I have a new-to-me 50cc SBach and I'm looking for a starting point for control throws for IMAC. Any insight is appreciated!

is your plan, to be strictly IMAC, cuase I was just watching the troybuilt guys set-up vidz, for IMAC and 3D!

you basicaly set-up for 3d, then you set the duel rates at what they call IMAC settings, which is abou 12* ta 15* on the elevator and ailerons, and around 25* ta 30* on the rudder! with about 30% expo on duel, and 65 ta 70% on full!

and I also saw somewhere, that if you don't plan on flying 3D, then don't set your plane up for it! you are wasting set-up! if you set a plane up for 3D and never use high rates, you are wasting upto are more then 1/2 your servo movement!

There really is more to it then what you think. It's much more then setting throws although that is where you would want to start. I'm going to assume you will be starting in Basic. This will simplify things quite a bit. IMAC sequence flying at basic level does not require a lot of throw. Elevators can be set at 10 degrees, rudder at 25 degrees and ailerons at 25-30 degrees. The amount of expo will be dependent on your personal preference. I would encourage you to start out at 35 on elevator and rudder and 45 of aileron. This would be your normal flight mode so set up your linkage to get these throws plus about another 20%. This gives you good mechanical advantage, resolution and is much less wear and tear on your servos. IMAC requires lots of practice and you don't want to be replacing servo gears every 100 flights. At first you may not like the feel as it will be soft compared to what you are used to. OK the reason for more available throw. Spin mode. While setting up for your spin you will need to enter a different flight mode that gives you more elevator and rudder. If you are able to stall your airplane with the elevator travel you normally fly with it's too much. The additional rudder travel is so you can control the direction the airplane breaks when stalling.

The next step after you have the throws set is to completely trim the airplane. There is a little black art involved as most sport pilots trim the airplane for strait and level at one airspeed. You need a cooperation of CG, thrust angles and incidences for the airplane to track on it's own so you can focus on control inputs and not correction inputs. I haven't done much competing in the last few years but to get an airplane really well dialed in for the Unlimited sequence takes me about 5 flights. I can get 85% there in the first flying session but that last 15% takes a lot of small adjustments.

I know this seems like a ton of additional information and in reality I have really only scratched the surface. The best thing is to set to the suggested throws and then report back. Let us know what your airplane is doing and I can throw some suggestions out there.

Originally Posted by exf3bguy

There really is more to it then what you think. It's much more then setting throws although that is where you would want to start. I'm going to assume you will be starting in Basic.

I competed once in Basic last year with a low winged sport plane. This plane is intended for IMAC (and will not be used for 3D)

This will simplify things quite a bit. IMAC sequence flying at basic level does not require a lot of throw. Elevators can be set at 10 degrees, rudder at 25 degrees and ailerons at 25-30 degrees. The amount of expo will be dependent on your personal preference. I would encourage you to start out at 35 on elevator and rudder and 45 of aileron. This would be your normal flight mode so set up your linkage to get these throws plus about another 20%. This gives you good mechanical advantage, resolution and is much less wear and tear on your servos. IMAC requires lots of practice and you don't want to be replacing servo gears every 100 flights.

Excellent point.

At first you may not like the feel as it will be soft compared to what you are used to.

No worries - I haven't flown this plane yet.

OK the reason for more available throw. Spin mode. While setting up for your spin you will need to enter a different flight mode that gives you more elevator and rudder. If you are able to stall your airplane with the elevator travel you normally fly with it's too much. The additional rudder travel is so you can control the direction the airplane breaks when stalling.

That I do remember from last year.

The next step after you have the throws set is to completely trim the airplane. There is a little black art involved as most sport pilots trim the airplane for strait and level at one airspeed. You need a cooperation of CG, thrust angles and incidences for the airplane to track on it's own so you can focus on control inputs and not correction inputs. I haven't done much competing in the last few years but to get an airplane really well dialed in for the Unlimited sequence takes me about 5 flights. I can get 85% there in the first flying session but that last 15% takes a lot of small adjustments.

This I was aware of. My club has an Aerobatic Interest Group and there are a couple of trim charts on the website. After I maiden the plane in the spring I'll get to trimming it.

I know this seems like a ton of additional information and in reality I have really only scratched the surface. The best thing is to set to the suggested throws and then report back. Let us know what your airplane is doing and I can throw some suggestions out there.

Thanks very much for all the info.