Malibu Outrigger

Discussion in 'Multihulls' started by BobBill, Dec 16, 2011.

  1. upchurchmr
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    upchurchmr Senior Member

    BobBill,

    I had an old wooden Tornado with 4mm occume (0.160") for a deck, but it had small stringers supporting, we walked on it with no problem if you are looking for lighter weight. You should be able to search for the plans to see what was done - free.

    Akas are much lighter and stiffer if they are hollow, they do have to be taller to get the stiffness. If you wanted one place to use higher tech this would be it. Either unidirectional glass or carbon on top and bottom. Anywhere you expect to put a bolt you should fill the hollow area with wood so it will not crush.

    Have you seen the Gougeon's book on boat building? It is available as a free download. Corley provided the location in another thread. http://www.westsystem.com/ss/assets/...k 061205.pdf This is the best modern reference I know. It might be applicable to the Malibu build.

    Good luck, looking forward to the build pictures.

    Marc
     
  2. BobBill
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    BobBill Senior Member

    Marc, Thanks. Was thinking about that...the aka advice is great...gave me couple of ideas too.

    Planning the ama to be surfboard-like construction, foam under glass, for lightness when trailed...as Dierking noted, can always make heavier...want to keep boat weight 350 (class min) to 400.

    Idea about making it higher just rang a bell regarding connection and being able to fold the iokas/akas.

    I have now learned the boat does kick up some splash, so working out that problem. Do not want to widen deck as plans note...not at this point, anyway.

    That and wish to have more open cockpit area need some thought, but I have some ideas, just do not want to dive in and later wish otherwise.

    I have the "brother's" book and some links, which may have been disabled, and most of the material from West I have normally incorporated in past projects. A lot of it is common sense and the carbon build material and epoxy information is super.

    To be candid, yourself, Tom Speer, Par, Clark, Alan W, CutOnce, Lord and some others I cannot recall now, and others describing their builds, have provided better and more practical advice, along with EpoxyMoron, Vegas and Gouvernail and some other kind and knowledgeable people on SA.

    I gather and apply as needed. Invaluable.

    Will keep the project posted here.
     
  3. upchurchmr
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    upchurchmr Senior Member

    BobBill,

    You are well beyond any typical advise I would have.
    I would be concerned with the idea that glass on "solid" foam (surfboard style) is automatically lighter than thin plywood. Foam sounds light but filling the entire cavity mounts up quickly. In a different arena, I have tried to do the same in secondary structure on aircraft, I always get the solid foam part ending up heavier - this may not be useful since it is significantly different types of structure . Just a concern.

    I built a relatively short aka for a 5' wide catamaran row boat. It was surprising that a hollow 2" square member was enough to hold my wife and I standing on it (375#) without any glass. The upper and lower caps were 1/4" cedar and the sides (shear webs) were 1/8" Baltic birch plywood - 3 ply non marine. The plywood was cut on a 45 degree angle to the panel, the overlap of the ply to cedar was ~1/8" with an epoxy joint - no real fillets. I was completely shocked to find it didn't break and had very little deflection. After glassing with 6 OZ cloth and West I expect the strength was doubled.

    This is not to suggest that design for your akas, since you will have much higher loads, just to show that the hollow design can be really good.

    I had replaced some 8# per aka (hollow) members with the 2# hollow ones. The original were just built by "eye" and not tested - obviously heavily over strength.

    This is probably more discussion you don't need, take it for what it's worth. (Free ????)

    I saw a newer Hobie 18 which has a very small feature for deflecting spray in the fwd hull surface. No idea how well it works.

    Good luck.

    Marc
     
  4. BobBill
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    BobBill Senior Member

    Marc. Much appreciated. Feel free to toss all you want at me, I am wide open for suggestions and advice.

    The ama I had in mind would be close to 11' MO original, save the idea of wave piercing bow and the surfboard like composition, might be a bit longer...foam shaped then glassed with epoxy and painted etc.

    Would be a bit more trouble than wood, but the ease of set up and travel with light ama seems worth it...at least at this point.
     
  5. Corley
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    Corley epoxy coated

    Marc's providing a very salient point here on a small boat, ply can often be the better solution. Foam Sandwich is great when you have large areas on a large boat where you would otherwise need many stringers inside the skin to support the loads. It's also great on decks where you can have large unsupported areas with minimal reinforcement.
     
  6. BobBill
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    BobBill Senior Member

    Malibu Outrigger Ama Material

    To be honest, the idea came from Dierking's book on building his Ulua and Wa apa outriggers...the foam glass idea.

    Dierking uses or used foam with a ply center line or vertical lengthwise stringer, which seemed, to me, quite a good idea, even if these designs are significantly lighter.

    I can go either way, but lighter is better for what I have in mind...and, as noted by Marc, such an ama would have to have more depth (height), it seems.

    But, I know squat, so have at it.
     
  7. upchurchmr
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    upchurchmr Senior Member

    BobBill,

    I might have mispoke. I was trying to suggest a hollow Aka (crossarm) would have to be taller in section than a solid one, to get equal strength. The hollow one would be significantly stiffer for equal bending strength.

    My understanding of the ama is that you should set the displacement you want first (100% or greater if you want to fly the vaka). The stretch out the length to make it thin so it will have less wave drag. Personally I always thought and 11' ama on a 18' vaka was too short. While I know many designers make tall thin amas, I always thought you would have less drag from a more semicircular type hull, but a more jerky ride.

    Marc
     
  8. BobBill
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    BobBill Senior Member

    Marc, I see your point. Jerky being hobby horsing...I am limited to 17 by rule with 19 foot hull, and planned to do the aka be removable and attach via hinge-pins (like dual pin door hinge) metal locks about three feet to four feet from ama.

    The akas would be about 2 feet above water. Had not thought about the wave drag...they have to be flat as well. So, I could form ama with high deck/attachments or add tall brackets per plans. I figured the former, somehow, using Dierking's ideas about the shaped foam/glass piers or plain high deck ama, which seems the better choice.
     
  9. BobBill
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    BobBill Senior Member


    Marc, I have been mulling all of the above over and other stuff, and now leaning your way with ply idea over foam...for lighter and more practical ama, plus hollow akas, but now moved to slightly wider hull bottom and higher freeboard on main hull, and now wondering how to determine the CLP when two hulls present.


    Great advice...thanks.

    Slowly coming around. I am very deliberate...
     
  10. PeteCress
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    PeteCress Junior Member

    Bump...

    I would offer up the following from my experience building/sailing a Malibu Outrigger in Hawaii a looooong time ago.

    • Perfect beach boat? Original Hobie 16
      .
    • Perfect surf boat? Original Hobie 14.
      .
    • Ultimate chick magnet: Malibu Outrigger
      .
    • I wouldn't mess with the freeboard. A lot of builders, however, added bow planes to deflect spray.
      .
    • If you are going to moor it, don't forget to glass the inside of the daggerboard trunk or teredo worms will get in.
      .
    • Be serious about weight. I was not and wound up with something of a turkey. Wasn't a big deal for me bc I moored it, but I would not have wanted to haul it up and down a beach.
      .
    • For efficiency, consider an existing rudder/rudder assembly from a beach cat. The wood/alu is OK, but I managed to fold mine a couple of times. OTOH, folding is recoverable - at least until the alu breaks.... breaking is not.
      .
    • Consider water depth if you're going to sail with a dag. The one thing I wished for over-and-over with the Mailbu Outrigger was a form of lateral resistance that would fold on impact.
      .
    • Don't obsess about upwind ability. I sailed mine during the Hobie 14 world's off Waikiki and I was staying with the pack upwind. Don't recall downwind, but my bet is that with enough wind, I'd have smoked them.
      .
    • Consider floatation. This is a beeeeeg deal because if that hatch comes loose and you swamp it you need enough freeboard to be able to bail faster than the chop washes in. You can also ship water around the stubby. There are all sorts of inflatable bags available. I'd have one in front of the stubby, one from the stubby to the dag trunk, and another in the stern - leaving enough space for an anchor and a few other things but not a lot of space. Monster pool noodles (the ones that are about 8" in diameter) might work too - and be more fault-tolerant if they don't suck water long-term, albeit heavier. Scrap foam... better pick the stuff that does not suck water.
      .
    • If it is not going tb moored, I wouldn't go crazy on the glass. Maybe something on the bottom... but I'd ask around and find out what the absolute minimum is. I knew a guy in Hawaii Kai that had one in his yard and I'm pretty sure it had zero glass... and weighed about 240#.
      .
    • Think seriously about splicing old windsurfer masts for the spars. They are muy light and strong whereas those long spars in wood are pretty heavy. I've done the windsurfer mast thing on my hawaiian-style outrigger canoe and it definately be da bomb.
      .
    • Don't try to get cute with curved iakos or Tahiatian-style off-the-deck iakos. I did and broke the hull/iako connection a couple of times before making it strong enough. Save that for later.
      .
    • Subliminate (is that even a word??) the safety ama idea to the concept of being fully recoverable from turtle. The leverage is no problem. Anybody with a length of line can flip the thing back up. That leaves floatation and water-tightness in the main hull. Don't put your money on it being water-tight... just have enough float in there so you can bail it if the hatch comes loose or too much gets in around the mast. Capsizing is part of the fun. Trust me on this one.... Also, the safety ama thing can be done just as easily later on....
     
    Last edited: Jul 4, 2012
  11. PeteCress
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    PeteCress Junior Member

    I'd stick with it to the letter as far as dimensions go. I'm no engineer and maybe this says more about my limited brain power than anything else, but I see a sailing craft as a very complex interaction of vectors - way beyond anything I'm equipped to fool around with.

    Also, stuff happens that no engineer or designer ever thought of - and something "that just works" may incorporate features that nobody would even recognize, much less design in to the craft.

    One of the TED presentations touched on this: "Tim Harford: Trial, error and the God complex" as in http://www.ted.com/talks/lang/en/tim_harford.html .

    He gets specific at around 09:10.
     
  12. BobBill
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    BobBill Senior Member

    Malibu Outrigger Build Opinion/Advice/Comments

    Peter Cress, much much thanks for your advice and consideration.

    I had already decided to to much of what you noted.

    Already have surfer carbon for spars...to use with bottom Force 5 section, but may go with fractional sloop rig, unstayed, with jib...

    Open hull amidships will be complemented with transom bailer...big one.

    Already have rudder head and kick-up blade, and now thinking about a Doug Lord idea of using slanted board...do no intend to surf or beach launch regularly, if ever...not much surf in Great Lakes, still, freeboard will likely be higher.

    Glass will be must as intended to use lighter ply, but getting wood here is a problem which now has become a big problem.

    In that regard, I may acquire a cast off Windmill hull, very narrow, and use that with outrigger, hoping not to offend many.

    Seems an excellent alternative to the lumber problem and less labor and cost intensive.

    Best of both worlds, can beer-haul-cruise and fly. Am some years beyond the chicksa hunting, but I do ogle some still :]

    Flotation - pool noodles, of course. Functional, low cost, unless I buy the above glass hull. Will decide this week.

    I will let you know, as it goes along. Am adding carbon to the surfer spars this week to stiffen...and will test next week on my wee Kite dinghy.

    Thanks again for very thoughtful and knowledgeable reply.
     
  13. PeteCress
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    PeteCress Junior Member

  14. BobBill
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    BobBill Senior Member

    Very nice. I take it the amas are former 18 hulls...and the akas are humongous.

    I think the Windmill hull would offer more comfort for a couple of adults and kids, however.

    Looks to be very viable project, with or without lifting foils...very many possibilities with foam ama and 12 foot beam (trampoline/planks), indeed, and grossly easier than constructing main hull.
     

  15. upchurchmr
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    upchurchmr Senior Member

    BobBill,

    Don't even think about a windmill hull. you will be trading a 1' wide ama for a 4+' wide windmill. not only will it be slow and heavy it will get you laughed off the lake. No one will ever let you call it a Malibu Outrigger.
     
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