TG yachts was founded in 2010 for design & engineering of advanced and lightweight yachts. Part of our business is engineering of special structures - that needs high performance with low weight. We are team of 4 engineers with strong educational background and significant experience in field of our expertise.
Main point of interest is in sailing yacht design, and engineering of advanced marine vessels. We have been involved in more than 30 yacht projects in range of 40 to 150’. Most of our projects were with carbon pre-pregs, but we have experience as well with simpler materials such as aluminum and GFRP.
Design brief – this is single most important part for the project. It sometimes can evolve during the project. It is common that future owners of Yachts have not 100% specified needs & requirements. In some cases, such as Magnus Zaremba project, owner has extremely detailed design brief.
Concept Design. Very initial stage of design when something starts to be visual. Base proportions and general overview starts taking place. We can start defining base parameters – such as length, width, initial sail plan. Depends on clients needs and requirements some parts are more, and some other are less important.
Preliminary design. Some proper engineering starts to happen – initial weight estimate, base sail operations, machinery etc. Important is to know what is possible and very often what is the cost of proposed solutions and how they can be achieved. Not always shipyard is involved at this point, but sometimes boats are being designed around shipyard capabilities and experience.
Detailed design. Custom boats requires good shipyard cooperation. Design budget for custom boat is lower than for production boat, and therefore amount of details is normally smaller on custom boat, or just typical details for previous boats are used. At this stage shipyard is a “must have” so what is designed can actually be manufactured. Depends on shipyard background and skills different materials & approaches have to be taken into account. In the same time very often the same components can be manufactured with high or low number of man working hours – this has significant impact on final boat building cost. It is important to balance complexity, weight and yard abilities to have a successful project.
Drafting is one of the most important parts of the projects - and most time consuming. Not all shipyards have their own in-house drafting departments, where production drawings are being made. Depends on the project we can provide either only engineering drawings or full set of detailed production drawings. In some cases only hand sketches are sufficient to progress
We do work entirely in 3D design environment. As our origins are in aerospace (so we do not finish our job on nice pictures only😉 ) we use high end software. Our 3D cad modeler is CATIA V5, which is not only full parametric cad package, but as well combines scripting and ability to implementation of rapid changes. Over last 10 years we developed quite significant library of typical details and modelling techniques so we are very efficient. Use of this type of software enables us to make good exchange of CAD data between other engineering tools – such as CFD and FEA.
Velocity prediction is important part of design process. In principles this is just solving of motion equations. Ultimate outcome are speed data for different states. In general – this is very complex. And outcome depends highly on what is input. It is important to note that results are always based on some assumptions – like flat water, perfect trim etc. We use 3 different VPP tools:
All have some pros and cos, and depends on design stage, and project details not all needs to be used. VPP based optimization of boat can be tricky for typical cruiser, and it is worth noting that there are few critical parameters that future yacht owner should be aware of:
Weight & CG
Depends on manufacturing method and shipyard skills just structure weight can vary significantly. Typically the biggest unknown, at design process is interior weight. Th same story is with all systems – which without detailed design are a difficult to estimate (unless data from similar boats is available). Just electrical cables on 60’ cruiser can weight ~300-400kg. So weight and position of CG in general is place were biggest mistakes can occur. Weight & CG has direct impact on stability. Righting moment is something that defines how much sails can be carried. And more sails means more thrust – which means in simple words faster boat.
Depends on boats aims we can use different sails. Not all sails suited for all boats obviously. Typical cruising boat has one set of sails, that is fitted for all different weather conditions, while offshore racers has large inventory. Depends on the boat intended user scenario & systems sometime limitations might be on sail weight – so one person can handle it. If intended crew is not professional sail sizes, and therefore loads needs to be limited for safety reasons. For the same principle dimensions sails can be optimized for different apparent wind speed and angle.
Bigger boats (50’+) needs some attention to overall stiffness. Not everyone is aware of simple fact that when rigging is in tensions both lines themselves and boat deforms. If boat is not stiff enough it is not possible to have tight sheets. The biggest problem is with foresails in upwind conditions. Juts to show some numbers – 100’ cruising yacht can deform 300mm in typical upwind conditions, while racer will have only 100mm. Tools for tensioning of rigging is essential for racing boats, but not always practical on cruisers. This aspect needs to be considered, and it has an impact on overall performance.
Computational Fluid Dynamics is a simulation tool for flow around hull and appendages. Depends on a project it can be used for hull lines development and for optimization of appendages. It is worth noting that CFD is analysis not design tool. It means that just by checking flow around given hull does not make it optimal. In the same time CFD is quite an expensive from computational point of view – so it requires some hardware resources and software as well. So use of CFD in a project highly depends on a design budget and expected outcome.
In many cases it is worth to spend more budget on detailed & weight saving engineering, than optimization of hull lines with CFD without consideration of building methods and materials. In other words, well optimized and overweight boat will have worse performance than boat designed with analytical tools (but still some inputs are based on CFD – such as drag surfaces) but lighter.
Final Element Analysis is another simulation tool that is widely used in yacht engineering. We use ANSYS ACP for composites and we found it as very efficient and effective tool. With python scripting we are able to significantly speed up design process by use of multiple layups in automatic way. Due to fact that all of our engineers use as well CATIA we have established very good process of geometry exchange between CAD and FEA. There fore we are able to short entire design process significantly and use FEA in most suitable way.
As we have significant amount of in-house analytical based tools, in many cases FEA is used only for validation and verification of more advanced failure modes, such as stability and normal modes.
This one of the biggest underestimated factors. Professional crew, with experience, can push boat to the limits – and typical velocity predictions are for boats on the limits (ideal performance situation). In the same time real world is non-linear and boat handling (for highest performance – this si what VPP is giving us) requires skills and ability to tune all adjustments.
TG Yachts - Yacht Design & Engineering
ul. Konopnickiej 19, 05-822 Milanówek Poland