Line length vs engine size?

[Phil Krankowski]

There is a handy page in the useful link section that denotes line type and diameter vs engine size or model weight, but it does not give starting points for line LENGTH vs engine size (or model weight). 

Obviously tuning is required to get the most out of a model, but I am looking for a starting point for fun flying.  Currently I am using 30 ft lines with some Cox .049 engines on a couple models.  I plan to have more, larger models but have to build my skills back up some.

So is there any guidance,  suggestion, or look-up table for line length vs a given engine?  I am currently fun flying, but have interest in stunt (and maybe combat).

Phil

[Dave_Trible]

Hi Phil.  In the 'old days' there were printed charts around and helpful, knowledgable hobby dealers to put you on course.  Now you're best bet is simply to explain what you have and folks here will guide you to a starting point. 

Dave

[Phil Krankowski]

I have space for a 90 foot circle in the side yard between my house and my neighbor's house.  A little more if I fly over his property, which is downhill (they are cool with this).  If I convince the wife to let me cut a tree down I gain about 20-30 feet for my circle, (haha not gonna happen since the tree is healthy). 

There is another area of the yard that I might be able to fit a similar or slightly larger than 90 ft circle, but there are many more trees.

How big of a model can I put together and expect to have the line length to:
keep up with the airplane
enjoy myself

I am OK sticking to .049 engines and electric equivalent. 

Turning the question around to what I have...

I have a lil jumping bean with a open ported Cox Thimble Drome, and a lil wizard (I think) with an early Cox that is probably from a plastic model.  The Lil Wizard, which has been repaired several times and needs the elevator replaced, is a bit of a dog on 30 ft Dacron lines, it circles fine but does not seem to hold the lines tight in a wingover like I remember (been 20 years, and I don't have the lines from then, those are at my parents with my brothers' airplanes)  I got 3 good flights in yesterday  (AWESOME!)

The lil jumping bean I crashed on my first fight after it took off into a wingover, I looped it into the ground in a panic, and popped the motor mount bulkhead off, the glue failed...20 years since I flew it again.  I just finished washing everything with denatured alcohol and epoxying it back together.

Both airplanes lost their landing gear a long time ago.  I flew them hard for about 8 years when I was little and we did this as a family.  I was launching with a wing sleeve made from an old towel clamped to a table.  I used some foam board insulation with the lil wizard because it has...I don't know what to call them, air dams maybe... on the solid wings.  Worked good, the foam pulled out part way through the towel without snagging then the wing pulled free.  I had a pretty good up incline on the launch...which I should have changed for the lil jumping bean.

Some fun:

IIRC I built the lil wizard with Dad when I was 6 in one afternoon, and I built the Lil Jumping Bean with Mom over a couple weeks when I was 7 or 8.  The Lil wizard was painted dozens of times because I would paint my airplane while Mom was repairing Dad's combat planes!  Dad stripped it and then painted it with me the last time...the paint job on it now.  Boy was I in trouble for not being in any trouble!  That was just before I was given the Lil Jumping bean.

Phil

[Phil Krankowski]

If anybody has a copy of one of those charts I would love to see it.

Phil

[EddyR]

Phil do a search on here and put in" line length"
 You will find your answer

[Phil Krankowski]

Phil do a search on here and put in" line length"
 You will find your answer

Wading in the deep end here....

"1/2A" is defined up to .0504 CI displacement

Line length is officially measured from the centerline of the model to the centerline of the handle grip.

1/2A commonly fly on 25 to 40 ft lines. (or 42 ft) 

1 ft of line length changes the lap time by about 0.10 seconds, provided the model can pull the longer lines.  (10 feet of line length changes lap time by about 1 second)  This estimate in time change works for lengthening and shortening.

longer lines are less stable / shorter lines have more control

Similarly wide spacing on the handle is less stable and narrow spacing is more stable

Shorter lines are easier for the model to pull, which can improve performance in overhead maneuvers.

For line length tuning making up a set of 1, 2, 3, 5 foot sections allows for clipping in adjustments in length at the handle end (for reduced drag) of 1 ft increments.  These lines are not permitted at events, and probably not suitable for regular flying so a set of lines should be made up to match.

Recommended minimum tensile strength is listed in the AMA rulebook vs model weight.  For 1/2A 10g, or 10 time the model weight is the recommended strength.

Spectra fishing line make good control lines.

****

Looks like I am stuck with 1/2A on my own lot since I can only draw a 90 ft diameter circle.  (well slightly larger if flying over part of the neighbor's lot, but that hill is steep...)

Did I mess anything up here?  Anything I missed?


Phil


This thread is helpful
http://stunthanger.com/smf/index.php?topic=19535.0

After replacing the elevator on the lil wizard I should try a 5x3 prop and see if I get better performance due to engine unloading.

[kenneth cook]

          Hello Phil, I see you stated the use of 30" lines. I just want to add that the norm so to speak is 35' for the older design models. As you mentioned, center of plane to center of handle but I would certainly not hesitate to go longer from eyelet to eyelet on line length starting at 40' as you could always trim the length down.  This slows the plane a bit and gives you more room for maneuvering. The Lil Wizard is a trainer , so don't expect any performance out of it. It was built for durability and shock resistance. Yes, a 5x3 will make it unload and the 5x3 is my standard choice for reedie .049's. The Wizard is probably not going to do anymore than a extra large loop or a wingover. I do fly some of my Cox engines on 42' lines. This is the upper limit even if you do have a light and powerful engine. The Brodak 1/2A series kits are quite light and I've found every model  I built to fly as proclaimed. There are a few older designs out there that still perform quite well: Lil Jumping Bean, The Flite Streak etc. Built up wings fly far superior to all sheet wings not to mention they're typically lighter. They're a few sheeted wing planes that do defy what I just stated in my prior sentence such as Dick Sarpolus kits for instance. Having dual ported cylinders such as a Black Widow will certainly give you an added edge on performance. This will allow a slightly heavier plane to fly with a bit of authority. Since modern engines have come about, engines such as the Norvel uses a starting point at 42' with the ability to go out to 50'. I have one currently using a .061 Norvel and the line length is 46' eyelet to eyelet in which I use .012 stainless. I COMPLETELY given up on .008's. Theyr'e too much of a pain and they've become a constant maintenance factor. I've since gone to Spiderwire in the 30lb. variety. These modern engines have a lot of power compared to the Cox engines. I have tried to use TD's for practicing  1/2A combat on 42' lines which has worked but I'm running it as fast as possible to stay with the current modern engines. Ken

[Phil Krankowski]

I went with Power Pro braided line since it is "Kevlar" branded Aramid fiber, and the product I prefer spooling on my fishing rods, in 15#, since it is listed as .008 inch.  Made a new set at 35 ft, saved the Dacron, and made a 1, 2, 3 ft attachments, reriged so there is a short adjuster at the handle with clips/eyes at both ends.  Yes, snap swivels, but I took the snap off the swivel , and strung the line between the snap and swivel, like I make my fishing leaders because too many swivels invites trouble.

I weighed the Jumping Bean 158g and lil wizard 189g set up and "dry" (no fuel) 

Phil