From scale model to full size.

[tom_fry24]

A few months ago I started the process of building a boat, after consulting the threads regarding design I decided to build a model first as I have min computer design experience. My question now though is what is the best method for going about using the model to make the full sized thing? What is the best way of getting some kind of plan/cut outs out of the model?

Also I made the model out of wood... which was very enjoyable but I was wondering if I want to make another model what is the best material to use? Some thing moldable? and then also how do you get both sides of the mold to be identical? Thanks for your help in advance.

[Trevlyns]

Hi Tom

Working with changes in scale is not as simple as it might seem. For example, if you were to increase length by 50% (i.5 times), beam, depth and freeboard would increase by about 1.33 times to maintain the original proportions. Similarly, sail areas, section areas hull volume etc. all change at different multiples.

Try and get hold of the work of H M Barkla of the University of Saint Andrews, Scotland who has done calculations in this area. This info is also in chapter 2 of the book Principles of Yacht Design by Lars Larrson and Rolf R Eliasson – pretty much a standard among small boat designers.

Of course the ultimate question is will the boat float. For example, what is the volume displacement, pounds per inch immersion and a myriad of other criteria which go towards a boat that not only floats but performs well? This is best done by “normal” design methods and calculations where everything is scaled to the actual finished size. Again, the book mentioned is an excellent source of information.