In 1947 a gentleman named Clark Mills designed a small sail boat for kids to learn to build and sail called the Optimist. This boat was designed to be built from 3 sheets of plywood, with basic woodworking abilities. As time progressed, builders began to modify the boats to gain speed advantages - as happens with all vehicles.
In 1995 the International Optimist Association took the boat back to its roots and a set of dimensions were compiled to retain an exact shape of the boat, so as to remove design advantages from one boat to another. The Optimist is tightly controlled now with over 60 measurements and tolerances of the hull are generally +/- 5 mm. The tolerances do not allow the builder to exploit the possible variations of shape of the hull, but do allow a competent builder to construct a legal racing hull.
Half Moon Bay Yacht Club has a summer youth sailing camp. Through the years we have trained many a young boy or girl to rig and sail the small boats available to us. Normally in an older Laser or Coronado 15. In 2011, the sailing program decided that the Optimist had a place in our sailing fleet to allow the younger kids (7-15) to rig, launch, sail and retrieve the boats themselves while under adult supervision. We set about looking at the building of wood/epoxy Optimist sailing boats. We quickly focused on making racing legal hulls so as to be competitive with other surrounding sailing clubs. This is where the accuracy and repeatability of the ShopBot CNC router at TechShop of Menlo Park www.techshop.ws became an invaluable tool in our fleet building. I made it at TechShop. Due to the close tolerances allowed, and the desire to have an almost identical fleet of boats, the ShopBot fit the bill to the letter. Once I redrew the plans into CAD drawings and transferred to cut files the different parts of the boats were identical. Each group of people that wanted to build a boat only had small amounts of fitting, beveling and gluing to accomplish, with very little use of dangerous equipment needed and quick progress to show for their efforts, so kids fit right into the task of building boats.
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The jig produced on the ShopBot retains the correct shape and supports the boat, while it is being built, to retain the exact design measurements. The plans for the boat can be found from many sources for free on the internet. Plans are available in many languages, as well. One such source is http://www.optiworld.org/Woodguide05.pdf
Another guide to building an optimist is http://www.burcotboats.co.uk/howToBuild.pdf , as well as half a dozen other well written articles on the internet. But none provide CAD quality drawings or files to work with modern computer controlled machine tooling. Well, here they are: The jig as well as the major parts of the boat. The jig sides , mast step, rudder, dagger board , dagger board case ends and doubler pieces are made from 18mm or 3/4" ACX or marine grade plywood; (1219.2mm x 2438.4mm) 48" x 96".
Now to get started, the jig we have designed is the exact dimensions of a finished hull shape. Both ends of the jig have interlocking pieces to allow for inserting and removing as needed during the building of the boat. The cross members are standard 2" x 4" cut to 44" long and with a 3/4" dado 8" to each side of center to fit into the grooves of the forms. These should be cut so as to be flush with the top of the form and screwed into place to prevent movement. The bottom boards provide a stable platform for the jig to sit on. The jig should be placed on a flat surface for the build, as distortion to the jig will transfer to the boat being built. Save the scraps for blocking.
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I will add a bit to this to say we built 7 of these boats for our club. Summer youth sailing camp totally sold out and we even added 2 more weeks. Now we have an after school program going this fall. These boats have been an great addition to our sailing program. They took their fair share of bumps and hits and I think held up better than a Fiberglass one would have. You can see pictures on www.hmbyc.org.
I have sent those DXF files to a friend who has a cabinet shop with a CNC router. I will wait until your updated files to go forward. These machines can do bevels? Would a designed-in bevel on the bottom panel edges save some work?
You put the rudder and daggerboard on a file called 18mm cutsheet. According to the rules 18mm would be too thick for those items...
3.3.2.2 The thickness of the daggerboard (excluding bevels) shall be not less than 14 mm (12mm for wooden construction) and not more than 15 mm.
3.4.2.2 The thickness of the rudder (excluding bevels) shall be not less than 14 mm (12 mm for wooden construction) and not more than 15 mm.
Or run it through a planer a pass or two... And again the 12 mm version for our club wood boats is too fragile...Thanks for the critical analysis of it. Sounds like your serious. I have tweeked my drawings a little on our #6 and 7 boats. When I get the time I will post them. Change of the position of bottom doubler inward slightly, mast thwart outward 2mm and bottom 2mm wider at 1 spot. This hits the measurements a little more to middle of min and max.
http://www.burcotboats.co.uk/howToBuild.pdf
Links are in the instructable as well as several others in different languages also.
You can use one of the free online drawing programs to open the different dxf files.
Love One Design (just not a fan of One Design One Builder)
Always wanted an Opti, just so I could name it Fat Man in a Bathtub
I built it as a rowboat to use on Lake Erie, about 500' north of my house. The hull is curved and the whole thing is a bit more graceful. With one person onboard, it moves pretty good! Had a few scary times in Lake Erie, but survived them all! Very interesting ride with two folks and whitecaps.
I still have it and last used it about 15-20 years ago at Kelleys Island when my kids were smaller. Now I might have to take it out of mothballs and give it another summer. Sucker is going to be 51 years old in a couple months!
Thanks for the great article!
In the honor of my Fave Military Drama Show still on now. Your a bunch of Juinor " USMC Gunery Sergent / Special Agent Jethro Gibbs N.C.I.S. " in the making with this instructable! Awesome Job matey's! Make & Made Shipshape & Bristol Fashion! Thank you for a great job here keep it up , I'm looking forward to larger craft you might do again... And in the theme of another name droped As Old Master Yoda always says "Do, or Do not, there is no try" , becase in your future projects note I did not say or imply at any time the word "try" in any point implied. You do good work!
Great Awesome instructable here....8Dbd
Keep me informed thank you!
optimist is a rather fitting name for the craft lol
Your boat resembles the Puddle Duck Racers - I have helped to make several and sailed a few. You can vary the design, we closed in airboxes so it floats under any condition. On a few we used bamboo for the mast and tyvek house wrap to make the sails. There are patterns online for the sails as well. I was surprised at how fun and sturdy the boats are to sail.
thats interested, we build the optimist in the 60 and 70 in germany - east, GDR, German Democratic Republic. Pupils make regatta.
very nice - I remember me
for those who are not aware of what boat construction means, let me tell you : it is a hell of hard worth that asks for patience and time.
CONGRATULATIONS…
sailboat.