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Rudder alterations

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Joined
Jan 12, 2019
Messages
8
Location
South Bend IN
New builder here thanks for help. Got a question about making the rudder larger. I plan on going with a 2180cc or even a 2276cc engine and started to wander if I might need more rudder than what the original design is? (Torque and P factor) But if I go to big that is going to bring problems with ground handling and over control issues correct? I have noticed some with bigger rudders and some without.

Thanks for Help
Jeff
 
I added some area to the vertical tail but not the rudder. I extended the leading edge tube forward a bit. Not much but a little, mainly making a more pleasing shape to blend with the rudder. In my opinion, if you decide to add you would be better off increasing height more than width. My experience is the rudder is plenty powerful enough except in one case. That is an aborted takeoff from a wheels on, tail high position. When you chop the power the vertical tail/rudder loses effectiveness from prop wash and being so short is in my opinion blanketed enough by the fuselage that things get a bit exciting until you slow enough to plant the tail. A little more height would get some of the tail up higher into cleaner air and I think it would help out that situation. Maybe 3 or 4 inches is all I would do though without stiffening the vertical tail post.
 
I enlarged the rudder and 30% and the Fin 40% due divergent yaw and other significant issues.
Got the drawing from a builder in Idaho. Before if I presses on a rudder and it yawed 20 degrees, after releasing the rudder the yaw remained 20 degrees. With the enlarged rudder the yaw reduced to 5 degrees, Good enough.

I added some area to the vertical tail but not the rudder. I extended the leading edge tube forward a bit. Not much but a little, mainly making a more pleasing shape to blend with the rudder. In my opinion, if you decide to add you would be better off increasing height more than width. My experience is the rudder is plenty powerful enough except in one case. That is an aborted takeoff from a wheels on, tail high position. When you chop the power the vertical tail/rudder loses effectiveness from prop wash and being so short is in my opinion blanketed enough by the fuselage that things get a bit exciting until you slow enough to plant the tail. A little more height would get some of the tail up higher into cleaner air and I think it would help out that situation. Maybe 3 or 4 inches is all I would do though without stiffening the vertical tail post.
 

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The other day I watched a Youtube Thorp T-18 flutter test flight, taking the craft to Vne and maneuvering under max loads. The mods to the Sonerai rudder and Vertical stabilizer that have been posted seem to be safe, but wondering if anyone has actually flutter tested these mods to Vne under G max.
 
Thank you this is what I am afraid of by changing plans. I am a pilot not an engineer. So my question becomes what's the largest engine I can put on Soneria 1 without modifications to plans? Is 1600cc all I can without running into problems?
Thanks for all the help and helping out a new builder.
 
I don’t see any problems with any of the VW engines up thru a 2180. A lot of guys have used 1835’s. Jeff Lange has a 2110 with a turbocharger. As far as the rudder/vertical stab size is concerned, you can increase their sizes, and change their shapes within reasonable limits, just don’t make them any smaller than what’s on the plans. Google “Sonerai I” and look at the pictures. You’ll see all kinds of different shapes and sizes.
 
My Sonerai 1 has a Jabiru 3300 (120 hp) and has a slightly longer nose to accommodate the longer engine (standard engine mount length). Tail surface areas have not been changed from plan and it flies just great.
 
I have flown mine to 200 kts. But tha'ts VNE. You would not want to attempt any aggressive flight maneuvers at VNE.
No one I know would either.
BillE

The other day I watched a Youtube Thorp T-18 flutter test flight, taking the craft to Vne and maneuvering under max loads. The mods to the Sonerai rudder and Vertical stabilizer that have been posted seem to be safe, but wondering if anyone has actually flutter tested these mods to Vne under G max.
 
Could you imagine wacking the stick like that at 200 to check for flutter? Wounded if that’s how the old guys did it. Wouldn’t mind getting an idea how John originally tested things. Better yet if Walt Whitman was still alive (tailwind golden age racer) I’m sure he had some interesting ways of testing.
 
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