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

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

  1. daiquiri
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    daiquiri Engineering and Design

    Doug, I would be curious to see how did you manage to guarantee the exact shape of the airfoils was reproduced on such a small scale. Did you have a hot wire bent and shaped to match the airfoil templates visible in your post #427?

    The point is - you are certainly aware of the fact that foils are very sensitive to small changes to the chordwise distribution of thickness and camber. It is already painful to have it right on full scale, I can only imagine what it becomes at RC-model scales... :eek:

    If one cannot exactly reproduce (due to small scale and manufacturing method) the theoretical shape he desires, it might be less time consuming to use some simpler sections, perhaps optimized for manufacturing and not for hydrodynamic behavior?

    Cheers
     
  2. oldsailor7
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    oldsailor7 Senior Member

    In an earlier life I used to make F/Glass items by coating a shaped piece of styrofoam in Glasscloth and Epoxy. When cured I would then dissolve the foam away with petrol (Gasoline), leaving the F/Glass product.
     
  3. daiquiri
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    daiquiri Engineering and Design

    Neat. That technique could allow for a more precise control of the final shape, imo. However, it might be somewhat difficult to implement to model scales, because of the fragility of styrofoam. The male styro mold would be very thin and fragile.
    Don't know, Doug certainly has sufficient experience in RC model construction to overcome these difficulties. :)
     
  4. Doug Lord
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    Doug Lord Flight Ready

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    Slavi, no hotwire for section shaping-just two hands and the jigs(patterns). It's not a problem to achieve what I need to. The only problem so far has been the peel ply not working with the shape(darts would not work). But that only adds a bit of sanding and fairing-no big deal.
    So far, so good.
     
    Last edited: Jun 13, 2013
  5. Doug Lord
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    Doug Lord Flight Ready

    MPX Test Model

    The daggerboard ,where the peel ply worked perfectly, came out virtually ready to lay up. The ama foils -without the peelply- have the cloth weave showing thru. In the old days I would just fill and sand, but this time I'm going to try something I've never tried before. I'm going to use .03125"(32nd inch) sheet wax with an adhesive backing-if the first test works ok. Otherwise, I'll do it the way I've always done it.
    This system will produce foils that are virtual mirror images of each other with an excellent surface finish. They will be better overall quality than the production F3 foils that worked so well 18 years ago.(speed range 4.75 knots to almost 20 knots) Even if there were minor differences in the sections side to side, as long as the area and T/C ratio is the same, I wouldn't be concerned with it in the least. But my goal is to make them identical.
    The angle of incidence of each ama foil is adjustable as is the cant angle to a small degree. Initially, the foils will be at the max down position but later on I'll experiment with retracting them a bit which changes the foil configuration a lot for a small amount of retraction.
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    Pictures-note bucket seats-won't be used on test model but they are close to what the seating(for two max) will be on the full size 18' version.
     

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    Last edited: Jun 13, 2013
  6. Doug Lord
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    Doug Lord Flight Ready

    MPX /SRT Test Model

    Have most of the carbon cut for the foils. Expecting delivery momentarily from McMaster-Carr of the 32nd inch sheet wax. This stuff will be tested to see if it works as I hope it will-if it doesn't I'll have some sheet wax left over!
    ---
    Having a peculiar problem with the hydro-turf(the white material on the model): it's lifting around the edges a little bit. Quite annoying-used this stuff on my 16' foiler and it worked well out in the weather for about three years.
    I used a brand new can of 3M 77 contact cement so I have no clue what the problem is.
    The solution: I bought a small bottle of Weldwood contact cement and a small package of syringes(arriving with the wax) and I'll use the the syringe to apply a small amount right at the edge in the few places that are lifting. Hopefully, that will take care of the problem.
    ------
    Foil layup starting tomorrow( I think)-should go relatively quickly.
     
  7. Doug Lord
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    Doug Lord Flight Ready

    MPX Test Model-A,B C's(and L's) of AC foils

    This was posted in "Curved Foils" on SA and Evan posted it here in the AC thread. It is the best discussion I've read so far on the various foil configurations being used in the AC. http://carbonicboats.blogspot.de/
    I'm not sure I agree 100% with Dario's conclusions but I'm thinking a lot about it. One thing that seems to be missing is that a curved foil can have it's
    vertical lift adjusted independently of it's lateral resistance by raking the board top fore and aft. He does mention raking the board but doesn't seem to mention the unique characteristic of a curved foil-independent adjustment of the two primary forces created by the board. But I've got to reread his stuff several more times to make sure I understand what he is saying.
    It is very good stuff arising out of an AC that is already trickling down to the people!
     
  8. Doug Lord
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    Doug Lord Flight Ready

    MPX Test Model

    Sails! Well, Scott, my long term sailmaker sent me a list of the alternatives since his cutting software does not work with Sandy Goodall's design software-as I reported here earlier. I asked Scott to try the solutions that Sandy proposed, but the bottom line is I said I would pay half Goodalls design fee to redo the sail in the old software so Scott could cut it. I am not happy but this is my only alternative. I told Scott that the sails MUST be ready by July 13th-no later.
    This is very unfortunate and could have been resolved a couple of months ago-but wasn't. Too bad.
    ===============
    UPDATE: 5pm Thursday- Since the sail will probably have to be redesigned anyway, I've committed to add 8.5" along the foot=248.6sq.in.(1.73 sq.ft). This takes total SA from 3182sq.in.(22.1sq.ft.) to 3430.6 sq.in.(23.8 sq. ft.) which brings the scale SA up to the full size SA. Since the rig is reefable, I probably should have done this to start with. So, this will work out ok despite the delay. Also, since Sandy will be using the old software it is not capable of integrating the "peaked up" squaretop shown below. The sail will have a "normal" squaretop but will have some form of masthead buoyancy at some point. The masthead buoyancy may look something like the one on the Flyer 3-the largest RC tri I've built(length wise) below.

    Pictures-1)Sandy Goodall's main design, 2 & 3) Flyer 3 large RC tri with "endplate" masthead buoyancy. To get an idea of size look on the very left side of the last picture towards the top. You'll see a guy in a blue jacket(Dr. Bradfield) standing there: click--
     

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    Last edited: Jun 16, 2013
  9. Doug Lord
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    Doug Lord Flight Ready

    MPX Test Model

    For those just reading the thread for the first time ,here is a brief synopsis of what the model, and the full size boat it represents, is all about:
    -------------------------

    The foil system on this model is being built to a high level of finish with all carbon construction and meticulous attention to detail. But all that pales in comparison to how the system will work and what it could mean for small trimaran design if it works as well as I think it will.
    1) the system allows light air(5-6 knots wind speed) main hull takeoff of a full size trimaran weighing 750lb. Slightly lighter windspeed for mainhull takeoff of the model. This is the most significant thing about the system because it is being used on an oversquare platform that would have to have a 15 knot breeze, at a minimum, if it was to fly the main hull w/o the MPX foil system.
    2) Flying the main hull in light air will represent the single largest improvement in small trimaran performance in my lifetime. The new Bradfield Osprey weighs the same as the full size version of this boat but still requires 7-9 knots of wind for takeoff, but even so, it represents a giant leap forward in trimaran foiler design. The MPX system, however, is not limited to just foilers but will function equally as well (but a bit slower) with "foil assist" amas and or with planing ama's. The foiler versions of the MPX system will significantly reduce drag as compared to other three foil foilers*. The MPX foiler system, generally, unloads the main foils while allowing the ama foil to take the whole load with the riding angle of the ama foil(and sailing angle of the whole boat) controlled by the main foils with very little drag.
    All these combinations will be tested as far as possible on the model.
    3) Again, the main improvement represented by the MPX system is to be able to fly the main hull in very light air while at the same time increasing the degree of pitch control in heavy air with the option of increased RM from the main foil. There is no other trimaran anywhere that uses this unique system with bi-foiler configuration main and rudder foils and a dual wand altitude control system that allows the sailing angle of the boat to be precisely controlled from very low speed to very high speed.
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    *The MPX foiler system has four foils with three of them used at any one time, but as the mainhull flies the mainfoil is unloaded reducing drag considerably until the ama foil becomes the primary load carrying foil-virtually 100% of the load. The "foil assist" version works the same way but with a partially immersed ama or planing ama with about 70% of the load supported by "foil assist". The system allows, for the first time, over square platforms to be used with maximum performance in light AND heavy air. Oversquare platforms w/o the MPX foil system are problematic because of the high windspeed required to fly the main hull and the low pitch resistance of the platform.
     
    Last edited: Jun 17, 2013
  10. Doug Lord
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    Doug Lord Flight Ready

    RC Multihulls / Test models

    Most of the rc multihulls discussion on the Multihulls forum on SA has been hijacked by three individuals with zero experience in RC multihulls so , in addition to my leaving, Kampai(Chris) has left too-at least for now. He gave me this link to a German RC multihulls forum: http://www.rc-network.de/forum/forumdisplay.php/166-Mini-40
    I'm hoping Chris will visit here-he has done very good work and has a lot to offer.
    Look at the "Shinobi" thread by Kampai......
     
  11. daiquiri
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    daiquiri Engineering and Design

    That would be a pitty, Doug. :(
    What is the RC forum which has been hijaked?
     
  12. Doug Lord
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    Doug Lord Flight Ready

    MPX Test Model

    ==========
    It is a shame-almost two pages of personal attacks on me(and now on some others!) and generally uninformed commentary by chris ostlind(banned from here), "BB", and "ZTH".
    Paul Flados just said he was leaving as well. I took it for a while then blew up(June 12th) and left-after removing my posts and pictures of the new boat.
    ------
    Heres the thread: http://forums.sailinganarchy.com/index.php?showtopic=82807&page=5#entry4180023
    ========================================
    MPX Test Model
    ------------
    As reported earlier, a series of problems with the sail design software vs the
    cutter software has resulted in a delay on the main and the requirement that it be redesigned on the old software. Well, it's not a disaster, it's more of an opportunity. I had kept the SA lower than scale but now I'm going ahead and making the sail fully scale. Even the old sail plan would have had to be reefed
    in below 10knots of wind and this will have to be reefed just a bit earlier but it will help with very light air which is where I expect great performance including main hull take off at 4.75 knots of boat speed-probably 5knots wind speed.
    But, this means I have to extend the Forte carbon mast 12" so I contacted
    Clint today to do that. No big deal-.2 oz weight increase! $30-40. So another problem solved with a net performance gain-can't get better than that!
    ----------
    UPDATE-6/18/13-Problem: because of their schedule they won't be able to do the small piece until some time in August but they have a small piece of the spreader section already laid up -Clint will check that and see if it will work and get back to me . Will be heavier, for sure.
     
  13. hoytedow
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    hoytedow Old Woodbutcher

    I went to the German RC forum so I could observe the discussion. See you there. :)
     
  14. Doug Lord
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    Doug Lord Flight Ready

    MPX Test Model

    The adhesive backed .03125(1/32nd)" sheet wax arrived and worked better than I could have imagined. No problem fitting to the exact shape with one piece for the whole mold!
    The pictures show the ama foils and the daggerboard, the rudder is mostly complete. And the mainfoil, flap and rudder lifting foil will be cut from Dragon plate and shaped with a grinder and hand sanding. Also, a shot of the 5.7 oz woven cut double diagonally(45/45) and the uni ready to go.....

    click-
     

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  15. Doug Lord
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    Doug Lord Flight Ready

    MPX Test Model

    Whew! I came right down to doing the lamination and then realized I should probably get Resin Research's slow(low peak exotherm) version of the resin I'm using, the rr2000/rr 2000S. I've been thinking about it a lot . I thought I could do it but just barely(even though it's being done in the airconditioning) and finally realized that wasn't good enough-no point taking a chance with one-off molds. So a bit of a delay in lamination until I get the slow stuff.
    Resin Research is described in detail on page 5, post 69 of this thread.
    ----
    UPDATE-6/19/13: Got the slow resin and I was right: it has a much lower peak exotherm. Will take twice as long to set up which is excellent. But it cost $117-had to buy a gallon ........ Thats the way it goes.
     
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