Lecomble & Schmitt Autopilot Drives

When the Vendée Globe fleet left Les Sables d’Olonne, more than 20 boats out of 30 were fitted with L&S hydraulic linear drive units. At the end of the race, no failure has been reported on a Lecomble & Schmitt pilot, proving that the worst sailing conditions are normal for L&S hydraulic cylinders. Linear drives L&S 40ST16 and L&S 50ST20 used on IMOCA 60 are the same as the 20,000 hydraulic pilots fitted on sailing boats for more than 10 years. After checking the 40ST16 linear drive used by Michel Desjoyeaux during 90% of the racing period, it was established that the drive could have done a second round the world race without maintenance required!

Lecomble & Schmitt autopilot drive

Lecomble & Schmitt single rod hydraulic linear drives with integrated electrical by-pass. These are directly fitted on the quadrant. The overall compact design lets you install these on the floor, ceiling or bulkhead. Lecomble & Schmitt linear drives feature the best thrust/electrical consumption ratio on the market!

A separate reversible power pack which can be installed where ever you desire. The linear drive kits are delivered already assembled and bled, with 1.20m of flexible tube (other lengths available on request).

Lecomble & Schmitt autopilot drive cylinder

Cylinder

The cylinder is the dictating element in the selection of a system. It gives the pushing power to the steering system in function of its effective area and the pressure it receives from the power pack.

Lecomble & Schmitt autopilot drive power pack

Hydraulic Power Pack

Power packs are always composed of a reversible or non reversible electrical motor in 12 or 24 volts DC, or 220/240 V single-phased or three-phase, coupled to a reversible or non reversible axial piston pump or gear pump, with adjustable or fixed flow rate.

Receiving orders from the electronics, the power pack will suck or force back the oil in the circuit. The speed of correction is determined in function of the pump flow rate in litres per minute.

Our systems are fitted with lock valves which prevent cylinder movements once the boat is on the desired course until a new course correction is required. They are also fitted with pressure relief systems to protect the circuit against abnormal pressure increases.

Lecomble & Schmitt autopilot drive tubing

Tubing

Tubing is designed for hydraulic oil transfer under pressure. Tubing diameter is selected in function of the power pack flow rate.


Accessories

Here are some accessories that you may find helpful for your Lecomble & Schmitt Autopilot Drive system.


Please contact us and we'd be happy to assist you in finding the perfect Lecomble & Schmitt Linear Autopilot drive for you. Or if you would like to figure out the actual rudder load on your own below are two ways to determine this, by using a formula or if your boat has a modern hull, by boat length.

For boats equipped with a mechanical steering (wire ropes, cables, rack and pinion), it will be necessary to determine the following:

  • The rudder(s) torque
  • The available voltage on board (12 VDC, 24 VDC, etc.)

Method #1: Torque Calculation

For boats fitted with a rudder with speed not exceeding 25 knots, the torque (C) of the rudder or rudders will be calculated according to the formula and correction coefficients below:

C = S x [ (0.4 Lg) – Lc ] x V² x K

C = Torque in kpm
S = Total surface of rudder (H x Lg) in sq. m
H = Height of rudder in meters
Lg = Width of rudder in meters
Lc = Compensation width in meters
V = Maximum speed of the boat in knots
K = Coefficient according to total angle of rudder (Refer to the Coefficient Chart below)

Method #1 diagram

Coefficient Chart

(70° is industry standard)

Port to starboard 70° K = 15.89
Port to starboard 80° K = 17.80
Port to starboard 90° K = 19.52

Here's an example of how the formula works:

  • For sailboats: C x 0.5
  • For boats fitted with several rudders (catamarans, trimarans and monohulls): Multiply the calculated torque result by the number of rudders fitted on the boat.

Example

  • H = 1.2m
  • Lg = 0.7m
  • Lc = 0.18
  • Speed under sail = 12 knots
  • Speed with motor = 8 knots
  • S = 1.2 x 0.7 = 0.84 m2

Torque under sail = (0.84 x [(0.4 x 0.7) – 0.18] x 122 x 15.89) x 0.5 = 96.11 m.kg

Torque with motor = 0.84 x [(0.4 x 0,7) – 0.18] x 82 x 15.89 = 85.42 m.kg


Selection of the linear drives:

  • Torque not exceeding 50kpm: Linear drive type 32ST16 NEWAVE
  • Torque not exceeding 100 kpm: Linear drive type 40ST16 NEWAVE
  • Torque not exceeding 200 kpm: Linear drive type 50ST20 NEWAVE

In the above example, the calculated torque is 96.11 kpm. Therefore the correct selection will be a linear drive type 40ST16 NEWAVE.


Method #2: Boat Length Calculation

Note: for sailing boats with a modern hull and balanced rudder, the selection can be made in function of the boat length as shown below.

Boat Length Linear Drive Type 12v Part # 24v Part # Max. Torque
Length not exceeding 33 feet* 32ST16 NEWAVE* 2203063 2203064 Not exceeding 50 kpm
Length not exceeding 44 feet* 40ST16 NEWAVE* 2203066 2203067 Not exceeding 100 kpm
Length not exceeding 60 feet* 50ST20 NEWAVE* 2203068 2203069 Not exceeding 200 kpm

For boats exceeding 60 feet please contact us for assistance.

Data given as an approximation only.


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