IMAC

IMAC – in the Box

Great to see everyone! We have progressed through another month of the “New Norm” and its exhaustingly frustrating! Like I need to tell you that. We are all in this together and that is one thing that we can hold onto to get us through. I have been spending some time at the field, until I had a little “Quarantine Time”. Then, I just dreamed of being at the field. But, next weekend! Just wait.

So, what to write about? One thing that is shared between Pattern and IMAC is plane setup. As daunting as it appears at first, the more time and effort that you spend on setup the better the plane flies and the less workload there is on the pilot. That is a good thing and well worth any effort you put into it.

So, flying at the club as Bryan Hebert I hear a lot of comments on trimming. I have purchased and reference Bryan’s trimming guide with all my planes. As you may have guessed with all that information, you need to go slow and do things one at a time and note how those changes affect the flight of the aircraft.

With IMAC planes, there is not as pure of a flying experience as there seems to be with the Pattern planes (especially the Hebert designs). So, there are a few basic mixes that I put in my planes to try and tame some of the bad habits. But, if you mix on top of things you can fix mechanically, you run the risk of causing unexpected problems.

Because most of our planes come ARF or used and pre-built I don’t usually start with things like wing incidence and stab incidence. These come set and are usually in a pretty good starting place. What I start with is CG. I put the CG in the manufacturer recommended range (usually in the more neutral position). This is a good starting point before the maiden.

Next, I will check the Ailerons and Elevators. As with every balsa and covering plane, you have the issue of warping. So, I will use some alignment sticks that are offered by CK Aero. First, I center the surfaces, then I will put them on several places on the control surface, depending on the size of the surface and look that the sticks line up. If they don’t, then you have a warp. This will affect your trimming greatly. So, you need to keep the surfaces straight.

Now I will provisionally set my throws. With my radio set-up I can set a flight mode with my standard throws then they change with logical switches so I don’t have to switch any physical switches. So, I will set my Ailerons at 25 degree and my elevator at 18-20 degrees, with about 30% expo. I leave my rudder at 40 degree and use about 60% expo. I really don’t like switches when I fly. I match the surface throws with an inclinometer. I want to start as exact as possible. I also try to use my geometry to get as close to these throws as I can so I can keep the servo resolution as high as possible.

Now after all this, I finally get to fly the plane. I do the normal inverted 45 to check the CG early in the flight and make sure I don’t have any big issues, then I play around and see what the plane does. The Trimming guide had a lot of cause and affects to look at, but the big ones are knife edge characteristics. This is a focal point of CG and wing incidence issues. So, before you mix out that tuck to the canopy, see if you can make a change that can remove the need for that mix or at least reduce the amount of mix needed.

That’s the basics of the starting points. Just make sure you fly the plane a few times in between adjustments so you can really get a feel on what your changes are affecting.

Like I said, the Scales Aerobatic planes will not fly as pure, but you can probably improve the flying characteristics of that plane by making sure you have done everything you can to get the basics as close to correct as possible.

I hope this was interesting and helps you in the Scale or even Sport plane setup. Your time will not be wasted spending it on setup!

I hope to see you at a field soon! Rich Whitlow IMAC SC Regional Director.