Sequence for trimming

[tom brightbill]

Being a bottom feeder, I'd like to ask what is the recommended order for trimming a new plane.  Assuming perimeters are in the ballpark enough to get a safe initial flight, do I want to work with the airframe first (balance, flap twist, etc), or engine run, or line/handle adjustments.  Understanding that they all interrelate, if there was a flow chart for beginners it would be greatly appreciated! I know this is asking for a lot of work from others.  I promise not to delete your help. Thanks.

[David_Stack]

Good Afternoon Tom;

  Paul Walker worked up a flow-chart on trimming.  See the following post, where it is provided as an attachment...

  http://stunthanger.com/smf/index.php?topic=27095.msg261749#msg261749

r/
Dave

[Mark Scarborough]

There is also rumoured to be an upcoming article or several on trimming in Stunt News

[tom brightbill]

Thanks Dave.

[Tim Wescott]

Good Afternoon Tom;

  Paul Walker worked up a flow-chart on trimming.  See the following post, where it is provided as an attachment...

  http://stunthanger.com/smf/index.php?topic=27095.msg261749#msg261749

r/
Dave

Tom and I were talking about this at our mid-week flying session.  His question wasn't so much about trimming the airframe itself, but given a new airframe, a new motor, etc., do you get the motor run all tweaked in before you even think about making airframe adjustments, do you get the motor run sorta-kinda good then flog the airframe into perfection before you go back to the motor run, etc.

[Russell Shaffer]

Advice from Dirty Dan - Get the engine running reliably first.  If it quits in the wrong place you have a problem.  He was watching me beat up an airplane at the time. 

[Steve Helmick]

Yes, but as long as you are pretty sure the engine will run out the tank, you can still work on getting the wings level. Even if the wings aren't exactly level, you may be able to get a feel for responiveness, so you might consider adjusting handle spacing or CG.

Once you get the plane inverted, you can also notice engine rpm and see if it is a significant change. You might want to adjust tank height at the same time you do a flap tweek, it's allowed. I would not suggest multiple aero changes or multiple powertrain changes at once. 

One of the tricky parts is finding a good launch rpm for a new prop/engine combination. Use the tachometer! Then, keep using the tachometer on every flight, right Tim?  Steve

[Paul Walker]

There is also rumoured to be an upcoming article or several on trimming in Stunt News

Mark is correct. My first article is due to Bob in about a week. It covers the "basic" trim portion. Sounds like what you want.

Get the wings level first.
Then adjust the pitch sensitivity.
 Next work on the correct amount of tip weight.
Then try to get it to respond the same inside and outside.

That's a rough outline.

Paul

[Howard Rush]

Do you cover vertical CG (not that that would ever be an issue)?

[wwwarbird]

Do you cover vertical CG (not that that would ever be an issue)?

 Uh oh.

[Howard Rush]

You might want to adjust tank height at the same time you do a flap tweek, it's allowed.

On the very first flight of the very first stunt plane I built (in the modern era), I found that the two are related.  The plane was OK in the inside part of horizontal eights, but woozy in the outsides.  I assumed that the wing was twisted.  In fact, the engine was running at different speeds in insides and outsides.  Serge or Floyd would have picked up on this immediately, but it wasn't obvious to a person with an untrained ear.  

[Tim Wescott]

On the very first flight of the very first stunt plane I built (in the modern era), I found that the two are related.  The plane was OK in the inside part of horizontal eights, but woozy in the outsides.  I assumed that the wing was twisted.  In fact, the engine was running at different speeds in insides and outsides.  Serge or Floyd would have picked up on this immediately, but it wasn't obvious to a person with an untrained ear.  

I prefer to do my initial tank height check in level flight.  A few laps upright, a few laps inverted, listen, feel, and maybe even capture lap times with a stop watch.  Once it's close, then I start listening to the engine in the loops.

[Dan McEntee]

   I'll be looking forward to this. I'm at the point with most of my stuff, that, they fly as well as I can fly them. I know that proper trim is kind of an ebb and flow thing and always room for improvement, but you have to be able to recognize what that is. That takes a pilot of a certain skill level, and/or a coach of a certain skill level to help you get there. I know my models probably can be trimmed better, but I'm not sure what that is or means. If I can get me or my models over this hump and into that next level, I might be able to make that distinction. That is kind of my goal right now, get some models built that can help me get to that next level and learn from them. Earning a living and life keep getting in the way! That and about 12 inches of snow, ice and subzero temperatures!
   Type at you later,
   Dan McEntee

[Howard Rush]

I know when I need to move my leadouts, but I don't know which way.

[Steve Helmick]

On the very first flight of the very first stunt plane I built (in the modern era), I found that the two are related.  The plane was OK in the inside part of horizontal eights, but woozy in the outsides.  I assumed that the wing was twisted.  In fact, the engine was running at different speeds in insides and outsides.  Serge or Floyd would have picked up on this immediately, but it wasn't obvious to a person with an untrained ear.  

I think if you are already at the point of doing H8's, you should already have the wings level. Once the wings are level, move on. If the engine runs dangerously different between upright laps and inverted laps, get it closer. Fine tune with H8's later, as/if needed.  Steve

[Tim Wescott]

   I'll be looking forward to this.

Me too!

[Howard Rush]

We should wait for the Word from PW, but my inclination would be to use level flight to trim only the stuff that isn't a function of load factor.  Effects of lateral CG and fuel head are amplified in maneuvers, so that's where you'd fiddle with tip weight and tank height.  That's kinda simplistic, though.   This stuff gets esoteric and downright weird, as exemplified by my learning that a tad too much tip weight can cause an airplane to tend to dive in inverted flight.

[Brett Buck]

Being a bottom feeder, I'd like to ask what is the recommended order for trimming a new plane.  Assuming perimeters are in the ballpark enough to get a safe initial flight, do I want to work with the airframe first (balance, flap twist, etc), or engine run, or line/handle adjustments.  Understanding that they all interrelate, if there was a flow chart for beginners it would be greatly appreciated! I know this is asking for a lot of work from others.  I promise not to delete your help. Thanks.

 This was my try at it, from SSW and my SN article:

http://stunthanger.com/smf/index.php?topic=7798.0

   Brett

[john e. holliday]

Also if you had subscribed to Control Line World, Tom Dixon has a fine article in this latest issue.   Also some good read from Marcus Cudeiro down in Brazil.   Plus stuff covering other facets of our great hobby.  By the way the one point that caught my attention  was the one about running the engine at home instead of waiting til you get to the field.  Saves some head aches and time.   It gets even with the neighbors that party til the wee hours of the morning.

[Ward Van Duzer]

Hopefully it'll tel me why my saturn is falling out of he third turn of the Hourglass! Very scary!

Ward 

[Tim Wescott]

By the way the one point that caught my attention  was the one about running the engine at home instead of waiting til you get to the field.  Saves some head aches and time.

And sore arms from holding up airplanes.

[Steve Helmick]

Howard: Run your motors at home. When they stop smoking, they are ready to go.  Steve

[John Leidle]

  Hi Ward,  at the 2008 Nats Brett told me to fly behind my head in the Hourglass, I had been flying them in front & didn't realize it. He said I was flying about 80degrees ,,I started flying them at maybe 95 degrees & haven't fallen out of the Hour glass since.  Worked for me.

[Doug Moon]

Hopefully it'll tel me why my saturn is falling out of he third turn of the Hourglass! Very scary!

Ward 

I have seen this happen.  At the third turn line tension is usually down some due to loss of speed.  Oscillations from control inputs show up here big time causing that fall from the sky feeling.  Its trial by fire to get the right LO, TW, Rudder setting.  But that is what cured it on one of my models.  I really paid attention elsewhere in the pattern and noticed small oscillations in the square 8, especially on the second one.  Once I got rid of most of those the hourglass came around accordingly.

I cant wait to read what PW has written as well.  Maybe I can pick up a couple of points. 

[Brett Buck]

  Hi Ward,  at the 2008 Nats Brett told me to fly behind my head in the Hourglass, I had been flying them in front & didn't realize it. He said I was flying about 80degrees ,,I started flying them at maybe 95 degrees & haven't fallen out of the Hour glass since.  Worked for me.

  I think the actual suggestion was to fly it large enough that you didn't have that problem any more! You ought to fly it 90 degrees, unless you can't.

   By far, the biggest issue with the hourglass, time after time after time, is that the second corner is grossly too low, and not turned enough. It's very common to see the second corner started no higher than the top of the round loops. Then it's underturned, so that the top is climbing severely. Over and over, the airplane might be climbing up the first leg of the maneuver 45 degrees from vertical, then the top ends up 45 degrees from vertical in the opposite direction. The third corner has to be a near-180 to get back the the right position at the bottom, causing more issues yet.

     Brett

[Randy Cuberly]

Hopefully it'll tel me why my saturn is falling out of he third turn of the Hourglass! Very scary!

Ward 

Horse power.  It's really easy to have a stall problem here if power is marginal and especially if the airplane is a bit porky.  Keep the speed up in the vertical portion...We have a saying here in Tucson...MORE NITRO!   

Randy Cuberly

[Randy Cuberly]

I know when I need to move my leadouts, but I don't know which way.

Hey Howard...forward is the right direction...unless of course that doesn't work, then move them back...

Randy Cuberly