Design plans for Illusion

Illusion was designed with the simple to use Careene 2008 software written by Robert Lainé, 
Robert has kindly made the software available for download at the bottom of this page.

The program works in metric (mm) only - I would advise Americans to have a go at metric because the maths is much easier. Like most British people in their 50s I have used inches and mm since junior school. My feeling is that mm are more accurate for boat building. With care you can measure and cut to 1 mm, but measuring 1/32nd inch is hard and 1/16th is too crude - 1 mm fits nicely in between at about 1/25th inch.

So if you want the plans/offsets for Illusion download Carene, create a hull and enter these (metric) values for the bottom plank. She will be just over 3m or 10 feet, maximum beam is 39in as per Elusion:

Height forward and aft define the rocker, half width afterward is for the transom.

When you have pressed Validation, move onto these settings for the side planks:

You can now fine tune the design to suit your needs and the Hydrostatic page is great for seeing how she lies with additional ballast. Quickly you will realise that most of the weight should go forward, which is the biggest challenge I think.

File | Save | Development XYZ  will print out the curve offsets for each panel. 

Making the bottom panels from one piece of 9mm ply is tricky. She is mostly flat bottomed so it makes sense to keep one piece. But it is essential to make a saw-cut along the centreline about 2ft back from the bow to bend the V angle at the bow - without that saw-cut bending 9mm ply is impossible. 

So you have to bodge/adjust the design as you build it, which is part of the fun. If bending the bow V is hard, make the saw cut a few inches longer.

I was unable to fold the full V angle of 35 degrees so the bottom panel over hang the side panels by about 15mm. No worries I simply planed the overhang after the internal fillets hardened.

I trimmed the freeboard by 2-3in when the panels were stitched so the above dimensions are not 100% correct for Illusion. You have to make a choice between windage and sea-worthy qualities - there are good arguments for and against freeboard.

Rocker wise Illusion will sit with bow and stern on the waterline with a total displacement of 250kg. In hindsight I won't be getting near that displacement in sheltered waters, but from the videos on this site you will see she sails very well with 100kg displacement.  (100kg = 220lbs)