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Design and Dimensions
Getting it right the first time – hopefully
Thursday,9 October, 2014
7:39 pm
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Hallo,

after reading here and some other places for some months, getting some literature and reading various narrowboat blogs and building descriptions I have tentatively started my own design.

What do I want:

– Tug/Icebreaker along traditional lines

– liveaboard for some month at a time for one and place for two guests

– propulsion with steam plant (coal and/or diesel-fired, not yet fully decided)

– single handed operation possible

To provide the displacement for a relatively heavy steam plant I arrived at a length of appr. 46 ft.

 

Now some questions:

– length 46 ft, will this be a limit for some navigations? ( I know about the 57 or 58 ft limit, but maybe there are others)

– draft 2 ft 2 in (needed for a 19 in propeller), should be no problem?

– air draft 6 ft, at a pinch 5 ft 5 in (dismantling some parts on the roof), okay?

– beam 6 ft 10 in, should be standard?

 

I have some experience with steam plants and the applicable regulations and codes, so I know what’s ahead.

The rest of the machinery should be standard.

 

regards

M

Friday,10 October, 2014
9:47 am
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Dimensionally the only advantage I can see to having such a short boat is winding especially at the heads of some navigations where there is limited turning space. I find 60 feet length offers relatively few limitations.

Other dimensions would be fine although 19″ diameter seems modest for the prop, I believe steam driven working boats used up to 36″ diameter – depends on the gearing of course.

Regards – Richard –
Ecky Thump

Saturday,11 October, 2014
6:02 am
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Southam, Warwickshire
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You mentioned in another post that your boat’s beam is seven feet I think. You would find some of the narrow locks a very tight squeeze.

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Saturday,11 October, 2014
11:13 am
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Seven feet (and a half inch) is the beam of the steam launch I did research on. My boat will have the standard beam of 6-10.

 

Regarding the length I’m the opinion the shorter the easier the handling in tight places, finding a mooring and so on.

As this boat is no replacement for a home ashore everything really needed will fit in.

Anyway it is surprising how much storage space you can put in this length if you really try.

 

regards

M

Saturday,11 October, 2014
12:51 pm
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Montgomery said
Seven feet (and a half inch) is the beam of the steam launch I did research on. My boat will have the standard beam of 6-10.

 

Regarding the length I’m the opinion the shorter the easier the handling in tight places, finding a mooring and so on.

As this boat is no replacement for a home ashore everything really needed will fit in.

Anyway it is surprising how much storage space you can put in this length if you really try.

 

regards

M

Longer boats are easier to steer in a straight line. Not sure why you are so concerned over mooring – sure a smaller boat will fit in easier but there’s an awful lot of mooring space out there.

Another point a broker made to me many years ago and I have found to be very true is that boats shrink. What seems a challenge when first stepping aboard becomes a doodle to manoeuvre later.

Regards – Richard –
Ecky Thump

Saturday,11 October, 2014
12:58 pm
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richardhula said

Another point a broker made to me many years ago and I have found to be very true is that boats shrink. What seems a challenge when first stepping aboard becomes a doodle to manoeuvre later.

I second that. A frequent comment new boaters make when they come out with me is that the front of the boat seems an awfully LONG way away when they first stand on the back of the boat. A few hours later and they are happily chugging away the tightest bends and judging the length very well indeed.

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Sunday,19 October, 2014
7:11 pm
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Of course you are both right, I accept your arguments.

I have now arrived at 50 ft (hull length) because of the needed displacement for the heavier machinery without getting more draft.

Including a certain reserve (boats get heavier from alone) and generous supplies/storage/tanks.

 

If there is no argument from the navigation side I will stay with this length for the design.

Btw I found a lock on the system of 39 ft but this is much below my acceptable dimensions and it leads only to a short dead end.

 

regards

M

Sunday,26 October, 2014
6:10 pm
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Where the mood takes me, from the south coast to the canals of England/Wales
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I own a 50 footer with internal engine room. I would guess your layout would be similar to mine but with possibly a slightly larger engine room. My immediate thought having run coal fired steam engines that diesel fuelled would give more chances of automation of the boiler. I think if you go for a tug with a long front deck although the boat will be long enough for a couple, fixed double, bathroom, galley, the size of the saloon might be very tight to be also used as a twin berth.

Don’t know if you have ever been aboard a 50 footer with an engine room?

Sounds an exciting and interesting project

G

Monday,27 October, 2014
6:06 pm
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Hallo G,

the layout will be as follows (from the back end)

– small cockpit (storage both sides)

– back cabin (with solid fuel stove, sleeps one, tanks and condenser under)

– engine room, length appr. 11 ft (boiler, engine, batteries, switchboard, steam generator, aux. machinery)

– bathroom with passage alongside

– pantry / saloon (will sleep one or two)

– fore deck / fore hold (tanks, calorifier, diesel heating, diesel generator)

– gas locker (no gas bottles but storage for lamp oil / paint)

 

You are right, a diesel fired boiler can be automated easier for pressure keeping,

water level regulation will be alway done manually, that is no problem.

If a boiler is designed right, water level has to be checked once every ten minutes.

 

On most canals a coal fired boiler will be no trouble, as the speeds are slow and stoking would be required only twice in one hour

(short stop for two minutes or do it in or after a lock, or when waiting for a lock).

With normal canal speeds the boiler output would be less than 20 % rated power.

 

On a river or a tidal navigation this is a completely different situation, but even with an automated diesel fired boiler

I would not travel there without a crew for safety reasons.

 

And you are also right, that is is a very interesting and technically demanding project.

 

50-feet.jpgImage Enlarger

 

What I’m searching now for is some information on the design/sizing of skin cooling tanks

as it has to handle appr. 150 kW thermal load at full power, anybody has got any information in this line?

 

regards

M

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Tuesday,28 October, 2014
4:54 pm
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Found it, the info for the skin cooling tank:

http://www.betamarine.co.uk/do…..sizing.pdf

M

Tuesday,28 October, 2014
8:37 pm
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Hello Montgomery, 

Some thoughts that might help 

I assume the skin tanks are to condense the output steam back to water to go back to the boiler for reuse. 

If my maths is correct and the output via the water/steam is 150 kW (201 hp) then the cooling tank, assuming a swim hull depth of 2 feet will need to be 25 foot long. Are you sure it is 150kW? If my guess is correct and 150 is a typo, 15kW gives a tank 2 foot 7 inches long. 

One disadvantage of skin tanks I have come across is the insulation effect of the blacking. Over the years as more blacking is applied the efficiency of the skin tank drops and thus the engine has a tendency to overheat as efficiency falls. I was wondering if it might be an idea to install twin tanks from day one. Apparently the normal remedy seems to be to add another skin tank. 

Are you going to let the engine blow the exhaust steam to the skin tanks and then pump the cooled water to an open to air holding tank? 

On the drawing you have the batteries in the engine room with the boiler and engine. I am wondering if the temperature, boiler steam etc will mean the engine room will have a temperature in the 40C plus area and thus the battery electrolyte will have a tendency to evaporate because of the hot environment. Might the rear cabin or somewhere cooler alleviate the electrolyte evaporation? 

What do the BSS say about storing lamp oil, paraffin I am assuming, in the forward locker? Would they treat it as diesel and thus the same rules apply? 

Regards

G

Tuesday,28 October, 2014
9:27 pm
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Hallo GM,

the skin tank will cool down the cooling water from the condenser.

1st circuit: boiler – engine – feedwater heater – condenser – condensate tank – feed pump – feedwater heater – boiler

2nd circuit: condenser – skin cooling tank – circulation pumps – condenser

The figure of the thermal load was slightly off, I used the total amount, 150 kW is the boiler output, deduct engine and feed water heater

and there remains about 95 kW for cooling, this would mean one tank of appr. 3 m².

 

Thank you for the remark about the deterioration of the cooling capacity, I will provide two tanks with appr. 2.5 m² each

(one each side of the engine room would give the correct area).

 

The reason for a double circuit is as follows:

clean condensate is very agressive, it will corrode a mild steel tank in short time.

So the first circuit will be stainless steel/brass/copper (except the boiler)

and the second circuit will be mild steel with standard cooling water with antifreeze/corrosion protection.

The boiler itself is protected by the water treatment, which will build up a protective coating.

If it’s done correctly such a boiler will keep for 30 plus years.

 

The engine room will be relatively cool, the boiler needs quite a lot of air, the rest is good isolation.

I’m thinking about cooling the batteries with cold air from below the floor plates, this would also lengthen their lifetime

and anyway they will need positive ventilation because of gassing.

These traction batteries are 750 mm high and weigh 300 kg, so they need to be in an accessible place for installation and service.

 

Regarding the lamp oil / kerosene I have not yet checked all the details of the rules.

I think it will be treated as flammable liquid like petrol, so a separate vented compartment above the waterline would be needed.

But I will have to definitely study all the applicable rules, especially with regard to leakage and pollution prevention.

 

Thank you very much for your input!

 

regards

M

Wednesday,29 October, 2014
8:06 am
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On Joanie M, the skin cooling tanks form the engine bed so the cooling surface is the bottom plate and is unaffected by excess blacking.

Living retirement in the slow lane.

20 years hiring, 6 years of shared ownership and a Continuous Cruiser since 2007 but still learning!

Wednesday,29 October, 2014
4:36 pm
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Thank you pearley,

that is also an interesting variation, stored for further consideration.

How thick is your bottom plate?

Is a bottom plate never blacked, not even on a new boat??

 

regards

M

Wednesday,29 October, 2014
5:30 pm
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The bottom plate is the usual 10 mm. It is not normal for the bottom plate to be blacked as most of it would get rubbed off as you grind yourself along some of our shallower canals. I would estimate that the coming surface, is that bit of the bottom plate that is also the skin tank, to be about 8 sq.ft.

We do have a conventional skin tank for the built-in generator. You can clearly see the outline of this when in the dry dock as the blacking goes a different colour. If it is a case of excessive blacking reducing the efficiency then it would be a simple matter to always take this back to bare metal before blacking. Mine has been blacked 3 times, actually 4 times counting the original, but lack of cooling is not a problem

Edited to add that I’ve not taken into account that the tanks are about 6 inches deep so at 4 feet long that’s another 4 sq.ft. so 12 sq.ft. in total.

Living retirement in the slow lane.

20 years hiring, 6 years of shared ownership and a Continuous Cruiser since 2007 but still learning!

Saturday,1 November, 2014
7:01 am
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OK, I am curious, where is the galley planned for in your proposed boat?Confused

Saturday,1 November, 2014
7:42 am
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Forward, starbord side, in the area named “pantry/saloon”.

M

Saturday,1 November, 2014
7:46 am
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Aha, food storage and place to eat it – but I didn’t align that with place to prepare it … I’d hate to think you couldn’t cook your beans or sausages or eggs and bacon or toad in the hole and mash! KissCheers, Marilyn

Monday,3 November, 2014
6:52 pm
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re storing lamp oil,

have checked the BSS-guide,

petrol and other flammable liquids like paraffin are treated exactly the same as LPG, so a standard gas-locker should be acceptable.

Some provisions will have to be made for containing a possible leakage (pollution prevention).

M

 

ps: beans are only for emergency food Laugh

Tuesday,11 November, 2014
6:27 pm
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Stern of the boat:
except for the weed hatch there seems to be left quite a lot of space under the stern deck.
I don’t want to fit a tank there (it’s too far aft and would worsen the longitudinal balance)
– so what to do with all the this space?

The only use I came up with is to store some bulky lightweight items (like clothing or toilet paper),
anybody got some other/better ideas?

What do you use it for?

M

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