Please select your home edition
Edition
Rooster 2025

Jefa Autopilot Direct Drives - Simply the Best?

by Calanach Finlayson 3 May 2023 09:00 PDT
What makes up a good autopilot system and why the details matter © Jefa

The Jefa direct drives are something of a hallmark in autopilot drive engineering. Every aspect has been designed from the ground up to create an efficient, powerful and long-lasting pilot drive. In this article we explore what makes up a good autopilot system and why the details matter.

The below diagram from Jefa shows the basic components necessary for a good autopilot system. This is the same regardless of manufacturer. Let's briefly run through the system...

Autopilot control head

The brains of the operation. The pilot computer receives instrument data and calculates the required output control signals to maintain the programmed course (be that heading hold, TWA hold etc).

Rudder feedback unit

Measures the real angle of the rudder and feeds this back to the pilot computer. It is not enough to rely on the expected rudder angle.

Fluxgate compass

Provides the computer with vessel heading which is core to autopilot functionality.

Drive unit

Receives control commands from the pilot computer and translates these into mechanical actions to steer the boat. The drive unit is the component we are discussing in this article.

Linear vs direct vs hydraulic

The majority of electro-mechanical drives on the market are linear, meaning the actuator is effectively a telescopic tube which extends and retracts to move the rudder. This can be connected directly to the tiller arm below deck. Linear drives typically use a worm screw or ball screw to translate the rotary motion of the motor into a linear motion.

Conversely, direct drives use a planetary gearbox and feature an output arm which is linked to the steering system via a drag link.

The alternative to electro-mechanical is hydraulic. Hydraulic drives are also a type of linear drive but with the additional complication of a hydraulic fluid, pump etc.

Hand steering

An inherent drawback of linear drives is the added resistance when hand steering and back-driving the system. Even with the clutch disengaged, you are still pushing against the gears. Similarly, in a hydraulic drive you have all that hydraulic fluid to push through the system.

With the Jefa Direct Drives, the only component which remains connected after the clutch is disengaged is the tiller arm, running in a ball bearing. The net result is virtually zero additional resistance when hand steering the boat.

The motor and PWM

Most off-the-shelf brushless DC motors are designed to run continuously, at constant speeds. The use profile for an autopilot couldn't be further from that, partly due to something called pulse width modulation (PWM). PWM is used in modern pilot computers to better control motor speed using a series of short pulses, instead of a continuous on/off signal.

The Jefa direct drives feature a low inertia, flat wound motor. That might sound trivial but this is where the details matter. The benefit of this lightweight motor is low starting voltage & better start/stop control.

Gears

Jefa Direct Drives feature a planetary gearbox for superior efficiency and reduced wear as the load is spread evenly across a larger number of gear teeth. This is particularly important for boats with heavy steering wheels which themselves have high inertia and can destroy the gear teeth on some pilot drives.

Drawbacks?

Weight is the big one. The Jefa DD1 (suitable for boats up to 45ft) comes in at a sizeable 12kg which is almost double the weight of its equivalent sized linear drive. While this isn't an issue for the heavy displacement blue water cruiser, it's non-trivial for most racing yachts.

Although not really a drawback, a small point worth noting with the Jefa Direct Drives is they do require regular (but infrequent) maintenance, just like any other machinery on board. Jefa recommends a full service every 5-6 years.

Takeaway

There is little doubt that the Jefa Direct Drive is a superior unit than most alternatives on the market. But whether it's the right option for you is less clear cut. Many racing yachts choose electro-mechanical linear drives in order to minimise weight.

On the other hand, if you are setting off to sail around the world on a heavily laden cruiser, then the reliability and efficiency of the Jefa Direct Drive is a no-brainer.

If you have any questions please feel free to email us at , or click the link below to see our full range:

See the range

Related Articles

Soft shackles are a win-win solution
Upffront look at their use across multiple applications Soft shackles have surely penetrated the mainstream sailing in recent years. They are a popular alternative to traditional metal shackles. Made from single braid Dyneema® soft shackles offer several advantages over their metal counterparts. Posted on 8 Feb 2024
Vakaros Atlas 2 - sailing with ultimate precision
A careful review by the experts at upffront.com Recently upffront.com have introduced the latest Vakaros Atlas 2 sailing instrument to the shop and compared it in a review of other top sailing instruments. Posted on 25 Jan 2024
Sailing instruments from Velocitek/Sailmon/Vakaros
An introduction and comparison from Upffront.com The term 'sailing instrument' is broadly applicable to just about any onboard system with a sensor and a readout. While wired instrument systems are common, in this blog we discuss portable GPS sailing instruments from Velocitek, Sailmon and Vakaros. Posted on 11 Jan 2024
Introducing Ronstan Orbit Winches
QuickTrim feature allows line to be eased without removing handle or line Ronstan have just launched an all new range of Aluminium Self-tailing Orbit Winches in three sizes plus an innovative new QuickTrim feature which allows the line to be eased without removing the handle or the line from the self-tailer. Posted on 7 Jun 2023
Performance Code Zero Furlers
Options from KZ Racefurlers put under the spotlight We are pleased to introduce KZ Racefurlers to the upffront.com website. Racing sailors will need little introduction, as KZ have been gracing the bows of grand prix race boats for almost 30 years. Posted on 28 Jan 2023
How to Choose a Spinlock Deckvest
The main consideration is usage and application Lifejacket pioneers Spinlock are renowned for their sleek, comfortable to wear, high-spec lifejackets. In a previous article, we introduced the full range of Deckvests and took a look at the features and benefits of each. Posted on 16 Sep 2021
Best Sailing Boat Blocks in 2021
Review covers soft attach, snatch looper, open ring, beckets and more In this article we take a quick look at what is new and/or interesting in the sailing block world in 2021. Harken continue to develop soft attach blocks. Morfrac Systems are developing their product line to include becket versions of their blocks. Posted on 7 Sep 2021
Make Waves with nke Marine Electronics
Innovative systems for racing or cruising It's the age of information, and global technological advancements have revolutionised our lives and industries alike. As with many others, the sailing industry has benefitted from the introduction of marine electronics that make it easier. Posted on 23 Nov 2018
Introduction to Core Fibres in Modern Ropes
The majority are polyester or Dyneema There are many core materials used in rope making (e.g. Vectran®, PBO, polypropylene, hemp, nylon etc) but the vast majority of modern ropes are based on a polyester, or increasingly, a Dyneema® core. Get a basic introduction here. Posted on 9 Nov 2018
High Performance, Low Hassle Family Cruising
The radical - but not too radical - 39BEN How do you design a cruising boat that's fast enough to get your competitive juices flowing, but without scaring the family? That's been the challenge for Alex Vrolijk, who has drawn the lines for the radical - but not too radical - 39BEN. Posted on 26 Oct 2018
Henri-Lloyd Dynamic RangeExposure MarineSwitch One Design