What to do that Amas (Outriggers) aren't "dead space" for a Tri ?

Discussion in 'Multihulls' started by Skip JayR, Sep 9, 2015.

  1. Corley
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    Corley epoxy coated

  2. catsketcher
    Joined: Mar 2006
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    catsketcher Senior Member

    No No No No NO


    You are heading down a bad road here. You do not want to put batteries into the floats, the weight is exactly in the wrong place. Cav has an old design - 35ft long and 20ft wide. It is narrower than any design in the last 30 years. In his boat the weight in the float will be fine.

    If you are thinking of getting a racing type tri then you must change your mindset. Weight in the floats is not good, putting batteries in there will increase your roll and turn inertia. A little bit of weight at such a long lever arm, if the boat you are looking at is modern it will be wide, will greatly increase roll inertia.

    This means the boat will turn slower and rock slower. This could be a a good thing in Cav's boat but his tri has lovely fine bottom floats. Any F40 type tri will have fat bum floats that are going to smack the hell out of chop. I would not want any extra weight there to increase the energy required to lift a float out of the way of chop or beam waves.

    But the most worrying thing is that you don't seem to get the physics. Putting weight on both sides only produces bad results, there are no gains. Putting weight on the windward side is fine but not both, there is no magic here. You are still dealing with a CG that has to be to windward of a CB. No magic apart from increasing roll moment and for most of the time you don't want that.

    Batteries are heavy and small. You need to check them regularly as the only tri I saw burn and the only cat I had a fire on were both caused by battery problems (Vale Hired Hand). They especially are ideal for living in the main hull bilge, near the front bulkhead.

    Sail a F40 tri before you get one for cruising. It may be a very bruising encounter as they were designed for speed rather than comfort and when cruising it is comfort that drives how fast you go. I cruise faster on my 38ft cruising cat than I did on my 31ft racing tri - just a question of accelerations, spray and noise being higher in the tri leading me to slow down to have a rest. In the cat she handles herself with aplomb and I get on with trimming, reacher setting, guitar playing and bread making.

    But the cat can get it on, 10 miles in 40 minutes on one special trip, 7.5 knot average on the GPS last trip (over 1500 miles). Some days you are flying and doing high teens with the autopilot on. But those days are not the bread and butter days. Usually you go slower and you need a boat that looks after you, gives you complete security, and gets the miles done in a low fuss manner.

    In the old days when cruising my racing tri I sped 40 miles from one harbour to the next in 4 hours. In one hour we covered 16 miles! When we got to the harbour we spent the whole afternoon drying out and getting over being on the edge for so long. It is better for cruising to arrive 1 hour later but have the bed made, the yoghurt maker happening and get straight ashore and not have your partner ready to leave as soon as the anchor hits the bottom.


  3. cavalier mk2
    Joined: Mar 2010
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    cavalier mk2 Senior Member

    Give me a break Phil, I said batteries in amas bad, water you can pump to windward good, light or nothing in symmetrical storage.

    For the record my Vagabond is 37' at the moment, stock is 36 and normal beam is 20' 4". Quite the mutant by today's standards but extremely functional for how we sail. Being easily driven it uses a small inexpensive rig and those floats give a gentle ride. We keep it because the combination works, not out of nostalgia. Winding up to the high teens in a breeze when feeling the need for speed shocks newer boats.

    And I agree, one shouldn't pick a design then try to figure out how to make it work for something it wasn't intended for. The Nicol works for cruising because back then a boat was expected to have certain amenities, even a racer. Those got sacrificed on the altar of speed but you got it right on it being easier to sail fast on a comfortable boat.
  4. cavalier mk2
    Joined: Mar 2010
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    cavalier mk2 Senior Member

    I did tell him on cruisers forum that stowage in amas would increase ama wave impacts and should be approached on a case by case basis to suit conditions. Boat loading was talked of as a dynamic art and should be approached with the idea you might have to move things to suit conditions and course instead of a static "this goes here". I think Skip needs time on a Twiggy for it all to sink in.

    For the record I keep my batteries down to 1 or 2 in secure low stowage where they will be above the inverted waterline.
  5. tspeer
    Joined: Feb 2002
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    tspeer Senior Member

    The amas on a tri are not just dead volume. A trimaran may have a comparably sized cabin to a monohull, but the shape of the hull below the settee is completely different. With a monohull, the rounded bilges provide lots of volume for storing things. But in a trimaran, the narrow hull flares out to the beam at the settee. As a result, there's little room in the cabin for storage.

    The amas are the place to store bulky items that aren't immediately needed in the cabin. Fenders, dock lines, hoses, boat hooks, etc. all get stored in an ama. I often carry water in gallon jugs instead of using the built-in fresh-water tank, and these get stored in an ama. Food that is packaged in a way that is protected against moisture can also be stored in an ama.

    Look for plastic baskets or tubs that can fit through the hatch. Use these to organize and store smaller items. You can drop one through the hatch, then push it forward or aft and put in another one.
  6. Skip JayR
    Joined: Sep 2015
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    Skip JayR Tri Enthusiast

    thinking, re-thinking, new thinking....

    Guys, keep relaxed... I suppose most of us are not naval architects... so probably we are all wrong and same right in a way depending on the perspective :)

    Yes, Phil, I know.... but I do it by purpose, not unconciously.... so long I know I am on the bad road I can go back onto the good comfortable one.

    I am not only sailor (with a good technical understanding from engineering studies), I am also a journalist... so I am curious and can ask the "most crazy questions" not being scared with to hear answers most probably wont like to hear.

    Opening the mind into new directions means, think newly (or at least: re-think the old way)... and re-think + digest.

    Some folks out there allow themselves to think into new directions. And the result is something like this... a Hybrid Stability System. It was realized successfully in Netherlands under the name HREKO.


    All interesting/new ideas begin with building a model... :)


    Actually I like to get a feeling for what I am dealing with, as my future project... living + working on a Trimaran.

    Yes, it is kind of (small self) experiment. Why not ?! :) Is it possible to live on a 40 foot speedy/sportive trimaran ? - I give it a try with the risk to say in two years: "Wrong decision, wrong boat, lets take a roomy 50 foot catamaran." (This kind of life I already know as I lived on such a big single built Alu-catamaran over two seasons. Very boring like living on land.)

    I dont fear to make a wrong decision. But I have the trust, that I might feel well on a 40 Footer Tri, over such a period of time. It would be the right size of boat to start. - I can't make myself friend with sailing on a roomy Catamaran. Maybe in 10 years I will like it, who knows. Maybe tomorrow I find my "princess under sails", fall in love, start a family and all "old plans" are for nothing good anymore. So is life... :)

    I already have drafted (on paper) the trimaran I like to have, the dream boat... and it became a 72 footer. So I am very aware about that I am 32 foot far away from my real big target. But same here: so is life... success does not come over night.

    For now I dont have that budget to realize it to build an own Trimaran... maybe in 5 years ?? :) . Important is to go steps forward, not waiting till getting the perfect. I had cancer at the age of 25. I know how quickly life can end and Mr. Death knocks on the door and says: now its time to come with me.

    I have looked long around over last months... seen many different Tris, from foldable Trimarans to single built Aluminium Trimarans, and actually I found this one... see short video here of this 40 Foot Trimaran.

    Originally it was designed for off shore racing, but as seen in the short vid it is the crusing-racing version (reconfigured by designer) for long distance sailing. So it is not leight weighted (regularly something 2.6 tons); it is built "heavy weighted" (3.6-4 tons). I suppose it can go regularly 16-17 knots.

    The most critical aspects I see - after I try to digest all your valuable input.

    1. Can the cross beam connection handle the bigger loads in the amas ? (In the upper case of the boat in the vid, it is a cedar-epoxy hull construction; the cross beams are built with foam-cevlar epoxy.)
    We dont talk about heavy loads of + 500 kgs... maybe something of 200-250 kgs.

    • Does the heavier weight (in form of batteries or other stuff stored in the amas + trimming water ballast windward) has a negative "rolling effect" onto the boat ? (Rec.: Pitching I don't see a big problem as T-rudder (this boat in the video needs a new one as suggested by the designer) and foils can compensate the pitching risks.)
    Shortly I had a good discussion with one of the world leading foil specialists. They target at to offer "foil kits" for elder boats. It will come the times where boat owners of 15-20 year old catamarans/trimarans can pimp up / refit their slow boats to something more exiting. Just a question of time.

    About 1.) The upper shown boat I am interested in was built 20 years ago... unluckily the original plans are no more, same the warft is no more (tks to the financial crisis)... so it would need a survey by a naval engineer to answer seriously this question. So yes... it is kind of a risky project with this boat, maybe... discovering "unknown land", maybe entering the dirty path on the "bad road". I am aware of that.

    About 2.) Not scared about this question... the rolling effect easily could be tested on the water: put some tube tanks into the amas, fill them with water up to the weight of the batteries or whatever the extra load is, and do some sea trials under different conditions. - Sometimes practical tests are the best way to get the answers as neither we have the budget nor the technical datas to do expensive "computer simulation".

    So actually I see the risks within the built structure of cross beam connection. Indeed, this might be the real hurdle I can't overjump with this kind of boat.
    Maybe I have to look for an alternative to have more safetyness to keep control about what is going by higher loads within the technical structure. So it is in project planning: thinking, re-thinking, new thinking...

    But isnt it a beauty ?? :)

    Very true.... the boat isnt bought yet, still dealing with the owner about the prize (as mostly they have too highly expectations.)

    So no risks at all... thinking through different options doesnt pain ! It gives the chance to learn.

    Happy Friday ! - Happy Sailing ! - Skip JR

    P.S.: I think about other aspects of the "risks", too. Feel free to read in the Cruiser's Forum about "How to Socialize on Board of a Trimaran ?"
  7. trispirit
    Joined: May 2016
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    trispirit New Member


    Sorry if I'm wrong but I haven't seen anyone mention the fact you will need large wire sizes to cover the distance and reduce voltage drop if you install batteries along way from the items needing power, this adds a huge amount of weight on an already weight sedative platform.
    You also have the added problem of not being able to get to the batteries if your in heavy seas and the floats are underwater or getting pounded by waves. These then to be the times you need to get to them.
    Just my two cents.
  8. Corley
    Joined: Oct 2009
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    Corley epoxy coated

    Whenever I see a thread like this Dick Newick's triangle between comfort, performance and cost keeps coming to mind.

  9. rogerf
    Joined: Apr 2012
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    rogerf Junior Member

    Picking up from Trispirits theme when things get ugly you don't want to be having to find your way in the dark in a lumpy sea to the leeward ama to fix what may just be a loose connection.

    (Well I certainly don't want to be in that situation so why would anyone else)?

    Like keels amas are for stability.
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