SonexBuilders.net

I am wanting to use a simular system to the aeroconversions dial a trim, except I want to utilize the trim tab instead of the springs. Has anyone done this? How did it work out?
Do you feel it is better than, the same as or worse than the spring system attached to the control assembly? What did you use for a trim system setting indicator? thanks! Joe S/N 1510 :?:

I have to ask why would you want to do that? The dial a trim system works well and the lever trim system works well. What would be the advantage of combining the two systems. If you hook the trim tab to the dial a trim knob there is no way to see where your trim is set at before taking off. With the dial a trim you can feel the force on the stick to see where it is set. With the lever system you can see where the lever is set.

Keith

Well, Kieth, thanks for the reply! I am not really confortable with springs on the controls. Just me. I had flown C172 for many years with its direct system and am very comfortable with it.The trim tab connected to dial trim clone, has an in cockpit indicator on the instrument panel, in direct sight with no fumbling below the panel for a 'reading'. I like that too. It all uses bowden style cables and a jack screw. it has a crank knob on it so it can be turned quickly, but from what I hear(having not flown Sonex yet) that should not be a real problem. Also, this clone has cost me less than $5 for one of the bowen cables. Thats my story! Thanks again for the comment!

Do you have any pictures of your setup for an indicator for the dial trim clone? That seemed to always be the biggest drawback of hooking the standard trim tab to the dial a trim crank. If there was an easy way to add an indicator it would probably be usefull to those with even the standard dial a trim system.

Keith

Hi Keith! I will work up the pictures on my clone. I have not installed it yet as I dont have the spar tunnel and wings complete, and wont be for quite a while yet. But, I can show how it is intended to work.

As far as putting an indicator on the Sonex system, I have nothing to show. Some may not think my idea is sophisticated, but it will function properly. I have not decided just where to mount the indicator...on the pannel or on the glare shield. It will probably be a last minuet decision. You also have to realise that I am sort of a tractor mechanic....I tend to over build things! Maybe some one can use the idea to add an indicator to the Sonex unit.

If you want, send me your private email and I will return the pictures that way. Or, since I am a real nubie here, help me with how to post pictures, if that is even possible.

Thanks for the interest!

Joe

Hi Keith, two pictures are susposed to ber available from these url's. One is of the clone itself, mounted in place of the dial a trim, connecting to the trim tab with an uninstalled bowden cable. the crank handle is too long just now as I have not fittet it to the instrument pannel yet and will be shorter. second pix shows indicator that attaches somewhere to the instrument pannel, probably between a couple of the steam gauges I am using, and will have a some sort of scale behing it as a relati9ve reference to the trim tab position. No springs or anything to rub on the bottom of the seat! We shall see how it goes! Let me know if you can not get the pix to work

Joe, s/n 1510 scratch building TD

Interesting discussion with good options. Other than perhaps more primitive looks, I’ve often wondered why the Wittman pitch trim system isn’t more popular for aircraft like the Sonex with fairly balanced pitch characteristics (or so I’ve read – absolutely NO personal experience). The Sonex dial-a-trim is essentially a more refined (albeit more intricate, as well) version of the Wittman system – works by simply loading the loading the pilot’s pitch control mechanism to the elevator rather than the mechanical gymnastics of adding a trim-tab on the elevator and then running the actuation back to that. The Wittman system simply acts on the control stick itself – even more basic than the Sonex it appears to me.

Inquiring (albeit geriatric) minds want to know… :o

-- Larry

Personally ... I like the plans designed lever trim with a tab on the elevator. I've had the "Dial-A-Trim" system and it works but there isn't a visual way to see where the trim is set. You are correct that it loads the elevator tube as it removes the load from the stick. My biggest concern with the "Dial-A-Trim" system is that if the bolt from the elevator tube to the elevator bell crank were to fail (the odds are extremely unlikely) then you would have no trim to fly the airplane with.

Other advantages of the lever/trim tab are; quick to set, less weight, less money, and fits on the side panel out of the way. A quick glance tells me whether I'm set for take-off and it's very intuitive to learn how much to move it for different flaps settings and speeds.

Just one man's humble opinion.

Dale Williams
N319WF @ 6J2
Myunn - "daughter of Cleanex"
120 HP - 3.0 Corvair
Tail Wheel - Center Stick
22:30 hours - Phase One
Status - Flying

I have, since I posted my pix, re-done my trim system to be about 75% lighter and quite a bit smaller. It functions the same way, with the panel mounted indicator. I like it much better than the original....much smaller! Not flight tested for a great while, though. making nose ribs for the wings just now.

daleandee wrote:Personally ... I like the plans designed lever trim with a tab on the elevator...
Other advantages of the lever/trim tab are; quick to set, less weight, less money, and fits on the side panel out of the way. A quick glance tells me whether I'm set for take-off....

I've seen several builder's pics and the side-panel mounting certianly appealed to me for its simplicity -- but my plans have not yet come so I can only guess how it actually works...

-- Larry