When I run the numbers on various design possibilities using Raymer's guidelines or the quick LAA spreadsheets, it becomes abundantly clear why Bill Stout used to say, "Simplicate and add more lightness." Weight is the enemy, not only in the structure and power plant, but also in the amount you budget for fuel and payload, which makes everything else have to be bigger and heavier for the day you want to carry it all.
That said, people are taller (better nutrition) and fatter (more food, less exercise) than they were back in the golden age so what worked then may not make sense now. For example, a 1940 Piper J3C-65 Cub) had an empty weight of 765 lb (345 kg) and gross weight of 1,220 (550 kg) leaving a useful load of just 455 lb (205 kg). Add 12 gallons of fuel and a gallon of oil at 72 lb (33 kg) and you can see that two modern 200 lb (90 kg) guys are an overload, never mind any baggage.
Personally, I do not expect to be doing many cross-countries and, if I do try to fly to Oshkosh or the like, I'll probably be alone and happy to strap my bag into the passenger seat, so I think I'd be OK with 400-450 lb. Too much? Too little? Setting aside LSA or microlight regulations or any other artificial constraints, with the tanks full, how much payload is really necessary for a simple, economical, two-seat sport plane in 2018?
That said, people are taller (better nutrition) and fatter (more food, less exercise) than they were back in the golden age so what worked then may not make sense now. For example, a 1940 Piper J3C-65 Cub) had an empty weight of 765 lb (345 kg) and gross weight of 1,220 (550 kg) leaving a useful load of just 455 lb (205 kg). Add 12 gallons of fuel and a gallon of oil at 72 lb (33 kg) and you can see that two modern 200 lb (90 kg) guys are an overload, never mind any baggage.
Personally, I do not expect to be doing many cross-countries and, if I do try to fly to Oshkosh or the like, I'll probably be alone and happy to strap my bag into the passenger seat, so I think I'd be OK with 400-450 lb. Too much? Too little? Setting aside LSA or microlight regulations or any other artificial constraints, with the tanks full, how much payload is really necessary for a simple, economical, two-seat sport plane in 2018?
