Pitch trim help for a beginner?

There are four variables to mess with: 1)CG, 2)elevator throw adjusted at the elevator control horn, 3)sensitivity adjusted by line spacing at the handle, and 4)speed (higher speed would make the elevator more effective). What is the best sequence to adjust them? Or how do you trade them off against each other?

The airplane is an ARF Flight Streak.

Another related question is about a "dead spot" around neutral. Even in level flight the airplane will "wander". And small amounts of elevator have no effect until abruptly there is a bit too much and the airplane "twitches" off in the other direction. This is a real problem in the simple wing over: if the flight path is not right going up hill, I can't make small corrections across the top.

Help! Any suggestions? comments?

Tim

I've put a guide on the push rod to minimize flexing and there isn't any noticable slop.

Cy.

Stock Streaks tend to be pretty flighty and require a very fine touch on the controls. Otherwise, the only thing is to tune up your reflexes and learn to control your hand movements better.

<sigh> Somehow I suspected that this is the biggest part of my problem. But, I was hoping there was some hoping there was some way to tame the oscillations a bit.

If I recall my streak from a LOONG time ago, it was pretty sensitve--and seemed to like to fly too fast for my responses.

I know that people recommend those for stunt trainers, and I know that a good pilot could fly a 500pt pattern with one, but I would suggest that if you get to a point where you are trying to refine you pattern skills, move to a plane like the oriental profile, cardinal profile, or twister/banshee type that can be made to fly "pattern friendly" lap times without such severe speed-induced control response changes.

FWIW-- I'm sure many will suggest otherwise.

BTW-- the streak is a FUN plan to fly, and I sure dont want anyone to take my comments otherwise.

I'll second that. Since the demise of my Smoothie, I've been flying a Flite Streak I first built in 2001, and have rebuilt 3 times now. Just this past week, I've put almost 30 flights on it, and I'm having a blast. The tank is too small, so I only get 3 minute flights, so I'm not making a whole lot of progress, but I AM having fun! I have a larger tank on order, can't wait!

Tim

I think there is something wrong with the model and/or your choice of powerplant.

The ARF Flite Streaks I am flying, that I loan out at contests, do not suffer these problems, nor will some of the suggestions made here be to your advantage.

Balance point is a biggie, I begin at 1.5" back from leading edge. This can be moved further to the rear, but I advise caution. What has worked well for me is moving balance point rearward while also reducing line spacing at the handle.

You may have a misalignment problem. Worth checking.

You may have stiction in your control system. Again, worth checking.

As to the motor, my first ARF was hugely improved when switching from a self- and Stunt-tuned 25FP to a *very* similar motor which is just under a 21, just over a 19, and which I am no longer allowed to mention on this forum. (Full instructions, along with heated discussion, on an old thread.)

The performance is there, it's up to you to bring it out.

Next Bad Boy Stunt column in Stunt News will have pictures and never-ending "captions" which may be of interest. The only "new" news is that my Super Combat Streak--completely stock airframe, including stabilizer and elevator areas--described in forthcoming article used to win Classic Stunt at recent VGMC Western Canada Stunt Championships. "Thank you very much," spoken in a deep Southern drawl is an inside poke/joke which applies quite nicely.

Mike,

I couldn't disagree more. I understand the ARF FS is a lowly lil' critter, but if you were to fly mine, the claim that one can take a properly sorted, properly powered profile ARF to the top of Advanced PA in any and all local contests would seem pretty reasonable.

Your friend's model is not indicative of what can be done here. Trust me.

I understand and kind of supported your input saying that, in the proper hands, the streak can be made to fly as well as any. But in this case, the hands are everything!

I always am amazed at how well my old planes fly after just letting them sit around for a couple of years!

I was NOT impressed with how the airplane flew, but I assure you that it was NOT sensetive, was NOT twitchy, and responded very slowly to handle wiggling on my part. A LOT like a big .60 stunter, but without the line tension. The handle used was a GMA Magnum, with cables. I had been flying with Tom Morris' hard point handles for a couple of years, so that was somewhat of a shock.

Don't be selling the FS short. I built my first FS Jr. when I was in Jr. High, but widened the elevator. It flew quite well, I thought. After my 9th grade, I built a new one, stock, did a much nicer job on it, same Fox steel fin .15, and could barely fly it. I later came to the conclusion that the stabalizer was probably at negative incidence. Steve

However, a clean exit is one of the hardest things to do well, which is why good squares are hard - 4 exits per loop.

I reckon you might see a dramatic improvement at the end of the next 5 gallons of fuel...... a comfortable handle will help too. The "white knuckle grip of death" on the handle won't help at all - relax! Dont forget - the airplane wants to fly straight, its the hand on the handle thats making it move around - An old flying instructors joke/demonstration - "take your hand off the stick, fold your arms - see, the airplane flies just fine without interference from you!"

Hope this helps,
Cheers, Dave

One thing to bear in mind - the Flite Streak is among the most sensitive of any common model to the CG position. You may, while adjusting it, be making too large a change, and jumping from too slow to too fast and never hitting the sweet spot.

>There are four variables to mess with: 1)CG, 2)elevator
>throw adjusted at the elevator control horn, 3)sensitivity
>adjusted by line spacing at the handle, and 4)speed (higher
>speed would make the elevator more effective). What is the
>best sequence to adjust them? Or how do you trade them off
>against each other?
>

I would set the CG and handle spacing, and leave the elevator horn in some intermediate position- furthest-out hole that you can still get about +-40 degrees. You probably won't need that much, but you can dial it down with the handle. The longer the horn, the less slop, of course.

I would start with the CG at around 15% of the average chord, and only move it if it just won't turn at the beginning of the flight with full elevator motion. It gets noticably more sensitive as the flight goes on because the fuel running out changed the CG. And when you do adjust the CG, to it a little bit at a time. I wouldn't recommend any more than 1/4 oz at a time on the tail, and preferably less. It's touchy!

But I emphasize, the 15% CG is pretty well established - may not result in absolutely optimum performance, but it certainly will work! Move it from there only as an absolutely last result.

As for airspeed, it's not going to want to chug around at 5.5 laps. You want it to be going maybe 4.6-4.8 second laps on 60-62 foot lines. You didn't mention the engine/prop, but it doesn't want to have significant speed variations. I;ve seen cases where too much speed variation causes a small version of what you are talking about - a turn first slows the airplane, desensitizing the controls briefly, then the engine picks up to recover the speed, and it suddenly tightens up. I would suspect this is not really your problem, but somethign to bear in mingt.

>Another related question is about a "dead spot" around
>neutral. Even in level flight the airplane will "wander".
>And small amounts of elevator have no effect until abruptly
>there is a bit too much and the airplane "twitches" off in
>the other direction. This is a real problem in the simple
>wing over: if the flight path is not right going up hill, I
>can't make small corrections across the top.
>

Obvious question first - *is* there some slop? Hold the leadouts and see if you can move the elevator. If there's any free play, you have your answer. This is actually pretty likely if you used the stock controls - and it could easily cause the other problem, too. Solution tedious but obvious.

Other things to check -

stabilizer solidly attached and reasonably stiff? If not, it may be deflecting under load and altering your control input.

engine mounted with up or downthrust? Up, in particular, can make the the airplane very difficult to handle.

any binding in the controls?

general trim? too much, or not enough, tip weight, too much rudder, too much engine offset? If you really are just starting, the trim could be off enough to cause a problem, and you may not have the experience to tell

I note from your profile, you live in Houston. Go out to the local field and seek out the numerous top gun pilots. Chances are, there's either nothing much wrong but you can't separate flying skill and adjustment, or there's some straightforward and obvious (to someone with a lot of experience) problem that may be fixable in short order.

I think it's very safe to say there is nothing in the design itself that would cause this. Too many of them have been flying nice and stably for the last 45 years for there to be anything fundamentally wrong with it.

Details are *everything* in this event.

Thanks to all who chimed in here with help and especially to the good folks at Scobbe Field! There is nothing better than real time help.

I posted the question here because this forum is a great palce to get a multitude of responses. Some of it unique. I thought that perhaps other beginners were going through this same very basic pitch trimming process and the answers posted would be enlightening.

I flew yesterday evening in a field that I thought would not attract attention. I got two flights before the local gendarmes told me to go somewhere else.

But it turns out my biggest problem was trying to fly too slow. Lap times in the 5.2 second range. I went to a higher pitch prop, lap times went down to 4.8 +/- a bit and everything worked better except my reflexes

Steve

Harumph! Harumph! I must come to the defense of my poor ol' "demo" ARF Flite Streak, especially as it is the very best CL Stunt model Steve has flown in a whole year.

The GMA Magnum handle is a problem, at least for those of us who have become accustomed to hard-point handles. But the ease with which said handle can be adjusted, plus both model and handle designed by GMA, means it stays. Without apology.

As to the motor, it was on its last legs, weak sister of four used, uh, PF02s purchased from Mike Conner. Pumping it up with 15% and 20% fuel kinda worked for a few weeks, but still with a tendency to be a little too rich at beginning of flight, only coming on song about time for inside squares. And then going roaring lean at end of tank.

Discovering left thrust at the engine was a real shock. Several had mentioned light tension, apologies to all, but it wasn't until Pat Willcox said something that I took the input seriously. Even so, the model never went free-flighting off on anybody...

Grand-urchin Mateo just showed up--to be continued.

...nor did it exhibit any weird characteristics. I rarely fly this model myself, and from outside the circle never saw any line-tension issues. Well, less numerous times Preston Briggs insisted on flying maneuvers into the wind. (Flying AMA Combat models fitted with a Nelsoni 36 tends to make one optimistic as to line-tension issues.)

The day before VGMC contest in Vancouver, B.C., a new piston/cylinder set went in, .010 shims straightened the thrust up nicely. Friday I ran four 3-ounce tanks of SIG 10% through engine on the ground.

Saturday Neil Rodgers flew model in Classic, this following one practice flight and going in a click on the O.S. remote NVA. Neil had no problems at all, at least none of which he mentioned to me.

Give 'er another try, Steve-O...!

Incidentally, this model intentionally balanced 1.5" from leading edge. It is a little nose-heavy for my tastes, but then again there is the non-adjustable line spacing at handle to worry about. Brett is correct as to sensitivity of design to balance point. In these quarters that is regarded as a good thing, as changes give definitive results, and one can go from there. Controls were of course slowed down at the 'crank and during assembly. In any case, trim has to suit a wide range of fliers.

Someone mentioned hinges, as in stock or otherwise. The "demo" model use MonoKote hinges; very free (in action), very free (in cost, as scraps from the floor are acceptable), total sealing of hinge line, ease of installation. And an excellent choice if converting assembled model from stock spring-back hinges.

Damage was surprisingly minimal. Cracked the fuse behind the wing, split the elevator at the control horn mount, shot the temporary ¼ oz. stick on tail weight through the outboard wing panel and took out one rib.

The greatest damage was to the sheeting/wing area where it mounts to the fuse. The impact had pulled the push rod (stock with supplied fairlead) loose from the horn. I had replaced the bell crank (new Brodak plastic) and replaced the lead-outs (bushed) per general consensus. The controls were frozen after the crash and inspection (nice hatch!) showed that the pushrod had been forced forward and curled to the leading edge of the wing. I don’t know if I can describe it, but the bell crank was almost 90 degrees around, broke out the outboard rib mid section and the front of 2 ribs while it was wrapping the push rod into a sort of semi circle. I got the rod pulled out and was very surprised how soft the metal was. I just easily bent it back to shape with my hands. No way was this quality wire. I should have noticed this on the assembly side of the deal.

Relevance to this thread…….the rod seems to be soft enough to limit control input even with the fairlead installed. Replaced it.

Best,

I had picked up the speed to about 4.8 seconds/lap and everything seemed good, flying well if a bit fast for my reflexes. It turned well, had good tension over head... I was even trying inside squares (looked more like lumpy "Ds". That straight down verticle is a real b&** clencher). On the second flight this evening it simply failed to turn out of a wingover. Full "up" just got a large smooth arc into terra firma. At this point I'm glad the nose was somewhat flimsey. It totally distructed and probably saved the engine.

I've got a Mike Pratt "Primay Force" that I'd been planning to graduate to after I was able to put together a beginner pattern sequence with the FS. I'm a little reluctant to take chances with this one since I was hoping to take it to a contest or two this fall... But if I "keep 'em high" it may live to make a contest or two this year.