Larry DeCamp
Well Known Member
The 3B bellcrank is steel. Supposedly, the earlier RV3 ailerons were lighter in feel and not steel. Can anyone confirm the older bellcranks were different, and how so ?
As dimensioned on drawing dated 1-10-84 serial 10342. It's basically a triangle with the legs 137 degrees apart. The control stick leg is 3 inches and the aileron leg is 3-3/8 inches from pivot point. (5-7/8 inches apart) The plates are assembled similarly to the elevator bellcrank.
I built a -3 because many considered it the most fun to fly RV. I bought 3B wings from salvage. I complained here that stick force was disappointing compared to expectations from glowing pireps. Jim Winings said the ailerons were smashed too small on the trailing edge and several folks say the 3B bellcrank is not the same as the original 3.
So, I analyzed the kinematics of the 3B vs -3 bellcrank and the 3B IS disadvantaged regarding stick input force. Then I built two new ailerons to address the thin trailing edge issue. As many are aware, some aerobatic ships use thick trailing edges and some jets use nearly squared trailing edges.
I was very careful on the new ailerons to assure the skin entered the curved trailing edge radius harmoniously without bumps or undercuts. The end ribs supplied by Vans defined this geometry. I was surprised to find the resulting trailing edge radius was larger than the plans called for. A 1/4" dowell fits easily inside the skin at the trailing edge. It was theorized that bigger could be better, so they are on the airplane.
Ironflight suggested I update my VAF posting when I had results. RVbuilder2002 considered my findings logical with no misleading or unsafe conclusions, so here it is:
The reduction in stick force is DRAMATIC, to the extent you can roll the ship with index finger pressure. Hands off the stick is dead stable subject to normal trim (heavy wing) characteristics. RVbuilder 2002 advised that the thicker trailing edge is known to reduce stick force at the potential reduction in roll rate. OK, I won't compete with F22's.
The -3B can be disappointing and awesome. Pay close attention to ailerons. I hope this helps a VAF participant.