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Now for fellow builders, the nitty gritty.
The Rotec R-3600 swinging a 90 x 48 Culver propeller, static rpm of 1750 rpm prop and 2650 engine - BIG CAVEAT - tachometer has not been double checked. While well down the 3600 rpm range, this produced a healthy 550 - 570 pounds of thrust. I feel pretty strongly that once broken in, and perhaps other tweaking, it will easily reach 600 pounds of thrust.
With two electronic ignitions, it starts instantly. The throttle body injector is its own entity, and we are learning how to best use it. I STRONGLY feel it is superior to the stock supplied 40mm Bing carb. based on my limited experience so far. One trhing you do notice is that the Rotec 9 cylinder is much quieter than you expect, and very smooth. From the ground, vintage aviation author Eric Preston said it sounded much like a 80 hp LeRhone in the air.
The Sopwith currently has provisions for brakes, but not hooked up. At just over 1100 pounds test AUW, it is no little light airplane and has some serious inertia to be managed on the ground. This test was on grass, but it will absolutely need brakes on any prepared surface. The steering tailwheel was wonderfully positive, and at least for us frequent flyers, a very neccesary compromise.
On take off roll, not pushing the plane at all, the tail comes up smartly and the plane unsticks in about 400 feet. Climb out seems happy at 60 or so mph. We did not push the climb, but a normal climb rate of about 900 or so feet a minute was what it seemed. All of the controls were not neck jerking, but positive. One thing that impressed the test pilot the was the wide speed envelope of the airplane where no trim was needed; you just put it there and it stayed. I personally think this is probably attributable to the original Sopwith designers' mass concentration. For you technical folks, we have 1.5 degree wing AOI with 0 degree horizontal stab AOI, lower wing dihedral of 5 degrees and zero degrees for the top wing. The engine has a down thrust of 2 degrees. The test CG was about 24% MAC. Controls were described a sweetly harmonized and normal stick pressures - seems Sopwith got their control surface areas dead nuts on. Slips wonderfully. Did not do a full stall series this first flight.
At reduced power settings, the airplane would fly happily loafing between 80 - 90 mph at 1650 rpm indicated Lower the nose wee bit at same settings and it would easily pick up to 100 mph indicated. Again - these are indicated and not verified against an external source, but it was a new ASI.
Approach was tried at 70 and 80 mph, both worked fine. When the power is pulled, the plane does not slow as fast as you think it might (inertia), bur settles gently down to the runway conventionally. Without brakes or skid, it had a loooong roll out (inertia) of about 1000 feet.
Alas, weather, job and airline schedules intervened and we had to pack it up for OSH. Will continue testing after July.
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