SonexBuilders.net

Hi Guys,

I once had a Sonex. I loved the manual trim system. It was intuitive and quick. Just set the speed with the stick and trim off the pressure.
Question: Has anyone installed manual trim on a Onex? Pics?

Thanks,

I installed the factory dial a trim, works well but most of my flights are brief and constantly “mucking around “ . The stick forces are so light I just don’t play with the trim much,
Peter
Onex 120

Hi Peter,

Using trim in the pattern is ingrained in my mind. I like the speed set with no stick pressure. It just gives me a cue if I start flying off speed. I have seen videos of folks cranking on the Dial-a-Trim and it just looks like too much work, almost like a distraction. I understand the need on a Waiex but not on a conventional tail aircraft.

I also enjoy the speed and ease of the standard trim tab and lever, and have no plans to change to anything different. However, the factory has commented previously that if you find yourself needing to crank too many turns on the "Dial-a-trim" knob in normal operations that you may need to adjust the springs for more tension. If anyone is unhappy with their dial-a-trim, perhaps this is a place to re-look.

Jeff

Hi,
I have added an external trim tab to the left side elevator, 85% size compared to the 'old' Sonex trim tab and operate it with a modified trim wheel from a Piper Pacer. In order to operate the tab with a single piano wire, I installed a reduced size copy of the elevator idler system and a tension spring behind the seat on the left side.
Haven't flight tested it yet as I only moved to the airport a couple of days ago but it operates as a normal, intuitive trim system; forward turn to push the nose down, turn backwards to raise the nose...
Dirk
Onex 117

I certainly don’t need to crank the trim wheel, minor adjustment only needed to fly a circuit. I start my takeoff roll with the elevator absolutely neutral and it flies off in the 3 point attitude with no stick pressure. I have swapped to the 94 mm cylinders and high compression. At 80 kias I’m climbing at 1,000fpm or more, run up to 100+ knots downwind and always do glide/power off approaches at 70 kias on final, 65 over the fence and flare at 55 or less. Timed a circuit last week, take off to landing roll, 3 minutes,so trim not high on my priority list as stick pressures are never more then 2 fingers needed on the stick. Have I mentioned before that I love flying this plane!
Peter

My experience exactly. I don't change the trim until I've added 10 gal of gas and am at cruise speed. Don't touch it until I've burned off 5 gal or until the next take off and cruise. A very small issue in a Onex.

Hi Peter,

I'll bet it is fun. Hope to find out myself one day.

As far as the trim is concerned, I'm sure you're right. After all you are in a position to know, I am not. I've never flown a Onex and never used a Dial-a-trim. Just thinking out loud, not always a good idea. Now that I think about it I do remember Drew commenting in his pattern work video that Onex flaps don't generate the pitching moment like the Sonex flaps.

As Dirk alludes to though, It would be nice if the knob rotated about the trim axis it was controlling. That would be better than left right, up down. Or is it right left, up down. Oh yea, it is like volume, right is up, left is down. Tongue firmly in cheek :-)

Wes

P.S. Looks interesting Dirk. Let us know how it works out.

Hi Wes,
I have just under 30 hrs now on the Onex and I use the trim as follows: neutral for T/O and climb until flaps are up and rpm reduced to 3000.
Then just a trickle nose up trim to maintain 90 kias in the climb and when arriving at cruise alt, just a trickle down to maintain 110 kias.
Arriving back into the pattern, I reduce to below 90 kias, select 1/3 flaps , they are electrically operated via a screwjack, and a trickle nose up trim to maintain 80 kias during the descent, base 2/3 flaps and some nose up trim and on short final, full flaps and trim all the way up.
The trim system is very sensitive, only 1 full turn of the wheel from full nose down to full nose up, so some fingerspitzengefuhl is required!

I flew the "dial a trim" on a Sonex a couple of times and it took me all downwind to go from cruise to all nose up trim! This took way too long for my liking and the search for a better solution could begin.
I took some inspiration from very old Sonex plans which show an external trim tab and combined it with a proper trim wheel and an idler and a spring to avoid two cables to the trim tab.

Hi Dirk,

Sounds a lot like the Sonex with manual trim. The only difference was that I adjusted flaps and trim as soon as I turned final, no changes on short final. As far as one turn from nose up to nose down, the manual trim on a Sonex is only a few inches from full up to full down.

It was just so quick and easy. I remember I would just set the speed with the stick and then trim off the pressure. Then I would form a "doughnut" around the stick with my thumb and middle finger to verify hands off stable flight (70 MPH on final).

Dial-a-Trim makes sense to me in a Y tail or if center controls are wanted/needed. In the Onex I just don't get it.

If you have any pics of the routing of the trim cable out the back of the aircraft and/or part numbers for the trim cable (music wire) and cable housing I would find that helpful :-)

Wes

P.S. You should set up a contest to see which American can mess up the pronunciation of fingerspitzengefuhl the worst. Hint: Select contestants primarily from southern states.