True Round
Metal Boat Building
-  By Way Of  -
Approximate Development


The current 'Go to' methods for forming compound curved shell plating for steel and aluminum fabricated boat hulls are: 'Line Heating' for steel and 'English Wheeling' for aluminum. The down side is that both methods require highly skilled Craftsmen using very specialized techniques and industrial equipment.

These skill an equipment to fabricate True Round Steel and Aluminum are really exclusive to professional steel and aluminum boatbuilders.  As a 'One-of' steel and aluminum Designer and Boatbuilder I understand why the forgoing methods are their methods of choice. 

However, there are talented  'One of' Builders who would like to build a True Round sailboat hull, but the traditional  process of forming the shell plating for a True Round hull is stalled by lack of equipment and the high learning curve of operating that equipment. 

However, there is an 'Alternative Way' to form the shell plating for a True Round steel or aluminum hull that does not require the hands-on-skills and or  equipment required by 'Line Heating' and 'English Wheeling'.

If you can build a Hard Chine sailboat hull you can built a True Round hull without the use of an 'English Wheel' or 'Line Heating'.

The Alternative:

The True Round steel and aluminum Boat-building method that I am about to introduce was developed entirely by the author, and is the  result of his career in Architectural Metal Fabrication, CNC Programming, Sheetmetal pattern Development, and  his studies at the 'Westlawn Institute of Marine Technology'.

The Authors True Round Design and Construction method combines the traditional hand layout method known as 'Approximate Development' with Multisurf by Aerohydro's Marine Three-dimensional surface design software, that enables a Builder to construct a True Round steel or aluminum hull as easily a building an Hard Chine hull design.

How 'Approximate Development' works



The Prototype & Proof of Concept Build

Click on the below link (Hull Components) to see a preview of the Transverse Frames, Longintudinal Frames, and Shell Plate fabrication or (Building  the Hull) for  an overview  of how the Hull is fabricated.

Hull Components

Study Plans

Building the Hull


On the Right Hand Column are other aspects of 'True Round Metal Boat Design and Construction' that you may find Interesting:

Redesigning the classic, Plank on Frame Catspaw Dinghy for aluminum construction.

A simulated race (via VPP software) between a classic Day-sailor designed to be constructed in both Steel and Aluminum.

A simulated race, (via VPP software), between a Double hard chine hull and Her redesigned version to a True round hull form. (Note: This is not just a race between one person's steel Hard Chine Boat with another person's steel True Round boat, since the True Round Hull is a clone of the Double Hard Chine hull.) The result of the race will shine light on the long ask question. Which type of hull is faster, a true round hull or a Double Hard Chined hull?

The Layout and fabricate of custom Hatches, Port Lights, and more.

The advances in the 'English Wheeling' method for forming True Round Shell Plating.



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Fabrication of Hull Intergrals


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Katspaw Dinghy

About the Katspaw Dinghy

True Round vs Hard Chine

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"Aluminum vs Steel

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English Wheeling

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