Post your design ideas

Discussion in 'Multihulls' started by Brorsan, Mar 11, 2011.

  1. rob denney
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    rob denney Senior Member

    Masts are 17.5m overall length, the top of the lower section is 4.75m above the base, the bury is 1.9m. They are wing sections. Not sure of the weight at this stage, but they have the same rm as the mast in which weighs 120 kgs.

    Tabernacle is not really the right word. It is a hinge in the wing section mast. Everything is carbon. I will post some photos when I have them. It is a pretty impressive bit of engineering and building as the wing mast (incl hinge) sits on a stub mast which allows the internal halyards to exit at a fixed point rather than a rotating one.

    Minimum bury is difficult to answer. The smallest we have done was 0.75m on a 14m high rig for an 11m cat, about 6 years ago. I heard the other day that this rig is still up and performing flawlessly.

    The masts are lowered onto the booms. Presumably there will be some sort of gin pole to give some leverage once it gets near horizontal.

    The hinge is very strong, but I would not want to be lowering the mast in excessive conditions because of it's size. So flat water, except in emergencies.

    Cost is difficult as there were some extra bits and pieces, but $25,000 per unit, including engineering would be ball park. Production is booked out until the end of the year, so we could not supply until early 2013.

    I have attached some photos of recent work (clear finished beams for a Canadian production race cat) to give you an idea of the ability of the builders.

    Small world department: Brian, the guy building the Solitary Cats from Polycore is my ex partner, who built the mast in the video above. He's an excellent builder with some really good ideas. It would be a very good agency to have.


    Attached Files:

    Last edited: Jun 18, 2012
  2. ImaginaryNumber
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    ImaginaryNumber Imaginary Member

    I'll look forward to your photos when you post them.
  3. luckystrike
    Joined: Feb 2010
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    luckystrike Power Kraut

    A friendly “Hello” to everybody

    Live is funny and its interesting how ideas come out of nowhere. I'am following this thread for a while now and find it fascinating. Perhaps this is the right place to present the latest spark in my brain.

    We had regatta the last weekend and there was a little tri sailing on our racecourse beside other tri’s that overtook us one after the other. Iam still forced to sail on a monomaran, so there are a lot of people sitting on 34’ of boat. My skipper has a broken toe, so he was at the helm instead of me and I had time to watch that trimaran. After the race I walked to the other side of the habour to have a closer look. It was a Tricat 22 daysailor wich looked interesting and a little “retro” with its strong curve in the sheer. Beside the tri there was a old Hobie 18. Hmmm, “Hobie 18 is retro too” I thought ... “or just old???? ...old????? .... Cheap!!!! Old boats like the Hobie 18 are going away for 1500€ or so, complete with trailer. You just have to find a good one.”

    Suddenly there was some electric activity in my brain…...

    Why not pick up the Hobie 18 and give it a mainhull to make a cheap trimaran. Like Dick Newick did it with the Tremolino and the Hobie 16. The Idea was (and is) somewhat ingenius. If you have (or can get) a Hobie 18 in good used condition it would be the cheapest possibility to go sailing and cruising on a multihull. Exept for the beams you can use every piece of the cat’s equipment for the tri, so you just have to build (and pay) the mainhull and new beams, nothing else what is expensive!

    Today I looked for a good sailplan of the 18 and found one. I scaled it up to 1:20 and started freeship. I wanted a that retro look to match the 18’s lines and as few material as possible. So, the best way to design it is like Newick or Greene did it in the 1980’s. Small and low hull, curved sheerline , big cabin with (short) wings placed direct on the uninterrupted sheer, same place where the beams will be. Of course it has my favoured modern sharpie hull with flared sides for simple, fast and cheap construction as well as quite good hydrodramatics.

    And here it is ... the first sketch of the trimaran’s mainhull with the H18 amas in place . LOA/LWL 6.4m (21’), BWL 0.65m (2’2’‘), Ratio 10:1, Hull draft 0.21m (8’‘).

    A rough calculation for the needed basic material made it clear ... this boat will be really cheap!!!!!! 4 and / or 6mm plywood, marine grade Okume .... 10 sheets!!!!!!!, stringers will be nordic fir (or what you have in your area that is light and cheap). Following my experience you will need around 15 - 20kg of epoxy. (West 105 or similar). Two more sheets of 4mm ply for the interior ... some paint, consumables, bits and pieces ....thats it!

    My next task will be to find an Hobie 18 that I can measure, so that the final design of the mainhull can be done.

    So far for now, Iam open for comments! I will not build this boat, this a is a design project!!!!! But if somebody is interested in the design and wants to build it, feel free to contact me and we will see if I can speed up the design process.

    Greetings from the North Sea Coast, Michel

  4. dstgean
    Joined: Aug 2006
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    dstgean Senior Member


    As the owner of an old and very cheap but solid Hobie 18, I think this is a very good idea! Keep cracking...and BTW I like the ollk of the profile so far.

  5. arekisir
    Joined: Jul 2010
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    arekisir Junior Member


    Your initial profile looks fantastic.

    Some thoughts I have had in the past in relation to this type of concept:

    -The H18 floats like many beach cats dont have huge amounts of volume. As the beam is increases they are a bit underdone as tri floats. As a simple and cheap way to get more volume extensions at the rear of the hull can be added very easily, lots of extra volume can be created by 0.5m extensions and all the rudder gear would attach to the new transom. The existing transom is used as a bulkhead. This would increase LWL also both things being desirable.

    -As you go wider in beam the centre / dagger boards need to move forward in relation to the sail plan (this assumes the lee board is the dominant & loaded one. Advice from others will hopefully be given here but I would guess as a starting point the COE of the sail plan is projected through the Centre of lift of the current boards to achieve the new position at the increased beam. this determines the rig poisition which will be a bit back in relation to the position of the boards. I'm not suggesting moving the boards around just positioning the rig a bit back so that their is now a bit more volume forward in the floats which has to be a good thing.

    -If you achieve more volume you have more stability which is good combined with the extra weight of the main hull you have a much higher loads on the rig. Many ways exist of providing more rig stiffness spectra runners & lower stays could be easily added to keep the mast straight.

    Hope this makes some sense, this concept has been visited a few times but no one has cracked it yet, once again your profile looks great Alex
  6. Gary Baigent
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    Gary Baigent Senior Member

    Michel, I like the main hull profile too but if you're building in 4-6mm ply, 4mm being the sides, then you may be better off putting some curve, tensioning, the ply for more stiffness. 4mm is not very good in slab form (slight joke). I know people think flat panels are easier to build but a little thought and a little more time tensioning the area is not difficult either; you bend around the bulkheads, frames and stringers, not difficult - plus you get a sweeter, hydrodynamic, less draggy hull form. If you like chines in the after sections, well, you can run a stringer there at waterline and then make quite a hard turn over the stringer with the ply.
  7. luckystrike
    Joined: Feb 2010
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    luckystrike Power Kraut

    Hi Gary, Dan and Alex,

    just a few comments for today.

    Volume / Ama extensions: If you look at the Ama profiles you will see that they are already longer than original. The procedure is easy as can be, clean up the stern, glue a piece of styrofoam on, shape it into form following the lines of the hull and laminate 600gr/m² onto it. Operation done´. If you want to have the rudders there, which is not decided yet, glue in some wood as a reinforcement.

    Mast strengh: You are right the rig will have to face more stress on that boat. I think check stays from the diamond to the chainplate will secure it from bending the middle forwards. Additional stays from the spihalyard secure it above. 3 or 4mm dyneema will do the job. May be a reinforcement of the chainplate is useful.

    Balance: this is the greatest problem, because the position of the daggerboards are given. Iam considering a small board as a fixed "canard" forward in the mainhull, also to support a screecher and spinnaker. The Orma 60 Tris did it that way in the late 90th's.

    Pressing Hard: The width of the boat is totally undecided yet, but one thing is clear. The amas will lack volume, so that the boat cannot be pressed hard or sailed on the ama alone. I would guess that the H18 hull has 450 to 500 litres of volume. Then boat will be sailing on its mainhull and reefed early.

    Dan, can you invest 2 or 3 hours and measure your H18 hull? That would be very nice and brings the design process a good step forward.

    Gary: I will stay with the sharpie hull for fast and easy construktion. Also to get some usable space inside. With a round bottom as "Sid" has it, a additional floor to be built in, the hight would be less than it is now. Even thow here is just minimum sitting headroom in it now.
    Plywood will be 6mm /5ply all round and the bulkhead "flats" will have a slight constant radius. The boat can be built using sitch and glue technique. Two or three pairs of stringers will stiffen the skin. 4oz glass outside, a little more on the bottom.

    What I need is a simple idea how to make the strongly curved cabin top. Strip plank? Glass and foam sandwich??? We will see.

    Best regards, Michel
  8. ExecutiveBanana
    Joined: Jun 2012
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    ExecutiveBanana Junior Member

    Yes, this was posted in another thread, with much criticizm, but i am proud of my design and am sharing it again. (pictures soon)

    length overall- ~90 feet
    Waterline Length- ~50 feet
    Width- ~65 feet
    Height- ~35-40 feet
    Propultion- ~Electric motor powered by the sun
    Speed-~ at least 50 knots (yes, i know, its a bit outragous. dont get your knickers in a twist)

    It's a catamaran with each hull spreading out from the center structure (that is suspended over the water) and each hull is about half of the overall length of the vessel. The superstructure i call the "Nest" is a sort of teardrop shape to slice through the air. The idea was that is most of the vessel is out of the water, then there will be less resistance in the water to deal with.
  9. dstgean
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    dstgean Senior Member

    I don't know about hours of time, but I do have the boatr in the driveway. What measurements do you want?

    As for the strongly curved deck, you could make it in 4mm and make it in three pieces with a nice line to accentuate or contrast with the sheer.

  10. David Egas
    Joined: Jun 2012
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    David Egas New Member

    excuse me guys, someone I can provide a design of engine room in rhinoceros format?
  11. luckystrike
    Joined: Feb 2010
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    luckystrike Power Kraut

    Hi Dan,

    The most important basic measures for the moment are:

    Distances taken from the hulls bow (not the overhanging glue joint):

    Bow to middle of front beam (landing)
    Bow to middle of rear beam
    Bow to daggerboard case (leading and trailing edge)
    Bow to chainplate
    Bow to transom

    To estimate the longitidual center of flotation and the volume of the hull the measures are a little more difficult and its best if I make a sketch to explain how this will be done.

    Need a few days to do it. Have just a little spare time in the moment.

    Best regards, Michel
  12. Timothy
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    Timothy Senior Member

    It has been more than two years now since I have being playing with this idea and I am not sure if I am getting closer or farther away from a design that can actually be built. This latest incarnation would meet all of my original requirements stated as per post #82 0f this thread and I am hopeful that the structure could be engineered to handle the loads and still weigh less than 3000 lbs. The availability of cheap extremely light weight Chinese flexible high efficiency solar panels, advancements in lithium ion batteries, and my recent discovery of the Polycore panel product, makes me think that a stitch and glue version could be built at a cost equivalent to or less than that of a 30’ to 33’ production folding trimaran.
    Length 70’ 19’ 4” folded
    Beam 37’ over all 25’ ama centerline to vaka center line 13’ 6” in marina , at campground or rest stop 7” 6” for container transport or storage in garage 8’6” on trailer for towing by SUV
    Weight 3000 lbs
    Draft foils up displacing 4500 lbs 9” foils down 6’
    Construction flat cored panel carbon reinforced where appropriate
    4200 watt solar array 4 Torqeedo lithium ion batteries
    Propulsion 16’ skiff with remotely operated Torqeedo cruise with power tilt
    6’ 2 standing head room in cabin raised. 4’8” sitting headroom cockpit enclosed. 6’2” headroom cockpit hard top solar Bimini deployed
    Comments , constructive criticism, reality check?

    Attached is a short animation depicting the unfolding and movement of various components

    Attached Files:

  13. brian eiland
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    brian eiland Senior Member

    Rob, are you still building boats?

    Is that ex partner still around anywhere?

    Have you seen that lastest reefable wingmast that Randy Smyth developed?...with very little compression loading to the vessel??
  14. upchurchmr
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    upchurchmr Senior Member


    I haven't seen Smyth's wingmast, do you have a link or reference?


  15. brian eiland
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    brian eiland Senior Member

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