As it happens a huge thunderstorm washed chemicals into the pond where I sail my models. Whatever these chemicals were diluted the paint from the yacht, draining some of the paint off the model like trails of kerosine in water. That caused the yacht to list, as you see it by the shore leaning over about 20 degrees. It stays there, but this does not make for nice photographs. It’s like having Orson Welles on one bunk, the low one.
So I decided to wait for the city to drain most of the water out of the pond, which they did promptly. I made another model, the same 21″, with a cutter rig. But with this one, I made three decks and a rear deck house, just because I had several small pieces of 1/8″ plywood around. And I decided to seal the Behr paint with Helmsman polyurethene semi-gloss, as that seals wood securely.
Polyurethene is toxic, so if you use it have some ventilation going.
With this cutter, I cut the bottom out of 1/2″ plywood, then cutting topsides to fit around its’ sides. There is one detail which has to be right: the curve of the 1/2″ plywood sides cannot be straight anywhere in order to fit the curving topsides tightly. The bottom 1/2″ plywood curvature has to be a continuous gentle curve all along the waterline. I made the bow plumb with the stern leaned out as close to the traditional cutter style as I could remember.
I used soft pine 1/2″ wide and 1/8″ thick as a coaming from stem to stern on the topsides. I didn’t paint it. I used three tiny screws rather than glue, simply because I got tired of waiting for the glue to dry.
Looking on youtube, I saw several 2′ models with 18-24″ keels, weighted with around 10 pounds or more for ballast. It turns out that with a larger model the relationship between heigth of mast and depth of keel is important. While I don’t know the formula which should be used, I took the mast heigth and made it the keel depth, 1’10”. I used several stainless steel plates for ballast. What this taught me was the delicate significance of mast heigth and weight. The taller the mast (and therefore the greater the sail area high up), the more precisely symmetrical the boat must be and the more ballast there must be. I reduced the heigth of the mast twice to help it conform to the ballast. Eventually, I used 12 metal plates, 1 1/2″x 1/2″. I expect the plates all weighed 10 pounds, and this worked well.
My way of checking this was to hold the topside of one side of the boat. If the keel tips above 45 degrees, it isn’t heavy enough or the mast and sails weight too much, too high up. If the keel tips below 45 degrees, it’s all right but not the best. If it lists in your hand half of 45 degrees, then you’re in good shape. Bolger once said too much ballast never hurt a well-designed boat, and can make it faster in light air.
If I were doing this over, I would figure out the angle at the bow, which is usually around 35 degrees; then I’d cut an inner stem at that angle with a table saw or have someone cut it for me. Then securing the topsides to the inner keel would be easy, since there is no real pressure on the topsides until you secure them aft. That would make for a strong, stable bow from which the topsides can be curved around the bottom.
Then I’d use Elmer’s Wood Glue to fill in the joint from the outside. It sinks into the wood. While it is not as strong as Titebond, it creates a barrier on the outside of the chine. Then I’d use Titebond on the inside, allowing it to spread along the chine on the inside. It wouldn’t show outside, so the chine could be bevelled easily without risking any leakage.
And finally, I’d make sure the keel and mast are perfectly parallel. This makes for an efficient sailing craft.