WIDDOG wrote:Howard said earlier on this thread about increasing the size of the tail by 20%. I will build my next 500 Series kit with a 20% larger tail than what the instructions calls for. I am attaching a video and an explanation as to why I am going to increase the tail by 20%. The video starts out with a typical flight. The plane tilts to one side or the other and banks hard into the ground. On this crash the wings got knocked into a supper sized dihedral. There was some winds left in the motor so I gave it a launch. With the super sized dihedral the plane flew kind of well. I think the rubber motor and propeller are the correct size. Anyway I am hoping that by increasing the tail I can increase the stability and stop the tilting of the model in flight. BTW even with the wings at a dihedral to the bottom of the windshield the plane still tilts in flight.
I think I was misunderstood. It's usually not the TAIL that is undersized for rubber powered free-flight but the STABILIZER. I routinely increase the stabilizer outline by 115% of scale. You have to be careful when you enlarge the vertical tail because if you make it too large you create spiral instability.
The 500 series Rufe/Zero definitely needs an enlarged elevator and could probably use a little more tail area because it does not have as long a tail moment as the other models in the line. As a Rufe, the tail feathers are hopeless. Although there have been modelers who have built super light ones that have flown successfully with the float as a Rufe, they had to do what the engineers at Nakajima did, increase the size of the rudder and add a ventral fin. (With everything else that was going on at the time Mitsubishi did not have the production capacity to do the Rufe conversions.)
Dihedral is another issue. As a general rule of thumb for rubber powered, free-flight, scale models, you should have one inch of dihedral for every 18 inches of wing span. That means the minimum dihedral for the 500 series Zero is 7/8 inch. There are many successful modelers who use another rule, that if it is a low-winged model the wing tip should be level with the bottom of the cockpit canopy. This works well for most WW2 fighters of conventional, tractor configuration. You do have to be careful with dihedral however. Too much dihedral has the same effect as a highly swept wing leading to "Dutch Roll" (waddling in flight) and can induce roll-yaw coupling which can cause nasty instability usually ending in destructive spins. When doing a design for production, in order to get the best scale appearance, I will build several prototypes (or one with easily adjustable dihedral) starting with the 1 inch per 18 inches dihedral and reducing it until I find the minimum flying dihedral for that particular design. Then I go just a little up from there for production.
If you are trying another Zero (And, I must say I admire your persistence.) I'd go with the 1 inch for 18 inches dihedral rule and make the elevator 120% of the original, the tail 110% of the original and see how that works.