lap times

[jjorgensen]

What is the formula to increase lap times by increasing line length?  I have 62 foot lines running between 4.5 and 4.8 second laps.  I'd like to increase lap times to 5.1 to 5.4 range.

[Ralph Wenzel (d)]

It's a direct relationship. That is, to increase lap times, you must lengthen the lines.

5.1 (desired lap time) / 4.5 (Current lap time) = 1.333 X 62 (Current line length) = 70.267 ft.

In other words, you can't do it by simply lengthening the lines; you gotta slow the plane down, too, by some other means. Lower pitch prop or greater prop diameter (which will slow the engine), or . . .

 

[Nils]

Each additional foot will add about .1 second to your lap time. All else being equal.

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[Paul Smith]

Each additional foot will add about .1 second to your lap time. All else being equal.

/\/\/

....like, ignoring the reduced speed due to more footaqe of line.

....like, ignoring the idea that the incease line length will create more slack and effectively shorten the radius.

The best approach is to make a set of 70's and use a stopwatch. 

[phil c]

Jim, the only use for measuring lap time is to get a quick read on whether or not something has changed between one flight or flying session and the next with the engine setting.  There is no magical number that works best.  The lap time you need is the plane speed and line length that lets you fly the plane the best.  If you are running 64ft. lines(62 ft. plus half the span, I assume), that is about 60 mph(88 fps) for a 4.6 lap.  That is pretty fast for most stunt flyers.  A typical airplane speed is 52-55 mph., or 5.3 sec/lap on your set up.  If you simply slow your plane down by adjusting the prop pitch, rpm, etc. the plane will fly slower, but you will find is is much less solid feeling on the end of the lines.   It will not pull nearly as hard and will require a lot more careful touch in various maneuvers to keep it flying smooth and straight.  Each combination of plane/engine/prop will have a flying speed and line length that will work the best for you, to match your reflexes and skill.

[jjorgensen]

Thanks for the info.  I'm looking for something I can fly in the wind.  I put an old fox eagle 60 on a Pathfinder I had retired just to see what it would do.  It still has the rc throttle and at full throttle with an 11/7 prop the lap speeds were too fast for me.  At about 7/8 throttle the lap speeds were good and it would motor right through the overheads with little effort.  Surprisingly it has a decent 4/2 break as well. 

[Just One-eye]

The recollection I have from the time that the Eagle 60 was new is that it was closely related to the Fox 59, which had a good reputation for both a classic 4-2-4 run, and for serious loudness. 

[Steve Helmick]

You're maybe thinking of the Falcon .60, which was just a .59 with slight updates. The Eagle .60 isn't a bad sub for a ST .60bb, tho not as well made. This was one of the first Foxes to have the flange mounted venturi/carby.

Remember to set your speed/lap time with prop pitch/line length, and engine load with prop diameter or number of blades.  Steve

[Just One-eye]

That's entirely possible just what I'd done. 

[john e. holliday]

As Phil C stated, lap times are good to see if any thing has changed over time.  An individual in my area kept complaining that every time he got the lap times he wanted the plane wouldn't fly right.  I told him to put the stop watch where the sun didn't shine and adjust the needle of the engine to where the plane flew right.  All planes have a speed they are happy with.  The engine also has a happy medium in which to work.  It takes a combination of props, fuel, line length and plane to get where you are comfortable.  Sometimes I have been accused of flying to fast, but, the plane and myself are happy.  Later,  DOC Holliday

[Bob Reeves]

....like, ignoring the reduced speed due to more footaqe of line.

....like, ignoring the idea that the incease line length will create more slack and effectively shorten the radius.

The best approach is to make a set of 70's and use a stopwatch. 

The best approch is to let LineIII calculate it for you as it takes all the vairables into concideration.

[Nils]

Well, you can make this simple little thing as complicated as you want, but when you're done screwing around with line drag, computer programs & so on you'll find that each additional foot of line length will add approximately .1 second to your lap time, assuming you don't change anything else besides your lines. The reverse is also true, if your airplane/engine/prop/needle-setting seems to be happy but you don't have good line tension you can shorten them &  it will increase your lap speed approximately .1 second for every foot you shorten them until you find what suits your particular setup. I KNOW this works for line lengths between about 56' & 68'. It's not exact, but it's *very* close.

Btw, "....like, ignoring the idea that the increase line length will create more slack and effectively shorten the radius." is the dumbest statement I've read in a while.

Now I remember why I quit answering simple questions for people in CL forums few years ago.

/\/\/

[Chris McMillin]

Thanks for the info.  I'm looking for something I can fly in the wind.  I put an old fox eagle 60 on a Pathfinder I had retired just to see what it would do.  It still has the rc throttle and at full throttle with an 11/7 prop the lap speeds were too fast for me.  At about 7/8 throttle the lap speeds were good and it would motor right through the overheads with little effort.  Surprisingly it has a decent 4/2 break as well. 

Jim,

What I noticed about your post on propeller selection for the Eagle 60 is that it is 2 inches smaller in diameter and has 2 inches more pitch than what I use on a Super Tigre 60.

Your reducing throttle is one way to slow the model, but the propeller can slow it and increase useable thrust at the same time with full throttle. Try a 12x6 and a 13x5 and see how it reacts and how well it feels.

Just another trimming thought to help you along.

Chris...

[jjorgensen]

I have obtained a c/l venturi and upped the prop to a 12/6 and it is much more manageable.  Quite the fuel hog though.

[Mark Scarborough]

you'll find that each additional foot of line length will add approximately .1 second to your lap time,
 I KNOW this works for line lengths between about 56' & 68'. It's not exact, but it's *very* close.

Btw, "....like, ignoring the idea that the increase line length will create more slack and effectively shorten the radius." is the dumbest statement I've read in a while.

Now I remember why I quit answering simple questions for people in CL forums few years ago.

/\/\/

Nils,
I feel ya man, I know , Your answer is totally valid and accurate. It was pretty apparant that the gent asking the question wasnt trying to get an answer down to .0001 percent, just wanted to get headed the right direction. I also agree that as a general rule of thumb, .1 per foot is VERY accurate and close.

However In jjorgensons case, it really sounds like properly proping the engine is a better starting direction.
that having been said, it would help a lot if when people asked trimming questions if they gave all the information to start with , then you are less likelyl to get obscure non related answers. Things such ans engine, fuel, prop, weight all have a huge affect on lap times and what will work and what wont.