suggestions for daggerboard section for 2m class trimaran?

Discussion in 'Multihulls' started by Corley, Aug 25, 2012.

  1. Corley
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    Corley epoxy coated

    I'm building a 2m class model trimaran at home for a bit of fun while I'm not able to spend much time on my other projects. It's a midnight oil design as shown in the following link.

    http://www.cornwallmodelboats.co.uk/acatalog/mar2607.html

    I'm just wondering if anyone else has tried different sections and what they found worked? There are no details on the plan the board measures as protruding 280mm past the main hull bottom has a taper and is about 120mm wide at it's widest point.
     
  2. Eric Sponberg
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    Eric Sponberg Senior Member

    Just about any foil section will work. You can use a NACA 0010 to 0015 section and it will work just fine. At this scale, it really doesn't matter what section you use. Any other section of about 10-15% thickness will do. What is more important is planform shape and area. Follow what is shown on the plan--hopefully there is some kind of detail of the shape on the plan. When the model is done and sailing, you can experiment with different planform shapes and sizes. Reduce area if you think the boat points well enough but is slow. Increase area if you think you need to improve pointing ability.

    Good luck. And thanks for the link to Cornwall Model Boats; I was not aware of them and I have saved the link.

    Eric
     
  3. redreuben
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    redreuben redreuben

    Doug will be here soon ! Although you should have put "foil" in the title ! ;)
     
  4. luckystrike
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    luckystrike Power Kraut

    Hey Corley,

    choose a slim profile with 6 - 8%, not fatter. You can take the Naca 0006 or 0007, but make a small nose only 50% of total thickness. Low resistance has top priority over lift. Make the trailing edge super sharp from a solid glass (or carbon) laminate.

    you can play with the profiles here...

    http://www.mh-aerotools.de/airfoils/javafoil.htm


    If I were you I would build your Hughes 40 as a model.

    Best Regards, Michel
     
  5. luckystrike
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    luckystrike Power Kraut

    yeah ... as soon as he gets out of bed ... the first question will be.... have you considered to fit lifting foils?

    just joking, sorry Doug , Michel
     
  6. Doug Lord
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    Doug Lord Flight Ready

    Corley, when I designed and built the F3 below I used a 9% section on the daggerboards and a 9% section tapering to a 12% section on the lifting foils.
    The boat was 59" LOA by 72" wide and was very, very fast. By the way the F3 was just a two channel boat-foils 100% automatic.
    Check out this RC multihulls thread on SA: http://forums.sailinganarchy.com/index.php?showtopic=82807
    And, oh yeah:
     

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  7. Doug Lord
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    Doug Lord Flight Ready

    Flyer 3-2m tri

    Here is a 2M RC tri I designed and built:

    Pictures: L to R - 1) Sailing in Melbourne,FL., 2) On the dock at FIT in Melbourne, boats 1 & 2. If you click on the photo and look in the upper left hand corner you'll see Dr. Bradfield standing there wearing a white hat. It will give you an idea of how really big these boats were., 3) Bradfield bought #2(white on the dock) and added hydrofoils to it as a test for his 40' SKAT design--
    PS- these boats were designed with a working screecher that set doused and gybed under radio control. Had lots of trouble with the system at this photo shoot and Bradfield didn't want it because he said he could go a lot faster putting the weight into much simpler hydrofoils!
     

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  8. Corley
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    Corley epoxy coated

    Thanks for posting that up Doug. If you find time you should really write up an article on your designs and prototypes it would be an interesting read.

    Heres an article by Andy McCulloch on his mini40 and 2m model multihull designs. I might look at some form of foil assist but will build it in later if I go down that path perhaps a semicircular c foil something like Ian Farrier has designed for the F32sr. I'm actually interested in deploying them with a pushrod on a servo with an arm that would deploy one foil and withdraw the other side. if the servo was centred both boards would sit level with the underside of the float hulls for when the wind is too light for any benefit.
     

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  9. Doug Lord
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    Doug Lord Flight Ready

    You're welcome..... Have you started your boat?
     
  10. Corley
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    Corley epoxy coated

    I cut out the hull sections over the weekend. I've set it up so that I'll build hull halves on a strongback and then turn the sections to build the other half. I have some 1mm balsa sitting around so I might build the hull shell with that to fair the shape then reinforce with carbon fibre. The other alternative is to use the half hull shells as a mold and build a carbon fibre lamination without any core. In such a small size core would be unnecessary weight I'd imagine.
     
  11. Doug Lord
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    Doug Lord Flight Ready

    2M tri

    ------------------
    My hull/decks were built out of a mold spraying in krylon paint(very light) instead of gelcoat and laying up within 30 minutes on the paint with epoxy/carbon. The laminate was 1 layer of double diagonal 5.7oz(per sq. yd.) woven carbon and one layer of 1.5 oz woven kevlar. Very light. I experimented a lot with different paints and ,as is usual, the simplest worked best. I used 1 coat of partall wax in the mold and then poured PVA into the mold. Took a bit to get the technique right but the PVA came out super glossy with no imperfections. The excess went back in the jug. Another reason why this is a good idea is that there is no wax imparted to the finished hull surface.
     
  12. Corley
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    Corley epoxy coated

    Thanks for that information I might take a similar approach (undecided) what is the thinking behind the kevlar? Puncture resistance perhaps?
     
  13. Doug Lord
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    Doug Lord Flight Ready

    -------------
    At the time I couldn't get lighter carbon than 5.7, so I used the 1.5oz.kevlar which wets out to about the same weight as 3oz carbon. A side benefit is a degree of puncture resistance.
     

  14. Corley
    Joined: Oct 2009
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    Corley epoxy coated

    Thanks Eric and Luckystrike I'll keep that in mind re: the sections. I do have details of the daggerboard planform so that issue is covered. Cheers for the info on the kevlar Doug, that makes sense.
     
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