Trailerable Multihulls

Discussion in 'Multihulls' started by JCD, Mar 4, 2008.

  1. JCD
    Joined: Jul 2006
    Posts: 359
    Likes: 3, Points: 0, Legacy Rep: 36
    Location: Coney

    JCD Follow the Bubbles!

    Hello to one and all,

    Olifin spun polypropylene is the strongest and most versatile of all the synthetic yarns and has a very high impact strength. The 4oz weave will provide bulk equivalent to 7.5oz and wets out readily. Dynel will be the outermost layer in all scantlings.


    I have looked into Dynel quite a bit, although I never used it. It is my understanding that it has excellent adhesion with poly or epoxy. Durability is also excellent. It is extremely durable and as a layer over glass it will reduce fracture crazing to the gel coat. It is very slippery so it reduces friction quite well. It also has a low weight to high tensile strength and can absorb loads up to 8x greater than glass whether working or impact. In fact, it will have reduced properties when used alone opposed to as an overlay therefore it contributes to the strength of glass underlay. It is easy to use, no fibers to cause irritation and resin to glass ratios are normal.


    This sounds like a great idea. Never did it so I wouldn’t know, but wouldn’t micro-balloons be a better solution for weight and ease of fairing?


    I guess that anyone would have a lot more sensibility about this than I. I don’t think that I can really point out a right/wrong or good/bad way for this to happen. I suppose bi and tri axial is always a choice, but I was trying to settle for the best property for the least cost. Two layers over 1 layer is always stronger if the weave is aligned to the loads so it is always worth it.


    Agreed. But with proper resin/hardner ratios, there will be enough time to lay up all layers wet instead of waiting for a cure. It will take more prep time before the layup but the design is small enough so that it can be done.


    These construction issues are tough for me to solve because there are as many varied ways to do it as there are construction materials. Secondary bonding is not an option for the many reasons already pointed out. It is hoped that the extra prep time to get all layers laid up in one shot will exceed the labor that will be required with sanding and fairing the entire area to be readied for the next layer.

    One layer is going to mean lots more print through and filling and fairing, as opposed to larger weaves and heavier glass closer to the core with smaller weaves and lighter glass outside. I suppose that the same required strength could be obtained with a suitable single layer, but I also think that the final labor and weight difference could be large due to all the fairing and filler.


    Really? Okay. I will look at it again. Durakore density is not very high but I thought that all the traverse bulkheads from furniture etc., would reduce spans quite enough to provide solid waterline areas from a 5/8” core.


    Initially, I wanted to lay down 8 or so layers of copper-poxy on the water areas for superior anti-fouling properties to the design and then I thought, hey, the skipper can choose the option if he is in the water for significant periods instead of dry sailing. The graphite is the way to go for this design to keep her bottom easily serviced and allow her to be as slick as possible while on her bottom to further reduce drag associated from an already heavier design.


    That’s funny.:D That's like saying he will never lose because he will never start.:D


    I have questions that I hope some of the more learned and qualified heavies around here may be able to answer or opine on the rulings made through interpretations.

    This is from German Lloyd:

    “The FEA model must correctly reflect the geometry of the rig as specified in the sail plan.".

    1. Does that mean that all EU governing bodies expect the mast to be designed according to an FEA result, or does it mean that they will just “analyze it” as such but will contribute little if anything by way of suggesting the mast geometry and scantlings? If it is, then which software would be acceptable to them for the study? It appears that they all like to provide ticklers such as safety factors for the mast components but steer clear of defining actual mast design criteria. Why is that?

    2. The RM is to be calculated at 30 degrees. If a cats maximum righting moment is when the windward hull flies, what would be acceptable? ISO wants the calculation to be made at first reef which results in a reduced RM, so which is the reasonable to consider for offshore conditions:

    a. Full RM as the hull clears the water.
    b. Partial RM at 1st reef.
    c. at 30 degrees, which results in a RM 13% smaller than zero heel.

    Thanks again,
    J:cool:
     
  2. Chris D. Brooks
    Joined: Sep 2009
    Posts: 1
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Georgai

    Chris D. Brooks New Member

    Disasemble hull from center in order to trailer!

    finally found a forum on trailering a multi-hull. I’m the newbie here so bare with me. I’ve raced tunnel hulls for several years and love the design. I’ve been looking to build a power cat but want one with enough room to sleep overnight, head, etc. The problem is I don’t want to keep in on the water and I need to trailer it. I’ve been sketching a design where you would disassemble the two hulls from the center living area and have both trailerable. Any ideas yet on this subject since 2008?
     
  3. redreuben
    Joined: Jan 2009
    Posts: 1,634
    Likes: 62, Points: 48, Legacy Rep: 349
    Location: Beaconsfield Western Australia

    redreuben redreuben


  4. blackdaisies
    Joined: Sep 2008
    Posts: 136
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Tennessee

    blackdaisies Senior Member

    I'm looking at this one, not a professional at all about boats, a newbie still shopping, but this one is clearly time proven. It has sail and power capabilities, dismantles, and is trailerable.

    http://www.hartley-boats.com/lively28.html
     
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