I have an old Sterling Stearman 60" wing 60-90 size engine. Its heavy...very heavy, so I put a os 1.08 for added nose weight and power. Heres the problem... Everything is ok except it wants to roll to the right real bad. I have full left trip to hold it level. Now, it is a little out of balance R to L but not that much. I think since I have a larger engine on it, the P factor is coming into play. Would shimming the engine thrust angle help this?


Joe

Joe,

Engine torque will tend to roll the aircraft to the left. You are getting the opposite effect. You may have a warp in the wings that you may be able to address with shims under the cabane struts. I don't know how yours are attached, but I have made wing incident adjustments this way.

Good luck,

Bedford

While I do love biplanes, they are twice as much "fun" to rig, when it comes to setting incidences and such. If it turns that hard to the right, you either have a warp in one or both wings, or they are mounted in such a way that tightening them down is pulling something out of whack. Look at the plane, set level on a table in good light, from the rear, looking at how the trailing edges appear, relative to each other, and from one side of the wing(s) to the other. You ought to be able to see a warp that bad. I presume the rudder is straight, and the turn you refer to is a roll, not a yaw?
On a somewhat unrelated note, there are some other threads that address a commonly agreed on design flaw in the Sterling Stearman concerning the incidence setup in the plans. Most biplanes seem to like the bottom wing set at or near zero and top wing -1 or -2 degrees incidence relative to the bottom. Might be worth hunting them down and reading.

Rick

When I setup wings (and it looks like you have a wing warp problem) I use 2 Robart Wing Incidence meters. I put one at the root and adjust incidence there as necessary. The other goes at or near the tip. I adjust the tip to match the root. I will move the tip mter from tip to tip but leave the root meter on so I get accurate relative readings al the way down.

I had a biplane that seemed to change flight characteristics from flight to flight. This method fixed it.

A lot of bipes have that problem. After balancing the wings, a sure-fire cure is to increase the vertical tail area. I would try simply taping on a temporary cardboard extension to the trailing edge of the rudder. Make the extension as big as you like, or try various sizes. If you already had enough rudder authority, just decrease the travel proportional to the cardboard extension area. I think that you will be surprised at the improvement in overall handling and user-friendliness at low speed. Bipes need big vertical tails, for two reasons.
1. They tend to have more wing area than monoplanes, and more wing area generates the required lift at a lower airspeed that reduces the yaw-reducing effectivness of the vertical tail.

2. The vertical tail flies in air disturbed by two wings and the cabane struts. A larger vertical tail is the easiest fix here. I like to use vertical tail area of about 15% of the wing area, and even larger is better, but starts to look a bit funny.