When you compare sales brochures from the various builders, you will note we all supply letters of endorsements from happy clients, some even “product compare”. We do not do this preferring to leave that to your own good judgment. There are however subtle differences in design construction, materials and building techniques that need careful evaluation to sort the wheat from the chaff. After you have evaluated the various sales brochures, we suggest you ask the following questions.

  1. Initial cost and resale value

  2. Construction methods and materials

  3. Fitness of purpose and long term reliability

  4. Builders experience and history building self steering systems

  5. After sales back up and ongoing factory support


All builders in some way incorporate Cams, Bevel and / or Worm Gears, Push Rods, Cranks, Gudgeons, Bearings, Sleeve Roller / Ball etc. It is often hard for the new client to understand what is best and how they different.

When you first inspect a Fleming Servo or Auxiliary Rudder System you will be impressed by the small elegant design only possible by the exclusive use of very high tensile stainless steel alloys and castings.

The user friendly , simple, award wining design continues the Fleming tradition. Our difference is the “Design Heart”, a small reverse acting 2/1 ratio servo arm, introduced in our prototype in in 1985 and maintained through to our present generation wind vanes. The servo swings around a main shaft not restricted by a space frame as in our previous models, thus allowing more design flexibility. This servo arrangement provides added light air advantage and eliminates encapsulated control lines on the unit frame.  The course setline is routed through a worm drive with 360 – one degree increment adjustment , controlled from a remote helmsman position.

Air foil signal to servo adjustment is carefully controlled by a bevel gear ratio to prevent over steering in any wind condition. Units are fitted with a high aspect NACA servo rudder plan form and cord profile to power our designs from as little as 1.5 knot hull speed to full gales. Air foils are polycarbonate and are supplied with both standard and storm size. The air to water drive train is floated in low friction roller bearings, requiring minimum counter weight introduction. Bearings are encapsulated in “quick removal” modules manufactured from the space age plastic derivative “Prep Ertylate”, providing lowest water absorption and excellent friction coefficient. Units can be completely dismantled in ten minutes and removed from the mounting frame with a “2 bolt / 2 minutes” quick removal procedure for under deck stowage.


There are three ways to fit this component into a mechanical self-steering system, vertical, vertical inclined or horizontal. Each provides the system with different steering power inputs and capabilities.

  1. Vertical – this has the airfoil revolving around a vertical shaft in a suitable bearing arrangement. When the boat yaws off a present course to the apparent wind (say ten degrees), the air foil will also move ten degrees. This arrangement is proportional to any apparent wind change, which is advantages but develops low output.

  2. Vertical Inclined / Horizontal – this has the airfoil revolving around an inclined horizontal shaft suitable bearing arrangement. When the boat yaws off a preset course to the apparent wind (say 10 degrees) the air foil will move 10 degrees so its power output is higher but is still proportional to wind change, which is desirable. It is the best all round solution and used in all of Kevin Flemings designs.

  3. Horizontal – this has the air foil revolving around a horizontal shaft in a suitable bearing arrangement. When the boat yaws off a preset course (say 10 degrees), the air foil tends to flop over till it stops, increasing rudder angle of attack, producing more lift than either of the other two arrangements, in the same wind conditions. It is not proportional to apparent wind change, so over steering develops in stronger winds to the detriment of the system.

The question is, can both configurations be combined and if so, does it produce a better system, better in lighter / heavy airs. The answer is YES & NO.

YES, because mechanically adjusting the axis is very easy to achieve and NO, because test results indicate improving in very light airs when compared to an inclined / horizontal axis fitted into a well designed system. The theory is sound as it deals with speed versus dynamic lift.

NO – Using the same air pressure lever, planform and high aspect ratio, we found it required a minimum of 1 – 1.5knots speed to develop enough HYDRODYNAMIC ENERGY to lift the servo rudder, regardless of inducing the premature angle of attack under that speed.

Over that speed as predicted, the system developed erratic “oversteering” and under comparing axis no noticeable improvement. So is it worth complicating user operation and mechanics? In our view no, however it does sound good in sales pitches.


In the early days prefabrication was the chosen build method. It was inexpensive to set up a small work shop and the low volume production required minimum machinery and financial outlay. The original builders incorporated bronze, aluminum stainless steels, plastic and even wood in their systems. Regrettably prefabrication and tube bending required extensive welding which introduced detrimental side effects known as work hardening and metal brittleness. Also the inevitable variation in fit prevented close manufacturing tolerances, so replacement component parts did not fit well.

Construction was labour intensive and produced the ugly mini oil rig often leaving the final product with a lot to be desired, certainly when compared to today’s product quality. As the industry developed, most builders adopted more professional building methods and incorporated cast components in their build programs, improving quality and eliminating welding side effects. In the main, old ways have passed the industry, with only a few diehards and entry level builders still battling these problems.



Today most builders have chosen to build and cast with aluminum metals, so we will look at this first. Casting offers constant uniformity of component parts eliminating past welding problems and minimizes the labour content. Aluminum alloys are light inexpensive to cast, fabricate easy work and forgiving on tools. Their tensile strength is however low (compared to S/S) and so component mass is quite large. They are not suitable for shafts or fasteners as required in vane design. Stainless Steel is normally used for this purpose. Regrettably, aluminium when “touched: by these necessary stainless steel fasteners and immersed in salt water, galvanic corrosion occurs to create a hard oxide, quickly expanding in tolerances spaces.

Tests show that in wind vane construction, corrosion becomes a problem long before parts actually seize, but when they do, friction is increased, reducing light air sensitivity performance and resale value. If you have ever had to remove a corroded bolt from an out board motor, you will have experienced this frustrating, unavoidable and expensive problem. Regardless of salesman hype and best efforts to “insulate” the different metals in the build stage, like “death and taxes”, it is unavoidable and will reduce the long term value.


Many stainless alloys are available, but only a few are suitable for wind vane construction.  Refer to “More About Steel” Fleming builds the entire unit with cast investment stainless steel components, developed and pioneered in its designs over 39 years ago.

A range of models, both servo and auxiliary, are available from 25ft to 65ft. Stainless castings provide a superior weight to strength ration over Aluminium,  so component mass is reduced and corrosion concerns are non existent.  Excessive structural welding and side effects are eliminated by Fleming design, with only the main turret tube welded. Parts are investment cast to close tolerances with minimum machining required, reducing labour build time and improving quality. Casting in stainless steel requires more initial investment than aluminium and it is harder to machine and work.

Careful attention to design and our manufacturing techniques has kept our Fleming in line with less expensive building methods, in fact today, units supplied by Fleming Marine Engineering & Sales, in most cases, beat our Aluminium Cousins.


In conclusion, we often hear from past clients or see units 20 or 30 years old still chugging along, many as original, substantiating our building program. We are further flattered by Fleming copies popping up worldwide, proof we got right nearly four decades ago.

Fleming vanes enjoy these margins of superiority over our competitors:

  1. Lifetime warranty on castings – two years on workmanship (first owner) – two years on bearings (first owner)

  2. Cast duplex stainless steel components (a Fleming pioneering building technique)

  3. Unequalled weight to strength ratios and salt water durability

  4. Very low maintenance requirements

  5. Exceptional sensitivity & heavy weather performance

  6. Unequalled resale value & competitive initial cost

  7. 40 years building experience with same designer and builder

  8. Quick easy vane disconnect from mounting frame

When you examine the various wind vane designs, we believe our product quality will stand out above the rest and that you will find our vane to be unmatched in the industry. Its ruggedness and reliability, coupled with the best customer support in the industry accounts for Fleming wind vanes being the choice of ocean racer and cruiser alike.

So why not buy – a FLEMING – with over 40 years of successful world wide sales and service.

Read more about Steel

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