Interesting question Serge.
I allways thought the Poor Boy/Dolphin was a simewhat simplified Ruffy: i.e, constant chord wing simple box fuse, I think no-cowl on the plans version, fuselage gear instead of the Ruffy's wing gear etc. The Ruffy was also about 40 square inches bigger. With regard to the ORIGINAL kits, every STERLING Ruffy I ever saw was heavy, and Sterling die cutting was uhh, legendary. I do not recall ever seeing a truly competitive example of the Sterling kit. The Jetco Dolphin (which I built in 1966) was a very good kit, though simplified it was later vintage than the Ruffy and presumably benefited from Lewis' later thinking.
Ted F built the RSM Ruffy, a definitely un-Sterlingish kit, and it finished relatively light, but not extraordinarily so. He wrote at length about his tribulations getting it trimmed. Ted certainly knows where he is going trimming a new bird, but it seems he had big problems trimming it. I think he concluded that a contributing factor was a too light weight, which of course perplexes me! I think (but cannot prove) that part of Teds problems were related to too much power or more accurately, too much prop. Both the Ruffy and the Dolphin were designed for Fox 35's turning 10-6 wood props. I think Ted said the Rufy had something like a 15% tail - which means it did not have a lot of extra turning power to overcome an oversize or over heavy prop. I suggested this to Ted but he said his tests did not support that idea. However my nephew has been doing a lot of experimenting with an electric powered Oriental, with one of the power systems tried, he fitted an 11-5.5e prop in place of a 10x5e and determined the bird got significantly worse, lack of turning power to overcome the larger disk. I know it flew well with a 9" prop and VERY well with a 10" prop. Later tests with the electric Vector (roughly same size as Oriental) showed that bird flies better with the 11" prop than with the 10" but it is not a night&day difference like it was on the Oriental.
Alan H: I think ALL of the Classic era airplanes are great candidates for e-power, including the Ruffy & the Dolphin. However I would tailor the power system so the bird can use the same size prop as what ever the original design called for - most likely a 10" dia.
For personal/Nostalgic reasons, given the choice of building a Ruffy or a Dolphin, I'd build the Dolphin, with Turnigy 35-36 motor, 4sx2350, a 10x5e, Phx-35 and Hubin Timer.
Topic: Lew's DOLPHIN has started an addiction to so many flyers over the decades (Read 3528 times)