This is an article written by LeRoy Cook for Kitplanes magazine, it was published in March 1993
NAVIGATING BY NORTH STAR
Custom Flights' bushplane kit offers welcome variations on a Super Cub theme.
When Morgan Williams wanted a Super Cub floatplane, he couldn't find one that was suitable, so he built one. That simplified story sums up the creation of a new Canadian kitplane, the North Star ‑‑ but there's a lot more to the tale. Such as, who is Morgan D. Williams, Jr., and why does he think his airplane will find a market?
Williams is a lifelong airplane junkie who has spent much of his adult life maintaining, rebuilding and restoring airplanes. His firm, Custom Flight Ltd., has assisted homebuilders in various projects and specialized in custom‑built aerobatic wings for Pitts biplanes. Through it all, Williams took note of where certain airplanes fell short in the durability and accessibility departments.
He knew Piper's PA‑18 Super Cub was an excellent performing airplane, but he also knew it could be improved, even after the aircraft's 40 years. Rather than work over an existing hulk ‑ something he has done for clients far too often ‑ Williams opted to start afresh and design his own Cub.
"Every time I go to an air show," he says, "I run into someone with a new idea that I can incorporate in my airplane." The little details are what makes the North Star a bigger, better Cub, even though it will be mistaken for one even at close range. There's the familiar split door that folds up and down for unlimited surveillance, photography, or cabin access ‑ but Williams has one on the left side as well so a floatplane pilot can bail out to grab a dock on either side. Williams loves to fling the door open in a half millisecond to show how his heavy‑duty underwing latch will grab the window and keep it out of the way when you're in a hurry to fend off before wrinkling a float. It may look like a Super Cub, but there are a host of improvements that set it apart.
A WORKING WING
The North Star's airfoil is the same as the Piper's USA 35B (not the Clark Y I had always supposed it to be), but Williams squared off the tips, sacrificing the elegant Cub tip bow for some extra lift in the extended rear corner and better low‑speed control from the wider aileron span. The flaps are 2 feet wider than the Cub's. Four notches of flap extension are provided, up to 52 degrees. The airflow‑spilling space left between the flap and the fuselage has been eliminated, preserving lift in that area.
Internally, the wing is strengthened for the job of hauling bush‑strip loads. According to Williams, he started with the wing from the PA‑25 Pawnee agplane, which grossed at 2300 pounds instead of the stock PA‑18's 1750 pounds. An extruded aluminum spar and stamped aluminum ribs are used, with an .020 aluminum leading edge sheet that extends 4 inches aft of the spar on top of the wing, much farther back than the Cub's. The C‑channel compression struts are aligned with the flap and aileron hinges to pick up the air loads from the aft spar. This allows the same bolts to mount both a strut and a hinge. Heavy 3/16 ‑ inch drag wires are used.
The fuel system consists of two 26 ‑ gallon, TIG‑welded, baffled‑aluminum wing tanks, which are strapped securely in place. Unlike the Cub, however, the North Star tanks are curved to conform to the shape of the wing's airfoil. The fuel gauges are those paragons of honesty, a sight tube in each wingroot. As the aircraft is usually mounted on floats, to avoid confusion, the gauges are only marked for level flight. Fuel selection is merely on/off, and there is no header tank under the panel. In addition to the fuel strainer on the firewall, an extra drain is located aft of the baggage area, accessible from the left side of the fuselage. Fuel vent tubes are under the wing's leading edge, with Citabria‑style ice and bug deflectors mounted in front of them.
LANDING GEAR AND FUSELAGE CHANGES
The landing gear looks a lot like the Super Cub's, but Williams points out that the airfoil fairings under the belly are considerably smaller. This is because there are no shock cords inside them; the North Star kitplane uses hydraulic shock struts instead, a simple and rugged system that requires little maintenance. The gear is also 3 inches taller for improved propeller clearance and a higher angle of attack for liftoff. The test airplane had 8.50x6 Cleveland wheels and brakes installed, with a Scott 3200 steerable, full‑swiveling tailwheel under the rudder post. The inboard axles are extended an inch to allow a bushing for wheel skis to be mounted. Williams says his plane wears wheels only a couple of times a year, when it comes south for air shows and demonstrations. The rest of the time it's on floats or skis ‑ in its natural element.
Instead of going to a simpler trim tab, Williams retained the adjustable stabilizer, and two heavy‑duty ground‑maneuvering handles are welded to the aft longeron. Inspection and access covers around the rear fuselage cutouts are shingled, rather than overlapped, so the forward and upper edges do not protrude into the wind or leak. The fuselage belly contour features a deep V‑shape, designed to prevent water accumulation; Williams brags that one can hose the belly out from front to rear because there are no hidden pockets to trap moisture, and a large opening at the aft end of the fuselage allows water to escape. The turtledeck's flat shape is borrowed from the PA‑18‑A agricultural Super Cub, designed to match the wing's contour to cut drag and add lift.
A small baggage door has been provided so the pilot doesn't have to hoist everything over the rear seat back. The North Star baggage floor has been lowered to the bottom longerons and extended aft. An optional tube continues into the tailcone from the rear wall of the baggage compartment, expressly for fishing poles or skis. Baggage capacity is 90 pounds. If you need more space, the rear seat back is removable. Access to the battery in the aft fuselage is through the baggage compartment instead of through a leak‑prone access plate atop the fuselage.
The North Star's entire fuselage truss is built of 4130 chromemoly steel tube. The Piper Cub used less‑expensive mild steel in low‑stress areas. There are extra diagonals in the aft fuselage truss for added strength. A complete welded, internally oiled, fuselage is provided in the kit, so there is little or no welding required for assembly.
BETTER ACCESS, ALL AROUND
The cockpit area is 2.5 inches wider than the Super Cub's and the front seat adjusts over a 6‑inch travel to fit a variety of pilots. A boarding step is provided in front of the maingear leg as well as behind it, because some pilots like to fold their way into the forward seat over the front of the wing struts. The front footpeg also doubles as a step for checking the fuel tank. Naturally, the cowling sides unlatch and swing up for easy access to the 0‑320 Lycoming, which is installed in a Dynafocal mount that swings out if the mount's shear‑type bolts are removed on one side. The oil cooler is relocated inside the cowling. A compact, powerful quartz‑halogen landing light is fitted into the nosebowl, which can be cheaply replaced from automotive sources.
There are no sheet metal screws in the North Star. Instead, more than 300 nutplates are riveted in place to solidly anchor machine screws. If access is needed to the forward cockpit area, the boot cowl is fully removable with piano‑hinge pins. The rear windows are larger, although Williams has had at least one customer request Cub‑style windows for nostalgia.
IN THE COCKPIT
Once settled in, there is a feeling of homecoming for Super Cub pilots, and yet some features are foreign. The rear seat's throttles and carb heat knobs, for instance, are mounted below the left door sill, because there is no fixed sidewall in the conventional shoulder‑high area. The trim crank is halfway back on the lower left sidewall, accessible to either seat. There is no left‑hand sliding ventilation window, of course, with the extra door's fold‑up window. Plastic airscoops in the windows provide ventilation for those times when you really don't want an open window. An optional dual heater installation is available for northern winters.
The prototype's panel was held to basic enhanced VFR; no vacuum pump is installed on the 0‑320, and the directional gyro and turn needle are driven by a belly‑mounted venturi tube. The rest of the panel consists of an airspeed indicator, altimeter, rate of climb, tachometer, oil pressure and temperature, ammeter and an EGT. The magnetic compass hangs from the tubing at the top of the windshield. Avionics in the demonstrator are a hand‑held communications radio connected to external antennas and a loran receiver that has proven to be less than satisfactory, Williams says.
Under the panel, the fuel valve and flap handle are on the left. A handle to lift the float rudders is on the right side of the panel. A starter button is used, rather than a twist‑key switch. "Easier to use with mittens on," says Williams. An intercom system was mounted in the left wingroot area.
The rudder pedals carry toe brakes, although when I tried to taxi from the back seat, the plush upholstery of the front seat left little foot room to work the pedals ‑ something Williams is addressing in production kits. Pushrods are used to connect the rear brakes to the front (master) pedals. The rear stick can be removed for carrying freight.
THE PROOF IS IN THE FLYING
Pumping the throttle a couple of times, Williams pushed the starter button and brought the Lycoming to life. With headphones in place and the intercom on line, conversation was convenient. I weaved a bit in taxi, both to clear the path ahead and as a result of the limited clearance for my feet between the front seat and the side‑wall. Pre‑takeoff checks are straight‑forward: controls stirred, altimeter and directional gyro set, trim checked and a brief runup at 1700 rpm for mag and carb heat tests. This done, we latched up the doors and Williams yanked on two notched of flap for a STOL departure. Two‑up with half fuel, we were on the ground about as long as it takes to read this sentence. I estimated 300 feet of ground roll, with no help from the wind.
Williams' takeoff procedure is to pick the tail up after applying throttle, raising it just far enough to bring the tailwheel out of the grass. When 20 mph is indicated the forward pressure can be exchanged for aft pressure on the stick. Liftoff comes at less than 30 mph indicated, and we climbed out at 38 mph, showing about 750 fpm on the vertical speed. Flaps up after reaching 40 mph, best climb comes at 45 mph, generating a good 700 fpm. Clearly, the North Star is a classic stump jumper.
Leveled off down on the deck, the IAS settled on 91 mph at 2450 rpm. The 82‑inch diameter, 41‑inch pitch seaplane propeller obviously is not optimized for cruise. On Edo 2000 floats, Williams says he cruises at 85 mph. I found the ailerons to be more lively than expected from a staid bushplane; Williams work with aerobatic wings was showing here. The North Star rolls briskly from 45 degrees to 45 degrees in less than a second. The hands‑off stability and yaw coupling of rudder to pick up a lowered wing are excellent
Stalls were mushy sags with the stick back, the airspeed indicator showing a non‑number below 20 mph. We tried various power and bank aggravations, none of which gave us more than a moderate roll‑off. Williams says he has to work to get it into a spin, and the North Star claws its way out on its own despite full prospin controls in about a halfturn. He likes to demonstrate a 30‑mph pivot with full flaps, loitering over a spot at 2000 rpm in a near‑zero turn radius.
Anxious to switch seats, I headed for a 3000‑foot sod strip under the wing. My backseat approach was far too high, even with all four notches of flap deployed. At 45 mph, I stomped in rudder and slipped as much as I could, but the North Star's wing was just too fat with lift, and I had to settle for a touchdown at the 1000‑foot point. As Williams showed me later, the best technique for sloughing off excess altitude is to make some steep S‑turns at 40‑mph, coming down while you slowly inch toward the runway.
Visibility is adequate from the front seat, but it is still best to S‑turn slightly or to lean out the door to check the path ahead. Taxiing is a pleasure with unfettered rudder pedals. Lined up for takeoff, I fed in the throttle and added some forward stick as the rudder came to life. The tail was up for only a few seconds before it was time to bring in back pressure for liftoff. As Williams had said, 20 mph is the time to ask the bird to fly. On Edo 2000 floats, he quotes a 9‑second water run with an average load.
With my pattern extended for a longer final, I had no trouble seeing the threshold at a 45 mph approach speed. The landings were simple enough as long as proper tailwheel technique was used; hold the airplane off until it stalls on three‑point, keep the stick back and don't stop steering until the ropes are tied to the wings. Williams did a landing in 200 feet, touchdown to turnaround, with heavy braking.
Clearly, Morgan Williams has created a good bush plane, just as he set out to do. One might quibble about the veracity of the low airspeed readings when the pitot head is no doubt missing a few molecules of the slipstream, but one can't ignore the STOL runway performance. The North Star gets up and out fast, handles well over the treetops on a slow approach, and demands little from its pilot in taxi or cruise. Six are already on order, and to keep quality from deteriorating, Williams is limiting production to one kit per month.
One thing Williams didn't anticipate was the demand for wing kits alone. He finds that many Super Cub owners want to replace their wings with his more effective ones. He also has them going on Wag Aero Sportsman 2+2's, and stretched pacers.
After years of development, Morgan Williams is looking forward to supplying the back country fliers with a replacement for their old Super Cubs. Everybody with a grass strip or boat dock should have one!
Copyright © Custom Flight Ltd. 2013