How much is too much yaw

[RknRusty]

I searched Google and got a lot of engineering discussion, but nothing that clarified the answer for me.
I'm just now graduating from 1/2A sport flying, wild freestyle stunting, and am learning the ins and outs of my Shoestring. I rebuilt a badly wrecked Goldberg airframe that was given to me and after fighting fuel feed troubles, have finally got it flying out full tanks.

So, now that I've had some air time where I can think about other things besides coughing out and landing upside down, I notice two things that need attention. One, it yaws out enough that I can see the outboard wheel barely trailing the inboard wheel, looks like they're touching. Two, it's flying tip-high on the outboard wing.  I think the yaw saved my butt the other day when I started an  outside loop from normal flight and at the bottom, it went slack and straightened out and flew off inverted in the other direction. Between fancy foot stepping and luck I recovered it with a bodacious yank and kept flying. So maybe the amount of yaw I have helped save me. It flies outsiders from inverted perfectly tight. Regular inside loops are nice and tight too. I wanted to get some opinions from you guys about how much yaw-out is good and how much is a problem. As far as the tip-high condition, I'll add some weight. I'm flying on .015", 60' lines. With straight edges, calipers and my eyes, I can detect no warp in either wing. Regarding the yaw, I have 2 degree shims under the engine and some rudder offset as per the Goldberg plans.

Any advice about trimming a stunter like the Shoestring would be appreciated. I'm finding that they're a whole different machine from my beloved 1/2As.

Here is a video of my first successful excursion this past Thursday:


Thanks for any advice.
Rusty

[Dan McEntee]

   Hi Rusty;
     Looks like you have made some progress, it's a good feeling isn't it!!!?? Got some suggestions for you.
   1) Any changes you make from this point on, only do one thing at a time. That way you will be sure of what you have done and will know for sure what works and what didn't.
   2) Get the airplane as straight as you can, no warps, and wings and stabilizer level with each other, and square to the fuselage.
   3) If you can, get some help sighting the airplane in by having someone view from outside the circle. Fly level at 5 feet upright and inverted at the same level to see where the wings track. If the wing is constantly up or down in each direction, put a stiff aluminum tab about an inch wide and 2 or three inches long on the out board tip. You can tape it on, glue it on or cut a slit in the trailing edge and glue it there. It just needs to be stiff enough to hold a deflection that you put in it. Just a little at a time, then refly and check for wing tracking. Tip weight will be adjustable if the wing tip is down in both upright and inverted flight, or up in both modes.
   4) You can have too much outward yaw. Once you have the wing tracking, try removing some of the engine offset, again a little at a time. Take any rudder offset out  of it also. Make sure again that the horizontal stab is level with the wing and square to the fuselage.
   5) As you make progress and start doing more tricks, concentrate on flying smoothly. Get out of the habit of jerking the handle for control inputs. If you yank at the handle, you yank the whole airplane in towards yourself. Give smooth control inputs.
   6) Make sure your controls aren't too fast and deflecting too much. You only need about 40 degrees of travel and when flying a properly trimmed airplane of any kind, you never use all of that. Give it too much elevator too fast and you stall the model. Don't make loops too tight, use the whole sky. You can tighten them up as time goes by. Remember, the tops of most of the manuevers should be at 45 degrees or higher and bottoms between 4 and 6 feet. That's a lot of sky!
   7) Your engine run in the video sounded pretty good. I can't remember right now what you have for a prop but you must be in the ball park. You commented in the beginning about it not unloading, don't worry too much about that. It could be and you just don't hear it. A properly set up engine should go a bit rich once it is at full speed in flight and you add centrifugal force to the recipe. You are just interested in it doing it consistently. Your lap times looked to be in the 5.6 to 5.8 range, and that is fine. At this point in development, the stop watch will be a good tool. Time your engine runs with your wrist watch, and your lap times with a separate stop watch. Takes some practice but you'll learn. Or have some one else do it fro outside the circle. Always strive for consistency. Knowing how long you engine runs on a specific amount of fuel keeps you from running out of fuel at embarrassing times!
  You are in the ball park with the 60 foot line length. Line length is one of your tuning tools for lap times. So is the prop. The prop also helps with line tension. I think your engine is a Thunder Tiger .25? If it's like all the other .25 engines I have used, you can go up to 10" in diameter but no more than 4" of pitch. The APC 10-4 has been a real work horse for me. Take off ROMS with this prop should be in the 9500 to 10500 range and gives you more thrust without over loading the engine. A good hot glow plug is desirable also. Once you get the engine running sweetly, and your lap time are still too fast or too slow, speed the engine up or down to go the direction you want to go with the needle valve. If you have to make that adjustment too far for your liking, then longer or shorter lines are your next step. If the model is too fast, go to longer lines, maybe two feet or more, and carefully start the process over. I usually try to start out with lines a bit longer in the first place, and shorten them from there. It's easier to shorten lines, and no one has invented a line stretcher yet!!! Keep the words "one step at a time" in mind during this whole process.
   I like the look of your airplane, gotta build me a Shoestring one of these days also. Some people credit the Goldberg Shoestring with saving the company for Carl Goldberg at that time in history and keeping him in business. It's a decent airplane for what you are using it for and if competition is in your plans, it will get you through the beginner class and maybe into intermediate. The main thing is to do just what you are doing, having fun and making progress! Keep it up!
    Good luck and have fun,
    Dan McEntee

[Larry Fernandez]

Dan has given you a lot of good advice here, especially the part about getting rid of rudder and engine offset.
Does the plane have adjustable leadouts? Proper lead-out placement is used to set the flight path tanget to the lines.

Larry, Buttafucco Stunt Team

[Dan McEntee]

  Yeah, I forgot about lead outs. The older designs had them fixed and usually can be mover forward quite a bit. Sometime when you think you need more line tension and want to move them back, moving them forward slightly is the answer. If you can move them, I think the rul of thumb is between 1/2 and 1" behind the balance point as a good starting point. anything else would be excessive and let you see the wheels as you describe.
   In an issue of Flying Models Magazine, Paul Walker has his Impact NATS winning stunt model published with a flow chart for trimming airplanes, and that chart should be in everyone's tool box. I'll see if I can dig that out, or maybe one of the guys that has it and is a lot better at the computer than I am wil post it.
   Keep us posted on your progress,
     Dan McEntee

[RknRusty]

Thanks for the replies, that was a lot of good information. I'll get a chance to re-read it more closely and digest it later tonight. And I'll answer some of the questions Dan asked. The leadouts are not adjustable. The line tension is very tight while it's burning circles. A good bit less, but still tight enough when it's sputtering around during the rich runs. It took me a couple of flights in that video to learn to trust it.  In fact, after that emergency yank I gave it the other day, I'm considering rewiring them with stronger wire. Being an old 1/2A guy, I underestimated the pull and only used 45# test, 7 strand black plastic coated steel leader wire from the fishing store. They are crimped properly.

And I do have to get away from my habits of jerking the plane around like I do the little ones. A couple of my favorite planes are a pair if Baby Flite Streaks, one of which is 7.2 ounces with a Norvel .061, and I just murder the sky with it. All of my little ones are bladder fed, so the hard tank on the SS has caused me plenty of headaches. Ken Cook and Mark Boesen, if y'all know them, have been a great help working me through that.

Thanks for the help, be back later,
Rusty

[Dan McEntee]

 Hi Rusty;
    That model won't pull your arm off, but should have a good firm line tension. As you work through the trimming process, you'll feel an improvement. And upgrading those lead outs is a good idea. I usually use 1/32" music wire or the larger cable kit that Sullivan sells in most models, even small ones.
   Old habits are hard to break, but they will show up more with the larger airplanes, you just gotta work through it. It will pay off in the end.
  Good luck and have fun,
    Dan McEntee
   
   PS:  Just to add, your lap times, or model speed, will affect your line tension and tracking also. From what I could tell in your video, you were almost 6 seconds, and that is pretty slow, but the model seemed to pull OK for that speed. Just a few hundred RPM more on that engine will pick up your speed some and increase line tension, and try to shoot for 5.3 to 5.6 lap times. Being consistent in this area will help you develop a rhythm that you will find comfortable and help your confidence.

[john e. holliday]

Rusty, while you are relaxing back home at the computer from all that flying.   Go to the Search box at the top of the forum.   Type in Trimming and spend the next couple of hours reading.  In there somewhere is the trimming chart for the planes.

If you do the search look for "Paul Walker's Trimming Guide".   Finally figured out how to do it.

[Allan Perret]

Hey Rusty: Great video, love the captions and commentary.  I am jealous of that fantastic flying site you have there, and don't know that I've ever seen a prettier blue sky.  Private property ?  Where you located ?  I wanna come play in your back yard. 

I agree with getting rid of rudder offset and most of engine offset.  One washer max under front engine screws.  Would be good to retro fit adjustable leadouts.  Include that for sure on all future stunt birds.

Here's my input.  You seem to be flying maneuvers nearly all around the circle.  Not good.  Do all stunts straight downwind.  (2 exceptions are wingover and overhead 8's, start those directly upwind).  I think the time you lost it was a combination of starting partially upwing and flying the loops too tight, open them up a little.

[RknRusty]

You guys are great Thanks. I put on a 1/2A exhibition this afternoon for the neighborhood and then settled down for beers. So I better not to try and sound too intelligent right now, so I'll just toss in a couple of comments.

I knew someone was going to notice my wandering stunts. The wind was jumping around from every direction. When I do a wingover I start with the wind in my face. When I do loops I have the wind at my back. It was a very turbulent unpredictable day and I had to pay close attention and check the wind on every lap. I think I missed one really bad and almost lost the plane, but I managed to guess right most of the time. One good thing about my baby plane experience is I'm used to flying what I lovingly like to call "controlled panic."

In the video, I'm flying the SS at my club field. Jackson Flyers Association is a field we have leased for several decades at Fort Jackson, SC in Columbia. I'm a newbie there. I joined the day after I hit an oak branch last August after lengthening my lines to 40' on my Baby Streak(that flight is the feature video on my Tube channel). I was outgrowing the church courtyard across from my house. Sometimes I fly for the kindergarteners and the pastor thinks it's really cool. But a boy has to grow. I can still cram it in if I put an APC 6x2 on the Norvel with 35'. That's what I flew today. On the weekdays I can fly on the main runway, which is nicely manicured. The CL circle has a helluva slope on one side. The trees break the wind better, but I'm dangerously close to the ground if I fly level over the rise. I think it's about 4' higher than the downside. Fine for my babies, but not so good for the SS. On the weekends, they are fascinated with my CL antics, because they've all forgotten about how to have real fun with a plane. They take a break from yawning and flying 3 mistakes high, to wander over and watch me fly 3 second laps, 1/100th of a second from destruction. But the SS only gets to play during the weekdays when nobody is there with their big fat ARFs.

Since I'm used to being a speed demon, I was thinking I would like to fly the SS at 4.5 seconds in the flats. That might be unrealistic, but I'm going to start taking a note pad and writing down what happens with different props, needle settings, etc. 5 seconds is probably acceptable. The Thunder Tiger won't do a pretty 4-stroke like a Fox, but it seems cooperate well enough. If I hit the right combination I can settle on a good compromise. I might need to shim the back of my tank out a bit if I keep flying with that yaw.

I took a quick look at Paul Walker's Trimming Guide and will study it over coffee in the morning. I have some trusted advisers at my other forums, but I'm glad I found Stunthanger where the knowledge runs deep. I just wish I knew how to build planes as pretty as yours.

Now, maybe it's just the beer talking, but I'd like to show you my fleet. So here it is, my favorite go-to flyers:

Baby Streak I, Tee Dee .051, bladder fed. (the babies are all bladder fed)


BFS II Bottom right, Norvel .061(my bath mat wing stooge to the left)


Li'l Satan, Tee Dee .049


Refried Bean, Norvel .061


You all know the Shoestring, Thunder Tiger .25


See y'all in the morning... oh, damn, it is morning.
Rusty

[Allan Perret]

For the SS/ThunderTiger25,  laps of 5.0 sec is good.  
When and if you move up to 40 or bigger size planes,  5.2~5.3 is better.  
Gives you more time to think..

I have a 1/2a Pathfinder/Norvell.061.  Fly it on .08 x 45' lines with that APC6-2. 
I think it would handle up to 48' lines on calm day.

[RknRusty]

For the SS/ThunderTiger25,  laps of 5.0 sec is good.  
When and if you move up to 40 or bigger size planes,  5.2~5.3 is better.  
Gives you more time to think..

I have a 1/2a Pathfinder/Norvell.061.  Fly it on .08 x 45' lines with that APC6-2. 
I think it would handle up to 48' lines on calm day.

When I fly the Norvel/Streak at the club field, I use a 5.5x3 or a 5.75x3 Master Airscrew, on 45' Spiderwire lines. The Tee Dee/Streak, I fly with a 5.25x3 MA prop. The Refried Bean folded its outboard wing flying on a 5.5x3. It's on my fix list. That one weighs less than 7 ounces and really sets the circle on fire.
I like the Master Airscrew props for my general purpose workhorses. I've been meaning to tinker with my assortment of APCs but haven't really gotten around to it since I'm happy with what's working now.

[Howard Rush]

  If the wing is constantly up or down in each direction, put a stiff aluminum tab about an inch wide and 2 or three inches long on the out board tip. You can tape it on, glue it on or cut a slit in the trailing edge and glue it there. It just needs to be stiff enough to hold a deflection that you put in it. Just a little at a time, then refly and check for wing tracking.

This is advice I'd disagree with.  Countering a wing warp with a trim tab will give you an airplane that will misbehave in anything but gentle maneuvers.  That particular wing structure is easy to warp with covering, but it's also easy to get the warp out by bending it while heating the covering. 

[john e. holliday]

And what do you do when using sticks/rods, eyeballs and other people you can't find a warp.   Even the stab is on straight in all directions.   I had a ARF Flite Streak that flew with the wing down when flying level and wing up inverted.   There was a coke can modification added to it by my flying partner at the time as he kept thing it was going to come in at me during maneuvers.   Never had slack lines during a pattern the whole time.   The coke can material made the wings fly level, but I didn't notice any change in the flying aspect of it.   I have even had other planes in which I had to do a trim tab to get wings level.

[RknRusty]

Other than a quick late Saturday exhibition in the church yard for the neighbors, I haven't had time to think about planes this weekend.
This one flies with the outboard tip high, both inverted and right side up. Before the next time I head out to the field, I'll double check to see that everything on the plane is still straight, and take some extra weight for the outboard wing tip. And some aluminum in case I try a tab. I'll try to set the camera so I can fly low straight at it and get a better picture of what it looks like. Or if I'm lucky, maybe a real live person to watch it fly. That's not likely though. I'll try not to hit the camera.

[Reptoid]

If the outboard is high both upright and inverted, you need more tip weight, not a trim tab. .

[Dennis Toth]

Great video, a couple comments. Watch the number of inside loops you do without unwinding with outsides. You don't want to do more than 6 - 7 or the lines will start to drag and be hard to maintain solid control. Second, on the yaw, hang the ship from the leadouts, it should be a couple degrees nose down. The rule of tumb is start with the leadouts on a light ship (say under 45 oz) 5/8" behind the GC at the tip, for a bigger ship start 3/4". Lap time on 60' lines should be around 5.0 sec. At 5.6 that you seemed to be flying it will be pretty soft on the lines and easily blow out of maneuvers.

You didn't mention the fuel you were using but make sure the oil content is at least 22 - 24% oil and a blend of castor and syn.

Lastly, know you flight time, many, many planes have been lost by fliers doing vertical or outside maneuvers near the end of the tank.

Best,        DennisT

[Dan McEntee]

This is advice I'd disagree with.  Countering a wing warp with a trim tab will give you an airplane that will misbehave in anything but gentle maneuvers.  That particular wing structure is easy to warp with covering, but it's also easy to get the warp out by bending it while heating the covering. 

    "2) Get the airplane as straight as you can, no warps, and wings and stabilizer level with each other, and square to the fuselage.
   3) If you can, get some help sighting the airplane in by having someone view from outside the circle. Fly level at 5 feet upright and inverted at the same level to see where the wings track. If the wing is constantly up or down in each direction, put a stiff aluminum tab about an inch wide and 2 or three inches long on the out board tip. You can tape it on, glue it on or cut a slit in the trailing edge and glue it there. It just needs to be stiff enough to hold a deflection that you put in it. Just a little at a time, then refly and check for wing tracking. Tip weight will be adjustable if the wing tip is down in both upright and inverted flight, or up in both modes."

   Hi Howard;
    Here is the whole quote, note step #2, and the first part of step #3 before I mention the tab. I don't necessarily rush to add tabs to a model if I can get it straight, and Rusty had already tried to cure a problem by inducing a new warp which made things worse. It's very hard to make a precise warp! Again, I prefer not to use tabs, but as in Doc's case, I also have had models that appear to be straight, but still didn't track correctly and I cured the problem with a small tab. If I have to, I prefer a tab because the effect is more subtle and you can be more precise with the adjustment. I usually mount them with strong tape, so they can be removed if necessary and/or repaired/replaced. Sometimes you just gotta do what you gotta do! And an extra set of eyes from outside the circle is best to help confirm what you think you may be seeing at the handle.
  Have a safe Memorial Day,
   Dan McEntee
   

[Tim Wescott]

If the outboard is high both upright and inverted, you need more tip weight, not a trim tab. .

Yup.  And too much tip weight is a much more comfortable place to start than too little.  Hinging is unsightly and makes your airplane jerk around weirdly in the square maneuvers and it really helps to keep the line tension in the overheads where you desperately need it...

If you mess with the leadouts consider making them adjustable.  If the cutouts aren't there in the ribs it may not be worth it unless you're stripping the covering, too -- but adjustable leadouts are a big help.

[phil c]

Nice job on the ShoeString Rusty.  The only thing I really noticed was that it only went out of control on a couple outside loops.  That indicates that the plane has a right roll in level flight, since it does fine on inside loops.  So I'd warp it to roll a little bit left- left tip TE up and the right tip TE down.  Maybe 1/16 in. at first, more if it continues to come in on outsides.

It doesn't matter what the plane looks like.  Warps can be very hard to see, and harder to measure.  So go by what the plane does.  If it gets light or comes in on insides it is rolling left.  If it gets light or comes in on outsides it is rolling left.  It's best to start with some large lazy eights- inside loop on the left, outside on the right, so the plane is turning away from the ground.  Makes it easier to catch if something is badly wrong.  If it seems to come in one way, correct the warp a bit and try again.  Gradually tighten up the eights, fixing the warp as needed.  When it can turn tightly both ways try two or three loops in a row.  Multiple loops and tight loops will emphasize any remaining warps.

Wing tabs can work if the wing won't take or can't hold straight when it's twisted and ironed(works on anything but a fully sheeted wing).  Using a tab puts a big discontinuity in the wing, so it may act funny when a gust hits it or you hit the wind a bit wrong.

Once the plane is reasonably straight, go on to all the other things, rudder, engine offsets, tip weight, leadout position, etc.

One other thing, hitting the wind right makes a big difference.  Doing outsides too far to the left into the wind, or insides too far to the right will make the plane glitch about 3/4 of the way around the loop, as it comes into the wind.

Phil C

[Mark Scarborough]

No mention has been made of where you do manuevers,, if you do your tricks in the wrong place,, carnage will ensue,, so, make sure you are aware of the wind, and use it to help keep lines tight,, in other words fly tricks with the wind at your back,,

[RknRusty]

Mark, look at post #8 in the second paragraph where I talked about the changing gusts while I was flying that day.
Phil, Thanks for the good tip on the lazy 8s. I'll definitely try that. when I get it in the air next time.

I've been taking all of you guy's generous advice for a few days, and have contributed nothing helpful to the discussion. I tinkered in the shop today, looking at the angle it hangs from the leadouts. It's hanging from the lines nearly 2" nose down. Then I got sidetracked by a leaky Norvel venturi and have nothing new to offer for now. But, weather permitting, I'll probably get out to the field with the SS on Thursday and try some of these suggestions and post back with a flight report.

Regarding the fuel; Someone suggested I use 22-24% castor. I first started with Sig Champion 10%/20% and was fighting uniflow problems. No foam, but the feed tube was sucking up a steady stream of bubbles crossing over from the uni vent. Impossible to set the needle, and running away lean after launch, causing it to die in the loops. I tried repositioning the tank, more padding, anti-foam juice, a filter, and had no results. I ordered some Sig Champion 15%/20% since the thunder Tiger manual said I could use up to 15% nitromethane and had the same results. I switched to normally vented and got much better results, which was the video from Thursday I posted here. I may get a more cooperative 4-2-4 with more castor, but I'm not sure this ABN ball bearing .25 is going to ever make a pretty break like a Fox does. But more castor might help keep it from heating up and leaning out. I'll add some to my next batch. I'm learning quickly I need to buy gallons instead of quarts.

Hopefully this week I'll have some useful information to give back to everyone who's helping me out.
Thanks,
Rusty

[Howard Rush]

I tinkered in the shop today, looking at the angle it hangs from the leadouts. It's hanging from the lines nearly 2" nose down.

That might be OK.  See http://www.tulsacl.com/Linelll.html

[Randy Powell]

Howard doesn't yaw. He pitches.

[Howard Rush]

And what do you do when using sticks/rods, eyeballs and other people you can't find a warp.   Even the stab is on straight in all directions.   I had a ARF Flite Streak that flew with the wing down when flying level and wing up inverted.   There was a coke can modification added to it by my flying partner at the time as he kept thing it was going to come in at me during maneuvers.   Never had slack lines during a pattern the whole time.   The coke can material made the wings fly level, but I didn't notice any change in the flying aspect of it.   I have even had other planes in which I had to do a trim tab to get wings level.

And when you have a flat tire on your car, I presume that you let the air out of the tire on the other side.  I have explained why dewarping is different from adding a tab, but it's "engineering discussion" that neither you nor Rusty want to hear.  You are intuiting that the lift curve slope is a straight line, in which case a trim tab would counter a warp at any amount of lift.  It ain't.  Adding a tab is easy, and suffices if you have sufficiently low standards, but even sport flying is more enjoyable with a reasonably well trimmed airplane.  

The process I use is to look at the wing from directly behind.  You can see if the TE is centered along the wing.  Once you have gotten it centered, fly it and see if it flies banked one way or the other.  If it does, you know which way to twist the wing, and you can usually see where the problem is by taking a more careful look at the back of the wing.  The object is to get the plane flying level while keeping the wing as straight as possible.  Having balancing warps in the wing is almost as bad as countering a warp with a trim tab.  

[Mark Scarborough]

Howard,
speaking of,, good eyes looking at my profile when you intended to be practicing instead of looking at my PP ( Dirty Dan speak for Pukey Profile)

which lead to discovery of an asymmetrical situation with the tail hinge-line, and to add insult , a small amount of in thrust was detected,, the last two discovered by the guys who came over to see what that "cool model " was,, whence upon I started complaining about the bizarre gyrations it made,, mind you it flew "balanced" in level flight,, all the nasties neatly masked each other,, until you started to attempt more than casual maneuvers at which time it would get ,, well,, strange, comes to mind,, then all these "admiring helpfulls proceeded to show my what I had missed,, sigh,, 

my point is,, it would appear to fly decent and then all the stuff would show its head and the thing would NOT be fun to fly, even casual stunts seemed to cause accelerated heart rates,,
correct the problem , dont mask it like Howard suggests ,

[RknRusty]

...which lead to discovery of an asymmetrical situation with the tail hinge-line, and to add insult , a small amount of in thrust was detected,, the last two discovered by the guys who came over to see what that "cool model " was,, ...

  I hope the brief embarrassment was worth the straight model in the end. As much as I would hate my oversights being exposed by the club goofball, I'd take it.

Weather forecast for Thursday is 90f and 5mph, so it's looking good for some more test flights.

[Steve Helmick]

Another point. You don't have to use .015" braided lines, when .012" braids are perfectly legal. Someone will no doubt complain that they will stretch more than .015's. But you may not notice that, and a typical cable handle will be far more detrimental than the stretch of .012" lines. 

I am more concerned with the multitude of inside loops and not enough outside loops to unwind the line twist. Get the wings level first. Since you are flying inverted, you're just a short step from flying the Beginner's Pattern. Two benefits of flying any of the patterns is that you'll keep your line twists minimal and predictable, and also you'll know when you're close to running dry on fuel...extending the life of your plane, generally.

If you setup your plane with the fuselage level, then you could put a couple of strips of tape on it to use as a visual yaw reference. One on the inboard wingtip, and one on the fuselage, inline, while fuselage is level. From the first flight (too slow!), and the way the engine burped awhile before quitting, I'd say to remove the rudder offset, and perhaps cut the engine offset to 1 degree.  I like a little right thrust, because it helps get the lines tight quicker, for when they do go slack. 

LOTS of performance in props! Experiment with APC's and Thunder Tiger Cyclone props. They generally work extremely well. The 9.5 x 4.5 APC might be a good bet for your .25...not so easy to find, tho.    Steve

[RknRusty]

Ah, a timely reply, Steve, as I was just about to log into Sig and buy fuel and a fresh set of lines. The ones I have are old ones given to me, and they seem a bit grubby. I think I'll try the .012".

You are quite right, I have been winding my lines up too much. I am going to make myself start working on the beginner pattern, or at least counting loops. Other than squares and overhead 8s, there is nothing in the beginner pattern I haven't done with my 1/2As while freestyling, but haven't necessarily entered and exited them correctly. I do overhead loops(circles) frequently, so learning an overhead 8 should follow without too much trouble. And I tend to fly laps too high rather than head high. I have a ways to go, but now that I'm getting it trimmed I can concentrate on those things.

I was hoping for a Thursday excursion, but me Mum called and wants to visit that morning. I could have said no, but at her age, you just never know when the last time you might see them could be, so I'll graciously postpone it. The upside is that Sunday, others will be at the field and I can recruit a spotter. I just won't be able to use the main runway, and the CL circle is 4' higher on one side, usually the downwind side.

Now here's a noob question that's bound to make eyes roll at me: Never having flown a big one, I underestimated the pull and used leadout wire that has me a bit concerned. It's 7 strand steel fishing leader, coated in black plastic. It is crimped properly, but it's 45# test. I'm wondering if I should be in a hurry to replace it with some heavier stuff.

Rusty

[Dan McEntee]

  Depending on what your model weighs, a proper pull test with a .25 shouldn't be more than 25 to 30 pounds. Again, this depends on the weight of the model. So I think you are safe with two, 45 pound test lead outs, as this model probably doesn't pull a whole lot anyway. Just keep and eye on them, and change them at the first opportunity if you still feel iffy about them.
  As to line diameter, I still use .015" for my .25 size airplanes. I don't feel that they impede the flight of the model any, have a good feel to me, and are a bit more durable. I just try to keep them clean. Run up and down the lines when they are rolled out witha paper towel soaked in a solvent of some kind. You WILL be amazed and the crud that comes out of them and you can tell the difference tyhe next time you fly with them.
  Good luck and have fun,
    Dan McEntee

[Howard Rush]

I underestimated the pull and used leadout wire that has me a bit concerned. It's 7 strand steel fishing leader, coated in black plastic. It is crimped properly, but it's 45# test. I'm wondering if I should be in a hurry to replace it with some heavier stuff.

Plastic leadout coating has been known to snag on metal leadout guides. 

[RknRusty]

The plane weighs 30 ounces. I'll keep an eye on the coated leadouts for snagging. I inspect the visible crimped ends every time I fly. If I have any more hard yanks like the one last week when it got loose, I'll perform the surgery and replace them. I just ordered some new Sig .012" x 70' lines. I'll rig them up so it's 60' from the bellcrank to the handle. I haven't bothered to measure my current set, but the Sig package says 60'. I was given a set of Sullivan lines that I use one of for my stooge pin, and even though it says 60', it's 5' shorter than my flying lines. Now that I think about it, that might be good to hack up and make leadouts with.

[john e. holliday]

I tried .012 cable when it became legal to use.   After a few flights went back to .015 cable and been happy ever since.   Even using .018 on the .46 size planes.

[RknRusty]

I took the Shoestring out to field Sunday, and by a stroke of luck the club President had brought his old control line buddy, a guy with a lot of precision stunt experience. I was just rigging up when they drove up, so he asked me to bring it up to the RC runway to fly. He had friends coming and wanted them to see some CL flying, a rare but fascinating sight at this club. I'm usually a loner out there. So finally I had someone who could spot for me, get lap times and run times, and offer me some much needed advice and critique.

I had a few props to try and needed to get some experienced eyes on the yaw and tilt as it flew. As it turns out, it is flying level and the yaw is only slight, about right. I had my tach and notepad to keep track of launch RPMs and write down notes about engine performance. I started with my Master Airscrew 9x5 since it had given my best runs so far, but slow laps. The best runs I got with the MA prop were launched at 11,600 RPMs, flew 5.6 second laps and consistently broke rich-lean-rich( probably as close to 4-2-4 as this Thunder Tiger will do). I think 5.6 is slower than I want, but it was pretty breezy and the lines were comfortably tight even on the upwind side.

I had an APC 9x5, same as the MA, and thought maybe it would give me faster laps. It's first launch was also at 11,600 and it was turning 5.2 second laps. Noticeably faster and tighter and I was happy with that until 2:00 into the flight when the engine broke screaming lean and rocketed around the circle. I thought that was awful soon to be running out of gas and I waited for it to cut off. And waited, and waited, turning circles, risking a loop now and then until it finally shut down at the 6:25 mark. I thought maybe the heavier APC was causing the engine to heat up too much to maintain a rich run. So I launched it again, richer at 11,100 RPMs. This time it was turning 5.4 second laps, which was acceptable, but I didn't like the sound of the engine at that RPM(hard to explain, it just wasn't a confident sound), and it leaned out again at the 2:00 mark and continued screaming until it shut off at the 3:45 second mark.

I had some other props, but since I was helping pit for the other CL flyer, and this had basically turned into a fun exhibition, I didn't try my Top Flite wood 9x6. And I ditched the idea of the APC 9x6 and the TF 10x4. I'm pretty sure they were out of range now. I'm close with the MA 9x5, just a little slow in the flat laps. I was using 60' lines. I have a new set of lines to rig up, and I might cut them to 58' as suggested, which might get me the lap times I want. The engine performs well with it. Or maybe I could add some castor to try and keep it rich for a full run with the APC, but I'm only guessing at what's happening with the engine going lean. I like the idea of sticking with the MA 9x5 and shortening lines best.

So, I'm getting there. In between fiddling with props and times, I tried to fly some stunts like they're meant to be flown. I flew huge loops from head high, 2 or 3 at a time. Not really keeping them in the same groove though, so I'll need to work on that. I kept track of the loop count and flew outsiders to unwind the lines, but hey weren't even as symmetrical as the insiders. No true figure 8s, but plenty of lazy 8's. I don't recall ever having to step back to keep tension, but they tend to grow larger causing me to bail after about three. And I did lots of wingovers, and really greased some snappy pullouts without wavering too much at all leveling off. Watching my flying companion, he eases out of wingovers, maybe because he had some nose heavy CG problems. I don't know how tight pullouts would affect a contest judge, but maybe that's another one of my 1/2A habits I need to iron out. He did tell me that I was not straight overhead, so I need to work on that too. I was nowhere near brave enough to try overhead 8s, but I did do a couple of quick overhead loops.

But best of all, I had a huge amount of fun and enjoyed the enthusiastic approval of the onlookers. I woke up this morning still grinning with a fun hangover. I had the camera, but used it all up videoing our early morning 1/2A antics trying to teach my friend how to fly one of my Baby Streaks. Not so successfully yet, but he's determined. And I did nothing that isn't already on the Tube.

And as to the original question of how much yaw is too much... well apparently it's a non issue. Sorry about that. Next time I have a question about a problem, I'll try to make sure I really have one.

Rusty

[Steve Helmick]

Master Airscrew props (most or all of them) are lower pitch than stated, thus less load. APC's are pretty accurate, but are a lot of load, due to their thick root airfoil, it is supposed. Try the 9-4 APC, especially on a relatively low-time engine. The leaning out is probably due to heat/overload, and commonly referred to as "runaway". As the engine becomes thoroughly run-in, experiment with the 9.5 x 4.5 and 10-4 APCs. More castor oil might help with the runaway, as may a bigger muffler outlet, a bigger venturi, and even more nitro. Less data is available for the TT .25, because they are far outnumbered by OS .25LA's and FP's. Not to say they aren't as good or perhaps even better.  Steve