NOTE: the computer printout of airframe parts should be cut out with a sharp knife and the pieces taped to appropriate balsa blanks to facilitate the easy formation of pieces needed. Note that all parts are laid out on these printouts with the wood grain running horizontally.

FUSELAGE
With a balsa stripper, strip 1/8-inch wide strips from 3/16th by 36 or 48-inch balsa and pin fuse top and bottom strips to the plan. Note the extra 1/8 by 3/16 strip glued at the wing saddle area. Cut and glue the former and diagonal strips in place. Take care to fit these as closely as possible to get a good joint. Remember there is a 3/16th sheet firewall/nose block to be glued onto the nose, so don't confuse this piece as a fuselage sidepiece in the plan side view.

While the fuselage side is on the building board, fill the nose sides and the area under the stabilizer with 1/16th sheet balsa as shown on the plans. The sheeting at the rear will support the pushrod exit points. Because this sheeting is 1/16th note that there is a left and right fuselage side. Also install the 1/8th balsa wing hold down supports after drilling the holes for the wing dowels. I used skewers from the local supermarket, which have worked well. NOTE: the hole sizes shown on the plans are approximate and should be determined by the type of dowels you will be using. Some people are using stiff nyrod and other types of plastic rod as hold down dowels.

Remove the first fuselage side from the plan and build the second with the same methods. The finished fuselage side will feel pretty flimsy at this point, but when assembled with cross pieces it makes for a strong and light structure.

Build formers F3 and F5 over the plans using 3/16th square balsa stripped from 3/16th sheet. Glue both formers to one fuselage side aligning carefully with a square. Glue directly on top of the F3 and F5 1/8th sidepieces already in place. Remove this side from the plan and place it (and the glued F3 and F5 formers) upside down over the plan top view. Lightly pin both F3 and F5 formers in place on the plan. Align the other built up side over the plans and glue to formers F3 and F5.

NOTE: The REAR WING HOLD DOWN BLOCK location shown in these pictures has been changed in the final version of the cruiser and is reflected in the plans.

Cut 3/16th square balsa pieces to fit across the fuselage bottom at formers F2, F4, F6 and F7, sanding the slight fuselage curvature as necessary into the ends before gluing. Note that formers F6 and F7 consist of 3/16th square pieces added during final assembly unlike F3 and F5, which are built up separately. The upright sidepieces of F6 and F7 are actually the fuse side formers built into the fuselage earlier. Remove the fuselage from the plan and turn upright. Cut and glue 3/16th square sticks in place at formers F2, F6 and F7 on the topside also. Note that there is no cross member at F4 on the fuselage top.

Cut the nose/firewall from 3/16th sheet and drill the motor and cooling holes. I used forstner bits for this. The motor hole should be cut slightly undersized and sanded gradually to fit your motor's gearbox. The whole firewall should also be cut from the sheet slightly oversized to allow a bit of extra area for alignment purposes when installing. The nyrod shown supports the gearbox mounting screws. The fit here is pretty close and some care is needed when cutting this piece.

Pull both fuse sides together, aligning carefully over the plans and glue the firewall in place. Pull the sides together at the tail and glue using a section of 3/16th square balsa to separate both sides the proper amount. Note: glue ONLY to the fuse bottom BELOW the stabilizer position. This spacing is designed to allow the completed stabilizer and fin assembly to slide into place.  

Cut and fit the 1/16th balsa sheet bottom nosepiece, which is installed between the sides from former F1 to F2.

Sheet the front windshield area with 1/16th cross grain balsa, beveling the bottom so it fairs into the nose top stringers. Now sheet the whole nose top from the windshield to the firewall F1 with 1/16th sheet balsa. Bevel the rear portion of this sheet so it fairs into the windshield. Note the cooling holes in this top sheeting which are necessary for motor cooling. I used 7/8th forstner bits to cut the holes. Operating without these holes and those shown in the firewall F1 will result in hotter running motors and shorter motor life. While not necessary for winter flying, some builders operating in warmer temperatures have been leaving a section of covering off the fuselage bottom immediately in front of the landing gear and former F3 to provide an exit for the cooling air.

If you will always hand launch the Pf-cruiser, there is no need to install landing gear. However, if you wish to enjoy it in a paved parking lot (under the lights at night is great fun) now is the time to install ¾ inch strips of 1/32nd ply across the fuselage as shown on the plans. They can be seen in the above picture.

WING CONSTRUCTION

Note: the wing is built in two pieces and joined with slight dihedral. Cut 13 1/16th balsa wing blanks, align them in a stack and tape lightly together. Tape the wing outline from the computer printout to the rib stack and cut the ribs using the hacker of your choice. Sand the ribs in a stack to remove saw irregularities.

Strip wing spars (3/16th square) from 3/16th medium to firm balsa, ensuring the grain is pretty straight and there are no imperfections, which could compromise spar strength. DO NOT use soft balsa for the spars. Pin the bottom spars to the plan. Cut a strip of medium 1/8th sheet balsa to form the trailing edge and pin to the plan. Both wing halves can be built simultaneoulsy if you are careful NOT to glue the centers together. Note also the two center ribs are NOT glued in place until later in this construction. Align all other ribs on the plan, and glue in place. Install and glue the top spar. Use a strip of 3/16th balsa to make the leading edge. Glue it into place.

Using the computer printout cut the wing tips from 1/8th sheet balsa. The lightening holes probably don't remove much weight, but they look cool and should be used. Sand the tips smooth and glue to the outer rib on each wing panel. Install the tip supports (1/8th balsa). Lighter balsa could be used here (1/16th sheet) but care then must be taken when covering so that the tips are not pulled out of alignment by the shrinking covering. Once both panels are completed, remove from the plan and carve the leading edge to the shape shown on the airfoil. Leave the trailing edge as is.

Place the finished right panel back over the plan and block up the wingtip one half inch. Using a square align the inner (remember the two unglued ribs) rib on this panel at 90 degrees to the work surface and 90 degrees to the leading edge. Glue the rib in place once aligned. Care taken here will result in a straight wing when both panels are joined.

Remove the first panel from the plan once again and go through the same procedure with the left panel, carefully aligning the inboard rib at 90 degrees and then gluing. Note that there will be a slight amount of sanding needed on the spars, leading and trailing edge of both panels to bring them in uniform lineup with the inboard spars. Once this is done, again place the right panel back on the plan. Block both tips one half inch off the workbench. You should now be able to glue the inner ribs together to make a complete wing.

In my earlier designs I've been using a plywood dihedral brace, but with the Cruiser I opted to use a section of firm 1/16th balsa instead. This has proven to be very strong. If you have doubts about a balsa brace go ahead and use 1/64th ply.

The ailerons are simply one inch strips of medium 1/8th balsa cut as shown in the plans. We drilled 16 5/8th holes in both ailerons to reduce weight. The ailerons appear a bit flimsy but in actual use are not and are very effrective on the finished airplane. Simple clear tape hinges were used here as well after the airframe was covered.

I initially designed the Pfcrusier to have ailerons powered by internal control rods placed through the wing. Well along into the wing construction we found the internal rods planned simply wouldn't work. There was too much friction inside the bent tubing to allow smooth movement. A quick call to our local dealer found there were no standard aileron control linkages deisgned for park flyers. The available ones were simply too heavy so we had to make our own.

To do this we started with a standard Dubro "micro pushrod system", (the same system was used for our elevator/rudder linkages as well). This neat packages comes with two park flyer sized ez-connectos and two micro ez-links. The trick was to use these ez-links to join the pushrods to the control system. After some brainstorming we decided to use a 3/4 inch section of 2.4 mm OD brass tubing (that's the next size down from 1/8th OD) along with the contents of the Dubro package.

The tubing sections were placed over the end of the music wire, crushed in a vice, and then hammered flat. This joint was then soldered to make it permanent. Use a file to clean up the edges a bit and then drill a hole for the music wire pushrod from the servo. The aileron control horn was then bent using a portion of the plastic tubing included in the Dubro package. You need to space the bends as required by your aileron setup.

A portion of each aileron was trimmed back to allow the pushrods to fit flush with the aileron leading edge. Drill a hole into the aileron leading edge for the control horn (careful alignment is needed here). Wick some Ca into the hole to harden the wood around it. We also used a pin to prick the wood surface around the horn entry area and used some CA to harden this area as well. We CA'd the horn in place and used the aileron covering to provide added support to hold the horns in place. A strip of covering applied to the finished wing when attaching the ailerons acts as the aileron bearing and works well.

We chose to install our aileron servo offset from center. The servo can be installed on the centerline by making a cutout in the center ribs. Either way a light balsa box needs to be built around the servo to support the covering in that area. A small cut out in the top sheeting at the cabin rear allows free servo horn movement.

TAIL FEATHERS

Build both the stabilizer and fin over the plans using the computer printout to cut out the sheet pieces. Do the same for the rudder and both elevator halves. Note that the elevator leading edge is actually one continuous piece of 3/16th balsa and is the easiest and lightest way to allow both elevator halves to work with one pushrod. Sand all assembled elevator and fin parts before assembly. On the prototype I sanded to a thickness slightly over 1/8th inch. Align the fin on the stabilizer to that it is 90 degrees to the vertical as well as 90 degrees to the stabilizer trailing edge. The whole assembly can now be trial fitted and glued in place on the fuselage. You may opt to cover these assemblies before gluing into place. In this case mark the fuselage outline on the stab bottom and cover just to this line, leaving bare balsa areas for gluing on final assembly.

Bevel both elevator halves on the bottom to allow a hinge movement. I didn't bevel both sides of the rudder; just one and this has worked perfectly. Clear cellophane tape over the entire rudder and elevator hinge lines after final assembly and covering makes for a simple and foolproof hinging system.

Make two control horns from 1/6th ply as shown on the plan and cut 1/16th slots in the rudder and elevator at the appropriate spots (in alignment with the pushrod exit holes). Run the outer pushrod guides at this time also. Glue both pushrods into place with Ca.

FINAL ASSEMBLY

Before covering the fuselage install the radio gear. Doing so now makes it much easier as you can reach things through the uncovered sides. Glue a 3/16th square balsa "spar" along each fuse side as shown on the plans. These pieces make up the base for a 1/16th cross grain balsa plate, which will hold the receiver and battery pack. I use either thick ca (wrap your finger in wax paper) or epoxy (sparingly) smeared over the balsa plate, which seals the wood and allows Velcro to stick strongly. Moving the flight battery fore and aft can easily change the center of gravity. The servos are installed on two 3/16th square balsa rails as shown. Wick a drop of ca into the holes drilled to accept the servo screws. Location of the radio gear shown on the plan has worked well. Larger heavier servos might want to be installed in a more forward position. Simply placing the gear on the balsa plate can give a pretty good idea of where things should go.

The motor installation is pretty simple. The gearbox is held to the nose block with two small screws. I installed two half-inch pieces of yellow nyrod in the nose block to support the screws. The extra length extending from the nose block inside the fuselage allows the motor to flex slightly which is good if you're belly landing the plane on grass. There is a two-degree down thrust built into the fuselage during construction.

Cover the airframe with a lightweight covering. The prototypes are using clear colored monocote.

After covering the complete airframe, run the two pushrods inside the previously installed outer tubes. . I use a z-bend at the control surface and an easy connector on the servo. Trial fit without hinging the elevator and rudder and determine the location of the plywood control horns. Cut a 1/6th slit in the leading edge of both surfaces and glue the control horns in place. (NOTE: Small control horns and easy connectors are now available for park flyers and you may opt to use these.) Now you can actually install the rudder and elevators using clear cellophane tape. I was surprised the first time I saw this used, but it is ideal for these small models. Some brands of tape have finishes, which makes it virtually impossible to see on your nice covering job.

Now is the time to install the landing gear. Bend 1/16th music wire as shown and install using small plastic straps cut from a margarine container or similar. Use very small lightweight screws. Use lightweight foam wheels designed for park flyers. The wire and wheels I use add 1.5 ounces to the airframe, which is about a ten percent increase in weight, about the same as adding a pound to a ten-pound airplane. The addition of wheels in a small lightweight plane like the Pf-cruiser is noticeable in performance and general flight characteristics. The plane is more agile hand launched without wheels. At the same time it is a different but very enjoyable airplane on wheels, especially if you, like me, enjoy touch and goes. If you use the wheels small plywood or wire skid should be glued to the fuse bottom as shown on the plans.

FLYING

Motor input in my setup is 28 watts (four amp static draw by 7 cells), which results in 12 minutes at full throttle on 720 MAH NIMH cells. I've gotten 16 several times this summer (full throttle) on calm days with just cruising around. My personal Pf-Cruiser has 3/8 inch up and down and .75 inch of rudder throw both ways. That is a bit much rudder, but it makes for really neat stall turns. I added quite a bit of expo to soften the rudder response somewha. The ailerons have 3/8th inch throw both ways and are very smooth at this setting. This airplane turns well with aileron/elevator input, but is especially neat when rudder is added along with the aileron input. Taking off from our rather tight paved circle I often add left rudder to skid the plane around to the left and avoid the steep bank in front of me.

It'll fly right out of your hand with a slight shove. Obviously you can't just drop it and expect it to fly off, but you do not need a hefty throw either. It'll loop from level flight early in the battery but might need some nose down to gain speed later on. It lands very slowly and easily by just applying slight up when almost down.

I attach the wing with four #33 rubber bands, two on each side. No more are necessary. Without wheels, just pick this little plane up, raise it over your head and give it a little shove straight ahead. It should be released level or slightly nose down as in all hand launches. There is plenty of power and the plane will just fly off. Landings are slow and easy and just a matter of removing throttle as needed and flaring just before touchdown.

Taking off with wheels from pavement with the Pf_Cruiser is done very easily. It seems we have gotten the wheels aligned right for a change and by easing the throttle on, the Cruiser moves off pretty staright, and as soon as the tail is up complete control is attained. It lifts off in about ten feet and juist flies away. Croos wind takeoffs, as usual, ahve to be watched a bit more, but as long as the nose is int he wind things are pretty staright forward. . What is really neat flying from pavement is the touch and goes. I find about 30 percent throttle works well when on final and it's almost like flying in slow motion. Taking off again during a touch and go is not the same as starting from a dead stop. The tail is still up and flying and the plane behaves like it's on rails as long as the flight path is close to being into the wind.

Any questions may be directed to me at astroflyer@rushcomm.ca