What step after the hull

Hello all,

I'm just starting with boat designing, I have few questions. What is the next step after designing the hull on a software like Delftship or shipfree?
can I export the hull as a surface to ProE as a reference for my structure?

thanks in advance for your help!

 

By designing do you mean drawing a hull or having done a SOR and all the calculations needed?

 

I drawn the hull and did the hydrodynamic calculations, my problem is that I don't know how to proceed further toward the physical/mechanical aspect.

 

It sounds like you are doing it backwards. Most designers draw a linesplan near the end of the design process. After that its just drawing, which is very different from designing

For starters you need to know the C of G and boat weight before you can draw a lines plan. And that means you need a fairly detailed interior/deck/engine/rig concept drawing. And you'll need a good feel for the loadings so you can guess the scantlings

If you really are starting from scratch you can assume that you will completely redraw the first lines plan once you've got further with the design. Even experienced designers will assume their first lines plan is just a a rough draft

What sort of boat are you designing?

Richard Woods of Woods Designs

www.sailingcatamarans.com

 

Actually I'm not that much into the design, I would like to learn more about the construction side but learn it well instead of building a rough model by eye.

my idea was to make a model of a PT boat.

 

to be honest I just wanted to know how do I get from the hull to the scantlings in a professional way. I'm ready to redo the hull as many times as possible to get a properly shaped boat but it's eating me that I don't know how to proceed once you want to actually build the boat.

 

Scantlings depend a lot on the speed and expected use of the boat. For example, a fast offshore patrol boat will get more proportionally slamming loads than a slow car ferry. The construction materials and system gets decided on before drawing the lines, because materials and methods determine what shapes are possible.

 

I it were me I would look at construction drawing for similar boats. Many can be found on the internet. Collect a file of them for reference, and then look for some books on scantlings , Geer has one that will familiarize you with the basics.

Remember you are not reinventing the wheel. The Info is there you just have to look for it

Try a search of this forum, I am sure there will be quite a bit. Boat construction is like building boxes, but more complicated.

 

okey thank you all for your help, I will try and look up something.

 

The scantling bit is a real killer.

Geer has some rules - they make a very seaworthy, but heavy boat.

You can personally review other similar boat plans - many of the old designs were done from trial and error of previous boats.

Even now, many small boat designs are based on the NA's experience and research, with a bit of math thrown in.

The ultimate mind-bender is Finite Element Analysis by an engineer. Time consuming ( read expensive ) even with special software.

Welcome to the hard bit.

 

Hi Weinstein,

The guys above are right - there is a whole lot more (before and after) to 'designing' than drawing a hull form and then a structure to go within it.

However, from your comment it seems you are keen to draw a hull, design a structure for that hull, and then build a model. All for the purpose of going through the process and learning, rather than attempting to produce some optimised design for a full scale build. I fully appreciate the motivation to just get on and make something...
Do you want a static model or an operational one? - this is critical as an operational one means you must properly consider structural arrangement, weights and powering etc (basically the full design spiral).

So, assuming you will build a basic static model -the process I suggest would be:

1. Find some drawings of a PT boat, including construction drawings and hull lines if possible. Im guessing theres plenty of info on the 'net.

2. Develop a hull form (which you have done already). Make sure it is fair! Also make sure that if you are using 'developable' surfaces then they are actually developable. Developable surface basically means a surface without compound curvature (ie a surface that can be done with a bent piece of plywood).

3. Export the hull form surfaces into your CAD software of choice (you mention Pro/E) - Usually NURBS surfaces will be best, but I don't know what software you use. If you have no preference or expertise in any in particular software then I suggest Rhino - it is quite spectacular in how magical it is, it keeps me warm at night knowing that Rhino is out there fighting the monsters while I'm tucked up in bed.

4. Put deck and superstructure etc on the hull

5. Put bulkheads and other structure in. You will end up iterating around between superstructure and internal structure to get something efficient to build. Actually you'll probably end up iterating around the whole process to get a design that you can build.

6. export the drawings to build, or export CNC cutting files to build

Note - remember that the surfaces in CAD have no thickness (unless you have defined it as having some thickness in some CAD programs -Pro/E can do that I think). So, for example, the hull surface will need to be given thickness (ie an outside surface and an inside surface) before you define the shape of bulkheads etc.

I hope that helps a little. It barely scratches the surface of all the things you will need to know or do in your project, but hopefully it helps a little.
Good luck.
Rob