Grumman F7F "Tigercat" Article & Plans
June 1957 American Modeler
Here is an example of the Grumman F7F "Tigercat," as presented in the June 1957 edition of American Modeler. Designed, drawn and described by Paul Plecan. |
"The Grumman F7F Tigercat was the first twin-engined fighter aircraft to enter service with the United States Navy. Designed for the new Midway-class aircraft carriers, the aircraft were too large to operate from earlier decks. Although delivered to United States Marine Corps (USMC) combat units before the end of World War II, the Tigercat did not see combat service in that war. Most F7Fs ended up in land-based service, as attack aircraft or night fighters; only the later F7F-4N was certified for carrier service. They saw service in the Korean War and were withdrawn from service in 1954." - Wikipedia
Long a favorite with scale fans, the Tigercat has been used with increasing success in the Navy Carrier event. Aerodynamically clean, moderately simple (as twin-engine jobs go) and devoid of "frills," the F7F is a "natural" Carrier job.
While not a beginner's project by any means, it is not unduly complicated for the slightly advanced model-builder it is a worthwhile project. Due to a fair number of parts that are cut from heavy sheet balsa, a jig-saw is a "must." For this we found a vibrator-type jig-saw best, but any powered jig or band-saw will do.
Construction can be started with either the wing or the fuselage, but do the wing first-it's a little easier that way. After butt-joining two widths of hard -3/16" sheet (3" wide) and splicing in an end piece to obtain an overall length of 43 or 44", trace the spar shapes. The two main spars are copied. off the front view. The rear spar is shown directly above the front view. Use firm, fairly hard balsa for these.
Once the ribs have been cut, proceed with actual assembly. Note that "tabs" are used on the rib bottoms to position them on the work board for proper incidence (since there is no "flat" section to the undercamber, it would be difficult to line up the ribs otherwise). Refer to the front view now and mark rib positions on the main spars in ink.
The three W1 ribs are pinned down on the wing plan then covered with ⅛" medium sheet. Sheeting for right and left panels butt into center section over outboard W1 ribs, so cover only to the "center" of these ribs, leaving some contact area for cement.
When cement is fairly dry, pins are removed from center-section area and wing assembly tilted so ribs on left panel touch workbench .. Once ribs are aligned in position, cement in place. Now cover entire panel with ⅛" medium sheet. It is easiest to use 2" x 10" sheets; they can be pinned down before the cement dries too much. If you are using a slow-drying cement, larger sheets can be handled. Or you may. prefer to "plank" the area with ⅛" x ⅜" strip •. In any event, overlap the trailing edges of the ribs by ½" (see Fig. 1) so the top covering can be beveled later to conform with the undercamber line. The right panel is made similar. Allow ample time for all top sheeting cement to dry before removing wing assembly from workbench. This prevents warps.
Remove assembled wing from work bench, trim all "tabs" Bush with undercamber. Cover bottom wing in same manner as top. To quickly trim trailing edge flush with undercamber line use a large flat sanding block with medium grit garnet paper. Note that the bottom sheeting protrudes ½" beyond trailing edge of top sheeting (see Fig. 2) so it can be sanded to conform with top camber line. Trim the trailing edge thickness to about 1/32" (or just under 1/16"). Add several coats of dope or sanding sealer to strengthen the wood against nicking. Sand sheet covering in front flush with ribs, add leading edges, allow to dry. Trim to airfoil shape, sand, then apply several coats of sanding sealer to fill in balsa. Note ⅛" sheet was used for covering; however, in using a flat sanding block and smoothing irregularities here and there, final thickness will be about 3/32", so don't worry about weight.
The fuselage can be assembled either by the crutch system or flat on the plan. If you assemble on the profile plan leave the fully-covered assembly pinned to the workbench overnight to allow cement to "set" fully. It is best to leave the top sections of formers F5, F6, F7 and F8 off in assembling the primary fuselage structure; once sheeting is trimmed to the undercamber curve, the wing can be added to the fuselage and sections 5 to a added before sheeting in area behind cockpit. Mark nacelle and fuselage .positions on bottom of wing (in ink) to facilitate alignment later. Lightly scribe aileron and flap lines at this time.
Tail surfaces are of orthodox construction, so no detailed description will be needed. Be sure all control linkages work smoothly with no binding at any point. Since this job is lugging two good-sized engines around, be sure of strength in all connections---doubly so in the mounting of the landing gear struts, wing-to-fuselage and wing-to-nacelles joints. Add a small cloth reinforcing strip at all these joints (sanding sealer will hide these later). Nacelle construction is straight-forward--similar to the fuselage and covered with ⅛" by ⅜" strips.
Cowls are laminated out of a series of balsa rings. Cement the rings together (cross grained) as shown and sand down to proper curvature. Make sure that the inner curves match, too.
Positioning of engine bearers is indicated for all types of motors. Only 29's or 35's will be the "easy" displacement in this design. Anyone contemplating 19's will have to use them at full power constantly and will have to trim weight here and there. The use of 49's or 60's is strictly for the big guy who has the arm to keep things in line-this model exerts quite a pull on the lines when flying with 29's or 35's, let alone 60's.
Finish and detailing depend on the builder's whim.
The "Tigercat" is a subject worthy of your best efforts. so take it slow and do it right. One of the most stirring sights the author has seen in a1moat 20 years of contest-going was the carrier flight made by one of the New Jersey boys at the 1955 RAMS (Republic Aircraft Model Club) meet.
Robert Killmer's "Tigercat" was the same size as the one we show and mounted two K&B-Allyn 35'11. It had retractable landing gear and 2-speed engines. Bob made a real short take-off. Once airborne, the wheels tucked up in true prototype sequence-first the nose, then one of the main wheels, followed by the other. High speed run was signaled by the dummy pilot in the cockpit raising his hand over his head-rudder in neutral, as the lines were real tight. Upon completing the high speed run, the flaps came down, ditto for the wheels, and the rudder popped over about 20 degrees to maintain line tension as the engines were put in slow speed. Once the slow-speed run was completed. down she came for the landing. This was quite "hot," and the model went off the end of the carrier deck:-the only damage sustained was a thrown nose tire. It might be mentioned that the landing would have been normal, but the "deck hands" were so bug-eyed watching the flight that no one stretched out the" arresting cords" and sandbags that stop the model on the carrier deck. It was such a beautiful sight watching those yellow-tipped prop arcs! I Oh, yes--the landing gear struts on that job were fully machined. much dural, and working "scissors" to keep the wheels aligned.
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