What we do

We were contacted by an owner whose boat did not perform very well at higher speeds. The stern was too low in the water and the boat was carrying almost 285 kg of lead in the bilge.
The concept was to replace the lead bulb of the keel with a heavier bulb with a centre of gravity further forward. The additional weight in the keel would allow removing the lead in the bilge without reducing the righting moment.
We carried out the design of the new bulb completely in 3D which allowed accurate predictions of weights and centres of gravity. The result of the modification was a reduction in boat weight of 165 kg, a centre of gravity that is 100 mm further forward and an increased righting moment compared to the original design. Besides that, the new keel has a much more efficient T shape instead of the old L shape.
The created 3D files were sent straight to the foundry and used to CNC machine the mould pattern with high accuracy.
We are looking forward to learn how the boat performs after the modifications. 

Three days after the launch the Bondi 36 went onto a 2-week holiday trip to the Baltic Sea! Everything is working as it should and the performance is outstanding. On a close reach she easily cruises at 8 – 10 knots with only two people on board.

The regular sailing area is the river Elbe in north Germany. The river has a strong tidal current of up to 5 knots. Sailing with the current from behind but against the wind can lead to some very nasty wave conditions. We can report that she passed the test sailing close hauled at up to 30 knots of wind against steep, standing waves.

This weekend she is on the way to Heligoland, a small Island in the North Sea.

After 5 1/2 years of sweat, blood and tears the KJ Engineering designed Bondi 36 was launched in Hamburg in front of an impressed crowd. Even the sky was mostly an unusual blue colour.

The bondi 36 is probably one of the most sophisticated home building project completed by an amateur. The design is an exciting mix of racing and cruising features to meet the requirements of the owner. Except for the lead bulb, keel fin and engine all major parts are made from carbon to minimise weight. Unusual for a racing yacht is the full interior with proper galley, head, heater, fridge and running water. The owner couple wants to cruise the Baltic and therefore need comfort below when the conditions are unfavorable outside. To make sure a reasonable amount of sails can be carried with only a crew of two, water ballast tanks are located in the aft cabins.

The quality of the work can only be described as exceptional. It will be difficult to find a boat built to this standard anywhere.

Infusion technology was used to laminate the hull and deck. There is plenty of time to place the reinforcements. The infusion process itself only takes a few minutes and is very clean without resin mess everywhere.

We are looking forward to the results of the first sea trials. Speed under engine was 8.5 knots which is very encouraging.

KJ Engineering designed and engineered the hull, keel and rudder structures. Additionally we supported the built process with tips, tricks and detailed instructions.

The final drawing for the Bondi 36 lead bulb has been issued! The information provided by us included the paths for the CNC mill. As a result, the casting pattern was completed a few days after the files were provided. 

The mass of the lead will be approximately 2.3 t for a total ballast ration of 52%. To achieve such a high ballast ratio, it is important to reduce the mass of other structure. This was accomplished by using carbon fibre composites for the hull, deck, mast, rudder and interior fit out. The only major steel parts are the keel fin and the engine. A high ballast ratio allows to carry larger sails for increased performance. 

We are very much looking forward to the launch and a first test sail.

The keel fin is the only major steel part of the Bondi 36. For the safety of the boat and crew it is important that this part is reliable over many years. A lead bulb of more than 2 t weight is mounted to the tip of the keel fin to keep the boat upright. Stress ranges are therefore high, especially during tacks, gusts and wave action which can potentially lead to fatigue issues. 

To ensure safety and high fatigue performance a very innovative design was developed by KJ Engineering. The keel consists of a CNC machined top plate to which the load carrying strut is welded. The strut is made from two plates bent into a C - shape. This ensures that all welds on the strut are parallel to the main stress direction and located in the neutral axis to avoid fatigue issues. 

The most critical weld is the connection of the strut to the top plate because of high stress levels. For optimum performance the top plate is shaped in such a way that the weld connection to the strut is a butt weld located away from the stress concentration due to the radius between the top plate and the strut. Butt welds have good fatigue strength compared to other weld types, ensuring maximum fatigue life. Non-destructive testing was carried out after each weld run to ensure this critical weld is crack free.

To complete the aerofoil shape, another C - shaped sheet is welded to the front and two sheets to the back. The inside of the keel was zinc coated after manufacturing to prevent corrosion.

The first prototype of the Python robot has been assembled! All systems are working. The robot can reach precise positions thanks to its stepper motors. While underway it can measure accelerations, battery voltage and current and write all the data to a log file on a micro SD card. Obstacles can be avoided thanks to a distance sensor mounted to the front. 

The next steps are to control the robot via WiFi and to add a camera so that it can execute spy missions. The extension headers for this are already on the board.

We are proud to announce a new exciting project! 

We are developing a micro controller based robot which is programmed via MicroPython. The aim is to teach kids micro controller programming. Billions of micro controllers are sold each year and they all need skilled software developers so that washing machines wash, airbags deploy and music players play music.

We selected MicroPython as the programming language because it makes programming very easy. All that is required is a text editor. The memory on the micro controller appears as a flash drive for saving Python files. This also makes loosing files very difficult.

The following things can be learned with the robot out of the box:

• Switch lights on and off
• Dim lights via PWM
• Blink lights via timer interrupts
• Read battery voltage and power consumption via an analogue to digital converter
• Read button status via external interrupt
• Operate the stepper motors
• Communicate with the accelerometer via SPI bus
• Program the accelerometer to create an interrupt
• Store logging data on the SD card

The robot has been optimised for use by kids. There are no jumpers that can be lost and the reset switch can be disabled. We hope that the cost of the parts can be kept to approximately $25 to allow as many kids as possible access to the robot.

The interior of the Bondi 36 finally sparkles in snow white instead of carbon fibre black. The time span between the ‘before’ and ‘after’ picture is almost exactly 2 years. In this time the deck was bonded, the interior fit out completed and major equipment such as the engine installed. Countless hours were spent filling and sanding the surfaces and two layers of primer were applied to ensure the final appearance is perfect.

The Bondi 36 is a very advanced home building project carried out in Hamburg, Germany. The whole boat has been built using foam cores and carbon fibre skins with epoxy resin. Both deck skins as well as the hull outer skin were vacuum infused which is usually a technique reserved for the best professional yards. The whole yacht has been designed by KJ Engineering using 3D CAD software. As a result of this the built tolerances are around 1 mm. Such small tolerances ensure that all parts fit into the boat the first time without needing adjustment. This in turn speeds up the construction process significantly.

Launch of the Bondi 36 is scheduled during the European spring 2016.

We are pleased to announce the release of the Naval Architect Toolbox pro version. The pro version has all the features of the free version. Additionally hulls can be analysed automatically at a range of heel angles which is great for calculating the righting moment curve and finding the heel angle at minimum wetted surface area. 

It is possible to analyse quite complicated hulls such as multihulls and hulls with reverse chines. 

The pro version also makes it possible to calculate the mass of objects modeled in Rhino. Mass properties can be assigned to materials and the data is stored in the notes box of the regular Rhino material. It is possible to assign densities, area masses and point masses to materials. 

When calculating the mass the plug-in detects if the object is a solid object, surface or point automatically. The volume of solid objects is multiplied by the density, areas by the area mass and point objects simply have the point masses applied. 

Material properties can be assigned directly to the object or via the layer. The object material has precedence over the layer material and therefore it is possible to group objects with different properties into one layer.

Materials can be stored to files and imported which makes re-using of the data easy. A demo video is below.

The pro version can be purchased in our shop.

KJ Engineering Consulting is pleased to offer a new photorealistic image rendering service. The images are produced directly from 3D cad models and are ideal for presentations and marketing material. It is possible to show what the product will look like before a physical prototype has been manufactured. Different materials and colour schemes can be explored with the click of a button to explore design variations.

The render software allows manipulation of detailed camera settings such as lens length and aperture for depth of field control. Animations are rendered with motion blur depending on the shutter speed. 

Large objects can be modelled in a virtual photo studio to create dramatic light effects that would be difficult to achieve with the full scale product. 

Below are some samples of yacht concepts and our USB charger.

KJ Engineering Consulting has developed a plug-in for the popular Rhino 3d design software. The plug-in is currently being tested and provides tools for the naval architect to more efficiently design and analyse yacht hulls.

The analysis tool calculates a great range of hydrostatic properties of the hull. The results can be written to a csv file for archiving or analysis in Excel. Additionally a graph of the cross section areas can be plotted in the Rhino window.

A balance tool adjusts the sink distance and pitch angle of a hull so that the centre of buoyancy matches the centre of gravity and the specified displacement. This allows to visually check how the hull would float in the water depending on displacement and centre of gravity location.

The most complex tool creates and analyses balanced hull surfaces in a range of heel angles. Each of the hulls created has the longitudinal centre of buoyancy located at the x- position of the centre of gravity and the displaced volume matches the input value. All results are written to a csv file for later analysis in Excel. In Excel it is easy to plot graphs of the righting moment, wetted surface area and other hydrostatic parameters depending on the heel angle.

A free evaluation version can be downloaded at food4Rhino. A pro version is available in our shop.

Below is a demo video of the naval architect tool box plug-in for Rhino.

The Bondi 36 which is currently under construction in Hamburg received the first coat of primer! 

This hull analysis plugin for Rhino is currently under development. It calculates the following values when designing a hull surface:

• Hull length and width
• Waterline length and width
• Displaced volume
• LCB
• VCB
• Cp
• Cross section area curve

I would very much appreciate and comments and feature requests.