V-Stab area considerations

[Gene Bond]

OK, I have a biplane that I can tell needs more V-stab area. How? When rudder trim varies with speed, I figure the V-stab is too small. ie: it yaws right at one throttle setting and left at another.

So, to rework the V-stab, is it only the vertical height, or also the chord? I believe both are probably close to equal in consideration, but was curious if anyone had any comparative experience.

For example, let's say my v-stab is currently 5" tall and 3" in chord. I feel I want a tad more, so I add 1" in chord, or 1.5" in height... Same effect?

[peterangus]

For most aircraft with a single propeller [producing a torque asymmetry and a helical slipstream], you should expect to see some trim variation resulting from power variation.

[Sparky Paul]

The mechanically easiest way is to extend the chord. Scab on a stick to the leading edge.

[Gene Bond]

I know from experience with many other biplanes, that the problem is Stab Area, realizing that the swirling torque issue is another effect.

Yea, Paul, I was just trying to convince myself that area is area, as long as it's in the back, it's all stab! Just like all the vertical nose area is 'anti-stab' :D

[Jimmbbo]

An easy way to increase yaw stability is to add a dorsal fin ahead of the vertical stab.. a little area goes a long way. Since a dorsal fin doesn't see a lot of stress, you could tack on a larger one and cut the bottom as required till you're happy...

Cheers!

Jim