15.9 oz/sq. ft. at 38 ounces (7-800AR NiCad); 17.5 oz./sq. ft. at 42 ounces (8-2000 NiMH)
Futaba S-133 on elevator; FMA S95 on rudder
The Easy Built Models Pilatus Porter is an inexpensive sport scale kit based on Laddie Mikulasko's design published in RCM in June 1991. The kit is an all balsa and ply design for motor, elevator and rudder control.
As an interesting side note, the Swiss Dhaulagiri Himalayan Expedition set a record for the highest altitude landing for a fixed wing aircraft using a Pilatus Porter on May 5, 1960. A group called the Porter Vintage Association is attempting to raise enough money to rescue the damaged airplane and restore it to flight status.
The kit includes full size rolled plans with both wings drawn and fuselage front, top and side views. Parts include band sawed and sanded ribs (and the original printwood ribs), printwood balsa and ply formers, a two piece vacuum formed cowl, prebent landing gear wire, elevator joiner and pushrod wire, sheet balsa, a bundle of balsa sticks and water transfer decals.
The wing is constant chord and is built in three sections; a two bay wide center section and separate wings. The wing is extremely lightly constructed. It basically consists of 1/16" balsa ribs with 3/16" balsa main spars top and bottom. Secondary spars from 1/8" balsa are located at about 75% of the wing chord. I tipped the innermost ribs on each wing panel to account for dihedral when joining the wing sections. Leading and trailing edges are shaped from strip stock. I found it easier to preshape the trailing edge stock before notching it for the wing ribs and then attaching to the ribs. The wing does not have any shearwebs as designed. After fighting to keep the wing true during covering, I would add shearwebs if I built another.
Wing ribs and plans.
After building the three wing sections, 3/32" plywood dihedral braces are used to join the wing sections. I found the dihedral braces shown on the plans and the dihedral called for in the instructions incompatible. New dihedral braces were drawn and cut from plywood sheet that resulted in the dihedral called for in the instructions. Total time to build the wing was about 10 hours.
After completing the wing, the fuselage was built next. The rear of the fuselage is constructed completely from 1/4" balsa sticks. The front of the fuselage is built separately from 3/16" sticks and is completely sheeted on both sides. My kit was short on 1/16" balsa so the difference was made up from my balsa supply. In both cases, the fuselage sides were built flat on the plans and then joined with formers and cross members. Since I dislike rubber-banded on wings, especially on scale planes, I added a plywood rear wing mount and attached the wing with blind nuts and the original front dowels.
After sheeting the front of the fuselage, I turned to the cowl. The cowl is vacuum formed from clear plastic in left and right halves. I glued the cowl halves to the balsa cowl former and reinforced the butt seam from the inside with 6 oz fiberglass cloth. It was a bit difficult to fit the cowl pieces to the former and mate smoothly with the fuselage front former (firewall). In retrospect, I would make the cowl first and adjust the front of the fuse to fit smoothly. The tail surfaces are constructed of 1/8" balsa sheet. The basic fuselage went together in about 14 hours.
Since the landing gear wires were prebent, it was easy to wrap the joints with copper wire and silver solder the pieces together. I added small washers to the gear where they came into contact with the fuselage. Wheel collars were used on the inside to hold the gear in place.
I covered the Porter with Black and White Top Flite Monokote and True Red Goldberg Ultracoat. In all cases the red was layered over the previously applied white material. The cowl was painted with black and white Krylon while Goldberg Ultrapaint was used to ensure color match to the red. I had completely covered the wing in red and white as shown on the kit box when I came across a color picture of the real red and yellow airplane. Oh well! The black on clear water transfer decals really dress up the scale appearance of the model.
After checking the control throws and the CG, it was time for the maiden flight. The plane took off from our short grass runway with no problems with an excellent climb rate. Throttle was reduced dramatically to fly slow and scale. For the first flight I used a 7 cell, 800AR pack and landed after 6.5 minutes. The all up weight of 38 ounces is right on spec with that pack. A couple of flights later, I took off with an 8 cell, 2000 NiMH pack (42 ounce total weight). That flight lasted 11.5 minutes with 1 minute of power left before BEC cutoff on the ground. Based on rated pack capacities, my average current draws were 7.5 and 10 amps for the 800 and 2000 mAh packs respectively. The Porter loops quite nicely from level flight but the one barrel roll I've attempted so far was very ugly. Short takeoffs and quiet touch and goes is where this plane really shines. Landing can be a bit tricky to get the speed right. I'm experimenting with some down trim during landing to keep the speed up on approach.
While not a "shake the box with glue to produce an airplane" type kit, the Easy Built Models Pilatus Porter builds into a very nice flying sport scale airplane. As discussed above, build the fuselage to match the cowl rather than the other way around and you should get a better fit. The recommended cobalt 05 powertrain works very well. A geared motor should allow a much closer to scale sized prop if you have one available.
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