F8F Bearcat

Model Airplane News, Jan 1999 by Ryan, Jim

Hot Speed 400 Warbird

WWII CREW TO A CLOSE just as a whole generation of advanced combat aircraft was entering service in the U.S. armed forces. One of the most impressive of these was the Grumman F8F-1 Bearcat, which was literally en route to the Pacific Theater at the time of Japan's surrender. Although the family resemblance to its famous forebear, the F6F Hellcat, is apparent, the Bearcat owed its inspiration to a detailed study of a captured German Focke-Wulf 190A.

To surpass the Fw 190, Roy Grumman directed his design team to build the smallest practical airframe around the same 2,100hp Pratt & Whitney R-2800 that powered the much larger Hellcat. All other factors took a back seat to minimum weight and maximum performance, and the result was astonishing. The fighter that rolled from the Bethpage plant on August 21, 1944, could take off across a typical runway, and it set a time-to-climb record (10,000 feet in 94 seconds) that stood throughout its service life and well into the jet age. Even today, a modified F8F-2, Lyle Shelton's Rare Bear, holds the world speed record for pistonengine aircraft with a blistering 528mph. For all that, the true genius behind the Bearcat was manifested in its outstanding handling characteristics and wonderfully balanced controls. The result was an aircraft that could make a strong claim as the finest piston-engine fighter in history.

Many modelers who have built my Speed 400 Hellcat design (see the July '97 issue of Model Airplane News) have suggested that I design plans for the other wartime Grumman fighters, the Wildcat and the Bearcat. The products of the "Grumman Iron Works" provided the decisive margin in history's greatest naval war, and these immortal fighters have held a special place in our hearts ever since. So with flight operations CNX'ed by rain one weekend, I sat down at my computer to design a model of Roy Grumman's masterpiece.

CONSTRUCTION NOTES

The airframe was designed in AutoCAD. The fuselage is a balsa semi-monocoque structure, and the wings are foam sheeted with 1/32-inch balsa. The weight goal for the empty airframe is 7 ounces. I use regular thin CA for most construction, but this adhesive will attack foam. For all wing construction, I recommend foam-friendly odorless CA or an aliphatic adhesive.

The foam wing-cores and vacuumformed canopy are available from me for $24 postage-paid. Send check or money order to Jim Ryan, 6941 Rob Vern Dr., Cincinnati, OH 45239; (513) 729-3323; email: jimryan@sprintmail.com.

THE WING

The foam cores are lightly sanded and cleaned with a shop vacuum. The 1/16inch sub leading edges are installed with odorless CA and trimmed flush. The wing skins are glued up from l/32-inch balsa; I recommend Pica* Gluit, which won't leave hard glue ridges. After sanding and cleaning the skins, attach them with light coats of 3M Super 77 adhesive to save weight. Trim the skins flush with the sub leading edges, then install the 1/s-inch leading edge (LE) caps. Trim the roots and tips flush with the cores, then trim the trailing edge (TE) to the chord shown on the plans. Finally, install the 1/2-inch balsa Gringtips and sand them to shape.

Cut the ailerons from the wing panels as shown on the plan and apply 1/8-inch balsa to the exposed TE. Trim 1/4 inch from the LEs of the ailerons and install their 1/8-inch balsa LEs. If you wish, you can trim the ailerons shorter and face their inboard ends with 1/32-inch balsa.

Before joining the wing panels, you need to bevel the roots to the proper angle. Align the root of the wing panel with the edge of your work bench and block up the wingtip 1 1/4 inches. Use a sanding block to bevel the root. Repeat with the other panel. Then, again blocking each wingtip up 1/4 inches, join the wing panels with thick odorless CA. Apply 1.5-ounce glass reinforcement tape to the joint with thin odorless CA.

Next, install the aileron torque rods. These are made of Ihs-inch music wire and 3/32-inch brass tube. Note that the torque rods mate with the ailerons at the very end, forming the inboard hinge for the surface. The easiest way to install the torque rods is to cut through the bottom sheeting, remove the underlying foam and then install the torque rods with thick odorless CA, being careful not to get any glue inside the brass tubes. Next, fill in the slot with 1/8-inch balsa and sand it flush. Cut the hinge slots and dry mount the ailerons. I recommend installing the l6-inch-ply aileron servo mount after covering the wing.

THE FUSELAGE

The fuselage is built over a crutch, which makes it easier to ensure a light, straight assembly. The crutch shown in the plans is cut out of 1/8-inch hard balsa and marked as shown. Note that the crutch is to be removed when the fuselage is complete. Do not glue any of the formers to the crutch!

Slide each former over the crutch into its marked position. Dryfit the 3/16-inch square top stringers into place and, after making sure each former is exactly perpendicular to the crutch, glue the top stringers to the formers with thin CA. Repeat this step for the 3A6-inch square bottom stringer, again making sure the formers are square to the crutch. Note that F-6A and F-6B must be beveled and joined at the proper 30degree angle to allow removal of the wing. You'll also need to trim the slot in F-6B for the 3/16-inch stringer to seat properly. Finally, dry-fit the 3/32 x 3/16-inch upper and lower side stringers and CA them into place. You should now have a light and straight framework.