Full disclosure; This Sonex has had its wing/horizontal stabiliser, angle of attack increased by 1.6 degrees from factory/plans specifications.
Engine thrust line is defined by Sonex (factory) engine frame, with latest Sonex/Rotax "bed" adapter - I would hope that this would be well within design parameters.
Murray Parr wrote:I installed the dial a trim to my Waiex B and followed the instructions precisely and found the adjustable spring wasn't anywhere near strong enough to put the elevator in the desired position so I added a much stronger spring which acheived the specified position. I haven't flown it yet (soon:-) but I expect to need an aditional spring for this. I wouldn't be too worried about adding a heavier spring while stil utilising your inner spring (Bunnings has a great assortment to choose from).
I think you will struggle to get much experienced advice with your question as you are likely the pioneering test subject for this. Maybe reach out to Sonex tech support and see if they have any insite to add. I would just go ahead and adjust your ailerons in small increments and test to see if any improvements or declines in performance are made. can always adjust back if necessary.
If you have the conventional tail instead of Waiex, you could just convert to the lever operated adjustable trim tab which would give more range is another potential solution. I also don't think your 10mm elevator position above the stabiliser is an issue, a lot of the 10mm would probably dissapear with dynamic forces that don't show while parked, have you thought of that?
sonex892. wrote:
I would think your problem is the thrust line pulling the nose down and you just dont have enough tension either on the fixed spring or on the trim spring to overcome it.
I would check the thrust line by climbing high then whilst level hold a constant speed check the elevator position. Then go to idle and glide at the same speed to see if the stick is in the same or similar position. If the stick position is alarmingly different address the thrust line of the engine. My 3300 also pulls down but I dont have an issue with that as the trim has enough authority to be set at any c of g and speed higher that 70 kts. I only ever run out of back trim when slowed to about 70 kts.
Personally I would just add an adjustable trim tab as per the plans and move on, it is very effective.
Steve
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