Ideal length of lines?

[frank mccune]

     Help All:

     I was recently told that I have been doing it all wrong for all of my C/L flying days!

     I have been using 52' lines for .15-.25 powered planes and 60' lines for .29-.40 powered planes.

     I have been told that I should be using 52'-58' lines for my .29-.40 powered planes.  This information came from some very experienced stunt flyers.  They cited better line tension with the shorter lines.

    I have never noticed the lack of line tension when using 60" lines IF the engines were running well. I think that line length is determined by how much power the engine can provide.  I have Noblers powered by an OS .40 S.  and one powered by a HP .40. on 60' foot lines.  When the engines and props are working correctly, I have plenty of line tension.  I also use an OS .35S in a Midwest Me 109 and it too has tons of line tension on 60' lines.

    Am I missing something? If I am happy with my lap speed, line tension and engine run, 4-2-4, what else could I need?  How much line tension do you guys have when flying stunt?

    What prompted me to post this question was that I was flying a Nobler that had an OS .30 in it that would not produce enough line tension.  My diagnoses was that the engine was worn out and incapable providing enough power.  I pulled the engine to test it and replaced it with a circa 1972 Fox .36 that I know is a great engine.

    In summation, what length of lines do yo use for stunt?

                                                                                                                               Tia,

                                                                                                                               Frank McCune

[Brett Buck]

     Help All:

     I was recently told that I have been doing it all wrong for all of my C/L flying days!

     I have been using 52' lines for .15-.25 powered planes and 60' lines for .29-.40 powered planes.

     I have been told that I should be using 52'-58' lines for my .29-.40 powered planes.  This information came from some very experienced stunt flyers.  They cited better line tension with the shorter lines.

    I have never noticed the lack of line tension when using 60" lines IF the engines were running well. I think that line length is determined by how much power the engine can provide.  I have Noblers powered by an OS .40 S.  and one powered by a HP .40. on 60' foot lines.  When the engines and props are working correctly, I have plenty of line tension.  I also use an OS .35S in a Midwest Me 109 and it too has tons of line tension on 60' lines.

    Am I missing something? If I am happy with my lap speed, line tension and engine run, 4-2-4, what else could I need?  How much line tension do you guys have when flying stunt?

     It's more or less impossible to make blanket statements based on engine size.  If what you have is working pretty well, I would suggest making a set a foot shorter, a foot longer, and see what effects it has. Note that you might have to re-trim it to optimize it at each point before you can make any good conclusions as to whether it is is better or not.

    It's not really about line tension. If you hold the same lap time, you get more tension with *longer* lines, not shorter, because the airplane will have to go faster to maintain the same lap times, since it is further around.  If you hold the same airspeed, then you will get more line tension with shorter lines, but the lap time will be shorter.   That's all sort of beside the point, because the trim effects of even a foot or so of line will completely swamp these sort of static line tension effects.

     Most people run shorter lines than would have been used in the olden days (of 25 years ago...) because you tend to get more control precision, and, we have much better control over the engine, so you can afford to let the maneuvers get physically smaller. Recall that the maneuver sizes are specified as angular dimensions, not absolute size, so the shorter the lines, the smaller the physical size of the maneuvers. Part of the possible advantage to running longer line is to give the airplane more room in which to maneuver - so shorter gives you less space.

     With better engines we can corner harder and control the speed and acceleration, so you can use generally shorter lines and still maintain reasonable maneuver sizes.

    Part of the trim changes you may have to deal with:

    Shorter lines - less tip weight,  more flap differential, leadouts forward, more handle spacing, less flap, less nose weight, less pitch, less wash-in, less venturi
    Longer lines - more tip weight, less flap differential, leadouts aft, less handle spacing, more flap, more nose weight, more pitch, more wash-in, more venturi

     The tip weight effect is obvious, I think. The fore-aft CG effect is less obvious.  What tends to happen with longer lines is that you have less control force in the rounds, since they are larger, and the tracking tends to go away. You can get that back by moving the CG forward. The converse is that with smaller round loops, you have to apply more force to hold the radius, and moving the CG aft reduces that. The rest of the effects are for similar reasons and some of them ("wash-in? wash-in of what??*") are pretty obscure.

     All that having been said, I suggest if you try one foot changes, just do it, and change *nothing*. If you are not already in optimal trim for your current system, you might be closer to optimal when you change. And it's really fast to change lines. I do suggest that you do something to make sure your line lengths are consistent enough that you can switch them without having to spend 5 flights setting the neutral.

     Bottom line - start wherever you are, and experiment from there. Line length, even a foot,  can make a remarkable difference, and you can't just say, a priori, what length to use. Old baffle-piston engines, like the Fox, I would run them as short as I thought I could get away with (because that's what  Bob Gieseke said to do). But with anything llke a regular stunt plane, choose something about the same as what other people are using, and then experiment around there.

   Brett

*wash-in in the prop pitch, i.e. how much, if any, the pitch increases at the tips.

[EddyR]

 You said "This information came from some very experienced stunt flyers.  They cited better line tension with the shorter lines."
 You also said  " if" They are experienced and are watching you maybe they have seen your poor runs more than the good ones and suggested the shorter lines.
Ask them why to explain why shorter lines. There must be a problem they are seeing.
Ed

[frank mccune]

    Hi:

    Thanks for the great replies!

     What I am going to do is increase the air speed of the models that do not appear to have great line tension.  This is perhaps the most simple change.  If I do not like what I experience, then I will go to more complex changes, Occam's Razor approach.

                                                                                                                      Stay well my friends,

                                                                                                                      Frank McCune
                                                                                                                                           

[john e. holliday]

I had a flying partner that used to say that for stunt, a plane should be flying about or between 60 to 65 MPH.   Each plane is different, even those of the same design fly different.  As Brett says, try different length lines.  Also line diameter comes into play also.   I remember I tried .012 cable on my .25 planes.  Went back to .015 cable, length between 58- 60 feet.  It is what makes you comfortable while flying.  Some say I fly too fast.

[Paul Smith]

Since the radius of "square" corners is a constant, longer lines make the pattern look better and score better.  So you need to select equipment that lets you use the full 70 feet.  Anything less is suboptimizing.

[FLOYD CARTER]

You should remember that the 70 foot number is the maximum radius of the plane flying.  You must subtract arm length, and airplane wingspan.  Otherwise, you exceed the 70 foot figure.  My longest lines are 66' 6", and that is pushing the limit.

Floyd

[Tim Wescott]

Since the radius of "square" corners is a constant, longer lines make the pattern look better and score better.  So you need to select equipment that lets you use the full 70 feet.  Anything less is suboptimizing.

This is probably why the trend has been toward larger planes.

Having said that, though, for any one given plane it would make sense to fly that plane at it's optimal line length.  We could then argue about whether it's a good idea to go to a bigger motor to allow longer lines, and at what point that no longer makes sense (i.e., no, I'm not going to fly a Ringmaster on 70 lines with a 46LA.  Just -- no).

[Tim Wescott]

You should remember that the 70 foot number is the maximum radius of the plane flying.  You must subtract arm length, and airplane wingspan.  Otherwise, you exceed the 70 foot figure.  My longest lines are 66' 6", and that is pushing the limit.

Floyd

Always read the rulz before citing them.  70 feet handle to canopy:

The length of the control system is measured from the center point of the
grip part of the control handle (device) to the fore and aft center line of the
model.

[Brett Buck]

Since the radius of "square" corners is a constant, longer lines make the pattern look better and score better.  So you need to select equipment that lets you use the full 70 feet.  Anything less is suboptimizing.

     No, it is not, and almost no one currently competitive always runs full-length lines. For instance, all of the open flyoff competitors from last year were between 63 and 65 (which when measured from handle to centerline, is about 66-68).

     That having been said, a few specific airplanes would have been better off if they could have benefitted from overlength lines - the B-17 and many of Windy's airplanes like the Sweepers.

     Brett

[Dan McEntee]

   All the good stuff has been covered. I'll just add that when asked at the flying field, I always suggest the constant use of a stop watch and recording of lap times when trimming a new model. The ideal line length is what ever you get the best "feel" at the handle and the best comfort and confidence when flying the pattern. I always encourage a set of lines and handle for each airplane, well marked to avoid confusion. Another stop watch to time each engine run, usually my wristwatch, started at the signal to the judges. I keep a 100 foot tape measure in my flight box also to measure lines and ALWAYS refer to line length as the distance form handle to model fuselage center line. Start with the lines a bit long, then as you get the power plant happy, you can shorten the lines as necessary. Lines are getting expensive, so it's easier to shorten them, and they haven't invented a line stretcher yet! I usually make several flights  before I make a change in length to be sure that is what I really want to do. The other main ingredient in all of this is practice, getting lots of handle time and developing a good idea of exactly what it is that you like for a lap speed. no matter what anyone else is telling you. Listen to what everyone is telling you, but come to your own conclusions in your own mind on what youneed to do.
  Have a safe Memorial Day Weekend,
   Dan McEntee

[Chris Wilson]

     No, it is not, and almost no one currently competitive always runs full-length lines. For instance, all of the open flyoff competitors from last year were between 63 and 65 (which when measured from handle to centerline, is about 66-68).

     That having been said, a few specific airplanes would have been better off if they could have benefitted from overlength lines - the B-17 and many of Windy's airplanes like the Sweepers.

     Brett

I thought that the post that sparked this one off was more about its best to have equipment that 'enables' the use of 70' lines, not that you would choose to so.

I get that the longer the lines, the flatter the canvas the maneuvers are painted on and thus more truly like the flat page in the rules book but why do fliers roll their lines back from the maximum?

Purely for a + or - flexibility and adaption to varying conditions?

[Joe Gilbert]

The shortest lines the airplane and you are comfortable with, the airplane has to be happy with speed it is going to perform.  You half to be happy with speed in manunvers. Lap speed is NOT the holly grail , manunver and your comfort level in manunvers is what is right. Of course this is my opinion and who am I m

[bob whitney]

some guy that still flys Ringmasters in everything

[Brett Buck]

The shortest lines the airplane and you are comfortable with, the airplane has to be happy with speed it is going to perform.  You half to be happy with speed in manunvers. Lap speed is NOT the holly grail , manunver and your comfort level in manunvers is what is right. Of course this is my opinion and who am I m

  I more or less agree with you, but again, what would we know about it?

    Brett

[Joe Gilbert]

Yea Brent you are a national champ and you do fly very well and have a very good handle on your engine runs which I think is pearmounnt to good scores.  You do understand what it takes. There is no best prop or best line length or best nitro , it changes by the hour ,that is what makes stunt so hard , and so changeling I love it.

[john e. holliday]

Joe, I think that is what I have stated in the past.  Leave the stop watch in the box until the pilot and plane are happy with each other.  Then the watch comes in handy when some thing goes wrong.  Consistency is the secret with a good coach also that knows your pattern and can see mistakes.   The coach should be able to help you correct the errors.

[Paul Walker]

     No, it is not, and almost no one currently competitive always runs full-length lines. For instance, all of the open flyoff competitors from last year were between 63 and 65 (which when measured from handle to centerline, is about 66-68).

     That having been said, a few specific airplanes would have been better off if they could have benefitted from overlength lines - the B-17 and many of Windy's airplanes like the Sweepers.

     Brett

Almost is correct. One person who has won a few times always used 70' ctc, at least since 83'.

[Trostle]

--- the longer the lines, the flatter the canvas the maneuvers are painted on and thus more truly like the flat page in the rules book

Purely for a + or - flexibility and adaption to varying conditions?

Longer lines do not "flatten the canvas".  A 45^o maneuver (which is defined for the round loops, the square loops, the size of the loops for all of the eights, is still a 45^o maneuver, regardless of the length of the lines.  The hourglass and the vertical eights all go to the top of the circle (90^o) regardless of the length of the lines. 

For a given flight speed, longer lines do allow for more time in a maneuver, which can be desirable in some cases, particularly in the dive portion of the square maneuvers, the hourglass, and the triangles.  If longer lines could be taken to an extreme, they would make it more difficult to accurately place the bottoms of the squares, triangles, and the hourglass.  Think about how difficult it would be to get a 5' bottom on 200 foot lines as apposed to say 50' lines.  Yes, we are limited to 70' lines, so it is not difficult understand that that 5' bottom might be a bit more difficult to perform consistently than say 55' lines.  The only optimum line length for a particular model/engine/pilot combination is what works best for that arrangement, and that is only found in the trimming process.  And part of that trimming process is trying different length lines.  It pays to have a whole set of lines in at least 1' increments.  Evan a 6" difference can make a difference.

Keith

[Chris Wilson]

Longer lines do not "flatten the canvas".  A 45^o maneuver (which is defined for the round loops, the square loops, the size of the loops for all of the eights, is still a 45^o maneuver, regardless of the length of the lines.  The hourglass and the vertical eights all go to the top of the circle (90^o) regardless of the length of the lines. 

Hi Kieth,
                 I am going to fall back on the definition of a 'straight line' in the pattern, in as much it must appear so.
Basic geometry tells me that a larger hemisphere will appear flatter to the jugdes, no?

[Trostle]

Hi Kieth,
                 I am going to fall back on the definition of a 'straight line' in the pattern, in as much it must appear so.
Basic geometry tells me that a larger hemisphere will appear flatter to the jugdes, no?

Chris,

In one aspect, you are not wrong if you take say a 5' diameter circle from the surface of a 70' radius hemisphere, it will appear "flatter" than a 5' diameter circle from the surface of a 35' radius hemisphere.  But that is almost irrelevant when it comes to defining our maneuvers as prescribed by the rulebook.  A 45^o maneuver as defined for our loops, squares, and eights still take 45^o segments of the hemisphere regardless of the size of that hemisphere.  So those maneuvers are no more "flatter" on a larger hemisphere as they still take 45^o segments as on a smaller hemisphere.

Now, when it comes to "straight" line paths as defined in our pattern for the sides of various maneuvers (square loops, square eights, triangles, hourglass, vertical portions of the four leaf clover; and for constant elevations as in the tops of the square loops and the horizontal intersection of the four leaf clover, the longer the lines, the more space the pilot has to establish those "straight" line/constant elevation paths for the judges to see.  So in that consideration, longer lines can help the pilot establish those  "straight" line/constant elevation paths for the judges.  Then, it becomes the question if the model can handle the longer lines to take advantage of the increase airspace for those longer "straight" line paths.  It depends on the model (size, weight, power train) and the pilot and that can only be found by trial and error. 

Rather than discussing the flatness of segments from different sized hemispheres, the point that some of the experienced pilots are making in this thread is that with a good model (size, weight, power plant), a 6" to 12" difference in line length can make a difference on what an experienced pilot feels/sees/flies in those maneuvers.  That optimum can only be found by trial and error, not in a recipe book.

Keith

[Russell Bond]

Quote - "a 6" to 12" difference in line length can make a difference on what an experienced pilot feels/sees/"

Boy, you're not wrong there.
I was flying on 65' eye to eye and all was good. Then I tried 66' and it was horrible, the precision went out the door! Back to 65'.  

In fact I have noticed that at the World's most of the top pilots used 64 - 65 foot eye to eye length lines. (No longer.)
Of course we are talking about the average plane of about 60" wingspan.