Trimaran for R2AK & minimalist cruising

Discussion in 'Multihulls' started by scotdomergue, Nov 1, 2014.

  1. scotdomergue
    Joined: Jan 2009
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    Location: Twisp, WA USA

    scotdomergue Scot

    I’m designing a 19 foot very light cruising trimaran for the Race to Alaska (R2AK, http://racetoalaska.com) and for minimalist cruising for one or two – see drawings below.

    I’ve read a fair amount, but have never sailed a multi-hull, let alone designed a trimaran before, so I’m sure I have lots to learn. I will appreciate suggestions for reference materials as well as specific design ideas. A few particular questions:
    - Amount of Amas to be immersed when balanced at rest? My current drawings show the lowest point of both Amas 2 inches into the water at typical design water-line. This is little enough that they do not even displace their own weight. Is this good? Deeper? No immersion? Why?
    - Asymmetrical Amas? Pros & cons? Design?
    - Dagger-board size and location; similar to mono-hulls in relation to sail area and center of effort? Or?

    She is intended to be a very light sailing-row/paddle-cruising trimaran, particularly suitable for minimalist expeditions and expedition style races like the R2AK (EC, etc.).

    There are very small cabins (single berth each), both ends, with central cockpit. The narrow beam in the cockpit area facilitates double bladed kayak style paddling. Amas move in close to the Vaka for sliding-seat rowing with standard (ideal) scull geometry (intended only for calm conditions). There is storage below the cockpit floor as well as in the cabins.

    Construction is stitch & glue using mostly 3mm with a little 6mm Lloyds BS 1088 rated Okoume with 6 oz and 4 oz fiberglass, a little carbon &/or Kevlar cloth for the Akas, and West System epoxy & additives. I hope to build her this winter (starting within a month) and complete her early enough to do sea trials & modifications and then cruise for at least a month before the R2AK in June.

    I hope to keep her weight under 400 lbs, including all sailing & rowing gear & solar power system for electronics. My Marsh Duck, at 18 feet, weighed about 185 lbs including all this. It seems realistic to me. I hope to keep loaded race displacement with 2 crew of my size (165 lbs) in the range of 800 lbs. Cruise displacement for myself and a small (120 lb) partner could be similar, though might be a little more, depending.

    Current Sail-plan Concept is cat-ketch rig on free-standing carbon fiber windsurfer masts (adapted) with 250 square feet split 150/100 (see drawing).

    Thanks for looking at my project. Any reference suggestions and/or specific ideas and design suggestions will be greatly appreciated.

    Scot
     

    Attached Files:

  2. redreuben
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    redreuben redreuben

    Scot,
    repost pics so they can be expanded maybe.
     
  3. upchurchmr
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    upchurchmr Senior Member

  4. rwatson
    Joined: Aug 2007
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    rwatson Senior Member

    "I’m designing a 19 foot very light cruising trimaran for the Race to Alaska .......... I’ve read a fair amount, but have never sailed a multi-hull, let alone designed a trimaran before, so I’m sure I have lots to learn....:"

    Not being critical, from the questions that you ask - your newness is apparent.

    Why don't you get someone competent to do the design ?
     
  5. scotdomergue
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    scotdomergue Scot

    Thanks for responses. Yes, the wooden boat forum thread is one I started about the same time I started this one. There's lots of good discussion there. Scot
     
  6. jrtaylorinflag
    Joined: Nov 2014
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    jrtaylorinflag New Member

    Sounds like you are being nothing but critical.
     
  7. upchurchmr
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    upchurchmr Senior Member

    There is a popular mis-conception that anyone can do anything.
    Its not true - you have to have some knowledge, and the vast majority of people fail anyway.

    It is true that anyone can try.

    Most experienced people here do want to help.

    Its real simple. Many experienced monohull sailors have strange ideas about how to sail a multihull, which makes them dangerous to themselves. Not knowing what it takes to sail a multi makes it even more dangerous to try to design one.

    If all you wanted to do was to day sail around a local lake you would probably succeed. But not well - but it wouldn't matter.

    Good luck.

    If you reviewed a lot of previous posts you will see that RWatson is always trying to help.
     
  8. scotdomergue
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    scotdomergue Scot

    Perhaps I should answer the question.

    Years ago I realized that the boat I wanted didn't exist. I talked with professional designers and builders about creating it for me. The cost would have been in the $20,000 to $50,000 range. That would have been a real stretch! I played with design ideas for about 5 years (I've always enjoyed design) and learned a great deal, mostly on the internet and from people like all of you. One winter I realized it was time to build a boat or let it go. The result was the Marsh Duck. She was incredibly successful as a design and though the implementation was far from perfect, I learned a lot. I spent around $3,000 buiding, rigging, and getting her ready to cruise. Summer of 2013 I spent 3 months cruising all over the Salish Sea and as far north as Alert Bay - essentially all over the inland waterways between Seattle and the north end of Vancouver Island.

    Though I was an experienced small boat sailor, I'd never sailed a canoe (which the Duck is, essentially), I'd never designed a boat, and I had quite limited boat-building experience (though I've been a contractor and am generally pretty handy with such things). I borrowed design ideas and even dimensions from a variety of sources (the hull shape is based on the IC-10, the overall shape is reminiscent of ocean rowing boats). Many people helped along the way, a few in ways that were very valuable to me (I'd give credit, but I don't know whether they would want their names associated with the boat - suffice to say that I am very grateful). Overall, it was a great experience. And I've really enjoyed the design aspect, the learning, and the people connections.

    So, when I decided I wanted a tri, and realized that none of those I was seeing were what I wanted, it was pretty natural to try to design it myself. For the last year or so I've been reading a lot about tri's, including history and design, including everything I've found related to small cruising tri's. I haven't found designs that are what I want. I'm sure that hiring the design and build would be even more expensive than for the small, light mono.

    I don't know whether my design will work, though I rather expect it will work reasonably well for my purposes. I learned through the Marsh Duck experience and intend to be more careful with this one in a variety of ways. I intend to have the boat built early enough that I can do sea-trials, indicated modifications, and have the boat finished in time to spend the month of May cruising on her, seeking a full range of conditions in a more forgiving context before starting out on the race to Alaska. If all goes really well, I might even be able to explore a good part of the route I imagine taking in the race.

    Scot
     
  9. 2far2drive
    Joined: Nov 2011
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    2far2drive Senior Member

    I'm going to write something a little controversial but its something I have been thinking for awhile. Here goes...

    first and foremost, I commend you on your efforts. Many have tried and succeeded (Randy Smyth) to name one and many have failed. I dony have advice for this.

    second, I think you are cutting your window very close amigo. I personally wouldn't set off on the r2ak with a fresh unknown design and fresh build, and I've done a raid event. I did the Texas 200 on a known design (hobie 14turbo) but with fresh repairs and I'll tell you I finished.... Barely. The boat came apart by the end.

    last thing I will say... Careful with the advice in these parts and generally, blow it off. The armchair sailor/designer crowd is massive! 3/4 of the people in here dont even own or are currently building any boat! They fight about plans and design ideas all day but I'm doubting half have even sailed their buddies multis more than a few times. Now there are obvious exceptions, and you few know who you are, but for what it's worth.... I would take my questions elsewhere or take what you read here with a grain of salt.

    the thread you started on wooden boat is fantastic and much more informative by people who actually build,own and SAIL!

    Good luck to you sir and maybe I'll see you in a few years in the r2ak. Now let the bashing begin!
     
  10. scotdomergue
    Joined: Jan 2009
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    scotdomergue Scot

    Thanks for your thoughts! The part quoted is particularly important, I think (though all relevant and appreciated). As noted in previous post I plan to do some intensive shake-down, do indicated mods, and then spend a month on further shake-down before the race. Hopefully that will allow me to do the r2ak without more than the expected, inevitable difficulties. If I find the boat and I are not really ready, I'm quite willing to wait for another year or just go cruising or whatever. I'm retired, so free to do whatever I want.

    And yes, there's been some great discussion on the Wooden Boat Forum thread.
     
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  11. RHough
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    RHough Retro Dude

    This sound close?
    SPECIFICATIONS
    Crew: 1-2
    Length: 18' 6" / 5.64 m
    Width: 30" / .76 m
    Beam (Amas Folded In): 4' / 1.22 m
    Beam (Amas Out): 10' / 3.05 m
    Capacity: 600 lbs / 272 kg *
    Fitted Hull Weight: 124 lbs / 56.25 kg *
    Fully Rigged Weight: 190 lbs / 86.18 kg *
    Mast Length: 18' / 5.49 m
    Sail Area: 90 sq ft / 8.4 m2

    [​IMG]

    With less than a year to the start. Buy a boat and spend the time tuning yourself for a 750 mile trip upwind and up-current.

    Your condition and choice of equipment will have more of an effect than the design. If the goal is to participate and have a chance of finishing buying a boat that can be adapted for your purpose is a higher percentage choice than designing and building your own.
     
  12. scotdomergue
    Joined: Jan 2009
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    scotdomergue Scot

    I sailed along side an Adventure Tandem in my mono-hull 18 foot Marsh Duck when I was fully loaded in the middle of a 3-month cruise and he was sailing solo with nothing else aboard. The Duck was faster and pointed higher. Winds were fairly light and he was able to pedal to supplement and stay a little ahead when he did that. The Duck has 107 square feet of sail, reef-able to under 25. Her cabin, while small, is quite comfortable for sleeping. I slept aboard (full variety of NW weather) all but 3 nights during the 3 months (early May to early August between Port Townsend and the N. end of Vancouver Island). She also has LOTS of storage space inside the boat (not on top or in the cockpit). When there wasn't wind I typically rowed her at 4 knots, occasionally for hours at a time.

    The TA specs are not what I'm after. Try:

    SPECIFICATIONS

    Crew: 1-2 (yes, that's the same)

    Length: 19' (not a big difference)

    Width: 26" to 36" (26 in the cockpit area so double bladded kakak paddle works well, 36 for cabin comfort and better, stronger aka mounting)

    Beam (Amas Folded In): 5' 6" or maybe up to 5' 8" (for ideal sculling geometry w/ oarlocks mounted on the amas)

    Beam (Amas Out): 14'

    Capacity: 500 to 550 lbs (she will handle significantly more, but with a loss in performance)

    Fully Rigged Weight: 350 to 400 lbs (including solar power system for running electronics and all sailing and rowing gear)

    Fully loaded design displacement: up to 900 lbs (again, higher is viable, but with loss in performance)

    Sail Area: 250 sq ft

    Cabins, 2 - each a comfortable single berth also having a variety of other uses

    Lots of sealed, water-tight storage

    Amas with buoyancy of 125% of fully loaded displacement of the entire boat (each ama).

    These specs define a boat that will be much faster, far more seaworthy in a full range of conditions, and far more suitable for extended, live-aboard, minimalist cruising as well as for the Race to Alaska
     
  13. UNCIVILIZED
    Joined: Jun 2014
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    UNCIVILIZED DIY Junkyard MadScientist

    To get some ideas on liveability, & built in survival features of the boat (not to mention mindset) you might read some of Roz Savage's stuff. As she rowed solo across the atlantic, & at least from San Francisco to Hawaii, if not further.

    Good luck with your race, & I hope that you own a good drysuit or three!
     
  14. scotdomergue
    Joined: Jan 2009
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    scotdomergue Scot

    I've read a couple of her books and visit her website now and then. Good stuff. I've read other ocean rower's stories as well. I hope not to deal with anything quite so extreme!

    I use NRS Paddle Pants and Jacket that are the closest thing to a dry suit you can get without the discomfort and expense (my opinion/experience). I don't know how long they'd keep me comfortable if I was immersed for a long time, but when I was doing capsize testing in a lake that had been frozen over only a month before I was in the water for 10 minutes during a 20 minute period and was quite comfortable. The one time I capsized during my 2-month cruise on the Marsh Duck, on the edge of Haro Strait (southern end of the R2AK race area) I was probably in the water for no more than 2 minutes and didn't notice any discomfort. So part of the plan is to not be totally immersed for long periods of time . . . which should be possible if I'm reasonably conservative about conditions - and at 67 I'm more cautious than I was decades ago.

    Thanks for the interest and wishes.
     

  15. UNCIVILIZED
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    UNCIVILIZED DIY Junkyard MadScientist

    If memory serves, Danny Greene designed a 16'er that was setup to row & sail. It was for beach cruising/coastal camping (with his kids). Which had a LOT of unique features that were well thought out. Including easily attachable/detachable canvas covers for much of the boat, & a multi-tiered dodger for the primary rowing station, that could be lifted up or down about 6" at a time. Kind of like a pram hood/baby carriage lid.

    Thus, for the 50% or so of the boat which didn't have a hard deck, it took but seconds to cover or uncover everything. Although even when fully covered, it had plenty of ventilation. Which was a wise move, as the boat was designed with bunks at both ends also. So fresh air was needed to keep the drip factor (off of the canvas) down.

    I want to say that I saw it in "Wooden Boat", but I can't be certain. Google might turn it up.

    What is it about drysuits which causes you discomfort? Exertion, & sweat level, or something else?


    PS: I'm a bit sleepy to be throwing around multihull specs, but on any of the trimarans built for speed, when they're at rest, only one ama is in the water, & barely at that. We're talking a couple of inches max, & the other is several inches above the water's surface. Also, & it be smart to talk to a designer on this, but volume wise, I want to say that buoyancy wise, amas run about 300% of the mass of the entire vessel. Though these are racing tri's, meant to be sailed with the main hulls airborne.
    You might want to do some research into proas also, as it sounds as if your current design has many characteristics in common with them.
     
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