Porterfield Collegiate (oz6187)

About this Plan

Porterfield Collegiate. Scale model for electric power and RC, by Robert Boucher. Wingspan 69-1/2 in, wing area 675 sq in. For geared Astro 15 electric motor. Scale is 1/6. Model # pl-789.

Also kitted by Astro Flight.

Quote: "Introduction. The Porterfield project has been a lot of fun. I wanted to make a new model using the new mechanical speed reducer designed for the Astro 15 flight system and the new Astro electronic motor control. The speed reducer lets you swing a big prop for maximum thrust and aerodynamic efficiency. The recommended prop is a Y & 0 wood 13/8, but you can use a 12/8, 14/6 or 14/7 just about as well. A 6 foot span high wing monoplane from the golden era of aviation seemed just perfect since these planes had 32 to 36 foot wings and, therefore, at 2 in to 1 ft scale, the scale size prop would be 12.5 in and the wing area would be about 700 sq inches, right in the middle of the recommended wing area for the electric system of 600 to 800 sq inches.

Now which model to pick. A review of the best candidates in John Underwood's 'Lightplanes,' and Joseph Juptner's 'US Civil Aircraft' gave us a nice shopping list. The J-3 Cub, Rearwin Speedster, Porterfield Collegiate, and Curtiss Robin all looked good at about 72 in wing span for the Astro 15 system.

The Porterfield was decided upon and the project was underway. The design is quite straightforward and fairly easy. It is reminescent of the old timer models.

The model was covered with dacron cloth and nitrate dope was used for the finish. Due to weather conditions, I ended up with about 10 coats. The cold and rain caused some blushing, however, the job was completed and still ended up at a total weight of 63 ounces ready to fly.

The first test flight was with a 12/6 prop and the flight was successful; however, it was a bit on the marginal side. The prop was changed to a Y & 0 13/8 and this was the answer. The flying was superb and very smooth with rudder response quick and positive. The Porterfield was airborne in about three plane lengths and flight speed was a scale-like 35 mph. Loops were tried from level flight and were clean and precise. The 12 ounce wing loading makes it a perfect trainer. It's docile and flies hands off, yet responsive to commands.

For even lighter weight. I would recommend using one of the plastic film covering materials and save about 6 to 8 ounces.

The model is designed to a scale of 2 in to 1 ft (1/6 scale), which gives us a nice size model that has scale-like power, speed and weight.

CONSTRUCTION: The construction of this model is quite straightforward with no tricky things to watch out for. It is like any old timer or free-flight job. First you make two framed-up fuselage sides from 1/4 in sq balsa, then assemble both sides to make a basic fuselage frame. Take the time to sand the balsa cross members to a good fit before

gluing this is the secret to a strong light fuselage. Make the parts fit and don't try to fill open joints with glue. After the sides are assembled into a frame with top and bottom cross members in place, the stringer which fair the fuselage sides to a slight oval shape are put on. This makes the entire structure even more rigid and strong. The sheet balsa cowl is then installed along with the plywood cabin floor.

Landing gear design is also from the old school; two brass tubes are epoxied to the cabin plywood floor, and the landing gear struts are simply plugged into the tubes. This allows quick and easy removal for transportation. A brass tube is epoxied over the strut ends to form a smooth and round axle. A retaining screw holds the wheels on. The landing gear is strong, light and easily made without having to solder any parts together. Epoxy has proven to be adequate on a number of my models.

The wing construction uses the traditional 'D' spar with spruce spar caps. This gives a light, strong wing which resists those evil warps which can make even the most graceful bird fly like a toad. The capstrips add a little work but make the wing smooth and will hide any boo-boo's that you might make.

The wing can be built flat or a little wash-out can be added - about 1/4 in is enough to insure a docile stall. This is nice if you are a bit rusty on the sticks and have a tendency to over-control in that down wind turn. It's cheap insurance and I would recommend it.

The tail feathers are also built up and built from 1/4 in sq balsa over the plan. Note that the fin plugs into the stab for a strong stiff joint. This is usually a weak point in many old time designs - they kind of tack the fin on top of the fuselage and it has an annoying habit of falling off at just the wrong time. Of course this means that you will have to fill in-between the fuselage longcrons with a bit of scrap balsa to cover the gap.

Good luck - I hope you enjoy building the Porterfield Colligiate."

Update 26/06/2015: Replaced this plan with a much clearer copy, thanks to SteveB, quote: - "I have had the plan of the Porterfield Collegiate (Plan ID 6187) for years (never built it), so I am sending in a clean version to replace the one you have, as its source was the magazine page. Regards,"

Update 19/05/2020: Added kit review (of Astro Flight kit) from Model Builder October 1989, thanks to RFJ.

Note there is also an old Ezone (1996) online review of the Astro Flight Porterfield Collegiate at https://www.rcgroups.com/forums/showthread.php?3972...

Supplementary file notes

Article. Updated 30/06/2015.
Review.

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