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Thread: Modelling a Propeller

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    Team Member Roflhat's Avatar
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    Default Modelling a Propeller

    Hi,

    For folks who don't know me, I'm studying Naval Architecture with high performance marine vehicles at the University of Strathclyde.
    For my fourth year project I want to model a surface piercing propeller, namely a through hub cleaver. I have an 11 x 18 pitch Mercury cleaver which I hope to use as the basis of my design. My aim in the future is to design and model my own propellers, but I would like to start by modelling and existing propeller.

    My plan is to get the propeller scanned and get as many figures from it as possible so I can model it. I hope to send it to a company in the UK for this. The prop is in very good condition but I'm going to send it to get repaired so it's perfect in order to start with as good a model as i can.

    I want to model this propeller using CAD software and possibly modify the design slightly, I want the prop to use a removable hub kit so it can be replaced if damaged or for use on a different engine.

    If anyone has any experience on this would be greatly appreciated, I'm expecting a steep learning curve.

    Thanks

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    Team Member zul8tr's Avatar
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    Exactly what are you modeling? With CAD that would just be the geometry. Are you going to model the hydrodynamics with CFD software + experimental data. The air water interface as well as the entrained air water mix is where the complication comes in with surface piercing props (SPP). Here are some articles I came across:

    http://www.well.com/~pk/SPAprofboat.html

    https://www.navalengineers.org/Proce...erer_Patil.pdf
    " Three may keep a secret if two of them are dead" Ben Franklin
    " ------- well Doctor what have we got a Republic or Monarchy? A Republic he replies if you can keep it"
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    Team Member Roflhat's Avatar
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    Thanks for the reply zul8tr,
    I've been speaking to a company in the UK who can scan my propeller and provide a parametric model in IGES format, which I could then modify in the software available at Uni.
    My initial plan was to carry out a CFD analysis but I've been advised by quite a few people that this is very ambitious, there are a few people in our department doing that for their PHD.

    So my plan now is to get a model of the propeller and modify it from there. I think for now I will leave the design of the propeller blades as they are and just modify the hub.
    Thanks for the links, I'll give them a read when I get a chance.

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    Team Member zul8tr's Avatar
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    Keep us informed on your progress.
    " Three may keep a secret if two of them are dead" Ben Franklin
    " ------- well Doctor what have we got a Republic or Monarchy? A Republic he replies if you can keep it"
    Benjamin Franklin, 1787 Constitutional Convention, as recorded by signer James McHenry's in his diary at the Library of Congress

    Location: SW Orlando, Fl

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    Team Member Roflhat's Avatar
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    Will do, sure I'll have plenty questions!
    I'm planning on changing the hub so it can use a removable hub kit, what would you recommend? I was looking at Ron's hubs or maybe a Rubex kit, so it can be replaced and also used on a variety of motors.

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    Team Member zul8tr's Avatar
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    Can't help on the hub Q, Ron is a good source for Q's on that. The interchangeable Rubex hub appears to be a good choice for your purpose.
    " Three may keep a secret if two of them are dead" Ben Franklin
    " ------- well Doctor what have we got a Republic or Monarchy? A Republic he replies if you can keep it"
    Benjamin Franklin, 1787 Constitutional Convention, as recorded by signer James McHenry's in his diary at the Library of Congress

    Location: SW Orlando, Fl

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    If you really want to learn about propellers, try making your own and running them. Since I run oddball Mercs (ex: Mark 78 on a Mark 55 tower) I have to build my own props; and it's been...educational. The latest, Prop #5 (photo), is working fairly well, but #4 self-destructed--not enough weld fillet. I actually have a video of its blades blowing off! Oh well...

    I beat the blades out of 1/8 stainless plate and weld them to a hub made from common pipe material. (Crude I know, but it works.) The hubs come from Surplus Supply.

    Jeff
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    Team Member Roflhat's Avatar
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    That's really impressive, do you balance them yourself? I was looking at getting a static balancer.
    If this project goes well I hope to get a model 3D printed in plastic so I can at least see if it works. There's a lot of exciting technology happening in relation to metal 3D printing, although I think the prices are still huge at the moment.

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    Team Member zul8tr's Avatar
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    Quote Originally Posted by Roflhat View Post
    Thanks for the reply zul8tr,
    I've been speaking to a company in the UK who can scan my propeller and provide a parametric model in IGES format, which I could then modify in the software available at Uni.
    My initial plan was to carry out a CFD analysis but I've been advised by quite a few people that this is very ambitious, there are a few people in our department doing that for their PHD.


    So my plan now is to get a model of the propeller and modify it from there. I think for now I will leave the design of the propeller blades as they are and just modify the hub.
    Thanks for the links, I'll give them a read when I get a chance.
    Once you get the propeller measured what will be your guideline parameters to mod the hub? What is your plan to perform the mods and test to determine the affects of the mod? Will the testing be done in the lab or on a boat in a lake? What will you be measuring to determine the affect of the mod? Have you defined the variables and how you will control them? There are many for the prop + the power source used + the water? I have done lab and field testing and control of variables and what will be measured are key to get reliable results that relate to the mod being done. Do you plan on any statistical analysis of the measured data to determine the reliability (consistency to reproduce results) and significance of the mod results?
    " Three may keep a secret if two of them are dead" Ben Franklin
    " ------- well Doctor what have we got a Republic or Monarchy? A Republic he replies if you can keep it"
    Benjamin Franklin, 1787 Constitutional Convention, as recorded by signer James McHenry's in his diary at the Library of Congress

    Location: SW Orlando, Fl

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    Team Member Roflhat's Avatar
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    It's not going to be that complex, we don't have too much time for this project. If I want to go into further detail then it will be in the future and in my own time. All I want to do for this project is change the hub so I can use a removable hub kit, and change the shape of the bits which connect the inner hub to the outer hub, so they are effectively a continuation of the blade (as if you took an over-hub cleaver and changed it to through-hub). This should allow me to modify the same design in the future to create an over-hub propeller from the same model.
    I do want to learn more about propellers, but for this project I've been told to keep it relatively simple. I don't have enough experience to be able to modify the design of the propeller itself, so I'm trying to keep it realistic.

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