Designing your own mini yacht

Hello all;

Greetings from a rainy day,

I always had an idea of having my own small pleasure craft, yet which was more important than having it is being able to design it by myself. I do know how yacht builders approach that kind of question and take method along their journey; however, i have no deep knowledge nor experience in deep aspects of detail designing.
Gathering ideas on how that boat will be used, what kind of specifications it should hold, under what conditions it will be used and on are not quite difficult and anyone can sketch a draft for them without considering the concerns of naval architecture. Resistance, propulsion, bow and aft form, stability, strength of construction are to be analysed independently.

How do we decide the construction and main dimensions for the hull structure and get other datas for decision making in consistence with the discipline of naval architects?

Thanks.

 

So, your logical first step would be to start with everything mentioned in the quote above.
Establish your Statement of Requirements, detailing what you want your boat to be capable of.
Sketch a draft general arrangement.
Post your SOR and your GA on here for feedback and comment.

You could work through these items with the good folk on here, once you have the initial SOR and GA established.

The construction will probably be using the type of material that you are most happy with / is most easily available where you live.
The dimensions are dependent on the displacement which is driven by the load carrying capability of the boat - do you need to carry provisions for one week, or trans-atlantic?

 

Generally you buy a book. You might also get some value from a set of study plans of an existing, similar design.

PS, welcome to the forum!

 

My first choice for yacht design books is "Principals of Yacht Design" by Lars Larsson and Rolf E Eliasson. The math is clearly written so an engineer of any discipline can understand and implement the math in spreadsheets. Generous diagrams and drawings help generalize the math for non-engineers to grasp the main concepts.

I would strongly recommend building models out of balsa strips before building a full size boat. It introduces you to building concepts and challenges.

 

An alternative book for beginners is this excellent introduction to boat design by John Teale -
https://www.amazon.co.uk/How-Design-Boat-Power-Sailmate/dp/1408152053/ref=sr_1_1

 

The structural strength of small boats usually does not need to be considered (mainly controlled by stability rather than strength). The correct result can be obtained by referring to a boat of similar size.

The main issues are the following:
1. The material and thickness of the hull plate
2. The spacing of the frame
3. The structural integrity of the entire boat

The problems of 1 and 2 are very simple, and there are a lot of ship data for reference.
The problem with 3 is mainly a design problem. A good structural engineer can usually easily judge that the design of some places is fragile. Or you can refer to a classic boat of the same type, which is usually reliable.

Some references for 1:
Plywood is better than aluminum, and aluminum is better than steel. This is mainly due to the material density that causes the thickness of the shell to be different. The stability of a thick sheet is higher than that of a thin sheet.
The design of a steel ship is easier to convert to aluminum (because the hull becomes thicker), but the reverse is troublesome.

2 is actually a continuation of 1. Generally speaking, only the structure of the hull plate itself is not enough to produce sufficient stability, and the frame must be added to stabilize the structure of the entire boat. Stability is difficult to calculate accurately, so empirical judgment is generally better and more accurate.

In addition, for durability, some extra thickness must be added to the hull to resist corrosion. For corrosion, it is a fixed amount, independent of the size of the boat (this will result in a relatively thin hull of a large ship).

In the end, refer to the size of a time-tested boat to determine the structure of your boat will have good results.


Give some reference data
A 30-foot boat needs 3mm steel plate to build the hull. Aluminum needs 150% of steel plate, which is 4.5mm. Plywood needs 4 times of steel plate, 12mm.

This data can be changed up and down in small increments. For example, if you want the boat to be stronger and more durable, you can also consider using 4mm steel plate (the price of this is that the draft of your boat will be deeper and the speed will be slightly slower). There are also some designs that are more extreme. They also use 3mm steel plates on 50-foot boats.
The problem of cost will not change much, because the general material cost is less than 10% of the total cost.

 

Some books often tell you how to calculate this design. In other words, what they teach you is only: After you design (determine the size), how to calculate whether the size is strong enough or not suitable for use. But it didn't tell you how to determine this size.

For example, the mast height of a modern sailing boat is usually 1.5 times the length of the hull. Why is it 1.5 times instead of 1.9 or 1.1 times?

Similarly, the width of a typical sailboat is 3 times the length. What is the difference between making it 2 times or 5 times, and what are the disadvantages or advantages?

In fact, these attempts are all possible, but the design of the boat is complicated. If you try a different size, the problems you encounter are all new, and too many problems to be solved lead to your design. Progress was slow and ultimately impossible to achieve.

So most of the time, some empirical data is used in the design.

 

One question... What do describe as a mini yacht? I go on this and another American based forum.. it seems on the other forum to many a mini yacht is 30ft.
Whereas this side of the pond a mini yacht is 16 ft..

 

If it has a head and you can sleep on it; I consider it a yacht.

 

If a bucket is acceptable then 16ft is it...

 

This little boat was marketed as a 36 foot yacht.

I would say it was any boat you find pleasure in and want to call a yacht.

 

I used to have one of those. It got lost or thrown out over the last 50 years or so.

 

I would look at the top 10 commercially built boats or boat plans that you like, the ones that are almost what you want, but not quite there.
Then decide what you like and dislike about each, compare their sizes, sections, underwater shape, hull speed, anything and everything you can think of that matters.
From that you should be able to come to a reasonable set of measurement and features that you can use as a starting point?

Be open minded too, instead of saying "I want a 17ft boat", think about why you want it - so it will fit under cover when not in use, becuase you want to single hand it, or your car wont pull anything larger. Compare exiting designs to your requirements, then take all the best bits and make a list of must haves, like to haves, and don't wants, then you have a starting point for your own design. That's when the real fun starts.

I have just posted my own dinghy design here, after doing just this, and people who know more than I do are giving me advice on how I can turn it into a viable boat.

Simon.

 

Designing your own mini yacht sounds like an exciting project! It's great that you have a clear idea of how you want to use your yacht and what specifications it should have. However, as you mentioned, it can be challenging to navigate the technical aspects of naval architecture and ensure that your yacht is safe, stable and efficient.
One option to consider is hiring a naval architect to help you with the design process. They are trained professionals who specialize in designing and analyzing boats and ships for safety, performance and seaworthiness. They can help you understand the technical considerations and ensure that your yacht meets all the necessary safety and design standards. You can also check out https://www.fancyboatsibiza.com/ for more information on boats, yacht design, and other related products.

 

I think that the first question you need to answer, is "why do you want to do it?". A bad design will result is a lot of time and money wasted. It may also capsize or sink and kill you. Good designs are based on experience and historical data. Modifying an existing design could be a better route. In fact, it would be really rare for a designer to start from zero. Designs are normally based on previous ones.