Ben I previously had an 1835 with large 2180 jugs for a 1915cc engine with Zenith Carb. I was originally told by two recommended prop people to put on a 52x48 prop, but this killed the power, and restricted rpm to 2100 rpm. I bought a prop on ebay 52x42 and loved it. Solo I was getting 1000 fpm climb thru 3000 feet (I live in Florida so we are always starting near sea level). I did several flights with the new prop very happy and began really enjoying it, and testing speeds etc After about 28 hours I began to test more weight, working up to passenger weights. I reached 120 pounds with full fuel, and me at 200, 15 gallons of fuel, for a total takeoff weight of 1050 pounds. All previous testing had been on similar days to Oscars flight, winter days with temps 50 to 60 degrees F. This particular day was 80 in late February, with a humidity of approximately 85 to 90%, typical of normal summer days in Florida. I originally took off from Sanford with half fuel, because Massey Ranch Airpark (yes the same place WW operates out of) had fuel available to the public for nearly a dollar cheaper per gallon, and was in my test area. So I flew directly there about a 15 minute flight, landed uneventfully and filled up. Fired up, engine run up, and away I went, time now the middle of the day 12 to 1:00. The KR2 accelerated poorly, and would not build sufficient speed to break ground. I always had previously lifted off before mid-field, and this takeoff I was still rolling then. I finally forced the KR2 into ground effect by using a soft field technique, and accelerated with approximately 5 feet of altitude. At ¾ of the field I hit 100 mph, and did a 2 G pull up to clear the trees at the end, and the KR settled into a 150 to 200 fpm climb. I had to maneuver to the west to avoid an antenna which should not have been an issue, but this time was. At 500 feet the engine seemed to gain power, and continued to climb at approximately 450 to 500 fpm. This was my last flight with the 1915cc engine.
After this flight, it was my contention that my personal experience and the reports of other pilots through the Krnet confirmed that anything less than 2180cc in power was too little power for two people. I good solo plane could be built on less, say 1835 or 1915cc, and do fine. But a true two passenger plane would need the 2180 or better for weight over 900 pounds. I felt like I had truly tested this engine with 3 different props, and different weights, and found it just too small. I sold it and now have a Corvair that I am finishing the conversion. I am not saying that two cannot fly with an 1835 or 1915. What I am saying is that based on my testing, on any day that is not ideal for making best power, hot humid days, increased elevation, etc the safety margin of performance goes away. In my opinion, and to quote my DAR who has completed 15 aircraft in his lifetime Jack Murphy, Colin, you can never have too much horsepower. Thats why I am putting a Walter turbo-prop where an O-360 used to be on my latest 4 place plane. As always your results will vary . Colin N96TA
