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What is the process to follow for making a small steam-boat

  1. Jul 25, 2015 #1
    Hello people,
    Before Physics Forum closes my post like they always do, I just want to say that I have really searched for this subject on every search site and looked in more than 15 fluid mechanics, thermodynamics, heat-transfer books and I have found very little about steam engines. And I'm not as smart as you guys, I don't have a BS,MS,PhD in anything. I just want some help for this project.

    I want to make a small boat that runs on a steam engine. How can I start my calculations. Should I first choose the engine , the pump or the boiler ?or should I first build the boat without those components then calculate the power needed to make it move at speed of 20km/h or whatever?. I just need help in knowing the steps more than the formulas and equations
     
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  3. Jul 25, 2015 #2

    OldEngr63

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    Design of anything (including a steamboat) is an iterative process. You begin by assuming a few basic parameters (often based on what you already have existing), and then see what you can build consistent with those limitations.

    The design of a boat is actually a very complex project, particularly if you are intent on achieving a specified speed. The hull length and general shape will limit potential top speed. Read up on wave making and Froude's work for more on this.

    The amount of sinkage (depth to which the hull sinks) will be influenced by the weight of the whole ship. This is unknown until the whole ship is specified, so the whole thing becomes an iterative process.

    I had the opportunity many years ago to observe an expert design a small sail boat, and it was a process that took months of work on the drawing board just to get the design down. It was an excellent small sail boat when it was built, but I was amazed at the amount of time it took to design it. And that is with just a sail for power; no machinery involved.

    You also have to consider how you will transfer power to the water. Will you use a screw propeller, a paddle wheel, or perhaps a ducted internal flow system (Tom Clancy, Hunt for Red October)?

    It is a lot more than just pulling together a few equations and making a single pass.
     
  4. Jul 25, 2015 #3

    jack action

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    With complete freedom, this is how I would do it:
    • First, you have to determine what your boat is suppose to do. What do you want to transport with it, volume and mass -wise. Based on that, you will estimate the volume and mass for typical equipments (engine, rudder, propeller, etc.) for a boat that size and add it to your boat;

    • Then you determine your desired speed;

    • Then you can design your boat hull;

    • Then you can determine the drag force at the desired speed;

    • The drag force and the speed will set the effective power needed (at the propeller) to move your boat. You can then re-check if the engine/propeller/etc. size needed corresponds to your first estimation. Repeat the process if needed.
    Of course, if you have constraints, they will guide your design. For example, you might be stuck with a given engine and instead try to design the largest boat you can for a desired speed. Or you might want a maximum size (to be able to tow it behind a car, for example), which will restrict the hull design and with it the payload (including the equipment). Then you determine the speed and find the power needed, which leads to the engine size.
     
  5. Jul 25, 2015 #4
    I really can't thank you enough for your answer. I was so lost in all those parameters and where to start in building it but now I get that it can't be solved as a "homework problem" ..Thank you so much
     
  6. Jul 25, 2015 #5
    Those are the type of answer I wanted, you rock dude. Thank you so much :)
     
  7. Jul 25, 2015 #6
    Thank you guys for your reply. I'm gonna start making the boat from today..For Science ! :D
     
  8. Jul 25, 2015 #7

    russ_watters

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    I can't possibly fathom a thermodynamics book that doesn't provide excruciating details about how steam engines work. Please provide the names of the books you looked at.
    Since it is your project, you must tell us what you want to do. We're not mind readers. But I can prompt you somewhat:

    1. What do you want this boat to do? Is it carrying cargo? Does it have a size requirement?
    2. How fast should it go?
    3. Do you have a particular type of steam propulsion you prefer? Paddle wheel? Propeller?
     
  9. Jul 26, 2015 #8

    Nidum

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    I can sympathise with your problems on finding books and websites about steam engine design . For every book about practical design of steam engines there must be thousands on steam engine thermodynamics .

    Have a look here :

    https://www.google.co.uk/search?q=s...ei=Rqu0VeyVFMm1UeL5gwg#q=steam+launch+engines

    https://www.google.co.uk/search?q=s...&ei=Rqu0VeyVFMm1UeL5gwg#q=steam+engine+plans+

    https://www.google.co.uk/search?q=s...gwg#q=steam+boat+association+of+great+britain


    Search also on 'Model Engineering' and 'Stuart Turner' .

    One final note - you can design a completely viable steam engine without any detailed knowledge of thermodynamics whatever .
     
  10. Jul 26, 2015 #9
    Thank you for your reply, I really appreciate it but I'm not looking on how to design the steam engine itself. I want to design a boat that runs on a steam engine. But the thing is, I was stuck on how can I choose the steam engine for the boat. I mean based on what ? the pressure and temperature of the input steam ? the mass flow rate of the steam ? the power that is needed to push the boat ? I cant pay 200$ on a small steam engine that won't push my boat. I hope you get what I mean because English is not my first language
     
  11. Jul 26, 2015 #10

    Nidum

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    If you have no technical background choose engine by similarity - just study several existing designs and see what they use .

    Doesn't matter really if they are steam or diesel to estimate HP of engines required for different sized and configuration of boats .
     
  12. Jul 26, 2015 #11
    Of course thermodynamics books have a lot of information about steam engines but they don't provide too many real-life examples such as a boat ..they only let you calculate the efficiency of the engine and they care a lot about theoretical stuff like Carnot cycle..I know that if I read and understand all those theories and spend probably a year connecting those laws to real life problems I would eventually understand how to calculate accurately all those parameters. But its really really hard work and I don't have the time for that I just won't simple answers on how to choose the engine, the boiler, the pump and how much would all that weight ...etc.
    I'm imagining the boat would be only 1.5 meters long and it's only for a capstone project so it's like a toy not a cargo or a big boat.
    I just want it to move not fast not too slow like 10 km/h.
    also im thinking about buying this engine from ebay but it doesn't have any info about its weight, HP, and pressure that it can withstand but the video looks cool :P
    http://www.ebay.com/itm/Model-steam-engine-Danni-premilled-material-kit-/130582358558
     
  13. Jul 26, 2015 #12

    Nidum

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  14. Jul 26, 2015 #13
  15. Jul 26, 2015 #14
    Do you want a steam boat or a project. If the former see how much of the kit you can buy ready made, hull, boiler, engine (if you're really ambitious team turbine) etc, if a long term project you'll need to start reading up on hull design etc. do you have any kind of model engineering club locally, they might be a good source of information, if your going to build your own boiler you might have to talk to regulatory authorities, in the UK the HSE would be a good place to start. Good luck and check that you can get it out of the workshop before you start.
     
  16. Jul 26, 2015 #15
    Thank you for the reply :) I'm doing the project by myself because I'm really interested in this subject and unfortunately my university professors don't want to help me because they say they "don't have time" ..I also live in Turkey where people there only speak Turkish so Its hard for me to find people who like this kind of stuff ..but I have my brother who studies mechatronics engineering, he will help me build it in his lab.
     
  17. Jul 26, 2015 #16
    So I have another question for you guys, should I use a stirring engine instead of a steam engine ?
     
  18. Jul 26, 2015 #17

    Nidum

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    Stirling engine is a possibility but not first choice .

    First choice for such a small boat is actually electric motor and batteries .

    PS: If you just want a 'heat engine' boat for the fun of building one you could use a 'pop pop' engine - no moving parts .
     
    Last edited: Jul 26, 2015
  19. Jul 26, 2015 #18
    I meant stirling* btw
     
  20. Jul 26, 2015 #19
    Ages ago I built a model 'jet-ski', that was fun.
    It was basically two wooden skis linked by a wood bridge (well also a smaller strut near the front end).
    On top of the main bridge I mounted a model aircraft engine housed inside of a piece of plastic pipe.
    So I was sort of spoofing a fan jet type of engine.
    The model overall was about 50cm long and 30cm wide, engine was something like 10cc diesel, not very expensive from the local model shop.

    (Unfortunately one of my parents trashed it, but all is forgiven now)
     
    Last edited: Jul 26, 2015
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