Category Archives: Boat Design

All things related to the design of small boats including naval architecture and structural design as well as 3D and 2D CAD

Designing a Boat Part 1 Initial Considerations

The first step in designing a boat is to have some idea as to what you are intending to do with the boat. This applies to many  other situations including buying a boat, building your own boat or buying a kit boat. It pays to write down your answers to these questions to help you stay focused on  what you want because you may forget why you chose a characteristic and seeing it in print will help you keep track of your thought process.

Questions to consider are:

  1.  What kind of waters are you going to use your boat on. Examples, ocean, lake, river, protected bays. When considering these waters you must know what kind of water surface, rough, smooth, fast currents. While ocean water will have all of the above characteristics, lakes can get rough, rivers can look smooth but have fast moving currents, bays can be rough and have days of being calm depending on the tides. Depth of waters you will work in is also an important consideration. Shallow waters mean a flat bottom or others hallow draft type of boat that does not set deep in the water. The bottom line: KNOW YOUR WATERS. This will primarily determine your hull shape under the water as well as topsides. A designer can help or one of the many Forums on the internet.
  2. Powering. Sail, power, oar or other? Obvious, but this must be thought of in unison with the waters you are using the proposed boat on, and do you want a relaxing ride or want to move like a rocket.
  3. How big a boat do you want? Things to consider here are: number of people you are going to take out, your experience level at handling certain size boats, what kind of creature comforts you desire (day boat, or overnighter with some protected sleeping space), actual use of the boat (fishing, cruising, etc.) , and the biggy, HOW MUCH ARE YOU ABLE TO SPEND. Also  bear in mind that boats over 30 feet usually can’t be hauled on a simple trailer, they need to be professionally hauled so you have to plan on getting marina or mooring space and plan on hauling twice a year. If this does not appeal then a trailerable boat is the answer. This will keep the maximum length at 30 to 32 feet.                            This question is loaded and requires much thought because the success of your experience with this boat is all in the answers to this question. There will be plenty of compromises to be made unless you can go over 100 feet in hull size. A serious thought, just because you have the money don’t go after a boat that is bigger than you can safely handle, an error made to often. You will be dangerous and may not use your boat. That translates into a waste of time and money. One must always walk before running in the boat world. Your life and other’s may be at stake.
  4. What building material do you want? Now we are getting a little technical. If you are building a boat yourself, plywood would be the logical choice. Many kits and plans are out there for plywood boats. Plywood  using today’s techniques works out real well, it is rugged and easy to work with and almost as easy to maintain as fiberglass. If you know how to weld and can work with steel, then steel might be a way to go. Steel is rugged but it (in my opinion) keeps you away from boats in the under 30 foot category due to weight of hull. Also coating the steel to control corrosion is a must and ongoing process until the end of the boats life. Aluminum is a great material for boats. It is light weight, strong and practically corrosion resistant. But you will need a builder who builds in aluminum unless you can weld aluminum. Rivets can be used but eventually they can develop leaks. The last choice is fiberglass (FRP or GRP).  FRP is okay if someone else is going to build your boat. Building a single hull in fiberglass is expensive and time consuming. There are no kits out there to my knowledge so you will be buying plans or having plans designed for you. If you want to do it yourself then be prepared to learn a lot about fiberglass chemistry and technique. There are other wood options out there such as conventional wood planking and a technique using wood strips called COLD-MOLDING. These are professional techniques. I will discuss these further in a future post. Of course a professional designer knows all of this and may be your best starting place.  You need some of this knowledge even if you are going to buy a kit or attempt a simple design yourself.

There may be other questions to consider, but these are the major ones you have to ask yourself.  As you consider these questions you need to be aware that there will be compromises that will have to be made, particularly if money is a major consideration. While writing these answers down think of other things that may pop into your mind. Write them down and think hard about them.

For this example boat, these are the answers to the questions above:

  1. The waters are bay and salt marshes. Which means the waters are protected… no real rough water, no river currents. Water could be real shallow.
  2. Propulsion will be power using a small outboard with a  trolling motor.
  3. Boat will be used for fishing, duck hunting and casual cruising the local bays and marshes. No more than four people on board. This will be a day boat with a small cuddy cabin. The length will be around 18 to 19 feet.
  4. The boat will be plywood as it is a home build project. The plans will be designed for plywood ( such surfaces are called developed surfaces) so there are no  curved surfaces that plywood can’t conform to.

With these questions answered we can start thinking about the hullform and other major structures to match your needs. Once the design begins you may have to visit your requirements repeatedly to help refine the ultimate hullform and structure of your boat. As mentioned earlier the more thoroughly you think about these questions and possibly come up with others to think about, the more successful your boat project will be as well as your experience using your boat.

Part 2 of this series will cover the initial design of the hull.

Designing a Boat

One of the tasks that I thought would be interesting for this blog is to chronicle the design of a boat from concept to finish. Finish meaning that all of the drawings required to build the boat are finished. I will try to be as clear as possible in the explanations of what I am doing as well as including some pictures of the design process as I go along. This boat will not be complex but it will illustrate the design process. I will be putting the first post of this series up in a couple of days. I hope you enjoy it and learn something about the boat design process.