Non-foiling trimarans under 20'

Discussion in 'Multihulls' started by Tom Makes Things, Sep 25, 2019.

  1. Tom Makes Things
    Joined: Sep 2019
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    Location: Portland, OR, USA

    Tom Makes Things Junior Member

    I've been doing research on the options for building a small trimaran under 20' that can carry 2 people (more or less). I'd like to summarize what I've learned and see if it fits with the general consensus. I'm no expert, and I welcome all advice from those with more experience than I.

    Seems like we can break up this category of sailboat into 3 main branches:

    1) Triple Hotdogs: Long skinny shaped central hulls with long amas, sometimes with auxiliary propulsion like Hobie Mirage drive, pedal/prop drive, oars or paddles. Benefits to this design are lighter weight, easier paddling, better in light winds, lower cost to build/own. Drawbacks are limited weight capacity, lower top speed, wet ride.
    Boats in this category include: Hobie Tandem Island
    Metz TriRaid 560 Metz Boats - Triraid 560s Trimaran http://www.metzboats.de/htm/designs/multihulls/triraid560s/triraid560s.htm
    Frank Smoote's Slingshot 19 New Page 1 http://www.diy-tris.com/2012/11-19-footer.htm


    2) Skiff with Training Wheels: Wider planing central hulls with low volume amas mounted higher that act more like training wheels for a sporty skiff or dinghy. Benefits are more weight carry capacity, faster top speed when planing, more exciting to sail. Drawbacks are- heavier than above, still a wet ride, lesser performance in light winds, slow below planing speed, and difficult to paddle/peddle. Are they better at pointing due to being sailed like a monohull?

    Boats/Projects in this category include:
    Weta: Weta Trimaran - Wikipedia https://en.wikipedia.org/wiki/Weta_Trimaran
    Sea Rail 19: http://www.searail19.com
    Astus 6.5: Astus 16.5 http://www.astusboats.com/astus-16-5-copie.html
    ISO Skiffmaran: ISO Skiffmaran https://www.boatdesign.net/threads/iso-skiffmaran.56971/
    I14 Training Wheels: I14 training wheels http://forums.sailinganarchy.com/index.php?/topic/208203-i14-training-wheels/

    3) The original: Wider planing central hulls with larger volume amas that provide greater righting moment. These boats might have higher freeboard, small cuddies or cabins. Benefits include more carrying capacity, dryer ride, higher top speeds? Drawbacks are heavy weight, high cost to build, difficult to paddle/peddle, slower in light winds than #1 due to weight.

    Richard Woods Strike 15 Sailing Catamarans - Strike 15 trimaran performance daysailer http://www.sailingcatamarans.com/index.php/designs-2/27-trimarans-under-25/223-strike-15-trimaran
    W-17 W17 Trimaran | Main Page https://smalltridesign.com/W17/greybox/W17-Trimaran.html


    Can anyone add to my list and or correct my assumptions?

    Thanks very much.

    -Tom
     
  2. Richard Woods
    Joined: Jun 2006
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    Richard Woods Woods Designs

    I'd class my Strike 15 in the narrow hull category. And I'd suggest the Strike 20 as more suitable for you

    Richard Woods of Woods Designs

    www.sailingcatamarans.com
     
  3. upchurchmr
    Joined: Feb 2011
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    upchurchmr Senior Member

    The wide central hull doesn't affect stability much, the fact that the ama or outrigger is so far off to the side is most of the influence.
    A wide central hull is mostly for accommodations.
     
  4. Dolfiman
    Joined: Aug 2017
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    Dolfiman Senior Member

    For the comparaison, I would also use the ratio Ama volume (liter) / [ light weight equiped + average targeted payload (e.g. 2 persons ~ 150 kg)] (kg) . Examples :

    ** For the Triraid 560 :
    Light weight equiped = 110 kg
    Ama volume = 180 liter
    >>> 180 / (110 + 150) = 0,69

    ** For the Astus 16,5 :
    Light weight equiped = 210 kg
    Ama volume = 500 liter
    >>> 500 / (210 + 150) = 1,39

    Triraid 560 will be little powerful, cannot sail with the a full flying central hull, but its capsize mode will be around the central hull (ratio < 1) , more easy to prevent. A boat oriented to raid sailings without high speed objective. And lighter to trail, to launch.

    Astus 16,5 will be more powerful, up to sail on the leeward ama alone. But its capsize mode around the ama (ratio > 1) can be more brutal , and finished upside down (critical if the waterdepth is lower than the mast height). Twice heavy than the Triraid (210 / 110), but the Astus 16,5 can be sailed quietly, reversely the Triraid cannot be hard sail because the limited volume of its ama.

    The Astus 16,5 is more relevant in your cat. 3 although the central hull is not specially wider planning, she is more like a baby oceanic trimaran racer.

    In your cat. 2 skiff with training wheels, when the amas are high enough for a sail on the central hull only, the ratio can be < 1 as the power (the RM) comes from the crew in hiking posture and the amas are for extra stability when necessary (more often during tacks , gybes, than for gust of wind).
     
  5. Dolfiman
    Joined: Aug 2017
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    Location: NICE (France)

    Dolfiman Senior Member

    Another example of skiff wider planing with training wheels, the Epoh, but for me can hardly be named a trimaran :
     
  6. Doug Lord
    Joined: May 2009
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    Doug Lord Flight Ready

    Just out of curiosity : why non-foiling?
     

  7. Tom Makes Things
    Joined: Sep 2019
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    Location: Portland, OR, USA

    Tom Makes Things Junior Member

    My list has grown since the original post, as has my understanding of some of the hull designs. I'd like to at least have a passenger with me, so I've removed boats that are too small for my needs, though you can argue that some of these are still too small to offer good performance with 2 onboard.

    My newly silly renamed categories:

    "Triple Pickles": Canoe/Kayak with floats- these are mostly lighter weight, carry less payload, and sometimes can be paddled, peddled, or rowed for auxiliary power. Generally it's sailed while sitting in the boat facing forward, which in some cases allows for a spray skirt or dodger to keep the spray down. Some love the "armchair sailing" experience, while other folks find the limited seating options uncomfortable. You can't really hike out, at least not if you are steering, as most steer with foot pedals.
    Commercial offerings include: Hobie Tandem Island, Windrider 17
    Buildable plans include: TriRaid560s (though it doesn't really support 2 people very well), TriRaid 620 (prototype), Slingshot 16 Tandem, Slingshot 19

    "Jack LaLanes": Narrow at the waterline, but usually with a larger cockpit- these are generally heavier than the pickles, allow for more seating positions, and rarely have a human power option. Some have small cabins. All are designed so you sit "on" rather than sit "in" them.
    Commercial offerings: Pulse 600, Robinson 5000, Ninja Spider, Astus 16.5
    Buildable plans include: Strike 15, Strike 16, Strike 18, W17, Trikala 19, Scarab 16, Scarab 18, Sardine Run, TC601

    "Kardashians": Wide planing central hull, similar to a sportboat with training wheels.
    Commercial offerings: Weta? Epoh?
     
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