for their concept of a canal Narrowboat?

 

  

 

I think that may well be the case and it tends to suggest that my comments about not really understanding narrowboats may be true. New materials need with different characteristics need careful thought so the design makes optimum use of the material. I am still wondering about why the back is just flat sheets.

[IanD]

9 minutes ago, Tony Brooks said:

 

If it is so light and easy to weld, I wondered why it was decided to make it brick shaped. If it were V bottomed, then it would sink further into the water, but it would probably preclude a side passage fit out.

 

Edited to add that it might also address my concerns over longitudinal hull flexing as well.

A V-shaped hull -- especially a shallow one -- is tender, it rocks a lot from side to side if you move across it. Not good for a boat for living/sleeping on...

[magnetman]

One does wonder if it will ever get a wet bottom. 

 

It would be cool if it does as it is always nice to see new ideas but practicality could get in the way. 

 

I think a catamaran with the hulls able to be filled with water would be the ideal solution. 

 

There is something very nice about a boat which is all on one level ie no step down into the cabin. Water filled hulls each side and a cabin on top. 360 pod motors at each end. Nice. 

A boat for untall people.

Edited February 1, 2023 by magnetman

[PD1964]

4 minutes ago, Tony Brooks said:

 

  New materials need with different characteristics need careful thought so the design makes optimum use of the material. I am still wondering about why the back is just flat sheets.

Maybe it’s easier and less cost? Looking at the Video it looks like they’ve made wooden formers to heat and shape some smaller rounded corners. I don’t know how easy larger HDPE panels would be to curve or the tooling involved? I imagine this is a concept project and still in the R&D stages.

[magnetman]

I imagine they will cut a bit out of the middle and make it into a narrow boat or a catamaran. 

[shaun15124]

all brilliant questions and thank you all for your feedback

 

honestly, any advice on fitting this out would be brilliant 

 

anyone is more than welcome to come and see this for themselves in the workshop

 

(as I have said I will be getting this back to tweek certain issues and will be showing more pictures of progress ) 

 

[Jerry Rhum]

I've followed them on YouTube as I'm intrigued to see what happens once they get it on the water. 

[Tony Brooks]

The latest image seems to show a very different rear swim to the one on the truck so either it was a camera angle illusion or it has been modified. Anyway it looks much beter now.

[IanD]

If you compare the mechanical properties of HDPE with steel you can get some idea of the relative strength and how resistant to damage it will be -- bearing in mind that the sides are 15mm thick compared to typically 6mm for steel. Anyone who doesn't like maths, look away now... 😉

 

The Young's modulus (stiffness) and tensile strength of steel are both about 140x higher than HDPE, the elongation at yield is similar (about 15%) -- if you stretch either by more than this (e.g. bashing into a concrete lock corner in between the beams) it will stay stretched, so you'll get a dent. The fact that the HDPE is 2.5x thicker increases panel stiffness by 6.25x, so this means a 6mm steel hull is 23x stiffer in between the I-beams than HDPE, and has 56x more tensile strength. So if you bash the boat into something hard the HDPE will bend a lot more than steel (about 5x) but will spring back if you don't hit too hard; if you do hit too hard it will first bend permanently and then break.

 

If you crunch the numbers and compare them to steel and work out how fast you can ram the concrete, the boat speed to cause a permanent dent for HDPE is 1/5 that of of steel and to make a hole the figure is 1/7, which are *huge* differences.

 

I've seen a fair number of steel boats with dents in them, so presumably with HDPE the number would be a lot higher since they would happen at a much slower speed. I don't think many steel canal boats have been holed by impacts (though I bet some have...) but the difference here is even bigger, so the risk of holing an HDPE boat in a collision must be *much* higher.

 

GRP is *much* stiffer than HDPE but also can't stretch as much, so boats built from this are less robust than steel (hence why their owners don't like them hitting things or being hit by them e.g. steel boats) -- but nowhere near as bad as HDPE.

 

I hope Shaun has taken all this into account, because it suggests that HDPE in these thicknesses isn't a good choice for big heavy boats in the rough-and-tumble canal environment -- and may be difficult or impossible to get insurance for, given how much more fragile it would be than steel, or even GRP... 😞

 

To be as robust against impacts as 6mm steel (which is probably thicker than needed...) HDPE would need to be about 70mm thick, which would make it about 50% heavier -- and presumably a *lot* more expensive... 😞

Edited February 1, 2023 by IanD

[magnetman]

16 minutes ago, Tony Brooks said:

The latest image seems to show a very different rear swim to the one on the truck so either it was a camera angle illusion or it has been modified. Anyway it looks much beter now.

It is the same. Just a camera angle thing. 

 

Good point about insurance @IanD

 

this is the sort of thing that could be overlooked quite easily. 

[PD1964]

  If you know a little about boats and how they’re built and fitted out, then this project conjures up more questions than answers.

  I think it will be a long time before we see HDPE in this form on the canals. 
 

[magnetman]

I think for boats permanently moored it could be a useful material. One of the advantages I can see is being so light you could get it into the water in more places. Slight issue is that the CRT require boats on their moorings to be capable of navigating so if you deliberately put a boat which was too tall between two bridges it could cause some issues. 

 

I can see a use for this material where access is difficult and you want to build the top up from the hull. I wonder if one can run a plastic welding setup from a Honda EU20i. 

 

Cue 2 storey houseboats turning up somewhere near Kensal Green. 

[Ken X]

Thinking about the ballast issue, could it be fitted with water tanks similar to the Sea Otter design?

[shaun15124]

Our boat was based on an old canal boat called the gypsy lady,

 

yes, the pictures are the same boat just different camera angles,

 

I appreciated everyone's comments my hope is to have this at shows etc so hopefully, you can all see it for yourself 

 

it's resistant to water and chemicals.  mechanical composition is extremely strong on impact and tension. Normally the tension resistance is 225-350 kgf/cm2 and heat resistance is above 100 OC.

 

HDPE is widely used in pressure pipes, gas distribution pipes, liquid containers, machine and home appliance parts, and in insulation. Lately, because of its resistance to water, it is also used in tank and boat manufacturing.

 

 

[magnetman]

As someone above mentioned it could be worth looking at using internal water tanks to get some of the ballasting done. Only problem is being 2.5 times lighter than concrete it would need more than 2ft of internal height to do get it down far enough. 

What is the height from the base to the interior of the top of the cabin?