Designing on Paper

I've looked around the forum, but I haven't had any luck with this.

How do you design a boat on paper? Everyone is talking about lofting, but then you need a table of offsets. How do you get a table of offsets? If I don't want to buy them, and I don't want to do it in CAD, is there a good way of doing this on paper?

If you were to make a simple round bottom slender cat hull, how do you make sure your stations don't cause a concave area on your hull? How do you know how far to offset your waterlines? Is there a way to do this without cutting up a solid model you carved from wood that may have similar problems?

I know you can't think of any line individually, but how can you plot it out on paper with accuracy?

Can anyone give me an "aha" moment, or suggest a book that clearly explains this? I just imagine building something and then there is a gap between a station and the skin.

Thanks for your knowledge.

Sabs

 

Skene's Elements Of Yacht Design

 

Thanks, any particular edition or are they all pretty much the same?

Or rather Elements of Yacht Design by Norman Skene or the one called Skene's Elements of Yacht design by Francis Kinney

 

Either will work, I prefer the Kinney edition.
As for a lines plan....
Lines Plan https://www.boatdesign.net/threads/lines-plan.29882/#post-310553

 

Ok thats really helpful thanks a lot!

 

The table of offsets are the coordinates of point on the surface of the hull. You don't start but finish with them. Lofting is enlarging the drawing to full size.

 

I know that. But most people building boats "start" with them by buying them and lofting plans from them. By lofting, I meant using batons to draw the boat on paper, full size or not, with waterlines and stations.

 

There is a huge difference between designing and lofting. Lofting is scaling up a design to full size. Designing on paper has advantages and disadvantages. I find that creating a curve with battens offers more freedom than programs that have predetermined algorithms. CADD makes volume and other calculations easier. However, you can design on paper and then transfer the table of offsets to a computer for calculations. Most hulls start with at least an idea of what the dimensions and shape will be. You can draw a profile of plan on paper and start adding stations. Usually the maximum beam and 1/4 length stations are set first.

 

Yeah that's what I would like to do. I find using delftship really frustrating since I am using Solidworks dailing at work, but that is not the best for fairing the surface. In my tests so far starting with a top view and side view of an existing canoe, and guessing at stations, I get concave areas towards the bow because one of my stations is the wrong shape. Last time I just went with it and added spackel to my mould to fill the negative space and shims on the inside to try to fill the gaps from the back. It would be great if I could get some of this really close on paper and then transfer it to CAD like you said.

I plan to also make a half hull model and cut it up to get the stations/waterlines, but also it would be interesting to know how it was done before CAD existed.

 

Another reference for pre-computer design process is Yacht Designing and Planning by Howard I Chapelle. No longer in print but used copies are readily available. Bookfinder.com shows average price of used copies is around $25 but the are copies available for less and for considerably more.

 

Thanks for the recommendation. I'm glad its a good one, it's already in my amazon basket.

 

I had a copy of Chappelle's book back in '91... Now where did I put that.

 

May be you can have a look at Gene-Hull, a free spreadsheet application dedicated to the generation of hulls , i.e. a linesplan with its 3 views for early stage project. Other output are the offsets (stations, keel line, sheer line, ...) and hydrostatics data. It is not a design on paper of course, but a similar approach in the same spirit and just need Open Office (free itself) to support it. Available here in the Forum Software, use Gene-Hull with the Search function, various versions are for fin keel sailing yacht, canoe, catamaran, dinghy.

 

Thanks I'll look into that too.

 

Here is a folder that contains the old design web page from the U.S. Vintage Model Yacht Group. The material is copied from Thomas Moore's "Build a Winning Model Yacht." Moore was a Naval Architect in the 1920's Although it deals with models, the material walks you through the traditional paper method of design. After you unzip the folder, open the file "design.html" and the pages should come up. Good luck.

Cheers,

Earl