Source: 2011 Q4 Beartracks, Glenn Patterson
Bob Barrows has tested the airfoil shaped ribs on the Patrol with good results on the Hor Stab and Vert Stab. Theoretically, there might be a 20% increase in lift or the same amount of lift but with 20% reduction in drag. It may allow the four degree down deflection of the Hor Stabs to go to three degrees. Flow over the Hor Stab surface will have less turbulence & therefore slightly more positive/smoother pitch forces. With more lift it is possible there would be more control authority. But it should mostly help with pitch stability. The airfoil shaped ribs on the Vert. Stab should result in somewhat more yaw stability.
No one has flown a four place Bearhawk with these airfoil shaped tail surfaces yet, but Bob feels confident there will be some improvement although how much is uncertain until flight testing can happen. Bob feels certain there will not be negative consequences. So – Glenn Patterson has decided to try this mod to his Bearhawk using instructions provided by Bob.
Glenn: Pieces of plywood were clamped to the flat side of the channels to aid in alignment. This first picture shows the work prior to commencing gluing the strips on. We used a notched board to do the initial clamp then used small wood strips and electrical tape to hold the pieces until the epoxy set. The electrical tape was used as it is slightly stretchy and would enough pressure on the wood so as not to squeeze out all the epoxy. We glued the strips on both sides of a rib as one step. All the wood surfaces used in the clamping process had parchment paper (used for baking) between the wood clamping pieces so they would not become part of the airplane. Wax paper would work as well. The parchment paper came off nice. The elevator ribs were sanded to bare metal, degreased & T88 epoxy used to secure the strips. The pictures show the process fairly well. We are using Stewart polyurethane and probably could have just scuffed the urethane and glued the strips to the painted surface. We did a sample glue on a painted surface and the wood broke off leaving wood attached to the painted surface. Definitely a strong bond either way. The tail turned out very nice. Best regards, Glenn Patterson