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Plastic Barge


Tim Lewis

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4 hours ago, blackrose said:

I think the biggest issue would be abrasion from lock walls, scraping the bottom, etc. Mind you, enough modern kayaks are made from HDPE and they last for years.

Didn't know that kayaks are now made of it. I've built several things out of HDPE over recent years. As the video shows, you need to either heat weld it, or use mechanical fixings. There isn't an adhesive that will easily stick to it, or a solvent that is practical outside a fume hood to solvent weld the stuff. It does seem to be nice and stable in sunlight. I made a covered bird table six or seven years ago that still looks like new. The video shows that the rigidity of the boat is down to the welded steel I beams incorporated in to the base.

Lock wall abrasion would definitely be a problem. The rubbing strakes and base plate sacrificial edge would need attending to on a regular basis. However, new strakes and repairs to the base plate could easily be done by welding on new HDPE. No blacking required, but it would still need to come out of the water on a regular basis for inspection and repair. Better for a <14' wide beam, than a narrowboat, as you could use it with lots of fenders down through locks. A big risk would be shopping trolleys and other underwater obstacles gouging out the base plate, which could easily sink it. With the weight of ballast, engine, etc, it is going to have a lot of momentum, so hitting a sunken sharp object at speed could do a lot of damage.

Be interesting to see it in the water. I'm assuming this is a practical project and the boat is going somewhere else for engine, fit out etc, after leaving the plastic fabricators.

You'd want to use it more like a GRP cruiser than a steel boat. Lots of fenders and built with compound curves to give extra strength, rather than large flat panels. This boat has been built like a steel wide beam, with mostly flat panels and simple curves and I'd worry that it doesn't have the rigidity, given the lower modulus of HDPE, compared with steel and lower even than GRP. The I beam support is a bit of a fudge. It would have been better to design it around the properties of HDPE, using heat to curve the material and complex curves for strength. Similar to kayaks. It would also look better. Instead, the've gone for really thick HDPE and lots of bracketing. I wonder how much mathematical analysis has been done on the strength and flexing.

Edited by Jen-in-Wellies
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Welding in plastics is a skilled operation, but on one level very simple.

 

Back in the 90s I worked for an engineering plastics company that employed to fabricators who made fantastic constructions out of various plastics.

This is an American video, but shows how and what can be done.

  

Or this, closer to home, shows some possibilities.

https://iep-ltd.co.uk

Edited by Stilllearning
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7 hours ago, blackrose said:

I think the biggest issue would be abrasion from lock walls, scraping the bottom, etc. Mind you, enough modern kayaks are made from HDPE and they last for years.

 Would fossile fuels melt it?

 

5 hours ago, MtB said:

50mm draft or one helluvalot of ballast to go in! 

 

No engine or prop or stern gear or rudder, so far...

 

 Keep it at a 2 inch draft and just use a small electric outboard?

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4 hours ago, Jen-in-Wellies said:

 A big risk would be shopping trolleys and other underwater obstacles gouging out the base plate, which could easily sink it. With the weight of ballast, engine, etc, it is going to have a lot of momentum, so hitting a sunken sharp object at speed could do a lot of damage.

 

 

That's also true. I've been on a couple of rivers with sharp rocks underwater on some areas of the banks. If you hit them with a 10mm steel baseplate and 6mm sides the boat's just going to bounce off and scrape some paint off, but with all that ballast in a HDPE hull the rocks could go straight through.

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1 hour ago, blackrose said:

 

That's also true. I've been on a couple of rivers with sharp rocks underwater on some areas of the banks. If you hit them with a 10mm steel baseplate and 6mm sides the boat's just going to bounce off and scrape some paint off, but with all that ballast in a HDPE hull the rocks could go straight through.

 

Given time even smoothish concrete goes through GRP and Seacrete in that situation.

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28 minutes ago, Mad Harold said:

What type of plastic are kayaks made of?

They look very robust and I have seen quite a few that are quite badly abraded and have aquired some deep scratches.They do seem to be moulded quite thick.

 

I believe they are HDPE (High Density Polyrthylene) and they certainly handle scratches well - our have quite deep cuts as well as scratches where they are dragged over sharp rocks and slate.

 

Surf Kayak from Fatyak™ Kayaks - designed for the waves! (fatyak-kayaks.co.uk)

 

All Fatyak kayaks are a one piece rotationally moulded which results in no seams and no joints and is manufactured in the UK to the highest standards, using high grade high density UV stabilised polyethylene. It is light too- at only 18kg making it easy to transport, and get on and off the roof rack of your car!

 

Edit - why do the pictures occasionally rotate ?

 

 

20210815-094441.jpg

 

 

 

 

This was when @rusty69 came to play, she'll do anything once !!

 

 

3a663b1b-9a52-428c-a4ca-ac4f2df6a78f-500x281.png

 

 

Edited by Alan de Enfield
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HDPE has a number of disadvantages that would make it challenging for use in a boat:

 

Poor Weathering
Highly Flammable
Sensitive to Stress Cracking
Not Resistant to Oxidizing Acids
Not Resistant to Chlorinated Hydrocarbons
High Thermal Expansion
Poor Temperature Capability

 

The fact that it melts at 115c and produces toxic smoke when it burns does not go well in a confined space.

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9 hours ago, Jen-in-Wellies said:

Lock wall abrasion would definitely be a problem. The rubbing strakes and base plate sacrificial edge would need attending to on a regular basis.

The obvious solution is to cover the entire  base plate and the sides with steel, which would also act as ballast.

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1 hour ago, MrFish said:

HDPE has a number of disadvantages that would make it challenging for use in a boat:

 

Poor Weathering
Highly Flammable
Sensitive to Stress Cracking
Not Resistant to Oxidizing Acids
Not Resistant to Chlorinated Hydrocarbons
High Thermal Expansion
Poor Temperature Capability

 

The fact that it melts at 115c and produces toxic smoke when it burns does not go well in a confined space.

But how does HDPE compare with GRP in these respects?

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11 hours ago, Jen-in-Wellies said:

I made a covered bird table six or seven years ago that still looks like new.

 

I made a bird table too, back during Covid.

 

My girlfriend got very upset about it because I'd put her in at No 3. 

 

 

 

 

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21 minutes ago, MtB said:

 

I made a bird table too, back during Covid.

 

My girlfriend got very upset about it because I'd put her in at No 3. 

 

 

 

 


So who were numbers 1 & 2?


Frankly, that’s a better debate than plastic boats but I do believe I passed one on the Soho loop today, a workboat named the Poly Roger.

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6 hours ago, Chris G said:

I don't think that carbon dioxide and water are toxic.

 

58 minutes ago, MtB said:

 

Have a read of this:

 

"How Does Carbon Dioxide Poisoning Kill a Human?"

 

https://healthyliving.azcentral.com/how-does-carbon-dioxide-poisoning-kill-a-human-12152576.html

And Dihydrogen Monoxide is incredibly dangerous and kills loads of people every year. 😀

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