High Performance MPX Foil/Self-righting Trimaran-The Test Model

Discussion in 'Multihulls' started by Doug Lord, Dec 28, 2010.

  1. Doug Lord
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    Doug Lord Flight Ready

    MXP-SRT Test Model

    Rudder head, gantry and stage 1 of rudder layup. The rudder is made with three solid carbon rods down the center of the balsa shape. To be carbonated with more uni and woven after shaping.
    Rudder is mounted to a carbon retainer which in turn is mounted to the carbon gantry tube. The angle of incidence of the rudder can be adjusted by pivoting the retainer. Rudder has an 18.75% lead.

    click on drawing for better view:
     

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  2. boradicus
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    boradicus Senior Member

    I always wondered how people shaped styrofoam. Using a hot wire never occurred to me. Did you make a jig for the wire and run the jig along the surface of the mold? Looks great, BTW!
     
  3. Doug Lord
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    Doug Lord Flight Ready

    MPX Test Model

    No, it was cut on a computer controlled hot wire table by Sharon Dixon.
    ---
    Amas shaped-just daggerboard to go, then glassing.
     
  4. Doug Lord
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    Doug Lord Flight Ready

    All styro molds shaped and ready for glassing. When the styro was cut it was done by hot wire and that causes a bit of a problem when sanding: the hot wired surface is much harder than normal styro so when you're doing detailed work like this you wind up sanding two different densities of material. No big deal-it just requires greater care. This first piece went quickly-about 45 min. No trouble getting the jig lines exactly right(see the black lines). This is a system-the next stage is glassing with 6 oz cloth, then fairing to the extent required, then partall + PVA, then layup both halves at the same time. After pulling: final fairing and painting white. White is important to me because you can clearly see the foil when sailing. Also red lines corresponding to 10,13 and 17 degrees of heel will be put on the foil so they show up for pictures.

    click-
    Attached Thumbnails
     

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  5. boradicus
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    boradicus Senior Member

    I'm not sure what I said to deserve that - but I get the sense I am no longer wanted here so I won't respond to this thread any more. Nevertheless, good luck with the project - I have really enjoyed watching it come along.

    Blessings to you.
     
  6. Doug Lord
    Joined: May 2009
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    Doug Lord Flight Ready

    MPX Test Model

    ==============
    I humbly apologize for any offense taken! I can't imagine what you took offense to??? I was in a hurry and answered your
    question: " Did you make a jig for the wire and run the jig along the surface of the mold? " as best I could.

    My answer:

    "No, it was cut on a computer controlled hot wire table by Sharon Dixon." (She runs "Rockledge Architectural" and has done all my styro stuff since day one.)
     
  7. oldsailor7
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    oldsailor7 Senior Member

    Borad . I don't think you should take offence.
    I think you started off from the wrong end by approaching with mathematical/theoretical stuff first.
    If you had started with basic research, like reviewing BOA vs LOA, L/B ratios,
    SA/Displacement ratios, Drag reduction,(both hydrodynamic and aerodynamic),
    hull sections, Dagger and Rudder areas, plan forms and foil sections, sail areas and different sail/rig configurations, amongst other things----- you would not have got your knickers in a Knot. :D Please just lighten up and continue. :cool:
     
  8. tomas
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    tomas Senior Member

    Doug, he also distorted one of my posts as an insult as well.
    Neither you nor I have any interest in insulting people whom we do not know.
     
  9. Ad Hoc
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    Ad Hoc Naval Architect

    I'm curious boradicus,

    What is it you think Doug has said to upset you?....I simply cannot fathom what is argumentative or critical or anything at all in Doug's post. It was a simple statement of fact. In that someone is using a computer controlled hot wire....what is inflammatory about this?...please explain. :confused::confused:

    Your reaction is somewhat disingenuous to Doug's simple reply to your quiry.
     
  10. Richard Woods
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    Richard Woods Woods Designs

    fairly obvious I would have thought!!:D

    Richard Woods
     
  11. Doug Lord
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    Doug Lord Flight Ready

    MPX / SRT Test Model

    Lets let it go, guys.
    ---------------------------
    Tonight I glassed the styro molds for the foils. Had an unanticipated problem with the peel ply: it didn't like the compound curve of the ama foils(curve + section shape). I didn't think it would act that way on such a small curve-live and learn. Now all four ama molds will have to be sanded a bit. Depending on what I run into to fair these things satisfactorily, there is a chance to have both ama foils and the daggerboard done tomorrow-just a chance.....

    ama molds and daggerboard one off molds:
     

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  12. P Flados
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    P Flados Senior Member

    Agreed. I encourage our new poster to return.

    As far as "not insulting", I could only but dream if that was a more universal approach to posting at BDN & SA.

    A couple of items for Doug and others on foil build details.

    There are those (yes, the SA insulting kind) that have posted negative positions on Doug's method foil mold making.

    I would like to find a better small foil making method that an "average Joe" medium experience woodworker could turn out. I played with hot wire foam cutting and was not happy. I never tried template sanding a profile into foam. You seem to be happy with this technique.

    If Doug gets good results in terms of section accuracy and surface finish control, it is my opinion that he is either a "master" of a specific "art form" type technique or we all just need a better "how to" guide.


    I did a hand setup - linear router carved - wood core for a 4" x 5' NACA 0012 that I built up with carbon and then used bondo and template sanded down to shape to a good section. I ended up with a pretty decent section, but I am not sure of the quality that went into the carbon work. It will probably break on me, but as it was my first carbon build up, of course the failure will be chalked up as a "learning experience".

    I also did some experimentation and worked out a way to use a thin aluminum template to scrape a straight foil section (4" x 3' NACA 0012) into a chunk made from scrap candle wax. This made a what I felt was a very good quality mold for a one-off foil. It was actually more work to generate a good slab of wax than to carve the section, but I learned a lot.

    Also, for a non-symmetric cambered section, I am convinced that the existing choices are really not optimum for home builds. I do not think we really have section designers that place enough emphasis on providing a thicker section (for strength given home build limitations) with minimum loss of performance to allow getting good aspect ratios.

    Also, I am betting that the last 20% or so of the section near the trailing edge will do fine with no surface curvature. Again, this maximizes the probability that a home build will end up with the desired result.

    Sometimes I play around entirely in the world of "pure theory". Sometimes I play around in the world of "just make it practical". It is hard, but I really do see a need for blending these two things together more than is commonly done.
     
  13. Gary Baigent
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    Gary Baigent Senior Member

    Yes, the inflammable bit threw Bora.
    Take it easy cobber, we're all a polite bunch of jokers here, ask Ad Hoc.
     
  14. Doug Lord
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    Doug Lord Flight Ready

    =====================
    Paul, you should know that the two people making derogatory comments on SA include chris ostlind-who has zero model building experience and "BB" whose only experience was when he was a kid-neither have designed and built an RC or full size foiler- much less foils. Their inexperience in design and model building shows in their uninformed comments-but I don't think they care if they are right or not.
    Kampai, a very experienced German rc builder posted pictures of the hand carved and sanded foils done by Andreas on his one off AC 45 model foiler(earlier in this thread and that thread).
    As to my "technique": I've built one off model foils for 50+ years and am fairly good at it. This method is simple(if you have the skills to do the hand shaping), quick and inexpensive.
    I worked with Dr. Sam on his test model for the Skat(he used a platform designed and built by me) and one of the things he pointed out is that the section and T/C ratio for the model foils should be appropriate for those foils, and that the model foils will scale up perfectly if the area on the model is correct. With the full size foils you use the scaled up area with a T/C ratio and section appropriate for those foils. The model foils are substantially thinner than the full size foils-a fact that leads to the center flap design of the main foil on this boat(and on the F3 and a couple of other foilers I've designed and built)
    Having an excellent finish goes w/o saying. By the way, I designed the boat, the foils and built the tooling for the first production RC sailing foiler-the F3- 18 years ago-boat took off in light air and approached 20 knots in actual speed.
    So, it's important to try to get ones information about model foils from the most experienced people you can find , and try not to listen to people who simply don't have a clue.

    Pictures-Dr. Sams test model for the 40' SKAT using my platform(and his foils), the F3 and the center flap type of thin foil.
     

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    Last edited: Jun 16, 2013

  15. warwick
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    warwick Senior Member

    My only comment on this subject. What I think Boradicus just needs to remember, is that we are all busy on our jobs/projects. I have been trying to help off-line.
     
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