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HDPE Canal boat


shaun15124

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8 hours ago, shaun15124 said:

the engine we have in this is 

 

is 60hp canaline engine and control panel 

 

 you're not being negative at all your correct we have done a shell which in the few weeks we are going to be re-fixing issue , then fitting out, etc 

 

we know we have a long way to go to get this in the water correctly and fitted out 

 

I am not being negative, but 60 hp is way to big for this boat! My 57 x 12 had a 50 hp engine which worked fine.

It now has an electric motor which is lower in power and still works fine. Your boat will only be drawing maybe 10 inches so as others have said a pod Type electric motor could be best?

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In my view it fulfills most of the requirements of any boat. Firstly it will keep the water out above and below the waterline and as someone who has owned a variety of boats over the years that is something that many boats don't do. Secondly it is rustproof, all those nooks and crannies and the state of the baseplate under the floorboards are no problem.  There really is a lot going for it, integral tanks are no problem and no rusting inside, it could even be that mythical thing - the maintanence free boat.  Anyway, it's a start and I'm sure that many of the problems that it throws up can be sorted, Not sure about the strength issues though, walking or jumping on the roof might not be great and some of it could be a bit springy but if you fit out the cabin in much the same way as wooden boats used to be fitted then it'll be fine.  (Edit) 20 HP should be fine in this

Edited by Bee
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My first thought is: Sea Otter (reading the thread a couple of people had the same idea)

 

They used the fact aluminium was a relatively light material to make a canal boat you could stick on a trailer, but added a water ballasting system (basically a floodable chamber) which sat the boat lower in the water (but emptied out when you lifted it out the water so you had something a lot less heavy to sit on the back of a trailer). That could be an interesting thing to look into.

 

I'm not sure this is one for the traditionalists, but I can see a niche here if the problems are solvable.

 

 

Other random thoughts

 

- I guess some of the expansion problems are reduced if the boat interior people line their furniture and flooring up with is a minimally-expanding wooden cabin separated from the outer shell by a thick layer of insulation, though there would still be things like window alignment to consider. I suppose thick HDPE itself has slightly better insulating properties than a steel shell too, and not as hot to touch in summer?

 

- Sounds like it's not as impact resistant as a 12/6/4 steel boat, but significantly more robust than a GRP cruiser, right?

 

- If you don't have to paint it is a selling point, how easy is it to smooth out scratches from branches etc, especially at cabin height

 

 

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On 02/02/2023 at 13:13, Tracy D'arth said:

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........................................................................................................................................................................... 

If it used undepleted DU then that could provide the electricity for the propulsion...

 

Alec

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On 03/02/2023 at 08:35, shaun15124 said:

a third of the weight of a steel boat needs less than half the power to push it forward 

How do you reach that conclusion? The boat is the same shape as the steel widebeam you have copied, and will be ballasted down to the same depth to submerge the prop. So the resistance to movement through the water will be the same and hence the engine power needed will also be the same. 

The difference in shell weight will be offset by the greater weight of ballast, and the fitout will weigh much the same steel steel version.

 

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I agree with the observation that the subject boat will need to carry ballast to make it the same weight  as the narrowboat on which the hull design is based. Otherwise the prop will not be submerged sufficiently.

 

GRP boats generally do not have a flat bottom but a v shaped Hull in order to draw sufficient depth . This usually  avoids having to carry ballast . 

 

May I ask the OP how the engine cooling system  is going to work bearing in mind HDPE will soften if exposed to temperatures above 60 degrees for any length of time. The arrangements usually found on steel narrow boats will not be appropriate.

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48 minutes ago, David Mack said:

How do you reach that conclusion? The boat is the same shape as the steel widebeam you have copied, and will be ballasted down to the same depth to submerge the prop. So the resistance to movement through the water will be the same and hence the engine power needed will also be the same. 

The difference in shell weight will be offset by the greater weight of ballast, and the fitout will weigh much the same steel steel version.

 

 

Indeed, so the ballasted weight of this plastic boat will be the same as a steel boat, for the same depth in the water. 

 

Is the HDPE actually physically strong enough to cope with carrying 30 tonnes of ballast and coming to an instant halt hitting say, a lock sill at 2mph without rupturing somehow? 

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31 minutes ago, MartynG said:

May I ask the OP how the engine cooling system  is going to work bearing in mind HDPE will soften if exposed to temperatures above 60 degrees for any length of time. The arrangements usually found on steel narrow boats will not be appropriate.

 

I asked this way back, close to the start of the topic. I also pointed out that traditional keel cooling pipes might not be such a good idea on a flat-bottomed canal boat. I think I also asked about the thermal conductivity of HDPE compared with steel. I was told by another member that this was to be an electrically powered boat. Now we know the OP intends to fit a 60hp diesel.

 

A 60hp diesel in a steel boat will require a 15sq ft skin tank, so say 2ft x 7.5 ft, I think the thermal conductivity of HDPE is far lower than steel, so the tank would need to be much larger and I think it would have to be impractically large, so it will have to be heat exchanger cooled with the potential for the raw water system to clog and block on canal. At least that will allow a wet exhaust so the hull fitting will not be subject to such potential high temperatures. 

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45 minutes ago, MtB said:

 

Indeed, so the ballasted weight of this plastic boat will be the same as a steel boat, for the same depth in the water. 

 

Is the HDPE actually physically strong enough to cope with carrying 30 tonnes of ballast and coming to an instant halt hitting say, a lock sill at 2mph without rupturing somehow? 

No, unless it's 50mm thick which would make it roughly as rigid and strong as a 4mm steel hull -- but 50% heavier, and probably more expensive, and very difficult to build with... 😞

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Many years ago we had a 30 foot steel narrow boat. It was built of 1/8 " steel and had no ballast. The bottom was flat,but had the center of the bottom 12" deeper than the outside of the bottom. This narrangement gave standing headroom in the center passage and lower each side. The advantage of this arrangement was stability (avoids a v bottom like a Springer),light weight less boyancy from each side which removed the need for ballast. The shape of the bottom gave strength and rigidty.It also acted as a keel,so the boat performed well on a windy day.Driven by a BMC 1.5 d. Dont know the weight,but it could be towed on a trailer behind a large 4x4. Although the boat looked like any other small narrow boat in the water the inovative design worked well,

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42 minutes ago, IanD said:

No, unless it's 50mm thick which would make it roughly as rigid and strong as a 4mm steel hull -- but 50% heavier, and probably more expensive, and very difficult to build with... 😞

The question that the OP is failing to answer is the cost/expense, would love to know the cost of that shell, but it’s not really a working shell with lots of parts missing.

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49 minutes ago, nebulae said:

Many years ago we had a 30 foot steel narrow boat. It was built of 1/8 " steel and had no ballast. The bottom was flat,but had the center of the bottom 12" deeper than the outside of the bottom. This narrangement gave standing headroom in the center passage and lower each side. The advantage of this arrangement was stability (avoids a v bottom like a Springer),light weight less boyancy from each side which removed the need for ballast. The shape of the bottom gave strength and rigidty.It also acted as a keel,so the boat performed well on a windy day.Driven by a BMC 1.5 d. Dont know the weight,but it could be towed on a trailer behind a large 4x4. Although the boat looked like any other small narrow boat in the water the inovative design worked well,

 I think your size of boat, hull profile, being fitted with a small electric motor/solar and the benefits a trailabe boat would give, to cover all the inland waterways and lakes, would be a more attractive proposition to buyers then a full size Narrowboat/widebeam in this material. 
  I can see the boat in the Thread becoming an expensive project/concept boat and that’s it, not a viable financial investment to carry on further or to put on the market.

Edited by PD1964
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1 hour ago, Tony Brooks said:

 

A 60hp diesel in a steel boat will require a 15sq ft skin tank, so say 2ft x 7.5 ft, I think the thermal conductivity of HDPE is far lower than steel, so the tank would need to be much larger and I think it would have to be impractically large, so it will have to be heat exchanger cooled with the potential for the raw water system to clog and block on canal. At least that will allow a wet exhaust so the hull fitting will not be subject to such potential high temperatures. 

HDPE underground drainage pipes  can take 60 degrees with occasional short exposure to 100 degrees. 

Apart from the thermal  conductivity  the material will start to soften if 60 degrees is exceeded other than for short periods.

So I would say a skin tank is not viable.

 

HDPE expands/contracts with temperature change 10times as much as steel. Whether that is an issue I wouldn't  know.

image.png.1715aa645f7be2bf9a42780daa470464.png

 

 

 

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1 hour ago, MartynG said:

HDPE expands/contracts with temperature change 10times as much as steel. Whether that is an issue I wouldn't  know.

Register it with CaRT in winter. Cheaper license fees. Sell it in summer. More money for a longer boat. Don't try cruising at the size limit locks on hot days!

Edited by Jen-in-Wellies
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5 minutes ago, magnetman said:

Maybe this is why it is 40x10ft. No chance of ever getting anywhere near the limits on lock sizes. However hot the temperature. 

I wonder if the beam would drop below 7' before the canals froze? Could cruise the narrow canals in winter! Just make sure you are back on the broad canals before Spring.

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