Building the Optimist Strongback

The least complicated part of boat building is the strongback or base with which to attach the stations or molds. Clark Mills designed the Optimist with only three simple molds - bow, mid-frame, and transom. This strongback gives the builder a good base to attach the three cross-members that will set the precise distances for the bow, mid-frame and transom.


We are building three Optimist at once, so here is a quick look at our three strongbacks using the CABBS plans:

The Strongback - Advice from John Bridges

The CABBS blueprint of the strongback.

We received our plans from CABBS and started thinking about the first step to build the prams. My brother is in the process of cleaning out his garage for this project, and I haven't had a lot of time to go over the blueprints. It seems pretty clear that the first thing that needs to be done is the Strongback.

I contacted John Bridges who has been building Optimists since 1963.  I saw a post comment he made on the WoodenBoat Forum and traced that back to the work he has done with the Moraine Sailing Club. 

John (brown shirt) lifting a hull off the strongback.

"I first built Optimists in Trinidad back in 1963 using the plans as published in the Rudder magazine.  I think we just set up a pair of 2" x 6" timbers on the floor as a base to work from.  Since then I have built others in Chile, Colombia and Ghana.   Some where along the line I built the present strong back here in the USA  which has been used to build about a dozen Optis out of the 17 that I have helped MSC members to build. my strongback is on legs to raise the hull to a convenient height for working and avoid to much back bending. 

The first operation is to make the centre frame and two transoms.  These will have extended side pieces so that they align with the (straight and level) datum i.e. base of the strongback.   I have the cross bearer for the bow transom, bevelled so that the Bow transom can be screwed to this and it is important that the other two cross bearers are at the correct distance from the first one.

Strongback in use during one of John's group building projects.

I usually use ring shank Phosphor bronze ring shank nails to hold the plywood in place on the chines whilst the glue sets. Epoxy is messy stuff so we are usually using PL2 Construction adhesive these days. For several years we have used Lauan Plywood (Interior use but with Exterior glue) and have found that this lasts for at least 6 years without problems providing it is kept painted and stored out of the sun and rain.   

1948 Optimist Plans

It can be covered with fiberglass cloth which adds to weight and durability.  The USA made Pine plywood does not weather well.  For more permanence Marine Plywood is available for about $95 per sheet (cf 20 for Lauan) It is all a matter of, as we say in England "You pays your money and takes your choice".  (John's photos)

As we get started on this project we will be posting pictures and video of the Optimist project. We hope to create a good record of our mistakes as well as triumphs.

The Clark Mills Optimist - Short History

The Optimist Inception:
In 1947, the Clearwater Florida version of the “Soapbox Derby” called the "Orange Crate Derby" was sponsored by the Clearwater Optimist Club. There had been talk of creating a waterborne version of the Soapbox Derby racer. An Optimist Club member named Major Clifford McKay promoted the idea, and it finally made some headway with other members. He was in contact with boat builder Clark Mills about the idea and proposed a small sailboat that could be made for under $50.

Don Krippendorf, in 1952,
sails Sharkey

From the USODA Manual:
Mills started sketching and soon ran into a basic limitation. "Plywood was the problem. It comes in eight foot sheets. I could special order it ten feet long, but that cost a fortune, so I knew the boat had to be less than eight feet. Since it was hard to put a pointed bow in an eight foot boat, I made it a pram." So the size and shape of the world's largest class was dictated by the dimensions of a sheet of plywood and by McKay's $50 budget. Mills chose a sprit rig, to allow some shape in the poorly designed, often homesewn sails of the era. Mills vividly recalls the very first Optimist hull. "It wasn't pretty, because Major McKay wanted it fast, for the next Optimist Club meeting. I hammered it together in a day and a half with 10 penny galvanized nails, slapped on a coat of paint, and called her an 'Optimist Pram.' We rigged her up in the hotel lobby where the Optimist Club met."

Clark Mills in 2000

The Decline of the Pram:
The Optimist was mainly a Florida phenomenon until 1958, when Axel Damgaard, the captain of a Danish tall ship, visited the United States and was inspired by the design. With Mills' permission, he took an Optimist back to Europe, modified it, and renamed it the International Optimist Dinghy. The IOD had a battened sail and much simplified running rigging. The new design spread quickly, first through Europe then all around the world.

The IOD collided with a large, established fleet of Optimist Prams in the U.S. As more and more IODs landed on the shores of the U.S., regattas were scheduled for both Prams and IODs. As late as 1985, separate regattas were held for both boats. Many sailors from the 1970s and 1980s owned two boats, to sail in both types of regattas. In the early 1980s, the scales were tipping in favor of the IOD. The number of Prams steadily declined and, by the mid 1980s, Pram racing opportunities had dried up.Today, Prams are occasionally found in learn-to-sail and community sailing programs but they are no longer an organized class and are virtually never raced.

1948 Optimist Pram /  International Optimist Dinghy