RG 65 Design with Freeship – 1

Since I do my first RG 65 project , decided to take advantage and make a step by step how to do a project using Freeship.

The first thing a designer must make when starting a project is to research what already exists in similar boats and make a summary of data dimensions, weights, etc. Eventually over time we will form the project in the head and we have more or less the dimensions and weights, but we can also get off the ground and then this research is essential.

The Project should start by selecting the maximum beam, beam on the waterline, the hull draft, prismatic coefficient, wet surface, position of the LCB and LCF, the forward freeboard, freeboard aft.

Naval Architecture and Data Base page, here on the blog, which appears in the menu up there, you can see the meaning of these quantities.

The RG 65 has the following characteristics, according to my research:

Maximum Beam – 0.13 m to 0.18 m

Beam on the design waterline – 0.10 m to 0.17 m

Total weight – 0.7 kg to 1.1 kg

Bulb – 0.3 kg to 0.8 kg

Freeboard Fore – 0.05 m 0.07 m

Freeboard Aft – 0.02 m to 0.04 m

Hull Draught – 0.03 m 0.06 m

Prismatic coefficient – despite not having data on Cp, is between 0.52 and 0.58

Wet area – another difficult of knowing, I have a reference that is around 0.05 m² and 0.07  m², unreliable.

Let us define the following measures to begin our project:

Length – 0.65 m

Beam – 0.13 m

Draught – 0.04 m

The Freeship can be obtained here: http://www.hydronship.net/index.php?lang=en

If by chance you fall into a page with something in Russian, at the top of the page has a British flag, click on it and you goes to the English page, but this link is already in English.

The software is developed by a Russian. It is identical to Delftship but has a little more recurses. If you use Windows no problem, if Linux,  use the program in the Wine environment.

The problem using Freeship is that it is not so accurate for small boats, the calculations are rounded and has zero value. What do I do to solve this problem is to design a boat 10 times bigger, so I’ll make a boat with a 6.5 m long, 1.3 m in breadth and 0.40 m draft, ie I’ll work on a boat on a scale 10 / 1.

For values ​​calculated by the software for my RG I divide by 10 the linear dimensions, areas by 100 and volumes  by 1000.

Open Freeship and click on File -> New and you will see the screen:

The dialog box, comes already populated with some data and others in blank as Length , Beam , and draft that I fill up with data that I picked up.

The first two lines already filled with 6 and 5 which are the points of the control net of the hull form. The higher the numbers the harder it is to work, leave these values, which define the shape well, in the future you can raise them. Choose meters in the last row.

After filling in the dialog box, click on √ in green at the top of the box and you get the design of your boat:

Sure, the colors of my screen are not like yours, because I went to File -> Preferences and choose those colors as standard to help explain better, but the design is the same.

If you look closely you will see the drawing lines of the boat and a green mesh with green dots at the intersections of the mesh. These points are those 5 and 6 of the previous dialog box. You change the shape of the hull designed by clicking and dragging these points, which are 5 * 6 = 30 points.

I invite all interested peoples, to participate in this post with suggestions, data, comments and doubts. Only adding we will be better, in all senses.

Continued !!!!!!!!!!

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About Fred Schmidt

Engenheiro Naval interessado em projeto de veleiros radio-controlados. Naval Architect interested in RC sailboats design
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