Engine thrust line

[Skippydiesel]

[
Here is how I installed aileron (& elevator) electric trim.
viewtopic.php?f=3&t=6075&start=10#p45849

Thanks BRS - I don't think I need an external trim tab, even an electrically operated one.

My challenge is to "balance" my aircraft in flight, when;

I have a passenger
When transferring fuel from my 2 x 30L wing tanks to my central 40L header (located in the usual Sonex fuel tank position).

The fuel is not such an issue as , with care, I can take the same amount out of each wing tank, keeping the aircraft "in trim".
However a passenger (of any weight) results in extra work for me.
My Sonex has been trimmed for just me in the left seat. This makes sense as I don't often have the pleasure of having a passenger.
My last aircraft had a simple bungee & sailing cleat set up to work on the right aileron rod - the weight of a passenger could be easily compensated for by a few tugs on the bungee resulted in hands free level flight.
I would like a similar system in the Sonex but for the life of me cant figure out how to fit it.

[BRS]

The same rayallen servo I used on the wing could be used under the seat to pull the bungee. There is probably a simpler way but what come to mind is...
one bungee pulling left (balancing bungee) and another pulling right but connected to the servo.

I just went with the aileron trim tab (before ever flying the plane or any sonex) during the rebuild because that is what I have in the Sportsman and am used to it.

[Skippydiesel]

The same rayallen servo I used on the wing could be used under the seat to pull the bungee. There is probably a simpler way but what come to mind is...
one bungee pulling left (balancing bungee) and another pulling right but connected to the servo.

I just went with the aileron trim tab (before ever flying the plane or any sonex) during the rebuild because that is what I have in the Sportsman and am used to it.

Great minds think alike - If I continue with the bungee concept, it will have to be using a linear move actuator (or step motor) to achieve the in flight adjustments, as there does not seem to be a "path" from under the seat, to the pilot, for a simple mechanical system like I had before.

Have figured out the linear actuator will have to be attached to the control stick mechanism below the seat - this means that the whole system will move back & forth with the elevator movement.
Fixing the system to the airframe/floor would result in changes to aileron trim with pilot activated elevator movements.

I had moveable external trim tabs on the GA aircraft I flew - that's okay they belonged to someone else. For my last & current aircraft, I like to see a nice clean control system, so would only use external tabs if all else fails.

[CaseyCooper]

Murray,
I have thought about it, and I have shimmed for it and it makes a bit of a difference! Your plane looks wonderful. I hope you’re having great success building time in it. I had made considerations for that when designing my cowl. The engine had a tendency to pull down and left under load. If using a ring mount it would be less pronounced but I’m using the bed mount.
Did you use the Sonex mount or make your own?

[Murray Parr]

Murray,
I have thought about it, and I have shimmed for it and it makes a bit of a difference! Your plane looks wonderful. I hope you’re having great success building time in it. I had made considerations for that when designing my cowl. The engine had a tendency to pull down and left under load. If using a ring mount it would be less pronounced but I’m using the bed mount.
Did you use the Sonex mount or make your own?

Here's a link to what helped a lot with this: viewtopic.php?f=58&t=7309&start=10#p56148

I have the Sonex bed mounts. Given they only suit the Rotax, I would suggest that Sonex might be wise to explore making them with an appropriate amount of right thrust. Probably doesn't need much but I think getting it a bit better would add to the efficiency and wouldn't cost much other than a bit of testing.

I ordered a new E-Prop so I will have to modify the cowl for that and will probably add a washer behind the left mounting points where the mount attaches to the firewall at that time. When you shimmed for it, where did you put the shims and how much did you use?

I now have 20 hours in this awesome aircraft and loving every minute of it :-)