Easter project 2009: Hydrofoil!

Discussion in 'Boat Design' started by lmfoils, Apr 19, 2009.

  1. Frosty

    Frosty Previous Member

    Why did you choose naca 63412 foil?

    and what do you mean by flap 70%
     
  2. lmfoils
    Joined: Apr 2009
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    lmfoils Junior Member

    chengtc

    i) I think you are referring to the flap deflection angle. Angle of attack is generally used for an entire wing and not for a flap. If I remember correctly we could have about +/- 20° of movent, this is electronically limited to about +/-15°. Read the remarks in post number 9. The change in lift is very significant. I suggest you download xfoil and compute some results for an airfoil with various flap angles. You will see that the Cl will vary a lot. Be sure to have basic knowledge of fluid dynamics, understand the results and what lies behind. Plan to invest quite a bit of time for this.
    Our mechanism will only work for small relatively low speed boats. For a 8m boat have a look at linear actuators of various types.

    ii) Indeed it is the servo. For servo waterproofing http://www.societyofrobots.com/actuators_waterproof_servo.shtml

    ii) Google Axon microcontroller, we got ours directly from the manufacturer. Do you have a 1000 CAN budget to build foils for the 8m craft?! If so forget everything about using T foils, go with a set of V foils, with no moving parts like our first set, and plan on investing some of your own money.


    Frosty
    We chose a Naca 63412 because it provided good response to flap deflections and a few other factors.
    Flap at 70% simply means that the flap hinge line is at 70% of the chord
     
  3. Frosty

    Frosty Previous Member

    Naca 63412 is a good foil for a rudder as it the same both sides,--asymmetrical.

    I would have thought that a better foil for your application would be one with a flatter bottom to it, this would be less drag.

    As someone said, it would be interesting if you put a simple weighing scale in the towing line to read how much Hp it absorbed.
     
  4. Doug Lord
    Joined: May 2009
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    Doug Lord Flight Ready

    63412 section

    The 63412 section is an excellent asymetrical hydrofoil section with real good stall characteristics. It was used on the original Fastacraft Moth and I've used it on my boat. Here it is compared to a Bladerider section designed by Andrew McDougal-from the technologica blog and a picture of the Fastacraft 63412 carbon section:
     

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  5. chengtc
    Joined: Oct 2009
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    chengtc New Member

    Re: post #17 by Imfoils

    On the cost of your build, how much did you guys end up spending? (you mind sharing the BOM if you have one)? Teh 1000 dollars CAN mentioend was just a budget presented to us by our prof for the scaled model version of our design for the 8m boat. So my question to the steelrod flap control is whether it might also work for a real size leisure type boat.

    2nd question is, is there an advantage of V foil vs T-foil? I notice your design was in this \___/ shape. You have flap on each of the 3 sectional edges, and is so, are the movements of the flaps programmed to be controlled independently or together?

    Thanks again for all your input,
    Chris
     
  6. lmfoils
    Joined: Apr 2009
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    lmfoils Junior Member

    Since we do a lot of composite work, the various machines are at our free disposal and we have a lot of material lying around I really do not know how much the two projects cost us. Working with 1000 CAN will be difficult though.
    If done right it could work. Calculate the maximum load, add a safety factor, build one full scale flap control and do some tests if in doubt.

    Please do some general reading about hydrofoils so you can appreciate the advantages and disadvantages of various foil configurations. As specified earlier and in the original report our V foils had no moving parts, thus no flaps. Please take your time to read and understand the reports completely.

    I am happy to help but since this is your project there is no point if we walk you through every single step of the design process. Almost all the information you need can be found free on the internet.
    However if you have specific questions about aspects of our projects and you can not find the answer in earlier posts please feel free to ask!
     
  7. rickypigazzini
    Joined: Mar 2009
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    rickypigazzini New Member

    Wing sections

    Frosty: It seems that you must have a look at the basics of foil definition and theory, type "airfoil" on wikipedia or google it, for a basic introduction you will find enough material.

    "Naca 63412 is a good foil for a rudder as it the same both sides,--asymmetrical."
    1: Naca 63412 is an asymmetrical foil, so it will have a finite (positive)CL even at zero degrees of AOA, and its aerodynamical properties will be also asymmetrical trough a symmetrical range of AOA (example +20 --> -20 degrees).
    When you are designing a rudder, you MUST have symmetrical properties (same CL at -X deg and +X), and so a symmetrical foil, first of all because when you want to go straight you want the rudder to be in the middle (AOA=0) and have CL=0, (the only chance to satisfy this conditions is that the foil is symmetrical, you can prove it with potential flow theory).
    2: A good foil for a rudder can be the NACA 0012 or, a NACA symmetrical 6-digit series allows you to have a lower CD between a small range of AOA (drag bucket) but stall at lower AOA than the 00XX series. So if you want to design a rudder I recommend these 2 series of airfoils.

    "I would have thought that a better foil for your application would be one with a flatter bottom to it, this would be less drag."
    Early experimental hydrofoils (see Icarus) were built using sections like you wrote, known as Ogival sections, "modern" sections like NACA sections are an evolution of basic airfoils, allowing a better pressure distribution and recovery, so a Naca section will have better CL and a correspondent lower CD than Ogival sections or flat bottomed ones. (for a in depth theory of this i recommend you "theory of wing sections" by Abbott).
    The only pro of ogival sections is the ease of construction, but that is not a problem when you have a cnc hot wire cutter, so we decided to go with a better performance NACA sections.

    "As someone said, it would be interesting if you put a simple weighing scale in the towing line to read how much Hp it absorbed."
    See: http://www.youtube.com/watch?v=r_U09Eo02bw
    We measured the drag force with a Newton gauge, an estimation of the power absorbed by the vessel can be made only if you measure also the speed since Power is Force x Speed (P=dW/dt , dW= F*dx --> P=F*dx/dt=F*V).
    In terms of foil design it is interesting to measure the drag/lift of a foil, so you can compare with the calculated results. Power becomes interesting (and essential) when you have to design a hydrofoil with self-propulsion and you want a minimum cruise speed and take off speed, so you can have an idea of the necessary power the installed motor must have (you also have to take the efficiency of the propulsion system into account).
    This winter we will have a complete telemetry for our hydrofoil, stay tuned!

    I hope this will be helpful for you and for any other question on this thread.
     
  8. lmfoils
    Joined: Apr 2009
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    lmfoils Junior Member

    We are back again! This winter we bought and partially rebuilt a Yamaha 15A two stroke 15hp outboard.
    Easter came and the idea was to build a hull for our power plant. The hull had to satisfy the following conditions: simple and quick construction, maximise flying height on foils, enough volume to sustain two people and lowest possible weight.
    Many construction techniques and hull types were evaluated. After lots of discussion we decided to build an internal structure made of wood, glue blocks of foam around it and cover the whole hull in glass fiber. First the shape of the hull was modelled in CAD in order to have all dimensions of the internal structure. The idea of this structure is to absorb all loads from foils, motor and crew. A quick Ansys FEM simulation confirmed that it should be up to the job. The hull is 3m in length, maximum beam is 1m and at stern it is 150mm high.

    First the wood parts of the internal structure were glued together and reinforced with glass fiber, then the foam was inserted into the structure, cut to shape with a hot wire cutter and finally the whole hull was covered in skin of glass fiber. Finished weight is 21kg.

    The moment of the test came and yes, it floats! Flat out with a crew of two we reached 17.0 knots.

    Before summer some minor finishing work will be performed on the hull and the 15A will receive a new fuel filter assembly and a kill switch with bracelet. A prop with higher pitch could be an option.
    We plan to have a take off speed of 10 knots and break the 20 knot barrier.

    For a complete report please visit our new website www.hydrofoils.ch
     

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  9. u4ea32
    Joined: Nov 2005
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    u4ea32 Senior Member

    Looks fun!
     
  10. rickypigazzini
    Joined: Mar 2009
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    rickypigazzini New Member

    Easter Project 2010 Footage

    Here is some video footage of our Easter Project 2010:
     
  11. mihkel
    Joined: Aug 2010
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    mihkel Junior Member

    Where are the foils? :)
     
  12. lmfoils
    Joined: Apr 2009
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    lmfoils Junior Member

    Here they are!

    As announced at Easter this summer we built the foils for the hull!

    See the complete report at www.hydrofoils.ch

     

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  13. lmfoils
    Joined: Apr 2009
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    lmfoils Junior Member

    As Christmas came we started the core part of the Winter Project 2010.

    The aim of the project was to test a feedback control system for the T foils we built in summer 2009. As sensors we used four wands attached to potentiometers. Both manned and unmanned flights were successfully attempted.
    The complete report can be found here: http://www.hydrofoils.ch/index.php?...r-project-2010&catid=2:projects-2010&Itemid=8

    Video coming soon!
     

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  14. lmfoils
    Joined: Apr 2009
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    lmfoils Junior Member

    Here is the video!

    Notice the good roll stability given the noisy input of the wands.

     

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

    Doug Lord Flight Ready

    ================
    Two independent flaps for each foil,right? Very interesting video, thanks! Whats the next step?
     
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