Fiberglass technology GRP

Dotan ® marine engineers have developed a unique technology for the manufacture of fiberglass rudder blades and daggers.

The foils (blade and daggers) are made using our know-how technology. In the core of it is combination of very high pressure with thermo-shock. This technology gives our foils resilience qualities which are very important on a beat in choppy or rough waters. Let's analyze in detail the advantages of this method:

  • First of all, the production process takes place in specialized metal molds, which guarantee high precision and withstand high pressure at significant temperatures. Thanks to the use of this shape, the rudders and centerboards have a high-quality surface with an ideal hydrodynamic profile, which provides a lower resistance to water flow and, therefore, higher speed.
  • The main feature is that this technology allows an order of magnitude increase in the compressive force of the fiberglass laminate in comparison with the conventional vacuum forming method.
    And now the most important thing!
    • Due to the high pressure, all layers of the reinforcing fabric are compressed with each other with great force, so that the structure of the fabric of one layer "grows" into the structure of the tissue of the other layer. As a result, all layers are fused into a single whole, forming a homogeneous monolith.
    • Due to the high temperature at the time of compression of the laminate, the viscosity of the binder decreases, which helps to pack the reinforcing threads even more tightly.

Thus, we get a product with an increased concentration of reinforcing material and improved characteristics of strength, stiffness and what we consider most important with exceptional elasticity (Ability to return original shape after bending).

  • The next important task is to ensure optimal profile bending. For this, the reinforcing fabric is distributed in strictly calculated places and in places where the maximum loads are concentrated. As a result, the product bends along a pre-programmed trajectory.
  • One of the major problems with blade durability is ensuring a secure bond between the two profile halves. To solve this problem, a reinforcing spar is built into the inner part of the blade, which holds both parts together. So, a spar together with polyurethane reliably binds the entire structure into a single load-bearing structure, providing the rudder blade with excellent mechanical properties with minimal weight.
  • Usually, in the process of making rudders, manufacturers use glass mats, since they are easier and cheaper to work with. However, it should be taken into account that almost twice as much binder is needed to impregnate the glass mat, and given that polymers perform only the bond function, and the reinforcement (fiberglass or carbon fiber) carries the main power load, a relatively large amount of binder in relation to the reinforcement weakens the product and it turns out to be fragile, heavy and not durable. For this reason, we exclusively use structural glass fabrics of satin weave with eight-fold longitudinal reinforcement.
  • Dotan® Kick-Up uses the NACA 0009 hydrodynamic profile design basis for the rudder blade cross-section design

Cross-section of rudder Blade

The Longeron integrates all the elements of the rudder blade into a single powerful structure.

Conducting rudder tests on the Bimare Javelin 2 catamaran.


Dotan`s rudder benefits

  • Flick-of-the-Wrist Magic

    Dotan's conceptually brilliant rudder mechanism enables you to set the blade with a simple flick of the wrist. This action takes less than a second
    Say goodbye once and for all to ropes, elastic bands, fly-nut, screw-in rudder systems and multi-step setting and lifting actions.
  • Rudder Box: Constructed of Non-Corrosive

    Incomparably strong and matchlessly durable, using non-corrosive, composite materials which make the Dotan rudder box more steadier against dynamic loadings than aluminum boxes.
  • Rudder Blade 

    The rudder blade is lightweight and yet durable thanks to the integrated spar and special know-how of high-pressure technology with thermal shock.
    The Dotan rudder blade's profile is designed on the basis of the STEINER and NACA 0009 hydrodynamic profile (National Advisory Committee for Aeronautics). The Dotan rudder blade's shape minimizes wave and inductive resistance (more info.)

  • Rudder Adjustment

    The design makes it easy to adapt the rudder box to a variety of sailing boats and catamarans. The rudder box provides the ability to adjust the distance between the gudgeons.
  • Encountering obstacles

    When hitting underwater obstacles such as rocks, sandbanks, jellyfish, etc., the blade automatically kicks up.


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