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Sonerai I Rudder Cables

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Schmleff

Well-Known Member
Joined
Jan 2, 2006
Messages
2,714
Location
Waupaca, WI / USA
I am going to add tubes for the rudder cables in the cockpit. The simple act of pulling anything out from next to the seat is enough to put enough pull on the rudder cable to throw the airplane all out of whack in yaw.

Also, I would make the vertical fin larger while keeping the rudder the same. Since my tail is not stock, not sure what its like with the standard tail, but it would b nice to have more yaw stability in cruise flight.
 
HI,
If you enlarge the fin surface you had to reinforce the structure correct? Ther's any draw or photo of already modify sonerai?

The tail surface of stretched version are larger than original? or also streched sonerai is better with increase tail surface?

MArco
 
Marco, the tail dimensions for the II and II Stretch are the same (at least on my plan set). I can't speak to the S1. This pic is a couple years old, but you can get some idea of a 3" vertical stabilizer and rudder extension. I did not increase stab chord or rudder chord, only height. I did this because I built the turtledeck 2" higher at the rear of the pilot's position. I have no idea what effect this will have, if any, but it was suggested by people with experience. I will also build a second rudder with more chord and bottom end surface area, since I have leftover materials to do that. I will try both - one at a time of course, lol.

Tom
 

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Not sure yet either. I am going to extend mine from top of the front of the tail to a point further up on the turtle deck.
 
I would think that more chord in the vertical stab would better address yaw issues. The alternate rudder is an attempt to see what effect it may have in managing crosswinds on the runway. We'll see if it creates more problems than it solves.

Tom
 
Hi Jeff,
I don't know your rudder(tail) area, but when I think back to the time I had build hi-speed model airplanes, there was a typical effect when we increase the rudder: the plane become unstable on the vertical axis: this means, the plane had flown through the air like a fish and so go slower.
On my Sonerai with original rudder, the rudder is enough to start (also with cross wind) and on speeds above 150mph the rudder is very,very sensitive and at 190, I pull back my feet when I fly straight because it is very difficult to have the ball centered with active feet. On my plane, from start up to cruise speed, it is important to handle the rudder and aileron like a (motor)glider to have the ball centered.
with best regards
Juergen
 
I find the same thing at high speed, the rudder is very sensitive. Its almost impossible to keep the ball centered if there is any turbulence at all. That is what I am trying to address.
 
The Sonerai, like the Cassutt, suffers from a 'split identity' rudder....It doesn't quite cut it at low speed, but at high speed is super sensitive......I remember trying to do a hammerhead with the Cassutt, and felt totally useless, as I slid backwards at about a 45 degree angle....Then it went to a spin, and I could recover.....
I think when John originally built the Sonerai 1 prototype, with the short rudder and notched fin, he probably found that he had little to no directional control on the ground for the first few seconds of the takeoff roll....So the first winter, when he took it home, he modified it to the full rudder that is on the plans now. I still tell people to leave the tailwheel on the ground when taking off, till they are at about 45 to 50 mph, because otherwise the airplane will be heading off the runway, even with much opposite rudder input.
As the Cassutts got faster and faster at Reno, you started to see the fins getting enlarged. Yaw stability was going away as speed increased. Remember, the Cassutt was designed in the mid 1950's, when the midgets top speeds were right around 195 to 200mph.........So......As the faster Sonerais are built, they really need more fin area, not more rudder area........Ed
 
Hi Ed,
when I compare the pictures (side view) of Blueberry and Skye Racer, I see, the fin of Blueberry is smaller and the rudder is much smaller as on Skye Racer?
Is it right?
with best regards
Juergen
 
Juergen, Yes, you are right. Blueberry had the absolute minimum fin and rudder area. The airplane was stable in yaw to about 180 mph indicated, and then began to get very sensitive of imput above that. Blueberry was the first Sonerai of any type to have a squared off tail. In the building of the Super Sonerai, which I did not finish, I added 3" to the leading edge of the fin, and left the rudder the same as Blueberry's.....Ed
 
No, I don't. I lost 90% of that eras photos in a house fire a few years ago..For on-line pictures, you can google 'Blueberry air racing team'..Ed
 
Some of you may remember that I enlarged the Vertical Fin by 1/3 and the Rubber by 40% to correct for a longer engine mount.
I've also had a Ventral fin installed, though it is removed this summer.
If any of you want to know what it flies like, this would be the time to ask.
My SII will be coming home in the fall to receive a Jabiru 3300 engine.
I designed the Fin and Rudder with the new engine in mind.

Engine? I hope to Test run the engine tomorrow. YES!
Bill E
 
Ed,
On a 2L with a 2 inch raised turtle deck and standard fin and rudder would you:
1. Leave the fin and rudder alone
2. Add 2-3 inches to the fin leading edge and leave the rudder alone
3. Raise both the rudder and fin by 3 inches
 
With what we have all learned, I offer another consideration. In my opinion, the Sonerai does not need more 'rudder', but when raising the turtledeck, it should have more 'fin', so I would propose that the fin be raised 3" to hook up 'over' the rudder, (If you have the square tail)
You don't buy the same effect of increased area by adding to the 'leading' edge of the fin, because the volume area is based on the relationship between the size of the surfaces, and their distance form the wing's center of pressure.
The super sonerai I was building did have extra area on the leading edge of the fin, but I never got to test it.....Ed
 
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