Ryan St: A sport-scale military primary-trainer, The

Model Airplane News, Nov 1999 by Haffke, Henry A

ONE OF MY FAVORITE R/C models is Ted Strader s Ryan ST, which I saw in the September 1960 issue of Model Airplane News. In 1960, we rarely saw a low-wing R/C model and a low-wing scale model was almost unthinkable. With its 66-inch span, it was a big model for its day. When I built it, I added scale ailerons and reduced the dihedral to scale specs. It worked out well and flew beautifully for four seasons, including my first dozen R/C scale meets.

When the model was 26 years old, I decided to refinish it with modern covering materials, and it took first place in Military Scale at the 1995 MARCS Model Show in Baltimore.

The following year, I flew it at the Rhinebeck scale meet where the editorial staff of Model Airplane News saw it and thought it a good subject for a construction feature. I contacted Ted Strader, designer of the original model, and he agreed to let me redraw and modernize his design. He even supplied me with a copy of his original drawings, which were a big help.

The new plans include details for several of the Ryan trainer types, including the prototype ST, the STA, STM and military YPT-16, PT-16 and PT-20 versions. I include details and patterns for building a scale Kinner radial engine, too, so you can build a PT-16A or PT-20A. My model is a PT-20Athe first PT-20 delivered to the military (December 12, 1939). It was converted to a PT-20A in October 1940.

FUSELAGE

Start by cutting the sides out of 4-inchwide 1/8-inch-thick balsa. sheet.Unless you can find 48-inch-wide balsa, you'll have to splice sheets together to obtain the necessary length.

The splice is shown on the plans by a diagonal broken line above the wing saddle behind F-2. The sides, basic outlines are shown on the plan by arrow points. Note the portion cut out for the stabilizer.

Once you've cut the sides to shape, mark them for the location of each bulkhead. Be sure to make a right side and a left side while doing this. Note that in the cockpit area, the side formers and top formers are not in line with each other. Mark the locations for the side formers on the outside surface of the side and the locations for the top formers and the 1/4-inch saddle doubters on the inside.

Right behind the rear cockpit are two P-3 bulkheads. Score the outside surfaces of the fuselage sides between these two bulkheads so that you'll be able to crack (and reglue) the sides so that the sides will come together at the rear without bending.

Cut the fuselage bulkhead parts out of the materials shown on the plans. To ensure that both sides will be the same, cut the side formers two at a time (stacked on top of each other). Also, cut two each of the half bulkheads (top and bottom) as shown, and glue the halves together to form one-piece symmetrical bulkheads.

Drill holes in the firewall for the engine-mounting bolts, fuel lines and throttle pushrod. Start the fuselage assembly by sliding the 1/8-inch ply fonner F-2 into position oil the side parts (don't glue it yet). Cut a 2 1/4-inch-long, 1/2-inch-square piece of balsa, and clamp it between the aft ends of the fuselage sides to help keep the tail positioned properly

Place the firewall flat on your work surface, and stand the fuselage sides on their front ends with the firewall between them Use a square to keep everything lined up squarely, and epoxy the firewall and former F-2 into place. Now add the 1/2-- inch bulkhead F-l and the lft-inch riser side pieces on top of the fuse sides and in front of F-1.

Next, epoxy the 1/2-inch triangle stock into place behind the firewall. Glue the 1/4-inch-thick wing-saddle doublers into place against F-2. On the plan, the saddle doublers are shown by dark arrows. Install all the F-3 bulkhead parts (F-3SA, F-3SB, F-3S and F-3T) back to the first complete F-3 bulkhead just behind the cockpit. Let the glue set before proceeding.

"Crack" the sides so that the rear fuse sides can be bent inward, and make sure that the fuselage remains straight. It is a good idea to place a 1/4-inch-square stringer (without gluing) in the top and bottom stringer cutouts to help maintain the rear section alignment.

When you're satisfied that the sides are properly aligned, glue the F-7 bulkhead parts into place. Now run a bead of CA along the crack in the sides, and add the second set of F-3 bulkhead parts, followed by F-4, F-5 and F-6 bulkheads.

TAIL PARTS

The tail surfaces can either be built up of 1/4-inch stick parts as shown, or they may simply be cut out of 3/16-inch-thick balsa sheet. The lower part of the rudder has a soft, 1-inch-thick, balsa-block fairing glued to each side. To save weight, hollow out the blocks before you glue them into place. Be sure to test-fit all the tail-surface parts, and hinge them together temporarily before proceeding.

This is a good time to set up your servo installation and the rudder and elevator pushrods, both of which will be concealed in the rudder fairing when the model is finished. To ensure enough rudder-- pushrod clearance, you'll have to make a cutout in the rear of the fuselage side Once you've set up the controls, you can remove the tail surfaces and return to the fuselage structure.