HDPE Canal boat

[Ken X]

16 hours ago, Ken X said:

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

With reference to my comment above, I looked at the relative weights of aluminium and HDPE and aluminium is 65% heavier than HDPE. If, therefore, the HDPE was around twice the thickness of aluminium or more, the boat would weigh more than an equivalent sized Sea Otter.  I don't know how the ballast tanks are configured on a Sea Otter but if it works for the aluminium boat there would seem to be potential for water to, as least, partially assist in ballasting this boat.

 

A further thought was re. cooling and water ballast.  I understand an electric drive is proposed which needs cooling.  I have no idea how much energy needs to be shed but, if it is not a vast amount, could the cooling radiators be located within the water ballast tanks to protect them from impact damage.  The water would heat up to a degree but if the load is not excessive a balance may be achievable.  Exterior or interior access for maintenance would be required but would not be an insurmountable problem.

[Tracy D'arth]

To achieve a sensible headroom and floor height, ballast much heavier than water will be required. Lead would be better but expensive. DU would be the ideal but there are problems........................................................................................................................................................................... 

[magnetman]

Palladium? 

[rusty69]

The solution is obvious. Only use the thing in anticyclonic weather patterns. The pressure will push the vessel lower in the water.

[magnetman]

Also worth avoiding salty water. 

[Jon57]

1 minute ago, rusty69 said:

The solution is obvious. Only use the thing in anticyclonic weather patterns. The pressure will push the vessel lower in the water.

Or just clad it in steel 👍

[Ken X]

Boeing used depleted uranium counterweights in the early 747's.  What could possibly go wrong.🙂

[magnetman]

I think the larger sea otter boats are probably more of a round bilge shape rather than a pointy rectangle. 

 

The narrow ones do apparently have some water ballast but I was told it is self draining in other words not top filled tanks. Not sure what the point is but I guess it is stability related. 

 

A narrow bean sea otter would be quite a good boat to study if thinking of making an HDPE canal boat. 

[shaun15124]

yea that is one thought actually thank you for that 

 

regards to the salty water comment salt water is ok with hdpe actually as HDPE is used a lot in workboats as i have said before 

 

and yes I understand there is a difference between a workboat and a canal boat I was merely saying that HDPE is used a lot in all types of environments 

 

and I completely get the weight etc issue I must stress as of now we are at a stage where are fixing certain issue 

 

[IanD]

Just now, shaun15124 said:

yea that is one thought actually thank you for that 

 

regards to the salty water comment salt water is ok with hdpe actually as HDPE is used a lot in workboats as i have said before 

 

and yes I understand there is a difference between a workboat and a canal boat I was merely saying that HDPE is used a lot in all types of environments 

 

and I completely get the weight etc issue I must stress as of now we are at a stage where are fixing certain issue 

 

 

HDPE is probably fine for open-water boats where there's no risk of collision with unforgiving rigid objects such as concrete/stone lock entrances and other steel boats. Even though steel hulls are pretty strong, you still see narrowboats (or wideboats) with dents in them, some quite large -- a boat for canal use needs to be robust. The accepted minimum steel hull thickness -- including for insurance purposes as well as strength -- is 4mm, HDPE would need to be about 50mm thick to give the same strength and robustness as this when such impacts occur.

 

A 15mm HDPE hull might sound thick but it's *many* times weaker than 4mm steel -- it's actually equivalent in stiffness and strength to 1.25mm steel, and I'm pretty sure nobody would think this was thick enough to build a narrowboat out of... 😞

[magnetman]

My comment about salt water was related to the fact that boats float higher in salty water than fresh water. 

 

It was not about the material but a reference to the post before it. 

 

I'm sure HDPE would be a great material for fast sea going boats. 

[peterboat]

1 hour ago, Ken X said:

With reference to my comment above, I looked at the relative weights of aluminium and HDPE and aluminium is 65% heavier than HDPE. If, therefore, the HDPE was around twice the thickness of aluminium or more, the boat would weigh more than an equivalent sized Sea Otter.  I don't know how the ballast tanks are configured on a Sea Otter but if it works for the aluminium boat there would seem to be potential for water to, as least, partially assist in ballasting this boat.

 

A further thought was re. cooling and water ballast.  I understand an electric drive is proposed which needs cooling.  I have no idea how much energy needs to be shed but, if it is not a vast amount, could the cooling radiators be located within the water ballast tanks to protect them from impact damage.  The water would heat up to a degree but if the load is not excessive a balance may be achievable.  Exterior or interior access for maintenance would be required but would not be an insurmountable problem.

In something light with little draft an air cooled electric motor would work fine

[MtB]

1 hour ago, magnetman said:

Palladium? 

 

Or gold would make good ballast, too. Much heavier than lead. 

 

Interestingly I was looking at bullion prices the other day and until then, I had no idea that palladium is traded on the bullion market! 

 

 

[magnetman]

Palladium price went mad for a while. 

 

 

[shaun15124]

Apologies if my comment came across in a wrong manner towards the saltwater comment 

 

with everything that has been done so far including thickens was recommended by a canal boat builder 

 

 

[IanD]

2 minutes ago, shaun15124 said:

Apologies if my comment came across in a wrong manner towards the saltwater comment 

 

with everything that has been done so far including thickens was recommended by a canal boat builder

 

 

... who doesn't seem to understand how the properties of HDPE compare to steel. Sorry, but that's the truth of it... 😞

[Tony Brooks]

6 minutes ago, IanD said:

 

... who doesn't seem to understand how the properties of HDPE compare to steel. Sorry, but that's the truth of it... 😞

 

I think that illustrates the difference between a boat builder and a proper engineer or naval architect. Both the latter would have done the calculations such as you have done.

[IanD]

1 hour ago, Tony Brooks said:

 

I think that illustrates the difference between a boat builder and a proper engineer or naval architect. Both the latter would have done the calculations such as you have done.

 

The boatbuilder "rule-of-thumb/estimation" approach is absolutely fine when you're building things that you've built before and are familiar with and are known to work and be robust, like steel narrowboat hulls.

 

Where it all goes wrong is when you try and apply this experience to completely new materials (like HDPE) which are very different without understanding the different properties, and that's when proper analysis is needed... 😞

Edited February 2, 2023 by IanD

[magnetman]

Static houseboats innit. 

[IanD]

5 minutes ago, magnetman said:

Static houseboats innit. 

And maintenance-free HDPE would work well for them, because they don't bash into locks and other boats.

 

However the boat being discussed in this thread is clearly not a static houseboat...

[shaun15124]

we also have recently got a a naval architect involved who has made numerous HDPE boats and will address certain issue 

 

with the canal boat builder, this gentleman was the one who had made the original (gypsy lady ) 

 

you have no need to say sorry you are entitled to your opinion and that is why I put this on here to get many different people's opioins on this 

with the hdpe i totally understand that there are differences in regards to steel and hdpe 

 

[Peanut]

I think that houseboat suggestion is good, there could be a market there for the right product.

[magnetman]

27 minutes ago, IanD said:

And maintenance-free HDPE would work well for them, because they don't bash into locks and other boats.

 

However the boat being discussed in this thread is clearly not a static houseboat...

I know that. 

 

I doubt the pictured boat is going to be a powered canal boat. 

[Tony Brooks]

25 minutes ago, shaun15124 said:

we also have recently got a a naval architect involved who has made numerous HDPE boats and will address certain issue 

 

with the canal boat builder, this gentleman was the one who had made the original (gypsy lady ) 

 

you have no need to say sorry you are entitled to your opinion and that is why I put this on here to get many different people's opioins on this 

with the hdpe i totally understand that there are differences in regards to steel and hdpe 

 

 

I will thank you for putting it up, it has engendered much discussion and in my view was worthwhile.

[IanD]

2 minutes ago, magnetman said:

I know that. 

 

I doubt the pictured boat is going to be a powered canal boat. 

So why does it have a narrowboat hull shape, with a swim and uxter plate at the stern?

 

A houseboat can just be a rectangular box, cheaper to build and more space inside...