Douglas Skyray (oz366)

About this Plan

Douglas F4D-1 Skyray. Scale model for IC ducted fan. Wingspan 25 in, wing area 250 sq in, for .049 engines. Scale is 1/16.

Planfile includes full build instructions.

Quote: "The Douglas F4D-1 all weather fighter is the first of the Navy's supersonic carrier based aircraft. Powered by Pratt & Whitney 10.000 lb. thrust 2-57. the Sky-Ray holds the world's closed circuit record at 728.11 mph.

The inherent stability of the highly swept wings provide excellent lateral and longitudinal stability, most necessary to a good flying model. Long development of the ducted fan propulsion system and the attendant construction problems have resulted in this design. For maximum performance, light weight is of prime importance since the efficiency of the fan system does not yet equal that of the propeller as a means of moving a large mass of air comparatively slowly, an advantage at the low speeds at which models fly. Therefore, to remove all possible weight, the landing gear can be quickly removed when desired.

Before beginning construction, study the plans carefully. All balsa parts are identified by a letter and number. The letter indicates where the part is employed, - F for Fuselage, W - Wing, D- Duct, E - Elevon. The numbers are also arranged in the suggested order of installation. Remove parts carefully from the sheets as required during construction.

Note the modifications required for constructing a free-flight model (F-F) or a Controline model (CL). Although this is an unusual type model, with important internal construction, the method of construction and assembly has been carefully worked out with all basic frames assembled flat on the plan.

A flat soft workboard is recommended as a building surface. Only the usual model makers tools such as razor knife, pliers, and sandpaper are required.

BASIC FRAMES: Step I - Assemble the cone basic frame as illustrated in the detail sketch. Protect the plan with waxed paper. Remove from plan and add lower halves of formers and vanes.

Step II Assemble the fuselage basic frame on the plan, and add opposite halves of formers alter removing from plan. Cover motor mount section with F-8 panels, notching rear edge at proper height to receive plywood gusset to be installed across motor bearers.

Step III Assemble the wing basic frame on the plan, as illustrated In the detail sketches. As the wings employ a symmetrical airfoil section, both panels can be assembled on the same plan and then one turned over to provide the opposite right hand panel. Note the levelling feet provided under the tip rib to keep centerlines level. Join the root rib section W-1F and eelle. and taper the ends of the spars. Slide ribs on spars and position assembly on plan. Add leading and trailing edges.

CONE ASSEMBLY: Step IV Slide the vertical tail vane in place and fill in corners with D-18. Cover the cone with stiff paper panels. Roll panels Into tubes to preform material before cementing In place to obtain a smoothly curved shape. Add formed plastic nosing. Cement straightening vanes sections D-14, D-15, D-18 together to approximate curve shown in cone side view. Sand to smooth curve and cement to flat vanes. Finish cone assembly withseveral coats of fuel-proof dope.

DUCT ASSEMBLY: Step V Cement duct formers D-1, D-2, D-3 and D-4 at root rib. Install edging strips D-S on duct formers and cover Inner section of trailing edge with 1/20 sheet balsa. Cement duct lining panels in place, curling material as for cone covering. Apply fuel-proof finish to duct lining.

Tack cement exit jig sections to exit vanes. Slide cone assembly into one wing panel. Sand portion of plywood gusset exposed to intake air in duct to streamline section 0-0. Invert plywood gusset In oversize slot and slide opposite panel onto cone. Establish circular shape of fan section with plywood ring and disc. Adjust position of wing panel slightly if required and cement plywood ring in place with notch on centerline at top. Use care in this operation since clearance of fan and alignment of fuselage are determined by the accuracy of this section.

FUSELAGE ASSEMBLY: Step VI Cement top and bottom duct formers D-19, D-20, D-21 in place and attach duct lining. Join at centerline and fill-in forward portion between vanes with small panels, Radius entering corner of plywood ring.

Cement spacers to motor mounting web and add intake locating plates D-22 and D-23. Locate duct and wing assembly on top view blocking up tips to bring assembly level. Trim off projections on bottom formers D-19, D-20, 11-21 and slip 1/8 shims under them and 1/18 shim under D-17. Engage fuselage section in notch of plywood ring, locate section on centerline and block up with 1/8 scrap balsa. Pin sections to plan to prevent shifting. Cement 1/16 X 1/4 strips under straight edge of intake panel D-24 Flt panels in place and cement to locating plates D-22 and D-23. Install lower panels first. Remove assembly from plan when dry, and fit leading edge covering of 1/20 sheet. Add wing tip sections. Reinforce intake leading edges with 1/16 x 1/4 strips. Cut back lower leading edge of Intake and round off sharp edges.

ENGINE INSTALLATION: Step VII Proceed carefully with this operation since the Proper operation of the fan depends on the alignment of the engine relative to the duct. Of course the engine can always be shimmed or tilted if it should come out improperly positioned. Note that the motor bearers are shown bolted together on a joint, permitting the entire unit to be dropped out for cleaning out fuel sprayed inside compartment.

As an alternate one-piece mounts may be used but removal of the fan is necessary in order to remove engine. This can be done by removing engine bolts and tilting fan at bottom until shaft screw can be reached through bottom opening.

Join bevelled sections lightly with cement and bolt engine to hearers. Attach plywood disc or fan to engine. Work assembly into compartment removing engine if necessary and replacing on bearers when inside..."

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