Trailerable Multihulls

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

  1. Meanz Beanz
    Joined: Jun 2007
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    Meanz Beanz Boom Doom Gloom Boom

    Not much yet, still thinking through raising the mast step & the best way to do it. I have done some basic sketches, concerned about making it too high, I don't want to stuff the looks up too much and would like to achieve a look that fits the boat well. I want to get the boat on the hard to work on so I can play with some cardboard shapes, I am not good with visualizing drawings. Anyway I can't do that where I am, need land space and a trailer.

    I am doing the hardecks in polycore/GRP this winter, I figure I will be able to incorporate them into the pod if they are a success and it will give me some experience with the material. All thoughts and no action for the time being... frustrating but there you have it!

    Be interested to hear what you come up with Jeff.

    I will try and master FreeShip and model it if I can... I will post if the results are worthwhile... might take me sometime starting from scratch with no CAD experience at all!

    Cheers
    Beanz

    PS... Long shot here, anyone got a SW24 modeled in a format that FreeShip can use? Willing to share? Will beg :D
     
    Last edited: May 12, 2008
  2. masalai
    Joined: Oct 2007
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    masalai masalai

    See you in 3 to 6 weeks Heinz... Got a good supply of plonk, tobacco, Valium and Panadol?

    Just build it and post the pictures....:D:D:D
     
  3. Meanz Beanz
    Joined: Jun 2007
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    Location: Lower East ?

    Meanz Beanz Boom Doom Gloom Boom

    Yeah I figured its prolly no push over :D
     
  4. masalai
    Joined: Oct 2007
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    Location: cruising, Australia

    masalai masalai

    It is what you might call a "learning experience" are you going to 2.6 or the latest at http://freeship-plus.pisem.su/indexEN.html click on <support> then <downloads> and totally ignore the popups if you are a windows user...

    I got 2.9+ as the more recent may be a bit unstable as still under development...
     
  5. Richard Atkin
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    Location: Wellington, New Zealand

    Richard Atkin atn_atkin@hotmail.com

    Hi J. Would you like to comment on this? It's less stable but it's less hassle. Not offshore, but definitely fun.

    If I am not deterred I will continue this project in my own thread.
     

    Attached Files:

  6. JCD
    Joined: Jul 2006
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    Location: Coney

    JCD Follow the Bubbles!

    Hello Fanie,

    Hmmm. Me too at a smaller size. Will you be designing to a specific rating? You know I had to ask!:D Let me know if I can be any help.


    What is your legal trail width, length, height and weight?


    How many are you designing for? What kind of layout if you're stuffing the ends with berths? What about the "iron genoa"?


    Woah...that sounds a lot like the TR27B at full displacement. Is that all up for cruise or light?


    I assume cabin means cuddy? I don't understand by what you mean at the rear door of the trailer. Ten meters is closer to 32' than 30' so at 32 feet, the L/Bm ratio is 80% and at 30 feet it is 87%. That is extremely wide and it may be wise to reconsider the width. Pitchpoling and poor maneuverability could be a serious issue.Those are Trimaran widths. IMO I would place her at 64% maximum if you want to go really wide.


    The beams? Will they telescope, fold or hinge?


    You tested these already? What scale did you use? Got any pictures?


    No more fish to catch? :D :D The fish must fear you. If you can catch fish until there isn't anymore, you are a menace to the ecology! LOL. I agree, no sense keeping her dockside if you can have her home. At home you can sit in her and listen to ocean music with a rod over the side while the kids attache fish to the hooks so you can reel em in and land them. Being far from water is not a handicap..think of it as a setback to be overcome.

    Well, I would be interest in following your progress.

    Thanks
    J:cool:
     
  7. JCD
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    JCD Follow the Bubbles!

    Hello MBz,

    I think those big sections cut out a lot of buoyancy if they get chopped out from the sides. If you cut them out at the stern (much like The Green Lantern), you lose buoyancy but at least you don't have boarding waves from the bows. Something to think about.

    Personally, I like the boarding transoms a lot and believe them to be essential, but I think that several folding mast steps up the stern with attached ladder steps may be the way to go for the TR27B. A couple of hand rails outboard of the steps and it will look good and fold away while at sea or not in use. KISS, strong and, nautically aesthetic.

    Boarding the TR27B with ease must be a priority if the cabins are to be used while dry sailing her or provisioning. To board at sea after rowing exercise in the dinghy, a simple divers ladder from the aft beam is sufficient.

    Thanks
    J:cool:
     
  8. JCD
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    JCD Follow the Bubbles!

    Hello Richard,

    Yes. I like the laces in your rudder system.:)

    Thanks
    J:cool:
     
  9. Richard Atkin
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    Location: Wellington, New Zealand

    Richard Atkin atn_atkin@hotmail.com

    Hi Fanie.
    It sounds like you want your Boxy Fisher to be as big as possible, but you are restricted by the length of your property.
    If you want to go really really big, then why don't you just split the hulls in half (4 pieces)? Each half can be fully water tight, and they just bolt together from inside.
    You'll have a big, fast and SAFE boat!!
    Is transportation the problem?
     
  10. Richard Atkin
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    Richard Atkin atn_atkin@hotmail.com

    Regarding the Beachcat Cruiser fbm file I sent, I have decided to make it 10 ft wide, and not demountable, so it requires a trailer permit. Doing some research on masts.
    Sooo....no comments necessary unless anyone really wants to :)
     
  11. Fanie
    Joined: Oct 2007
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    Location: Colonial "Sick Africa"

    Fanie Fanie

    Rating ? It would fall under class B from it's size if I remember correctly... ?

    trail width is 2m500. The hull shape allows the wheels to fit in below the hull sides. We don't have roads to the sea without bridges crossing and from a windy point of view one would keep hight as low as possible, but it would be safe at under 4m. The hulls would be about 2m500 on the trailer, the cabin about 3m500. Length max including towing vehicle is 22m allowed here so it fits in.

    Max 8. Someone must clean up behind us and clean fish :D Yeah right ;)
    I haven't decided on a fixed layout yet, but have a couple of ideas.
    Iron genoa ? No idea what that is.

    I'm still wrestling with the width. I sked an explanation why it would pitch pole as to a narrower width and has not gotten an explanation yet.
    The main reason for the width is I don't want a crampy setup. Trouble starts when you have to climb over someone elses' wife to get to somewhere :D But it's mainly for comfort. The narrower width would make the beam construction easier though.

    Nope. Proper beams. I will make some drawings on how I plan to do it and how they will work, but it's really simple.

    Most frustrating currently... so I'm collecting the thousands of accessories and making stuff for er on the fly...

    I'll respond to the other posts a bit later on when I have time, thanks for the interest...
     
  12. catsketcher
    Joined: Mar 2006
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    catsketcher Senior Member

    Pitchpoling and width

    Hello Fanie

    JCD is correct in his view on beam. There is a rule of thumb for multis that you don't want your boat to be much more stable sideways than fore and aft. I had a boat a bit like this - a Twiggy tri and it had some unsettling characteristics.

    It had a large rig because it was stable sideways but when you went square running the bows would depress too much. We couldn't push her anywhere near as hard running as reaching. This assymetry of stability is very bad when you get caught in a blow and want to run away with it.

    You can always ease sheets going upwind and reaching but easing sheets on a run doesn't prevent a capsize.

    On top of that your weights will go up dramatically. Assuming your beam works as a simply supported beam you will increase the loads in the beam by the length squared. Reducing width allows a big reduction in strength.

    Look at John Shuttleworths site on multi seaworthiness. He has a great read on the subject.

    Fanie - I would urge you to consider making a cat from a plan from an experienced designer- one of Richards would probably suit you well. You will avoid simple mistakes that will cost you many thousands of dollars and maybe thousands of hours too. At the risk of offending you and I do not mean to - going that wide is a pretty basic mistake. There are many many more pitfalls to make.

    Any expense in plans will be paid back ten or twenty fold just in resale, let alone the cost of wasted materials and then there is the huge - absolutely huge amount of time that you need just to research the design. Give it some serious thought. A newbie designer makes a hard to sell boat. Building from good plans is great - just ask a Farrier builder.

    cheers

    Phil Thompson
     
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  13. JCD
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    JCD Follow the Bubbles!

    Hello Richard,

    Finally got some time...the little ones have left the building!
    Anything in particular that you wanted me to look at or compare to? Give me a day.

    Thanks
    J:cool:
     
  14. JCD
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    Location: Coney

    JCD Follow the Bubbles!

    Hello Fanie,

    Ohh...I thought all the old timers knew. When winds were so low that the hull speed made the trip brutal, the skipper would make an executive command decision to "bend the iron genoa" and he would then turn the key and go to his motor. So an "Iron Genoa" is the motor.;)


    You are not going to get a response about pitchpole for a "narrower width". Pitchpole makes itself more readily possible for cats when the width gets to "wider widths". If you're looking for at least that width as a comfortable set-up, you're going to have to go longer.

    On a positive note, if you assign the width as the "base" criteria, then you can just allow the width to be half the length and reduce size that way. At 8 meters width, you are now looking at 16 meters length. WOW!

    Yes, I suppose that trouble would definitely start after carefully and slowly climbing on top of someone's wife. The amount of trouble will be decided on how long you take to get to the other side and what happened on the way there!:D The arms locker should be under lock and key when this maneuver is being executed?

    Thanks
    J:cool:
     

  15. JCD
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    JCD Follow the Bubbles!

    Hello...

    I also would offer the same advice and believe it emphatically. I would never choose to offend you either, and I would not discourage you from learning it and possibly making time to design and build her, but if you're wrestling with the width, which is about as established and empirical as dirt, then there is either lots of learning to do, or plans from accomplished and respected designers should be considered.

    If offending you will help me to save your life, then let me know and I'll be happy to oblige.:D

    Thanks
    J:cool:
     
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