Hydrofoil boat design.

Discussion in 'Hydrodynamics and Aerodynamics' started by lassjus, Jan 21, 2013.

  1. lassjus
    Joined: Jan 2013
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    lassjus Junior Member

    Hi. I do not have much experience when it comes to hydrofoils and boats, but I am going to build one with a friend of mine.

    I am wondering, I have seen the sport foil tutorial. It uses V-shaped foils. I guess this is self regulating foils, since they will create lift until it is so much over the water that the lift equals the weight....?

    http://gpnp.net/backshelves.gpnp.net/projects/TheSportfoilPlans.pdf

    But With these kind of foils you use a lot of energy to push outwards as well, right? So a T-foil would be more efficient? But will a T foil create lift until it actually goes up in the surface? How do you calculate how large foils you will need? And what are the advantages and disadvantages with the different foils?
     
  2. lassjus
    Joined: Jan 2013
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    Location: Oslo

    lassjus Junior Member

  3. Number4

    Number4 Previous Member

    Hi lassjus,
    Did you catch this thread?
    http://www.boatdesign.net/forums/hy...ler-design-foil-assist-full-flying-40894.html
    Also if you use the search, you will find lots of good stuff.
    In the multi hull thread there are many foilers there too.
    If you read all posts by Doug Lord, you will learn quite a bit about foils.
    Is this boat going to have control surfaces? Front or Rear?
    Good luck with your boat!
    Keep us updated with its progress.
    Best Wishes,
    Adam
     
  4. lassjus
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    lassjus Junior Member

    Hi. Thanks for your response. I have done some search on this forum, but it is so much information, and hard to find exactly what we need to know :)

    We dont have too much time to spare, so we want to make it as simple as possible, so no adjustable foils, just static ones. Thats actually my main question, will we be able to make a stable hydrofoil boat with static T shaped hydrofoils, or do we need to make them V shaped?

    Thanks for the good wishes!
     
  5. Number4

    Number4 Previous Member

    Hi lassjus,
    I am no expert on foils at all, but they interest me very much.
    The lift from an aerofoil or a hydrofoil is proportional to the square of the speed.
    So a flat foil will keep making more and more lift the faster you go.
    The advantage of an angled foil, is that the faster you go, more of it will come out of the water, so the surface area underwater is decreasing.
    I think this is why many fixed foil designs use angled foils.
    T foils obviously work, as we can see in your video.
    I hope an expert will turn up soon and correct me.
    How fast are you planning to go?
    What will be the dimensions and weights? How much power?
    Cheers,
    Adam
     
  6. lassjus
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    lassjus Junior Member

    We are going to make a one man boat, as light at possible. And use a 4HP motor. That was quite informative. But that means that if we have some way of varying the angle of the foil, we would be able to find the right angle, and then mount it permanent in that angle... But as he writes in the video he needs to add adjustable flaps so he is able to bank in turns. I guess this is quite important to have a pleasant ride? Could this be done by adding flexible plastic flaps that you can bend up or down with wires? Just an idea. As I said, we want to keep it simple so we will actually make this. :)
     
  7. Doug Lord
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    Location: Cocoa, Florida

    Doug Lord Flight Ready

    ---------------------
    Lassjus, welcome to the forum! If you go to the second post of the sailing foiler thread you'll find the information on Ray Vellingas book "Hydrofoils-Design, Build, Fly"-I strongly urge you to order that book. It addresses every question you have. The book is about power foilers with a little on sailing foilers. It's written for the one off builder in understandable language.
    Good Luck!
     
  8. Number4

    Number4 Previous Member

    Hi lassjus,
    If you look at the first page of the thread I linked to earlier, you will see the lift formula, and a few posts by Ray Vellinga. User name RVELL
    Ray has written a book about hydrofoils, and it is not too complicated to make a self levelling foil. ( I see Doug beat me to it!)
    http://www.youtube.com/watch?v=Va1bM3hE9yc
    The plastic flaps bending with wires you have invented are called ailerons. This is how aircraft bank. Planes and hydrofoils have much in common.
    I suppose that a boat with fixed angled foils, when it starts to bank, that the lift increases on that side and that it will try to right itself.
    Looking at the gallery here http://www.foils.org/gallery/index.htm it is hard to spot a fixed foil boat without angled foils.
    Cheers,
    Adam
     
  9. Doug Lord
    Joined: May 2009
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    Location: Cocoa, Florida

    Doug Lord Flight Ready

    Power foiler

    There are two major groups of foil types-fully submerged and surface piercing.
    Fully submerged requires an altitude control system and surface piercers do not.
    Get the book and consider it as doing your homework-it will tell you much more than if I wrote all day today. After you have the book and have read it you'll be in a much better position to decide on the foil types, position etc.
     
  10. kvsgkvng
    Joined: Jan 2012
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    Location: *

    kvsgkvng Senior Member

    Hello, I think that the left boat is better than the right boat because it has self-regulating foils. Also, the front foils on the left boat should be inverted not like "A" but as "V" It will add to self-regulating the roll.

    Now, the foils area is something which needs to be adjusted, even as the boat is finished. Weight is the problem. Another thing to watch is distribution of the lifting force. If you have a lot in the aft, and nothing in the bow, then your boat will dive.

    I would use equal foil surfaces or near equal surfaces, lets say 60/40 division. If you make "V" shaped foils long enough, and sticking out of water, the lift will equalize itself automatically.
     

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  11. Doug Lord
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    Doug Lord Flight Ready

    Power Foiler

    Again, the book is critical. There are major disadvantages and advantages to surface piercing and fully submerged foils. Placement of the CG is critical. Behaviour in a turn is important to understand. There are advantages and disadvantages to anhedral and dihedral. Vellinga is an expert at the design of just your kind of boat.
     
  12. Submarine Tom

    Submarine Tom Previous Member

    Lassjus,

    Indeed, welcome to the forum.

    Ray Vellingas book is very helpful but very limited, he is not an engineer.

    It will help you a great deal but it is limiting.

    Study and you will learn.

    YouTube is a great visual resource.

    Balance is critical as Doug L has said.

    Keep us posted on your progress.
     
  13. lassjus
    Joined: Jan 2013
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    Location: Oslo

    lassjus Junior Member

    Thank you all for the responses. A lot of good information. I have seen the book, I might buy it to deepen my understanding. How hard is it to create an altitude control system? Is this done with mechanics or only electronically?
    Could it be a good idea to attach the aileron to the steering wheel, so it will be controlled together with the motor, or is this a bad idea? I am just throwing out ideas here, some of them might be less good than others. :)

    I will take a closer look at the book, and see if I can get a copy of it, perferably digital, so I don´t have to wait for it to arrive :)
     
  14. Number4

    Number4 Previous Member

    Hi lassjus,
    Did you watch the video of Rays?
    That "thing" on front of his boat, that is it. Just a float on an arm with a hinge linked to the foil.
    I wonder about the synchronisation. Aircraft have wings, rudders, ailerons and elevators.
    How is your foil theory? You asked about foil size before.
    You need to grasp the relationship of foil shape, area, angle of attack, and speed.
    http://www.grc.nasa.gov/WWW/K-12/airplane/short.html
    https://en.wikipedia.org/wiki/Airfoil

    Cheers,
    Adam
     

  15. Doug Lord
    Joined: May 2009
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    Location: Cocoa, Florida

    Doug Lord Flight Ready

    Power Foiler

    ==========================
    I'm leery of giving you any advice at all because to the extent I know anything about hydrofoils it's about sailing foilers-and there are big differences-point of application of power being a major one. Some of the coolest power foilers I've seen were done by Kotaro Horiuchi and he always used a fully submerged foil system. One of his designs was briefly looked at by Yamaha and was really neat-with just two foils and waterjet power. You could probably google "Yamaha hydrofoil" and see a picture and video of it. You should definitely get the book-it will answer most of your questions and is indispensable for someone wanting to build a small power hydrofoil.
     
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