Length of Lines

[Allen Eshleman]

I have been flying a Magician with a B-40.  Before that, I was using the B-40 on a Smoothie which eventually went to airplane heaven after the controls tore inside.  In thinking it over, I have become convinced that the lap times were a little fast for stunt, though I didn't measure them precisely but it was under 5 seconds.  I have been using 60 ft. lines.  Is that long enough or could they be a little longer.  I have been using 11/3 and 11/4 props or 10 1/2 x 4 1/2.  I like the engine runs on the latter prop.  I am curious as to what length of lines others are using with 40 powered planes.

[Keith Miller]

I'm flying a Brodak 40 (10x6 prop) on a 526sq Ringmaster right around 5 seconds on a good 2-4 break with 60' lines. If I lean it out, times go down to 4.5. If I go richer, I can get 5.2. I'm a firm believer that the engine mixture and prop load should be used to set your lap times, not line length.
A quick bit of math: Changing line length by 1 foot only changes the lap time by 0.08 seconds (assuming we start at 60' and 55 mph). So adding 5 feet (60 going to 65 ft) for a fixed speed only gets you 0.4 seconds. I think it's much simpler to adjust the fuel/mix/prop to make that adjustment.

[Tim Wescott]

I use 60' or 65', eyelet to eyelet.

BUT: I build heavy and I compensate by flying fast, and then I compensate for that with long lines.

I'd get the lap times up to 5.2 seconds or so, then see what you think -- if the joy you get from actually being able to keep up with the plane in maneuvers in exceeded by the dismay of having it fall out of the sky in the corners, then you may want longer lines and a bit more juice in the engine.

I strongly recommend that you measure your lap times and at least try things out at various speeds from a lap time of 5 seconds and getting progressively slower until you just can't stand it any more.  Speed masks a lot of trim problems, so you may find that it's a dog at 5-second lap times.  If so, work on trimming the airplane at that speed before you go slower.  Then consider that changing speed changes trim requirements, so as you go slower consider that you may need to at least tweak the trim.

I'm flying a Brodak 40 (10x6 prop) on a 526sq Ringmaster right around 5 seconds on a good 2-4 break with 60' lines. If I lean it out, times go down to 4.5. If I go richer, I can get 5.2. I'm a firm believer that the engine mixture and prop load should be used to set your lap times, not line length.
A quick bit of math: Changing line length by 1 foot only changes the lap time by 0.08 seconds (assuming we start at 60' and 55 mph). So adding 5 feet (60 going to 65 ft) for a fixed speed only gets you 0.4 seconds. I think it's much simpler to adjust the fuel/mix/prop to make that adjustment.

Well, yes, but you're adjusting two different things.  I agree that you shouldn't just lengthen the lines just because you can't get the engine tamed, but that doesn't mean that you shouldn't make sure you're flying on lines that are right for you.

[billbyles]

I have been flying for years my Impacts powered with P.A. .40s with the Smith/Werwage tuned pipes using 70' (c/l of fuselage to c/l of handle) .014 solid lines at around 5.4 to 5.5 second laps.

[Allen Eshleman]

The PA is a different horse of an engine than a B-40. My guess is that it has a lot more torque.   I had a nobler with an FP -40 that inadvertently got connected to 70 ft lines.  I didn't know it.  Neither did the light pole in the expanded circle.  Thus, a badly mangled Nobler.  I didn't get to find out if that would have worked or not.  I might have to try the 10 inch props on the B-40.  I think the manual recommends a 10/5. 

[john e. holliday]

I keep telling people to put the stop watch away and fly the airplane where it is happy.   I have planes with B-40 flying on any where from 60 to 65 foot lines.   If the plane feels comfortable to you on the lines you are using great.   If it feels too fast try longer lines, too slow shorter lines.   Once the plane flies the way you like, then time it.   I was flying my Ringmaster Imperial on 65 X .015 lines with LA 46 and was happy with it but was told it was too fast at 4.6 second laps.  Before that it was 68 foot lines and was not a comfortable flight.   Guess it must be some of the old combat stuff still in me.

[Tim Wescott]

I keep telling people to put the stop watch away and fly the airplane where it is happy.

That's valid if you're really good.  But if you're a beginner at trimming, your airplane's "happy place" may be way faster than it needs to be because it's poorly trimmed, not because that's really it's happy place.

[Motorman]

65' lines center to center are pretty much standard for Brodak 40 or LA40. I've tried a variety of 11-4's but the apc 10.5-4.5 seems to be a magic prop. I like the longer lines, it lets you fly faster and do bigger maneuvers. Magician has 407 Sq In and would fly good on 60' lines with an LA25 or Veco 19. With a Brodak 40 you could have a much bigger plane, something with 550 Sq In. on 65' lines no problem.

MM  

[Allen Eshleman]

This is a Magician from an old kit, the bigger one.  It has had a few serious crashes so it is a bit porkier than a healthy Magician.  I have new 63 ft. lines from Tom Morris which I am going to try and definitely use on my Vector which has an LA46 on it.     We'll see how that all goes.  I do personally like the the B-40 run with the 10.5/4.5. It sure beats the McCoys I grew up with although I did have one really good RH35.  I do have one Fox with the anti-burp stick in it. That's pretty good too.  But I like the B-40 much better.

Back to lines length - Thanks for the thoughts and ideas.   

[Keith Miller]

Well, yes, but you're adjusting two different things.  I agree that you shouldn't just lengthen the lines just because you can't get the engine tamed, but that doesn't mean that you shouldn't make sure you're flying on lines that are right for you.

Yep, you're right there, sir.

[Brett Buck]

Doc is correct in this case. Put the stopwatch away and use it only to determine the consistency. Don't shoot for a fixed lap time. The feeling of staying in control/ahead of the airplane instead of feeling rushed or feeling behind the airplane is much more a function of how the engine runs than how fast the airplane is going. I have had 4.2 second laps feel perfectly reasonable, and 5.5 feel completely out of control. The difference is how predictable the engine is. If it's accelerating and decellerating too much, it can cause tremendously unpredictable results and you can feel like you are always trying to "catch up". You cannot have that and expect to be competitive.

The difficulty of making the 4-2 break, for example, consistent enough, is the reason that they aren't competitive aside from special cases (like the Retro which has a lot of the 4-2 break issues designed out).

   The lap times are useful to help explain changes in feel you might be having, but you shouldn't necessarily shoot for a particular number.  Ancient 4-2 break engines on 60's trainers need to fly pretty fast and sub-5 seconds is very common - if you want to get through patterns reliably in a variety of conditions. Most of what you heard about flying "6+ second laps in a 40 mph wind" back in the good old days is a steaming load. Put a 25LA on the same plane, it might go 4.5 second laps but be far easier to fly.

If you make a change, and the airplane feels different, you have to first determine that you just didn't change the speed. That's how to use a stopwatch.

     Brett

[Phil Spillman]

Hi Allen, Nice to read that you and your brother are still at it! For what its worth, your taste as to what is right and what isn't will change with just about every plane and engine combination! Especially as you become more proficient with flying yourself! remember to measure your lines eyelet to eyelet so that you can can be specific as to what's what! Ready made lines' length may vary from spool to spool and from vendor to vendor!

I prefer to get familiar with each plane and engine combination and analyze for my own likes which is the most comfortable set up for that specific combination. These tastes do change from time to time! Last year(flying season 2014) I flew my Brodak P-40 ARF with an ST .46 for power on 63' lines eye to eye. Over the winter I opined that slightly shorter lines might "feel better"; so I made up a set of 62' eye to eye lines just to "see"! I liked the difference and so that's what I flew this season(2015). In all likelyhood I am no better a flyer but I think the thing flies better therefore I have more fun in those few precious hours when I do get to go flying with my flying friends!   

Merry Christmas and Happy New Year to you and your brother!

Phil Spillman