Instructables
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Building the Wood/Epoxy Optimist

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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Step 1:

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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.

Step 2:

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The file for the hull bottom, midship frame, dagger board case sides and corner braces are cut from one 4' x 8' sheet (1219.2mm x 2438.4mm) of 12mm Marine grade plywood  If you save your larger scraps for doubling plates and gunwale rails, you will have very little waste.  The first cuts should be for the 6mm deep dado at both ends of the hull to join the bow and transoms to.   The second cut should be for the dagger board trunk cut out.  The third cut should be the outline of all the pieces.  In order to fit both sides of the dagger board trunk on one sheet, one side will have a joint to be epoxied together to match the other side.

Step 3:

The next setup  should be for 6mm plywood.  Again a 4' x 8' sheet will make both ends, both sides, mast thwart frame and again scraps can be used for doublers and clamping pads.

You now have a boat cut and ready for a little fitting.  Bevel the edges of the bottom to the approximate angles of 15 degrees with a block plane and you are ready to start your build.  I would recommend a dry fit of all parts prior to mixing epoxy.  This doesn't take long and may save you a lot of trouble with messy epoxy. 

Step 4:

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Center the bottom in the jig, stand on it to bow it and hold it down, and temporarily screw it to the 2" x 4" 's 130mm each side of center line to allow for gluing of the doublers without covering the screws, so they can be removed later.  The holes will be filled in when the boat is removed from the jig with epoxy.  Rip a 4' x 8' sheet of 4mm plywood into 1- 240mm strip and 2-80mm strips with a 45 degree beveled edge.  This can be done on the ShopBot or a table saw.  These are the doublers for the bottom to meet design minimum thickness while saving weight.  Once these are epoxied into place and trimmed you are ready to install the sides, mid ship frame, bow and transom.  The mid ship bulkhead can be used to position the strips in the correct place on the bottom of the hull.  Once these are epoxied in position, placing some weights on top, until cured, works well.  You will be covering the dagger board slot, but that can be easily cut out once the hull is removed from the jig and turned upside down for fitting the dagger board trunk and filling of screw holes.

Step 5:

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The plans show two temporary braces.  These can be made from any scrap plywood and are used to hold the proper shape of the sides while doing the assembly and glue up.  Once the gunwale rails are installed these will be removed and discarded.  The bow and transom fit into the dado at the front and rear of the hull bottom panel.  The sides wrap around the outsides.  A couple small blocks of wood screwed onto the jig at the bow and stern help in keeping the sides in position while clamps are applied.   A small slot cut into the two forward jig pieces to allow a small bar clamp of your choice works well to hold the two sides together tightly.  Once you are comfortable with the fit of all the parts your ready to mix epoxy.  Wet out each side with unthickened  epoxy.  Then add a small layer of thickened epoxy and assemble with the temporary braces and mid ship brace installed.  Next is the mast deck and thwart.   Fit and epoxy in place.  Some of the scraps of 18mm can be used for the doubler in these areas.  You can install the bow and transom doubler before or after this step.

Step 6:

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Gunwale rails and rub rails are next.  You can use layers of plywood or fancy colorful woods if you plan to use a clear finish to show off your work.   Build up the layers until you get to the final thickness required, per the plans.   Rip 1 for each side of boat starting with a 45mm wide piece stepping down 5mm for each 10mm of thickness.  Cut out pockets for and install the corner blocks next.   Form and shape the rails to the required shape and thickness and you are ready to remove the boat from the Jig.  We used a hand planer for the rough shape and finished with a belt sander.  It will now hold its shape and dimensions.  The jig can be used as a cradle to support the boat as you work on it either upside down or right side up.

Step 7:

Once the boat is removed from the jig, it can be turned over and all joints filled with thickened epoxy.  Install the dagger board trunk through the hull and epoxy in place.  We choose to put our club logo and hull # on the sides of the dagger board trunk.  Once again the ShopBot makes this a blank canvas for your artistry.  Below one of the boys is rounding the edges before the dagger board trunk is installed.  Shape the bottom of the dagger board trunk  to conform to the hull bottom from the outside once it is cured in place.  Install the doubler pieces on the inside to help support the dagger board trunk.  We installed a few wood dowels into the midship frame to add strength as well.   Sand, epoxy and finish the exterior of the hull as desired, with either paint or a clear finish.  On the inside of the hull fillet the joints with thickened epoxy.  Install the flotation attachment pads, and main sheet block pad.  Sand, epoxy and finish the interior of the boat as desired and the hull portion of your sail boat is ready for hardware installation.  We chose white enamel for the insides for a cleaner look.  You will also find the plans from one of the internet sites below.  Download these and print copies to have available as you work. 

Step 8:

To build a race legal hull requires a measurement by a certified Optimist qualified measure person.  Plan on 4 hours or more for this process.  The PDF file is the list of measurements for the hull.  The tolerances are close, but with the use of the CNC controlled cutting you should have a race legal hull that your kids can be fully involved in the building of.  The dagger board piece and rudder that was cut will need to be shaped and profiled.  Again we used a plane for the rough shape, followed by the belt sander.  Hardware kits are available online as well as sails, spars, FRP rudders and dagger boards at very reasonable prices.  One such site is :

http://www.mauriprosailing.com/Optiparts-Optimist/Optiparts-Optimist.htm?gclid=CKHtt7O1t64CFQ9-hwodHBRhrA

Step 9:

Sail Plan

The sail can be home-made, as well, but with mass production the prices just are hard to beat.  Again the spars can be made from PVC pipe, Wood or Aluminum tubing, but most can be purchased for a cheaper price than your time and investment.   You probably won't need the hottest racing level gear until you see if your kids are in for it.  Then watch out if they catch the bug!  You will be one proud parent to have started them out on such a great and rewarding life of sailing.

http://www.mauriprosailing.com/Optiparts-Optimist/Optiparts-Optimist.htm?gclid=CKHtt7O1t64CFQ9-hwodHBRhrA
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timmay164 months ago

Hey I know about the rules and laws around the moulds for fibreglass hull, but has anyone ever made one or attempted one

superdave.morris (author) 6 months ago

http://www.optiworld.org/epoxy.html This link has most of the same stuff as the PDF did. I can not get it to open properly either now. Between that and the British link you should have what you need to build. Good luck. Hope it is a father child project.

Matatas6 months ago

Are you coach now? Do you have realy good sailboats such as winner and another good ships>? And good idea for new yachtsman :D, but i think after week they will need new light original ships. So where is no point to buy wood all parts. I think it's better to give older sailboats for new yachtsman and all costs for fixing will buy off

jphillips676 months ago

I have tried several times on several computers to get the optiworld pdf to open and it seems to be corrupted? Anyone have any alternatives. Please help/

Fikjast Scott6 months ago

wow - great work

superdave.morris (author) 6 months ago

Here is our fleet of Opti's we made. 2 years later they are going strong. Taught many young sailors how to sail. Taken a few hits but easy enough to repair. We added a foam fender to the bow which helps prevent damage from running into each other. I started to add pictures of a sailing class but decided not to put kids pictures on because of todays legal environment.

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mwuhrer7 months ago

Hi

I love the instructions on the site, but I cannot download any files. It just leads me to a list of numbers. I do not have autoCAD on my computer, but would send it an architect to print it out. Can you help me with that?

superdave.morris (author)  mwuhrer7 months ago
You should be able to download the DWG files. these would need to be opened on some type of CAD program. I use turbocad. Less capable than Auto Cad but cheaper and easier to use as well. Every automated cutting system I use reads a dwg file to convert to cut files. If you are just planning on cutting them out by hand and want full size prints to cut out you will need to take the dwg file to someone with a wide format printer. They would probably have the software to open them. Otherwise just go by the plans and lay it out by hand per the dimensions of the plans that are on the web. That is basically what the DWG files are anyway. Best of luck.
Echinda217 months ago
what a grate father and son project
arduinoer2 years ago
Why waste a great racing sail and spars on a wooden boat?
3 lbs lighter in the ends than fiberglass, as in, significantly faster in chop
much more durable than fiberglass
more collision resistant than fiberglass
it's art.
hello, long time sailor, first time building one. i am looking to build a 12-14 foot FJ/420/topaz type sailboat (2 person, mainsail and jib). any ideas? i was thinking of making it pretty much like a longer version of an opti (preferably narrower beam to length ratio than an opti though, as otherwise i would be looking at about a 6-8 foot wide boat.)
Why not go buy a used C-15. Just buying the hardware new for a boat like you described will cost probably 2x as much as a used C15 with a trailer. A friend of mine just bought a nice one off Craigslist for 600 with trailer and new sails. Needed a repair in the bow where it got T-boned but that took about $40 and 4 hours and now she has a great boat. Boat market is real soft here in the bay area. Put out a shingle on Craigslist for wanted small boat and go visit your local marinas and ask about abandon boats as well as boat storage yards for abandon boats. These Optis are so easy and inexpensive to build compared to most other boats is the only reason I would build these over buy them...Plus the fun/learning factor for the kids. Good luck...
are you suggesting i buy instead of build?!?!? you, sir are NOT WORTHY of being a member of instructables. (jk, i see the logic, but i want to have something that i built and can be proud of.)
The boat you have in mind I think is a FireBall. There are some gorgeous wood boats of that type up near the great lakes, and they are FAST.
cthompson549 months ago
Superdave this is a great gift you've put out there. My son and I built an opti without templates recently, I'll be NC cutting the next one for sure as we've been there and done that.
Thanks a lot
Hello from Greece. I managed to open the dxf files .do the crv and sbp files have the same content as the dxf ones.?Thank you for your reply
superdave.morris (author)  gkapralospls1 year ago
Those are exactly the same as the dxf files just converted to the machining files. All you should need are the dxf. Dave
superdave.morris (author) 1 year ago
Macbeath hardwoods was our source of marine plywood.
930 Ashby Ave. - Berkeley, CA 94710
(800) 479-9907 / (510) 843-4390
(510) 843-9378 fax
berkeley@macbeath.com

You can stop by Half Moon bay Yacht club and see the boats for your self. M-F during the 10-3 period they are normally all sailing in kids summer camp. Great fun to watch. Rest of the time they sit on the rack next to the launch ramp.
Thanks Dave,
Don't know if I can make it over there during the week due to work. But I'll give it a shot. If I don't make it over during the week, I'll come over on a weekend and take a look at them out of the water on the rack. Oh, and thanks for the marine plywood source w/ contact info. That will be very helpful.
Best,
Ben
Superdave.morris,
I'm a longtime sailor and a new Tech Shop member in the Bay Area. I'm excited to tackle making an Optimist Dingy. I grew up sailing in Dyer Dinghys and Sunfish and I think this will be a great little boat to try my hand at for a first Tech Shop project. I'll be taking the necessary classes at the SF and Palo Alto shops to build this boat. Any advice would be much appreciated. And I'd love to come by and see the ones you made for the kids in Half Moon Bay sometime. Do they race regularly in the summer?
Best,
Ben
superdave.morris (author)  benjaminshaw1 year ago
Half Moon Bay Yacht Club is located in Princeton harbor. Monday -Friday during the day the youth sailing summer camp will normally have all the boats out sailing in front of the club.
Why can't I open the crv sbp and dxf files
superdave.morris (author)  gkapralospls1 year ago
I can not tell you why you can't open the files. I just checked them and the DXF files open in my cad program. I can't open the crv sbp files except on the shop bot Which has the software to do that.
So how much would one of these cost to make in it's simplest form? Like, a Home Depot budget form?
superdave.morris (author)  ssmithsonian1 year ago
We figured our cost per boat about 400. We purchased prefab sails, daggerboards and rudders due to the kids beating up the wood ones. The FRP daggerboards and rudders hold up better.
hope you get a kick out of this one.
my point is to make a sail boat able to sail freely on a lake. what i want is to make a boat like this.
yoo hoo yoo hoo a pirates life for me and relly bad eggs.jpg
could you extend the frame and add a second sail.
If you did, it would in no way be an opti. Could not race in the opti class and there fore would be a one design sailboat. Which you could do. But it won't be an opti. The purpose of the instructable is to make a legal, measurable, race able opti....

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.
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Mick B2 years ago
Superdave,
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?
superdave.morris (author)  Mick B2 years ago
Just added the 18 mm dxf file as well..
superdave.morris (author)  Mick B2 years ago
I just edited the instructable with the 2 revised DXF files. These change the bottom width 2mm to bring it into the center of tolerance. I would just bevel by hand. A hand planer works great and takes 3 minutes. Programing time would be more than that. At the dry fit you can see if you need to add more bevel. The revision also moves the bottom outer doublers inward and adds to groove for these in the mid frame and mast thwart. The items on the second sheet of 12 mm are for the daggerboard case sides, daggerboard and rudder. For our club boats the 12mm daggerboard and rudder are too fragile. Probably fine in a private boat. On the DXF file the size of the plywood is drawn as an outer line for reference only. Superdave.morris@gmail.com
Mick B2 years ago
Superdave,
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.
superdave.morris (author)  Mick B2 years ago
And 12mm is too thin and fragile for our club boats. So the belt sander and the layers of ply for guides makes for a easy shaping of the material to end up with the desired thickness, contour and shape. You could also cut it out of a 12mm and 4mm but would require you to buy more wood. Belt sander is quick and easy. With the DXF files there you can pull any piece out of the drawings to cut it out of what ever material you like. We are actually buying the rudder/dagger board FPR combos for our club boats due to the fact that the kids run the boats aground and the dagger board takes a great deal of abuse. A private boat probably wouldn't see that abuse.

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.
Mick B2 years ago
You can download the official Optimist plans for free from the USA Optimist site. The International site will charge you. Go to http://usoda.org/ and click on FAQs and then Wooden Boat.
nsijan2 years ago
Hi , Can u tell me where did u find plans? I would like to build one boat for my kid, but your pictures are too small to use them :(
aqwiz nsijan2 years ago
You can also find not only plans, but ready to assemble kits at http://bateau.com. as well as all the supplies needed to assemble a boat at http://boatbuildercentral.com they supply the Youth Sailing Foundation of Indian River County (Florida).
superdave.morris (author)  nsijan2 years ago
http://www.optiworld.org/Woodguide05.pdf

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.
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