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Jones Sopwith Pup
 
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Wes Jones discussed the feasibility of building a full-scale Sopwith Pup with Robert Baslee in 2005. They drew the major components on a dinner napkin later acquiring a set of drawings from Replicraft.
 
Earnest construction began in December, 2005. The plan was to build a Pup that for all outward appearances would look like an original Pup. There were some mandatory considerations, bank account, settling on a VW engine, instead of a preferred Rotec Radial. The Replicraft plans were used for placement of all uprights and longerons, so the dimensions would match the originals, but the materials are more modern and fit the bank account better.
 
Three-quarter-inch chrome-moly is used for the forward section of the fuse and transitioned to five-eighth-inch aft of the cockpit for the longerons. TIG welding the basic fuse took about a month.
 
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The fuselage and upper wing center section were built of tubular steel and aluminum, respectively.
 
The wing struts and cabanes were fashioned to the original dimensions out of straight-grain Douglas fir to fit welded fittings like Dennis Wiley’s Early Bird Jenny. The landing gear legs were fashioned from streamline tubing to exact specifications from the original 1916 prints.
 
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A set of horse racing cart wheels were used for rims and inner spoke attachments, and made a set of hubs on the lathe. The hubs gave 8 inches between the spokes at the axle.
 
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By using longer spokes on the outside and shorter spokes on the inside, it got the dished look of the original wheels.
 
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The steerable tailskid was built exactly following the plans of the original, since it was going to be out there for everyone to see. Another reason for sticking with the original skid is that, just like the original, the mains do not have brakes. This helps keep the Pup going straight down a grass field.
 
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The original tailskid worked well until it broke on landing. It was replaced with a piece of wood with conveniently-curved grain.
 
Wingspars were fashioned from 2-inch .065-wall 6061 tubing. Three-eighth-inch aluminum tubing is used to fashion the ribs la a Graham Lee design. The leading edge uses aluminum sheet metal instead of using nose ribs. Wing-root fittings were copies of the Early Bird Jenny’s root fittings, scaled up for the extra weight. Some expert assistance on rib stitching came from Dallas Shaw, Randy O’Conner and Brad Strohm.
 
The covering was lightweight Dacron using rhe Stits process from Aircraft Technical Support, since Jim Miller was good friend and neighbour. Since the WW-I originals were just doped on the undersides of the wings and fuse, it was decided to finish those areas using clear Poly-Brush fabric sealer, then adding some tint to the last coat to get an approximate look of old varnish brushed over doped fabric. The markings were done by hand with a brush to approximate what was done in the field back then.
 
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A 2180cc VW engine was built from scratch, using parts obtained from several VW suppliers. It used 94mm cylinders, an 82mm stroker crank, and was set up the compression for 6.67:1 for reliability. Valley Engineering supplied the 2.5:1 propeller speed reduction unit (PSRU), as well as the 96×65-inch prop. Due to some leaning problems with the progressive Weber carb, a single-barrel 34 ICT carb fit the bill better.
 
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A good friend and Dawn Patrol cohort, Rick Bennett, was able to find a correct-size cowling and arrange to have one delivered.
 
There was some help with the full-scale Vickers machine gun replica on the cowl from Willie Hill, a local expert on getting them to look realistic.
 
The OK to test-fly it from the local FAA representative, John Walsh, came in October of 2011 and there was only time for six or seven test flights before winter hit hard, so the rest of the time had to be flown off in the spring.
 
In the air the Pup flies is very stable in normal flight. The four ailerons give a solid feel in roll. Initial timing of the climb rate showed approximately 1200 feet per minute. The climb angle is like a space shuttle launch, although never actually measured.
 
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On takeoff, the tail comes up almost immediately (50 feet) and it gets off the ground in about 150 feet. Stall is around 30 mph and cruise is around 60. The plan to obtain another prop with a 73-inch pitch as soon as funds allow, in order to (hopefully) get the cruise up to around 75-80 mph.
 
About July, on a normally un-eventful landing, the tailskid wood split at about the halfway mark, leaving no steering and sending the plane into another groundloop. This time, the left upper wing got a slight ding in it due to the hair-raising trip into the woods that immediately followed. Fortunately, two days worth of metal, fabric and painting work sufficed to repair the damage.
 
A piece of ash with the grain conveniently running along the curve of the new skid replaced it; there have been no problems since.
 
There has been difficulty keeping the cylinder heads at an acceptable temperature (350 F). Normally it gets about 15 minutes of flight time and temps start to creep up to around 375. Changes with the cooling fins—making extensions to direct the air more smoothly over the heads —and a larger oil cooler with a thermostatically controlled fan may get the temps better.
 
That old British 10/10 airfoil makes the Pup handle amazingly well.
 
 
 
 


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