T 28 order


Marstrom Composites has been approached to build the beams and the rig for the T 28 trimaran. It is one cool little boat designed by Swedish trimaran Guru Stefan Törnblom (Gepard, T35, SeaOn96, T29 & KISS T30).

Designer's comments:

  • · Light weight, top quality build with performance focus but still rather roomy with basic accommodation for cruising
  • · Built in 100% carbon fibre/epoxy by Vaxholm Komposit in Stockholm, Sweden www.vaxholmkomposit.sestarting with a promo series of five boats
  • · An easily demountable trimaran to be built much lighter, stronger and to a lower cost compared with a foldable – the floats are easily handled by two persons
  • · Hull length 8.60m – Beam 6.60m – Sailing weight 1 100kg – Mainsail 33m2 – Overlapping jib 22m2 with reef – Asymmetric kite A3 68 m2


This boat is designed for a usage typical of Stockholm, Sweden – Single or double handed racing in the archipelago combined with cruising for the small family, two grownups and two children.


To keep the cost down, compared to my latest design the T29, I’ve chosen a little smaller and lighter format needing smaller rig, sails and equipment. I’ve also chosen to go for fixed carbon fibre beams and water stays which eliminates the need of structure to handle compression loads on the main hull. An easily demountable trimaran can be built much lighter, stronger and to a lower cost than a foldable one. For trailer transport and hard stand storage the floats can be easily handled by two persons.

The boat will be built in 100% carbon fibre and epoxy, the same for rig, beams and bowsprit. The reason to build an all Carbon fibre boat is mainly to achieve a stiff enough  platform to be able to carry a large foretriangle and the sheet loads.

The sail plan is, compared to the T29, designed with the mast further back for larger head sails, a little lower main sail and mast. T28 is light enough to do ok with a self tacking jib but for racing I see an overlapping max jib with a reef. The thought is also that the boat is sailed without screecher and with an A3 topdown furling, high aspect masthead kite. This combination of sails has proven to be efficient for shorthanded sailing compared to rating.

I’ve chosen to design the T28 with daggerboards in the floats, operated from the cockpit. Apart from better space in the cabin this also improves the performance of the boat. due to increased righting moment, depth when the boat is heeling and they are not surface piercing as a central daggerboard when the centre hull is skimming the water.


One common problem in the design of a trimaran of this type is the longitudinal placement of the daggerboard. A vertical DB. just aft of the mast can be designed with an efficient planform but its depth is restricted by the hight of the ceiling. If you want a deeper DB. It has to exit in front of the mast and with a backwards sweep to align with the Ce of the sailplane, that is not so efficient due to the not ideal relation between sweep and planform. If the Daggerboard is positioned in the floats they can be placed optimally lengthwise.

The motive for a central rudder is mainly simplicity, lower cost and weight. Also I’ve never experienced any steering issues on my designs when only skimming or slightly lifting the centre hull. High lifts are more for the photographer than performance efficiency anyway.

The floats are designed with a lot of volume in the ends for good diagonal sailing stability and with a lot of reserve displacement when pushing hard. The T28 should be non dramatic (fun) to sail with a skimming centre hull.

The boat will be built by Vaxholm Komposit, Stockholm, Sweden.  A promo serie of five boats will be built for delivery early spring 2022. The target is to have the first boat in the water late autumn 2021. With these five boats on water more boat orders are expected since there’s a true demand for a modern lightweight, performance oriented cruisingable trimaran and the existing alternatives on the market are few.

/Stefan Törnblom

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Marstrom Composite AB

Lucernavägen 9
593 50 Västervik | Sweden
Tel: +46 (0)490 89580
Fax: +46 (0)490 35302
E-post: mail@marstrom.com

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