If I interpret all the responses in the Negative Gs at the top of the loop thread, I should fly with enough airspeed and power that the plane always pulls positive Gs for any reasonably-sized loop.

I was practicing some the last weekend and this is what I observed.

If I make a nice big round loop I have to give it just a nudge of down elevator at the top of the loop, even at full speed and power. So from about 12 to 2 o'clock I feed in an itty bit of down elevator. If I don't do that with this plane, I will not get a round loop, the loop will pinch at the top. Now from what I learned on the other thread, that is not the optimum way to fly but with this plane, that's what I need to get a round loop. In fact one of the other guys in the club said that one of my loops was the roundest loop he'd ever seen. For loop, I give it a nudge of down at 12 o'clock and faded the nudge off to neutral by 2 o'clock.

Now sinceI do have to give it a tad of down elevator I have to be very careful if I'm trying to make any minor adjustment to the track of the plane with the ailerons. As explained in the other thread, if the plane is slightly banked at the top and the force goes negative for a bit, the track adjustment is reversed. If course if I can line up for the loop perfectly, I shouldn't need to adjust track but I'm still working on that.

I think perhaps my plane (Monolog 70) just flies heavy. It feels heavy compared to the smaller 3D planes I've flown. I've been meaning to weight it with battery but haven't gotten around to it yet. I do have more than enough power for unlimited vertical but the plane still seems to fly heavy. I'm flying with a 15x10. I have a 16x8 which I haven't tried yet but I would think that if the plane is heavy, airspeed is more important that pull and the high pitch prop would be better. Again, I still have enough power to climb straight up as long as I want.

-l2t aka Ken

PS

I really wish there were someone around where I live that know they were doing so they could fly my plane, then watch me fly, and give some advice. Maybe my plane sucks; maybe I suck. Maybe I just need more practice with this plane.

Ken,

There's a ton of AMA fields near Medfield (17 within 25 miles). My old club, Central Mass RC Modelers, is in Westborough and supposedly only 6 or 7 miles from Medfield. I know a number of the guys there would be more than willing, and able, to help out. Saturday mornings 10:00 to about 1:00 would be a good time to show looking for help. Charlie, Jack, or Ru should be able to help you out.

Ken, two things come to mind. First is it sounds like you are running nose heavy. The up elevator that most would trim into a nose heavy airplane actually creates a down force on the airplane as a whole and emulates an increase in wing loading.

second is that the airplane just plainly sounds out of trim. Have you checked the wing and tail incidences, thrust angles and fin alignment? In order to fly pattern well you need to trim out the airplane to require as few correction inputs as possible. An airplane that is trimmed for only a single flight attitude ( moderate speed, upright ) will change trim whenever the attitude is changed. This increases the workload as evidenced by your post of having to feed in down at the top of a loop.

The first step to successful pattern flying is the build/setup of the airplane. Being you have an ARF, you must now verify all the angles are correct and/or fix the discrepancies.

Back in the 80s when I started flying RC, I was in Central MA. That was the first club I joined. I left when I moved out of Worcester and the field in Westbury was no longer convenient. I believe the have a different field in Westborough now.

I'm hoping that maybe I can get to a practice Friday at a pattern meet next season. I didn't get a chance this season.

I've done a bit of trimming from the tutorials I've found but will try working on it some more. The plane doesn't seem unstable so I figure I could nudge the battery back a 1cm per flight and see how it feels.

-l2t

Ken, before you make any changes you should measure the airplane to see where it is. That's really the only way to know what direction to go.

What would I measure? The only static test I know of is the position of the CG with respect to the recommended CG.

I know some of the basic flying tests like fly a 45-degree up line, roll over and see how fast the nose drops.

-l2t aka Ken

Ken,

It's very useful to know where your CG is along the MAC (Mean Aerodynamic Chord). This is almost always expressed as a percentage of the line back from the leading edge, and that percent can be duplicated across different wing platforms with consistent performance results. The "roll over and see how fast the nose drops" CG test is inaccurate because that is also affected by thrust and incidence settings, and mostly irrelevant, focusing on that makes one or two things easier while ignoring more important criteria like tracking and rolling. I realize you are relatively fresh and flying the lower classes but I highly encourage you to try and absorb some of the fundamentals so that you can see success in the future should you move up in classes and start flying some more complicated maneuvers. I'd recommend reading Triangulation Trimming at http://www.ckaero.net/blog/triangulation-trimming-2/ . It's long but makes a good read for anyone who loves this stuff as much as we do

Here's a link to a useful MAC calculator: http://www.friendlyflyers.org/cg-calc.html

Hey Brett,

I just went thru the trimming guide which is an improved version of the first I read, and just on word "genius"

Regards

Alejandro

You need to know the wing and stab angles in relationship to the engine thrust line. I will bench set every aerobatic airplane the same. Stab and engine at zero, wings at +.5 degree and 3 degrees of right thrust. Once I know all that is sorted out I can begin the process of flight trimming. I initially set CG as close to 28% as I can figure. Elevator trim, pull to the gear while in knife edge and how much forward stick is required for inverted flight are all clues to where to adjust the CG. Getting the CG set is the first thing that must be done as it influences everything else. Once the CG is set you can start fine tuning the engine thrust angles. Watch what happens to the airplane during hands off vertical lines. Adjust engine thrust angles to get a true vertical. Now mind you that this will change as the airspeed bleeds off.

There is a lot to properly trimming an airplane - more than we can really cover in a single thread. I recently used Hebert's trimming method. I learned a lot while doing it (and following it to a T!) and have a remarkably straight flying airplane.

Anyway, (this is my opinion) since you're flying a 70 size plane in Sportsman, I suggest playing with the CG before buying tools and spending tons of time on the bench. I think a nose heavy CG is probably the most likely culprit. Most people fly airplanes with the CG too far forward. A CG shift takes a few minutes at the field. You can measure and tweak your airplane over the quickly approaching cold season. The reason I say this is because you could open a can of worms and find yourself frustrated or confused or aggravated. Wings and fuselages can warp and twist, and things aren't always lined up perfectly at the factory to begin with. If you look at the trimming methods, CG is tied to thrust line and wing/stab angles. It takes some time to go over everything and learn the trimming methods enough to start using them properly. Most of them have a very specific order so there is planning involved. I took the time to do this and it paid off immensely I think.

It is true that the '45 and roll' test is limited. But it is something. If you go into a 45deg climb, roll inverted, and your nose quickly drops you know you have a CG or trim issue. The plane should hold a 45 for 'a few seconds' at least and gently start to nose down. It should not nose down fast enough to pinch a loop. This test is very subjective but it will hint at a trimming issue if there is one. If the nose falls quickly, move your batteries back. You will need some judgement regarding how far to move them based on how quickly the nose drops. An inch can be a lot depending on where it is so move it gradually.

If you are that nose heavy, you will find the airplane becomes more 'sensitive' so don't be afraid to reduce your aileron/elevator throws. I moved my CG about an inch one day and had to change settings in my radio (I was a little AFT with the CG, moved it FWD and the surfaces felt less responsive).

It sounds like you took the right points from the other thread. There was a lot of stuff in there - it's nice to see you got some good knowledge from all that.