How to use the Amas (Outriggers) on cruising Trimarans best ?

Since couple of weeks I have this question in mind:
“How to use the Amas (Outriggers) on cruising Trimarans best ?”

56 Foot Scruising Trimaran (Designer: J. Shuttleworth, U.K.)

Amas with “dead zones” on a 56 Foot Cruising Trimaran (Designer: J. Shuttleworth, U.K.)

… as we see Amas which are just “dead zone”, nothing else than floaters with the function of “righting moment” connected by cross beams (akas) with the main hull.

I have seen amas on 30-40 Footers with no single space in side…. even no single hatch window. Just a screwed plate as “inspection hole”, e.g. for the rudder pole.

astern inspection hatches on deck side of the amas of a Trimaran RADIKAL 26 (Perspective Design, France)

astern inspection hatches on deck side of the amas of a Trimaran RADIKAL 26 (Perspective Design, France)

… simply glas fibre epoxy, carbon or marine plywood wrapping “space of air” for uplifting moment…. eventually with some trimming units, e.g. uplifting foils.

What to do with kind of bigger cruising trimaran, one gets the chance to buy ???

Taking the saw, open the ama for creating some extra storage room with installing 1, 2, 3 or even 4 hatch windows ??

A Farrier F-82 in Turkey with 4 hutches in the amas...

A Farrier F-82 in Turkey with 4 hatches in the amas…

Trimaran Vagabundo in Porto... with two hatch windows in the amas.

8 meter Tri Vagabundo (Dragonfly 800) in Porto/Mallorca… with two hatch windows in the amas.

If possible… what kind of storage ?? – Packing each two of 4 heavy weighted gel batteries into the port and starbord ama to get more space in the centre hull ? Or just keeping it light weighted for storage of little things like fenders and sheets in it ? – Or just glue some solar panels on it ?

SOLAR PANELS on Trimaran Paradox

SOLAR PANELS on Trimaran Paradox (Iren Nigels Design) + inspection hatches (for rudders/fins)

Or creating something more valuable space, e.g. integrating a berth (as known from Wharram Catamarans) or a toilet ?

Steve Fossett's Maxi catamaran Playstation at the beginning of the round the world regatta THE RACE (2001)

Steve Fossett’s Maxi catamaran Playstation at the beginning of the round the world regatta THE RACE (2001)

No joke… the toilet is seen on the starbord ama of Trimaran Tritium … see vid starting at 02:49…

There is extra storage on a Dragonfly 35 Tri…. because I have seen it there it kept running my question in the head. As the Danish constructors build sportive Tris I suppose they know what they are doing. 🙂 Cant be wrong…

Just did some screenshots from the “official promo video”…

Here the (original) promo video you can see the astern hatch opened from 01:49 min.

Such paddling kayaks can have a weight between 65-85 pounds roughly. This would be the equivalent for round about two A123-6T-Battery (round about 20 kg each) for long term use.

The Dragonfly 35 has another centred hatch window on deckside of the amas… so some more storage there…

Tri Dragonfly 35 from Danmark at full speed...

Tri Dragonfly 35 from Danmark at full speed…

Just by feeling I’d like to have on a 35-40 foot Trimaran extra storage weight of 150-200 kilograms, each side port + starbord. – It can be compensated by a higher mast, bigger main sail for righting moment, e.g. a 40 Foot Trimaran has a 60 Foot Mast… and some uplifting foils in the amas plus more stiffy construction materials to connect the cross beams safely, e.g. using foam-kevlar-epoxy.

Would be interesting to make some detailed cost calculations. Having 300-400 kg more transportation volume in the amas makes sense for long distance cruising Trimarans, isnt ? I’d like to get free 300-400 kgs more volume in the main hull using for other equipment. 🙂

With wave piercing bows the negatively bumping effect of heavier weight shouldn’t be too extreme. I will ask some multihull naval architects I know to get a more clear picture about such items…

Feel free to share how you expanded your amas into some valuable extra space… without damaging the sailing abilities and substance of the boat. (Rec.: The discussion about this question is also going in the Multihull Sailingboat section of Cruisers & Sailing Forums. Share there your experiences and knowledge with more than 142,636 members.)

Happy & Safe Sailing
Skip JayR (WTE)

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One response to “How to use the Amas (Outriggers) on cruising Trimarans best ?

  1. Thoughts from a qualified boatbuilder…keep it lightweight.
    The design of the wing that attaches the outer hulls to the main hull and the attachment of the wings to the outer hulls would be the critical areas to look at per different boat design.
    Extra weight whilst underway in the outer hulls could potentially cause failure. Perhaps a berth and or fender storage only.
    I have witnessed an experiment where a 100kg weight attached to a weight scale was dropped 300mm..it registers above 2000kg on the scale to halt its drop. This experiment was used in reference to fall arrest harnesses for safety in working at heights in my workplace training.
    My thoughts are also this …while if you made a berth there…at rest theres no problem. However the space you make as a berth can easily become a storage place for alsorts if an expedition is embarked upon. Weight in that area could go far beyond the designers intended stress on the critical strengthened areas at main hull and outer hull attachment areas. Once again ..batteries …very heavy items ..same problem.

    Like

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