Multihull Structure Thoughts

Discussion in 'Multihulls' started by oldmulti, May 27, 2019.

  1. redreuben
    Joined: Jan 2009
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    Location: South Lake Western Australia

    redreuben redreuben

    Ha, thats pretty funny.
    Has anyone ever seen a Michael Schact design that is out there doing it ? Me neither.
     
  2. Russell Brown
    Joined: Jul 2012
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    Location: washington state

    Russell Brown Senior Member

    And yet, at least one other designer talks a lot and talks very loudly and doesn't have a single boat "out there doing it", but you would likely defend him. What's with that?
    Michael doesn't push his ideas on anyone.
     
  3. redreuben
    Joined: Jan 2009
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    Location: South Lake Western Australia

    redreuben redreuben

    Come on, whats with the ambiguity ? Your talking about Rob Denny,(again) yes Ive defended him why not ? Ive also criticised him. He has ideas he puts out there and takes the criticism with remarkable good nature, he has a website where you can buy plans not just look at pictures.
    Ive also agreed with you from time to time and Rob hasn't chided me, as for no boats out there thats just ********.
    Grow up Russell ffs.
     
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  4. redreuben
    Joined: Jan 2009
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    Location: South Lake Western Australia

    redreuben redreuben

    @Russell Brown Prove me wrong, get me a table of offsets for this sexy beast.
     

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  5. bajansailor
    Joined: Oct 2007
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    Location: Barbados

    bajansailor Marine Surveyor

  6. jamez
    Joined: Feb 2007
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    Location: Auckland, New Zealand

    jamez Senior Member

    Guys, if you want an in depth discussion of a particular designer then please start a new thread.

    There is enough quality info to go through in this thread without including peoples pissing contests.
     
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  7. oldmulti
    Joined: May 2019
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    Location: australia

    oldmulti Senior Member

    This is about a real voyaging cat that you could build in 6 months from store brought materials. Minimus 11 has been featured 3 times before but the final version ready for voyaging is interesting. Minimus 11 is 23.75 x 13.33 foot weighs 1600 lbs and can carry 1200 lbs of people, food and equipment. The 4 mast rig carries 2 junk sails of 91 square foot and 2 smaller mizzen junk sails. The 18 foot masts are from 4" (102mm) pipe with a wall thickness of 0.072" (1.85mm). When we were finished, we had two 18' (5.5m) masts that were triple wall (0.216", 5.5mm) in the bottom third of the mast, double wall (0.144", 3.7mm) in the middle third, and single wall (0.072", 1.8mm) in the top third. The underwing clearance is 2.5 foot. The length to beam of the dory flat bottom hulls is 10 to 1. There was a concern the flat bottoms hulls might pound going to windward in choppy seas. She got well tested and hasn’t proved to be an issue. A daggerboard was added in the bridge deck to aid in tacking and added significantly to windward performance. Ropes hold the board in position when down.

    The accommodation has sitting head room in each of the 4 cabins. One hull has a galley, with a person in one cabin and another person in the other. They can see each other, converse and pass food through the open center bulkhead. They sleep in the other hull, head to head. The bunks are about 24" (61cm) wide and have found them comfortable.

    The build is 12 mm MDO plywood (used for outdoor signs) with 25 x 50 mm chine stringers. MDO doesn't require an additional layer of fiberglass to prevent surface checking. Instead, hulls, deck and cabin tops will simply be covered with 3 coats of epoxy and painted. Only the portion of each hull below the waterline will be fiberglassed for extra abrasion resistance should we want to beach the boat. The decks are 12 mm MDO. The wet deck is 150 x 25 mm cedar and some MDO. The cross beams are made from 3/4" x 8" MDO plywood capped top and bottom with pairs of 1-1/2" x 1-3/4" Douglas fir caps. They beams are strong. The beams are lashed to the hulls.

    The future plans are: “In Oregon in early March we'll need to put an additional coat of bottom paint on the hulls and load the cross beams, deck boards, masts, sails, equipment, etc. Then ideally, we'd like to trailer the boat to southern California by mid-March. We're looking into renting a small U Haul truck and towing the boat behind it, then selling the trailer in southern California right after launching. Then we'll need to have dock space for loading water, food and equipment. Overall, launching and loading the boat is about a 3 day process. Hurricane season in the eastern Pacific officially begins mid-May and if we voyage south or west, we'd like to be well ahead of that season.

    We're not sure yet where we'll be launching, but likely somewhere between Santa Barbara and San Diego. The boat takes 2 days to assemble. That includes setting up the temporary mounting beams on which the hulls are moved out to full width, then mounting and lashing the 3 main and 2 intermediate cross beams, lashing the deck beams, installing the rudders, 4 masts, sails, 2 boomkins, electrical harness between the hulls, AIS cable, compass, oars, etc.

    As to where we might sail, our thinking is to sail down the west coast of Baja, perhaps as far as Bahia Tortuga, about halfway down the Baja peninsula. Assuming everything looks good, we may hang a right. If so, Hawaii seems like a logical destination. With the various unknowns including the experimental nature of the boat, Covid, etc., we're not yet thinking beyond that. Basically, the plan is to head down the coast and take things as they come.”

    If you have big dreams and small finances, this is an excellent example of what can be done. The jpegs give the idea. The web address is Sailboat Project http://omick.net/adventure/minimus_ii/description/description.html
     

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  8. Scandinavian Proa
    Joined: Nov 2021
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    Location: sweden

    Scandinavian Proa New Member

    I'll take the opportunity to introduce myself as the Harryproa C50 was on the subject.
    First of all thank you Oldmulti for this all time high thread! I must have learned more from here than of all the multihul books i've ever read.
    This is my first post here but I have sneaked around this awesome forum for quiet a while.

    I'm the swedish dude that builds a custom Harryproa C50 (C53).
    We are doing great progress and the intelligent infusion is the key factor here, its so much more enjoyable to work with dry matherials in no rush compared to my former boat building experiance.

    That it theoretically compares to a 69foot paciffic proa is just crazy,we will see when we get there :)
    Funny that you compare it with a grainger raku40 because this was on our top list of designs of choice.

    As a side project we are designing a 5meter stepped hull tender, this will be an all electric speedster and so far it looks very promising.

    upload_2021-11-13_23-23-0.png
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    upload_2021-11-13_23-26-28.png
    upload_2021-11-13_23-28-45.png
    upload_2021-11-13_23-30-54.png
     
  9. oldmulti
    Joined: May 2019
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    Location: australia

    oldmulti Senior Member

    Rickard. You are very welcome to the thread. Your experience of Intelligent Infusion will be of interest to many. EG It appears you use foam with a channeled face for the infusion, is this a Chinese foam like UTEK? What vacuum bag material are you using? etc. Thanks again.
     
  10. Clarkey
    Joined: Aug 2010
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    Clarkey Senior Member

    I find Minimus 2 fascinating. Multis that do not focus primarily on performance (especially in light airs) really interest me with their moderate rigs and easy handling. I think with solar/electric propulsion getting progressively cheaper and more effective there may be a niche for cruising boats that mix this with sail to make a new type of small, light, motorsailer.
     
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  11. Scandinavian Proa
    Joined: Nov 2021
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    Location: sweden

    Scandinavian Proa New Member

    Thank you!
    You are correct, the foam is chinese and is channeled and slotted.
    Works great without any flowmedia.
    The vacuum bag im using is polyethene 0.07mm thick.
     
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  12. oldmulti
    Joined: May 2019
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    Location: australia

    oldmulti Senior Member

    The following is in 2 parts. This is about a coastal live abord cruiser that was lived on for 18 months down the coast of the Bay of Mexico. It’s a Pacific proa based loosely on Gary Dierking T2 as shown in the ”Building Outrigger Sailing Canoes” book by Gary. The modified version is 23 x 10.2 foot with a weight of 450 lbs. The hull offset are multiplied by 1.3 laterally as well as having the middle section spread apart to extend the T2 design from 17.75 foot to 23 foot. The float is 210 mm in diameter and 14.9 foot long. The bamboo mast is 15.5 foot high. The yards for the sails are about 25 foot long and made from 2 carbon fiber windsurfer masts per yard. The 7 sails range from 50 to 160 square foot depending on wind conditions and angle of sailing.

    Today’s item will focus on the construction of the pacific proa. Tomorrow will focus on the sail plan, sailing and the over 1000 miles of live aboard cruising over 18 months. The construction is strip plank western red cedar main hull built of 6 x 18 mm strips covered with 300 gsm cloth on both sides. The hull deck is 6 mm plywood. The 6.5 x 3.2 foot deck panel between hulls is 3 mm ply 25 mm foam and timber and 3 mm ply sandwich provides seating while sailing and a bunk base at night for the small tent for the live aboard component. The cross arms are laminated timber about 45 x 75 mm that are lashed on to the main hull and float posts. The basic structure has had minimal problems during several years. The entire boat has an epoxy and varnish finish. The builder designer says the proa is a forever build but the main structure took about 18 months of real time.

    The interesting part of any proa is the steering system. This proa is no exception. The original steering system was a long oar but was found to take to much effort to steer as the oar dipped in and out of wave tops requiring varying pressures and attention. The next set of rudders was a simple vertical rudder attached to the side of the main hull at either end, worked better but was not fully effective. The final version is kickup rudders at either end correctly balanced and easy to use.

    The “accommodation” is a tent on the wet deck and storage in the hulls for all the food gear etc. This is a camper cruiser more than a full cruiser but is still a live aboard as required. The jpegs give more of the story. The rig analysis and sailing will be tomorrow.
     

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  13. guzzis3
    Joined: Nov 2009
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    Location: Brisbane

    guzzis3 Senior Member

    When I first contacted UTEK they said grooving and perforations were free. Later they charged for them. When I ran the numbers flow media from them was cheaper than the charge. I guess it costs a little more resin but at least the weight isn't in your panel... 2c.
     
  14. Russell Brown
    Joined: Jul 2012
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    Location: washington state

    Russell Brown Senior Member

    Michael told me last week that one was built in Europe and is sailing.
     

  15. Michael Schacht
    Joined: Aug 2021
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    Location: Port Townsend

    Michael Schacht New Member

    [​IMG]

    I know Evergreen is a bit of a white unicorn, but yea, she actually exists.
     
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