............sound to me with the 3b prop you were getting a vibration problem,specially if you could see the prop hub move,............
=============
The prop hub vibration only occurs when throttling up through a specific rpm. Once it goes past that point, about 1/4-1/3 throttle, the vibration stops. It is also doing it on all 4 engines just the same. I'm hoping that the 9x5 two blades will cure that. Either the 3 blades are slightly out of balance, or the slightly larger prop hole is causing the problem. How that is leading to an engine out I don't know, but it will eventually cause problems in any event. The actual dfference in the hole and prop shaft is very small. I don't even think I could get a shim in it.
It is the Stafford B-24. I didn't put the tanks in behind the firewall like the plans showed. The tanks for the two inboard engines are in the fuselage, fuel lines routed out through the wing. The outboard nacelles had enough room underneath to get a Slimline 4oz tank in-BARELY! I have hatch accesses in the bottom of all 4 nacelles to access throttle servos, etc., and the tanks on the outboard engines.
The catch 22 to all this it that I had 4 near perfect flights on it with no engine problems. I'm still leaning toward the fuel foaming thing due to how tight the #1 tank was installed. I guess the next flight will tell.
Won't get a chance to check it tomorrow, also got some work to do on the retracts.
Randy