In the buildup to the Moth Worlds, we’re diving into the cutting-edge innovations that make up the Mackay Bieker BM-V3 Moth. This week we focus on the tech behind its wing. For foil and hull information, scroll down the page. 

Wing Power

Based on the ambitious goal of developing the “optimal wing”, the Mackay Bieker’s wing is designed to minimise aerodynamic drag, have an optimal strength-to-weight ratio for its structure and provide maximum righting moment opportunities.

How aerodynamic drag was reduced

Blending form with function was everything when it came to reducing the wing’s aerodynamic drag.

Built in-house, the Mackay Bieker’s carbon fibre wing is shaped to promote attached airflow, meaning the air will stay as close as possible to the wing's surface with minimal disruption. In getting to this point, an optimal fore and aft wing beam section shape had to be designed along with minimising the protrusion of fittings.

Here are some of the key areas the team focused on to reduce drag -

• Minimising protruding fittings

Every fitting on the wings deck was redesigned to keep the deck’s surface as clean as possible. This required our in-house design and component teams to develop some very cool carbon composite fittings. One of these fittings was the cleat plate which is incorporated into the wing’s deck. It allows the control lines to sit flush on the wing’s surface area, and the take-up control lines to run below the deck. This has a big effect on reducing airflow disturbance.  

• Streamlined connections

Creating a smooth surface between joins can be challenging. However the Mackay Bieker’s wing and deck connections are designed to lock together perfectly to create a smooth surface and keep the platform stiff and strong,

Hiking strap mount

The carbon mount for the hiking strap is another custom-designed and built fitting incorporated into the deck’s wing, also designed to minimise drag.

• Internal chainplate system

An internal chainplate system incorporated into the wing’s beam keeps windage around the fitting to a minimum. The internal chainplate uses a titanium rod that runs down the leading edge of the Moth’s forward wing beam and uses a threaded outboard end to make it easy to fit and remove stays.

How Righting Moment has been maximised

Wing shape was optimised to gain maximum width when hiking. Decreasing the radius on the outer edge of the wing gained valuable righting moment which effectively allows the sailor to hike 30mm further outboard than the earlier wing.
The wing angle is also optimised to allow the sailor to gain maximum righting moment when heeled to windward.

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Hull Power

Designing a hull for optimal aerodynamics, strength and stiffness, while keeping weight to a minimum incorporates many variables.

 

First off is the hull's shape. The carbon composite hull is a comparatively high-volume displacement shape designed for a wide range of Moth sailor weights. It has a rocker profile optimised for easy low-ride handling with un-sticky take-off characteristics. Getting to this point has required significant research and development into the hull shape, load cases and structural design.

Flow Analysis / Load Case Analysis

Flow analysis using CFD (computational Fluid Dynamics) at the project’s inception in 2019 revealed that the quantum leap in hull shape was made with the BM-V1 model. This was reviewed again more recently when we undertook the design review that led to the BM-V3. The review confirmed the hull design but led to a lot of aero gains in the wings and deck detailing.

Comprehensive load case testing using FEA (Finite Element Analysis) was done to find optimal stiffness and strength with minimum weight.  Needless-to-say conducting load testing is critical for a boat that foils at very high speed. With the Mackay Bieker, the load case image shows a very even stress distribution which points to a very efficient structure.

The hulls laminate uses a custom-made spread tow tri-axel pre-preg carbon fibre either side of a honeycomb core. This keeps weight to a minimum while adding torsional stiffness. High load points have also been reinforced with unidirectional carbon fibre patching. 

Hull mould development

The mould itself plays a big part in the Moth’s performance. Built from a hi-temp carbon tooling prepreg, the Mackay Bieker’s mould offers excellent structural properties for keeping the stability and accuracy of the mould for a longer period in a production environment.  Its structural properties have also led to a very high level of accuracy with the hull’s coming off the mould. This in turn has led to lighter hulls needing less paint and precise alignment of the components.

All in all, every millimetre of the Moth’s hull has been designed for aerodynamic optimisation.

 

Foil Power

Foils are a huge part of the Moth’s performance, with the accuracy and quality of the foil’s finish being exceptionally important.  

The Mackay Bieker foils are built in-house at Mackay Boats, designed by Paul Bieker, modeled by Riley Dean, engineered by Frederick Leopold, and overseen by in-house engineer Andre Terzaghi.

Let's take closer look into the technology involved in the horizontal and vertical foil -

The Horizontal

 

A range of main and rudder horizontal foils are built as each foil produces a different lift/drag profile to suit different conditions, sailor weights, and sailor preferences. The lift/drag profile changes with shape profile and sectional shape.

The Mackay Bieker horizontal foils are made with up to 100 individually cut layers of pre-preg High Modulus Carbon Fibre. These are carefully laid into an exact position in an aluminum mould and cooked under 30 tonnes of pressure.

In general, heavy-air foils are smaller while lighter-air foils are larger. However, we are experimenting with the sectional shape within this envelope and have seen subtle changes affecting performance.

 

The Vertical

Vertical foils are all about minimizing drag while retaining maximum strength and stiffness.

Vertical foils are made the same way as horizontal foils, with up to 70 individually cut layers of pre-preg High Modulus Carbon Fibre carefully laid into an exact position in an aluminum mould and cooked under 30 tonnes of pressure.

Vertical foils are made from a combination of metals like titanium and high-strength Stainless Steel spliced into High Modulus Carbon fibre.

The latest foils feature longer metal segments at the bottom to reduce drag then spliced into carbon heads to try and keep the weight as low as possible.

When developing a horizontal or vertical there are always tradeoffs; the trade-off on the Horizontal foils is lift v’s drag (more lift comes with more drag), while for the Vertical foil the trade-off is drag v’s stiffness and weight.