Sonerai II L larger rudder

[dwalker]

I have read about and seen a video of a larger rudder for the II L and was wondering if anyone had drawings or other information about it. I am preparing to recover the fuselage and it seems like the ideal time to build a new rudder.

 

[eschrom]

I made my vertical fin and rudder bigger while repairing accident damage but the airplane hasn't flown yet. The height increase is seven inches over the standard 2LS tail, based on advice I got from Tim Kline, who was the first to do this as far as I know. I hope to find out this spring whether the taller fin achieves what I wanted.

Ed
2LS

 

[dwalker]

I made my vertical fin and rudder bigger while repairing accident damage but the airplane hasn't flown yet. The height increase is seven inches over the standard 2LS tail, based on advice I got from Tim Kline, who was the first to do this as far as I know. I hope to find out this spring whether the taller fin achieves what I wanted.

Ed
2LS

That looks really cool. Is there any info from Tom about how it flew? The larger rudder I saw was on Matt Mayers(I think that is his name) II L and he just enlarged the rudder and added area to the rudder itself not the Vertical stab.

 

[eschrom]

Tim said it was rock steady in cruise, with no tendency to fish tail.

 

[Aviacs]

made my vertical fin and rudder bigger while repairing accident damage but the airplane hasn't flown yet. The height increase is seven inches over the standard

Just to verify based on the drawing (thanks much for that!):
Tim only increases the fixed vertical stab? Not the moving rudder portion?

Thanks!
smt

 

[Aviacs]

(Can't see how to edit above?)

or should hinge be understood to continue up through the top extension shown in the line drawing?

 

[Bil4381]

I made my vertical fin and rudder bigger while repairing accident damage but the airplane hasn't flown yet. The height increase is seven inches over the standard 2LS tail, based on advice I got from Tim Kline, who was the first to do this as far as I know. I hope to find out this spring whether the taller fin achieves what I wanted.

Ed
2LS

I did the same on my SII. The result is that when you depress a rudder pedal to the floor, the ball/slip indicator returns to within 5 degrees of centered. Also if you perform 90 degree reversing steep turns, without the larger rudder the aircraft is divergent. With the larger rudder it turns normally. (Divegent means that when you use the rudder to correct for yaw in the turn, the aircraft attempts to tumble. )
Bill

 

[dwalker]

Here are some pics of Matts larger rudder that inspired me to ask these questions-

 

[eschrom]

@Aviacs, the drawing is from MS Paint. Yes, the rudder hinge goes all the way to the top. I don't know whether that's ideal or not. Truth is, I didn't do much research. Except for Tim Kline's testimony it's a leap of faith. We shall see.

Ed

 

[vhbill]

Yaw stability compared with other aircraft by calculating tail volume.

From that reference ....

(1) It is easy to design a tail that is too small. It is difficult to design one that is too large. (2) Big tails are more user friendly than small ones. Hint: Tailheaviness can often be cured simply by the addition of horizontal tail area. Adding it by increasing the tail span is more effective than adding it elsewhere because the tail aspect ratio is then increased, making it more efficient.

For the Vertical Tail Volume Coefficient (VV) the equation looks like this.

VV = SV x LV / SW x b,where SV = vertical tail area, LV = distance from the vertical tail's aerodynamic center to the aircraft c.g., SW = wing area and b = wing span.

Using the plans dimensions:



It would be interesting to see what coefficient you calculate for your Sonerai.

 

[eschrom]

Vv = 0.05 for the Sonerai and 0.04 for a C-172 means the Sonerai should be more stable in yaw than the Cessna, right? And yet the opposite was my experience. The Sonerai always fish-tails in bouncy air. Others have said the turtle deck partially blanks out the vertical stabilizer and if that's the case then the formula for Vv doesn't get at the whole picture.

It is difficult to design a tail that's too large is an interesting observation. Look at Van's RVs - their vertical stabilizers are pretty big to my eye. That's what convinced me that I wasn't likely to come to grief doing this.

 

[eschrom]

@Bill Evans, do you have any pictures of your tail?

 

[mhflyit]

I have pics of my tail mod (with Ed Fisher's input) in my gallery.

 

[eschrom]

mhflyit's tail

Looks nice, Matt. Have you flown it? How is the yaw stability?

 

[vhbill]

I suggest you check my calculations. I may have made an error.

 

[mhflyit]

mhflyit's tail

Looks nice, Matt. Have you flown it? How is the yaw stability?

I put 30+ hours on it before selling. My turtledeck was raised 3 inches. The rudder authority was good and as expected with no fishtailing at cruise.

 

[Jester188]

I put 30+ hours on it before selling. My turtledeck was raised 3 inches. The rudder authority was good and as expected with no fishtailing at cruise.

I've added at least another 30 hrs and have found it very stable; slips well too.

 

[eschrom]

Good to hear. Sounds like I went higher than necessary with mine.

The fabric work is almost finished, then paint it and put it back together. Looking forward to flying it.

 

[tschwartztm]

I made my vertical fin and rudder bigger while repairing accident damage but the airplane hasn't flown yet. The height increase is seven inches over the standard 2LS tail, based on advice I got from Tim Kline, who was the first to do this as far as I know. I hope to find out this spring whether the taller fin achieves what I wanted.

Ed
2LS

Any update on larger rudder design?

 

[mcrae0104]

For the Vertical Tail Volume Coefficient (VV) the equation looks like this.

VV = SV x LV / SW x b,where SV = vertical tail area, LV = distance from the vertical tail's aerodynamic center to the aircraft c.g., SW = wing area and b = wing span.

Interesting. Pazmany uses the aircraft's CG whereas every other source I have says to use the quarter point on the mean chord of the wing. I wonder why Paz does that. The CG isn't always at 25% MGC. From his Light Airplane Design: