Non-foiling trimarans under 20'

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

  1. kleppar
    Joined: Jan 2016
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    Location: Stavanger, Norway

    kleppar Junior Member

  2. kleppar
    Joined: Jan 2016
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    Location: Stavanger, Norway

    kleppar Junior Member

    I think I shall bow out of this thread now, unless radical information about boats pertaining to the name of the thread emerges. I am not an engineer, and view and enjoy boats for their looks, safety, comfort and performance (not necessarily in that order). So my little fleet of boats include a Wales built and designed Storm 19, a François Vivier designed Jewell; an Erik Lerouge designed cabin trimaran (under construction); now I shall be happy to add a Mike Waters´ designed W17 (well, I am considering selling one or two monohulls). All my small craft are unsinkable, good looking (well, in my opinion), seaworthy and reasonably fast, and the fruit of sailor-architects with decades of experience. I find that reassuring!

    At present my sailing takes place on the Internet, as I am currently in landlocked Beijing, where I have been for the last 9 months, but we also live in Stavanger, Norway; that is where my real boating activity takes place. I have visited a number of trimaran websites, but none of them offer as much practical experience and advise about its designs as smalltridesign.com. Indeed, it was an interview with Erik Lerouge on Mike Waters´ website that lead me to choosing the 23. ft. Libertist 703.

    For your information: Plans for W17 bought today!

    Happy sailing in life and at sea to all of you!
     
    Last edited: Sep 5, 2020
  3. upchurchmr
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    upchurchmr Senior Member

    Kleppar - good luck with your fleet.
     
  4. Dolfiman
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    Dolfiman Senior Member

    I propose you this tentative rationale to determine the main features and a pre design of the main hull for such small trimaran when considering the usual ratios for multihulls, in order to show the influence of the payload on the minimum length within given criterias. In short (details in the document attached), I consider the main hull at 50% displacement in charge (assumed to be the average sailing condition) and look at Lw, Bw, D/2 , the ratios Lw/Bw and Displacement length Lw/(D/2)^(1/3) .
    I took Lw/Bw > 8 and Lw/(D/2)^(1/3) > 8 as thresholds, you may discussed my choices and adopt others in the application attached.
    For the net weight of the trimaran, I assumed 220 kg for a 5 m one, and a scale law as : net weight = 220 (Lhull/5)^2 .
    Here, use of power 2 instead of usually 3 for a scale variant because we assume this approach at constant heights : free boards, akas clearance, … so not reduced when considering a Lhull < 5 m
    With such rationale, for design payload of 140 kg, the minimum length is 16' the net weight is then 209 kg. With a design payload of 80 kg, the minimum length can be 14' and the net weight is then 160 kg.
    A pre design of the main hull 16' is also proposed.
     

    Attached Files:

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  5. Doug Halsey
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    Doug Halsey Senior Member

    In view of these requirements, you need to consider how you want the boat to float when capsized.

    Large-volume amas are great for righting moment, but the result can be that the main hull is out of the water & difficult to reach. Smaller-volume amas can often make it easier.
     
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  6. upchurchmr
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    upchurchmr Senior Member

    Doug,
    No question you are right.
    Of course I never flipped my Tornado.
    Some would say I wasn't sailing hard enough.
    I might say it was good seamanship - but that is probably bluster.
    Especially given one storm front where I ended up not in control, not being able to see past the front beam.
    Luck is a good thing.

    Any suggestion besides small ama's?
    The idea of being able to flood 1/2 of either ama is one.
    Just imagine how long it would take to recover from that. :D Still better than no option except a power boat (with visions of destroying something).

    I was really interested in the 18' Mosquito as discussed above, but the designer/ builder was not interested in creating plans.
     
  7. Doug Halsey
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    Doug Halsey Senior Member

    Instead of flooding, my approach was to make the amas easily detachable. That was the only way I was ever able to recover from turtling (even with help).

    It was simpler in my case though, because the amas were very small & only in the water at very low speeds. With somewhat larger amas, you might still be able to do that, but probably not with full-volume ones.

    It was also simpler because I could sail back to shore, towing an ama behind (thanks to the foils). I might have been able to reattach the ama without coming ashore, but maybe not in rough conditions.
     
    Last edited: Sep 6, 2020
  8. Scootrider
    Joined: Sep 2020
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    Location: Lake Champlain

    Scootrider New Member

    Just saw this, so this is a reply to Russell's question 'anyone sailed one of these ?
    Many years ago I used to sail a fast18ft tri so was interested to try out the W17 but skeptical about a flat bottomed tri .., so arranged to get a sail on one built about an hour away.
    To be honest I was pretty surprised .. this boat is quite amazing. The asymmetrical amas seem to work really well and the boat feels remarkably efficient, from its rudder to its rig. Rather than appear more resistant due to the boxy hulls, they actually seem to lower the resistance and I found nothing that contradicted the claims made by others on Mike's website. Perhaps the best day sailor out there ... certainly capable, solid, quiet, stable, dry and comfortable . and still a good performer too. I'd build one myself if I had the place to keep it. We met up with a Windrider 17 while out in quite rough water. Poor guy was getting soaked and without need for any wet or dry suit, we sailed through his lee like he was standing still. This boat just loves going to windward
     
  9. upchurchmr
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    upchurchmr Senior Member

    Windrider 17's are notorious for not going to windward.
    I assume it comes from not having an actual centerboard (or dagger or leeboard).
    I can't think of a boat I want less unless you were to talk about a Windrider 16, which I have sailed.
    I was crushed when I learned it was designed by Jim Brown, an old hero of mine.
     
  10. nwguy
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    nwguy Junior Member

    I totally agree. I've owned a Windrider 17 and 16. They get moving OK, but then you realize they're pigs. Very slow to windward. The foot steering is awful too.
     
  11. Russell Brown
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    Russell Brown Senior Member

    Windriders were developed as inexpensive rugged utilitarian boats that could be used by novices, rental companies, and people that wanted the experience of a good sailboat that could take just about anything and keep on going. You and up churmer can think what you like, but I don't think you get the whole picture.
     
  12. upchurchmr
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    upchurchmr Senior Member

    Russell,

    Have you sailed the 16?

    A novice needs to be able to go upwind. It's a safety feature.
    If it had a centerboard or a leeboard it would do everything you said and be better.

    Actually I've tried to imagine how to add a board and remove the keel blob.
    But then I'd be left with a minimal sail area boat.

    I'm really interested in if you have sailed one.
     
  13. Russell Brown
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    Russell Brown Senior Member

    I've sailed one a ton, including beating out through pretty serious surf. It's a great boat. Of course it would be better with a board. Got any other bones to pick?
     
  14. upchurchmr
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    upchurchmr Senior Member

    Bones to pick? No

    Although I would like more sail area after it got a board.

    I guess having an opinion isn't acceptable. Characterized as something unreasonable.
    We are seeing a lot of that now days.

    I actually have a great deal of respect for your opinion.
     

  15. Russell Brown
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    Russell Brown Senior Member

    Sorry I was a jerk. I don't own a Windrider for the same reasons you don't own one, but I do think they are great boats. They are almost impossible to capsize and they are almost indestructible. How many other off-the-beach sailboats can you say that about? I guess I also came to their defense for the obvious too. They are in my family, so to speak. Funny though that I haven't ever heard negative thoughts about them, just the obvious trade-offs.
     
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