Soarstar C.G.

[jimp]

I'm putting together a Soarstar as my second plane. First was a Firbird XL. I note that the instructions tell me to put the CG at 105 - 100 mm (4 inches) from the leading edge. This is about 40% of the cord which seems a little to far back. Any feedback or should I just follow the directions?

[CalmAir]

Hi Jimp,

I have a Soarstar that I have been flying for 8 months. The CG spelled out in the book is correct although it does make it just a little more nose heavy, which is good for your first flights.

Due to the large battery compartment the CG can be moved quite easily. Start out at the settings they call out. The aircraft flys well with this setting. Here is how I do mine now to make it quick. With their setting if you hold the plane at the exact point where the struts connect to the wing it will point down just slightly. When it is calm and I want it to float more I move the battery back to where it is perfectly balanced at the struts. However I prefer the stock setting.

Here are some flying tips. Start off with a large field without obstructions. This plane will traverse the field in short order. Once you get used to it you can move to a smaller field. This is a pusher, so you will end up with a little left rudder trim. I recommend hand launching until you get the trims worked out. Max the throttle out. When your partner launches it by hand it will drop a few feet while gaining airspeed and then you can give it some backpressure and she will be on her way. Easy on the controls at first. She is touchy and responds very well. Take offs can be a little squirrely until you get used to letting it fly instead of trying to correct every movement. When you make a turn you will need to feed in a little up elevator to maintain altitude. This plane banks very quickly. Once you are up you can reduce the throttle to 3/4 to cruise and feel it out.

It will take about 3 or 4 discharges and charges on the battery and it will start giving you some good run times. Typically 11 to 15 minutes depending on throttle use and how windy it is. The stock pack is excellent and the motor, gearbox, and prop selection is superb. Plenty of power. If it is calm you can cruise at half throttle with plenty of power left over for loops. Just be sure and use full throttle until it is airborn and then cut it back.

It will loop and it will roll. Stay several mistakes high at first, because this thing will roll quite quickly for a rudder plane. It will auger in fast if you let your mind wander.

Landing is another fine quality of this plane. If it is trimmed to stay level at 3/4 throttle all you have to do is line it up and at about 20 feet cut the throttle. It will maintain a perfect glideslope and at about 8 inches off the ground give it a smooth up elevator and it will slide right in. Landing in grass is no problem for this aircraft and it will stay on it's gear. Dont horse it in on landing just use the throttle to control altitude and elevator for airspeed. It lands itself and makes you look real good.

It repairs easily. Crashed mine on the first flight. I apparently missed glueing the rudder hinges and it seperated from the plane. Busted it like a watermelon and had it back together in an hour. Never wrecked since. It will handle winds up to 10 to 15 MPH with the CG just a touch forward. This is the plane I fly when I can't fly my lighter aircraft. The only mod I did was to put a cut piece of paper towel over the pylon dowel and then put a smooth layer of epoxy over that to give more strength to that area. The struts take most of the load, but there is not much area for that dowel to hold on to.

If you ever need an motor or gearbox you may order the complete assembly from Horizon Hobby for $18.00. It is the same one that is used on their Electajet. I have had no trouble with it, but my son purchased the assembly on a home built foamy he has.

I hate the Barbie doll colors, but this plane became one of my favorites to fly.

Sorry to be so long winded, but since I have a lot of flights on mine I just wanted to give you my thoughts.

Regards,
Dale

[Richard Miller]

Jimp,

The basic facts are these: Forward CG tends to require a lot of decalage = the angular difference at which the wing and horizontal surface encounter the air. This is advantageous for trim purposes. The aircraft will recover quickly from an upset, as a stall. Disadvantage: An increase in looping tendency with increased airspeed and a penalty in drag.

A rearward CG will entail reduced decalage, obviously, less drag and less tendency to loop, but incremental decreases in the time it takes to recover.

These are typically illustrated by a ball in a shallow bowl = decalage and the tendency of the ball to roll to bottom center representative of the tendency of the airplane to recover; a ball on a flat plate, which is airplane terms is squirrelly; a ball on an inverted bowl, which is DEATH.

-Richard

[Richard Miller]

A couple of things could be added to this. First, the operation of a principle: You begin with so much energy, or force, in the form of lift. The energy needed for trim purposes must come out of this.

The question, as with all such matters, is how much? and the answer is, at the point where the two curves cross on the plot. We pretty much know where this is, near the 25% chord point in standard configurations, further back if the tail is lifting.

The hand's-on determination. A launch at an airspeed somewhat in excess of the equilibrium gliding velocity. The ball on the inverted bowl = an inevitable crash. The ball on the flat plate = straight ahead. The ball in the bowl = a slight upward curvature in the model trajectory.

-Richard