Stabilizer Attachnment and Trim Options

[acrojohn]

Hello, I'm new to the group and hope to be adopting a Sonerai I Project in a few weeks. I've built a TEAM MiniMAX and an Acrosport II. A friend has a Sonerai II LTS that I have flown the Phase I hours off of. I liked the plane so much I've decided to build one - but just the single seat variant. I have seen the S2 plans and I'm fairly familiar with the construction of the plane I have flown. That said, I have only seen pictures of an S1 and I won't get a chance to see the plans for a few weeks - so I have a few questions.

I've studied numerous pictures of the project airplane and just about every picture of S1s posted here. Does anyone have a good picture of the horizontal stab attachment to the fuselage cross member at the leading edge of the stab. I'm especially interested in the detail of the slip joint that joins the left and right stab halves. A few words of description would help also.

Also, what trim options are available. The IILTS I have been flying has a controllable trim tab. I have also heard about the screw-jack trim on S2s. Does the S1 have that option? I have also heard about bungee trims such as those used on gliders and some other home-built. I'm not that fond of this option because it doesn't provide a back up in case a pushrod rod end bearing fails. Any info will be greatly appreciated.

John Andre
Chesapeake, VA.

 

[Raceair]

Hi John and welcome. I do not have any pictures of the Sonerai 1 stabilizer attach, so I cannot help you there. But, in close to 200 hours of Sonerai 1 flying, I rarely thought about the need for a trim system. Steve Wittman had a unique trim setup on the bottom of the control stick, that seemed to work on the V-Witt airplanes, but honestly, the fuel load on a Sonerai 1 is so close to the CG that heavy stick loads are rarely a concern.
Where is the Sonerai 1 that you are adopting coming from?….
The chances of a pushrod or rod-end failure are so low, I would not look at the trim system as a safety net. The elevator loads on a Sonerai 1 are very low….
While the basic Sonerai 2's tend to be nose heavy, the Sonerai 1's are opposite that….they tend to balance out to the rear of the envelope.
If a 200 pound Sonerai 1 pilot has the stab. adjusted for himself, a 150 pound pilot might feel the need to adjust a spacer washer from the Stabilizer leading edge attach bushing, to drop the leading edge. One standard thickness washer does make a difference…..
I try to keep up with the Sonerai 1 builders, keep us informed with your project!!..Ed Fisher

 

[JoeB]

Welcome John!
Please keep us updated on the status of your new airplane.

I searched for photographs of the stabilizer leading edge and spacers on my airplane but have not yet found any (yet). It is very simple, as Ed stated, using washers for shims between the fuselage cross tube and the 'slip joint' tubing, which each leading edge of the stabilizer slide into. There are two bolts securing the entire mechanism together. Once assembled it is fixed in place, adjustment requires removal of the bolts and adding/subtracting washers.

I wish I could find a picture, I can't remember how many washers where in there. Maybe a stack of 2 or 3?

 

[soneraii]

Below is an excerpt from a post from Dick Frederick. He devised a simple but effective pitch trim system for an S-1 that does not require a movable stab or trim tab yet provides back up in case of pitch control failure. I like it and will eventually incorporate it into my S-1 because I too don't like any single point control failures. If you search the site you can find some pics he posted along with his post.

Kevin

The system I have installed is similar to a Piper Pawnee. There are two opposing springs, one pulls the nose down (down elevator) and that spring is attached between the elevator horn (below the hinge) and a dead-man. The other spring is attached between the elevator horn (above the hinge) and a cable running to a verneir control in the cockpit. Pulling out on the control brings the nose up.



If I were building from scratch I think I would use a jack screw to adjust the stabilizer, but the above method is easy to retro-fit and does the job.

Photos attached.

Dick Frederick

 

[acrojohn]

Thanks for the inputs. It is always better to have experience guide the way. Again, I have 0 in the S1.

I do have about 100 hours in an S2 which needs a healthy dose of trim adjustment due to payload and power settings (this particular airplane). When trimmed it can be flown with thumb and index finger tips. This plane is the easiest airplane I have ever landed of the 20+ types I have flown - great flying characteristics also. The balance of the landing gear is perfect whether loaded or solo. That said, in flight it needs to be trimmed to get the loads off the stick and pitch control components. I am thankful this plane has a controllable trim tab. Glad to hear the S1 is light on the controls - thanks Ed.

I don't plan on flying the plane like I fly the Acrosport, but I would like to do some basic gentleman acro in it. What are the stick loads when pulling 3 to 4 g's on an S1? How are ailerons, elevator, and rudder inputs harmonized?

My MiniMAX didn't have a controllable trim tab and had light inputs, but a failure in that pitch system meant you were going to have a bad day. The Acrosport can be flown by controlling the controllable anti servo tabs almost as well as using the stick. It is sensitive, but it will do the job. Sean Tucker's rod end bearing failure and bailout story made a believer out of me. Even if the trim control isn't precise enough to land the plane, it is enough to climb to a safe bail out altitude. it is just nice to have options. It sounds like the geometry of the control lever/vernier, control horn, and tab area need only provide modest inputs on an S1 once the stab angle of instance is properly adjusted. If someone out there really likes their trim configuration, I'd appreciate additional information.

Thanks again,
John