The Seafoam is a Ken Willard design published in RCM. You’ll find the plan on Outerzone. I did this kit in an attempt to make more 10 size glow models available to use all of the 10 size engines that are sitting around with nothing to do.
The plane got its name from the Midwest foam wing and stabilizer set that was used to build it. The original foam wing had an extra thick airfoil to impart greater strength to the wing. I reduced the thickness considerably in my kit to reduce drag, as the extra thickness is not needed for strength when building with ribs and spars. When building the wing, use 1/4″ balsa sticks for the leading edge and trailing edge. Ailerons are 1/4″ x 1″ balsa trailing edge stock, or you can attach them to the trailing edge for 3 channel control. The wing is to be sheeted with 1/16″ balsa, either full sheeting or with cap strips on the ribs. Use triangle stock on the wing tips to make Hoerner tips for enhanced performance.
To build the wing, mark the rib locations on your sheeting, lay out a couple of perpendicular lines on a big piece of paper or directly on your table. Then stick everything together. Don’t worry, it’s really easy.
The stabilizer saddle is made to accommodate the flat balsa stabilizer included in the kit. You should build a hatch on top of the nose section, either for your lipo batteries, or for the servos if flying with a 10 glow engine. For the engine nacelle I have included the 1/16″ ply bottom, a pair of balsa sides, and a firewall. The original plan assumes that you’re going to throw a nacelle together somehow, and old Ken didn’t give much instruction on the matter. Even if you leave everything hanging in the breeze it will work, but I trust you to come up with something that satisfies your level of expectation for good looks.