Lap times: Fact or Fiction??

[Bill Little]

I see almost everyone quoteing lap times.  Why is this?
Each model we build will have an optimum *Air Speed* that it must fly at.  Do we sometimes get too caught up in a 5.3 lap (or any, take your pick) time and don't realize the full potential of the plane because of it?

To be honest, I only know what lap time I am flying when someone tells me.  I try to find where the plane is comfortable, then I will get a time for benchmark use only. If the plane is happy on 60' lines flying at the speed it needs to fly, but it's too fast for my liking, I will change to longer lines.  But I do not change the airspeed of the plane.  Of course lately I have not been physically ABLE to fly, a fact that I really hope to change tomorrow!(Saturday)

Discussion, please! 

Bill <><

[RC Storick]

K->

[L0U CRANE]

Bill,

I hope all goes well for the flying...

Lap times, like so many other rules of thumb, are - yes - arbitrary. However, they are the ones that most, or at least: many, top fliers use as a benchmark. There may be a connection, between our aging reflexes and laptime, that is as important as the airspeed.

On (nominal) 70' lines, which I hope means from center of abdomen to centerline of model, a 5.2 sec laptime means a certain MPH or fps airspeed. Many current top models may be designed (or tuned, or trimmed) to fly optimally at that airspeed - but most are almost clones of each other in the vital basic proportions. Ergo, if it is optimal for one, it should be d*** close for the others.

The model with which I was most consistently successful had a 6.3 to 6.5 sec laptime on (nominal) 70's. It crept around like one of Al Rabe's big "scaler's", but was consistent for me. I can be consistent with other setups, given practice. We all can.

HOWEVER, when the big guns are flying at ~5.2, the judges get the subliminal message that that's the way it should be. The guys flying that pace are established champions, after all. My 6.5 sec laps may not impress them as well because they take SOOO long.

The mixed blessing of the improvements in standardized judging standards over the past 33+ years... We say we're judging the flight, not the flier, but there is a subcurrent...

Don't misread that! The winningest guys have worked hard for, and fully deserve, their successes.  One trace of the 'old days' may still linger with us: Back in the 1950's, if a "name" flier showed up, how HE flew was too often the standard by which all others were judged.

"A certain organization" has done much to level that off, and to make judging standards more even around the country. Judges remain, after all, individuals, susceptible to stray influences. That still needs work...

[Charlie Pate]

I think its the same thing as when you say to someone"use a 10-6 prop on your fox35 ".
This may not be the optimum prop for your engine and ship , but it is adequate.
 If your ship flies badly with this set up , the prop is not likely the problem,
 If you can get a lap time of say 5.2 seconds on 60ft.lines with a 40 powered
ship, it should stay out on the lines and perform.
On the other hand , the best trimmed plane, 40 size will not fly well at a 9 sec. lap time on 60 ft.lines. Because--- the plane is just going too slow (airspeed)
Many new modelers simply do not understand things we old folks take for granted
Tip weight. line length, line Diameter!fuel mix,tank set up ect.

As to your question ;my opinion. If you can get proper line tesion , tracking and turn rates---- The slower the better.
I think most people fly 5.3 , because the plane doesn,t fly as good at 5.4

[Richard Oliver]

Bill, Like you I do not put to much stock in "Lap Times" per say. I will note that when practicing and working  on a set up or new plane I find that lap times do fall into a range that present well and give the plane/engine combo it's best chance. Depending on the type of engine run you are trying to use you will find differerant lap times that will work.
If you are trying to fly a pure 4-2-4 it will need to be a little faster than a 2-2-2 or fast 4 cycle breaking into a soft 2 cycle. I am referring to what gives you a better chance at scoring. An airplane that is flying slower will often times represent a maneuver that is sloppy and not well defined. This is where you have to walk the line between slow enough to maximize your reflexes and not so slow that you loose your definition and crispness. When you pull a hard corner(remember that rule book 5' radius!) the plane needs speed or raw power to pull it through. This is especially needed in the verticals. It is not that the top guns fly faster and that is the norm it is that any slower and the presentation changes. At the Nats in Muncie speed is a fact of life. The air is so thin that power and lift require more speed to keep the maneuvers well defined. Often a flyer is comfortable with a slower plane for reflex reasons but his plane suffers. It is a balancing act to say the least for you, your plane and your power package. The slower you fly the more difficult it is to fly a good pattern. My own observation is with the right set up for slower lap times you can go as slow as 5.5 to 5.7 and do well . Any slower than that and the sloppy comes in for most flyers. As far as for the fast side I have seen some really well done flights technically at 4.7 but they were not pleasant to watch. I would say that 4.9 to 5.1 is starting to get a little too fast.
All of this is predicated on how your set up and plane react to the "Lap Time" you are wanting to fly. If you plane is over weight you are going to have to fly faster. This is just a given. If you are underpowered you are going to have to fly faster, again a given. If you are overpowered you have to fly larger props and different needle seetings to accommodate and there we inter a whole new area.
This topic is a good one and many flyers can learn from trying to maximize their set up for their personal likes and their planes needed speed range. It is a balancing act for sure and can be fun, if you like that sort of thing. Props play a HUGE part in this and is the starting place for most set ups. Line length, engine,plane weight, lift available,flap/elevator ratio, tip weight/lead outs/cg, all play a part in finding the right speed for your plane and you.
RO

[john e. holliday]

That is what I tried to get thru to an individual at the NATS when he was complaining about how his plane was flyong.  He thinks all planes should fly 5.2 lap times.  I time him to throw the stop watch away.  Then adjust your needle to what your engine likes to run at.   The airplane also will tell you fi it is too fast or too slow.  That is where the prop comes into play and line length.  If you have a plane that is too fast on 60 foot lines go to longer lines and see if that helps.  When the plane is finally working to your liking then you can retrieve the stop watch and time your laps.   My flying partner is doing well on 60 foot lines going 5.0 laps.  But, flying and experimenting is what keeps this fun.  DOC Holliday

[Bill Little]

So far, I am hearnig good things from well versed flyers.  Richard, Charlie, Lou, Doc, y'all have been at this a while in one form or another and understand the basic of what makes our planes do what they do, and how to get better scores.

I often pose questions that I think will help those who are not very far along on the stunt ladder just yet.  And I think we need to pose questions so that they can learn what the real "scoop" is!  All too often someone will be doing just what Doc pointed out.  Looking at a stop watch and not "listening to the plane".  There are factors that come into play with each and every pplane we build.  I honestly do not believe that we can even build two planes from the same plans using the same wood and have them fly identical.  We might get awfully close, but to have them fly identical will take some trimming to each one.  and it will probably be something different needed to get them to fly the same.  So I am glad that y'all are pointing out some of the factors that do affect the flying of our models.

I am really hoping more will join in here with their ideas and comments.

Bill <><

[Richard Oliver]

Like Bill and a few others have said here, Do not get to tied up in lap times.
I can set up a power package that flies a 5.8 lap and the maneuvers will be way to fast. On the opposite side I can set up for a 4.8 lap and very comfortable maneuver speed. It is all in how you deliver the power of your chosen package.
If you fly a rich 4-2-4 with a hard break you will need to have the maneuver speed fast enough to get to the top but not so fast that it gets in front of your reflexes. This type of set up is also very hard to maintain because it depends on conditions that are very stable (weather) to not change from a good stunt run to the one from H**L. If you however use the stay in a 4 cycle type with no gear change in the maneuvers(ala 4 stroke eng, IE. Saito) then it had better enter the maneuver with enough momentum to carry you through. This usually requires a little more speed than the 4-2-4. The reason many of the top guns have gone to a Pipe set up is that it is more stable for most conditions. The fast 4 cycle is enough to give you good line tension and speed to start the maneuver and then it gives a nice soft 2 cycle burst for the drive out of the corner settling back into a 4 cycle quickly. This set up seems to not move much or require as much attention from day to day or location to location. Air Density is the number one factor in all of this and if you are in an area that changes much it is a constant chase to find what your plane needs day to day and sometimes hour to hour.
It is a lot to learn but that is the fun part of stunt, isn't it? The only way to get up to speed is to experiment and try new things. I knew how to get power and speed out of a motor but when I started to fly stunt I did not how to Not get Power when I did not want it and certainly did not know what to do about it either.
RO

[EddyR]

Good point Bill .I also have not looked at a stop watch in years.I have had many people tell me I fly fast yet when they time me it is 5.0-5.2. It looks fast to them but feels slow to me.Years ago when Windy came to fly with Bill Rich and myself he told me my Juno looked very slow and smooth.He also said my lines looked to short.I was on longer lines than Bill Rich and I was flying 5.0 . Some times we are fooled by the looks and sound of the plane.
Ed

[Rafael Gonzalez]

Well, Well...
This is the advantage of doing a search several ways to get the right answer to your question. Amazing... This site is what we need.  I was wondering about lap times for stunt. Thanks to all the inputs, I won't worry about it anymore. Just fly the plane!! 

[Ted Fancher]

Bravo Richard!  I've tried to make that point for years; especially about the supposed value of slow maneuver speed.

Because I've never been an engine wizard (thank you for my Ro Jett .61 which solved that issue pretty darn well for several years!), for many years I had been at the mercy of however the engine chose to run on a given day at a certain time.  As a result a good percentage of the contests I flew in I would have one comparatively faster and one slower flight.  Seldom was either out of control but the difference was enough to be noticeable. 

I believe I can say without exception the faster flight was always the higher scoring of the two...even if I personally preferred the slower one on a given day.  To be blunt I always more or less chalked it up to the fact that a faster maneuver time gave the judges less time to both see and evaluate any errors.  That plus the fact that brisk maneuvers, particularly squares and triangles, etc. always look a bit flashier when flown more briskly.  Thus, you can get the "positive 'wow' benefit" and the sneaky "they didn't see that did they" benefit all in one package (don't, by the way, take this as a suggestion anyone should purposely fly real fast in hope of fooling the judges.  Each flier has a comfort range they must fly within to avoid making mistakes so bad they can't be ignored).

I am also not a fan of picking some randomly popular lap time for a new ship while I'm still clear coating it.  The only lap time I'm interested in is the one that will allow the airplane to make the best possible impression on the judges while still being within my personal comfort range (which, likely, was a bit wider than for many others).  The most important aspect of lap times is that they are achievable with the airplane and powertrain operating in an optimum way.  If the pilot is lucky there may be enough "slack" in that performance envelope to allow lines to be shortened or lengthened a foot or two (almost certainly not more than two feet) if necessary to make the pilot comfortable with the maneuver pace.

Ted

[Jim Thomerson]

I think prop selection, as Richard said, is very important.  I came to this conclusion after trying a few similar props on one engine and airplane.  I like to fly as fast as I am comfortable with, assuming that this gives the judges less time to see my mistakes.

[Tim Wescott]

One other comment, that I don't think has been made yet: the amount of centrifugal force that your airplane exerts on the lines depends both on airspeed and line length -- or lap time and line length, if you prefer.  As far as I understand this whole stunt thing, what keeps you up in the air in the overheads is largely centrifugal force, and if you go too slow you're going to lose that.

So for any given line length there's going to be some minimum ground speed (not air speed) that must be maintained to keep tension.

Unless I don't know what I'm talking about...

[Brett Buck]

One other comment, that I don't think has been made yet: the amount of centrifugal force that your airplane exerts on the lines depends both on airspeed and line length -- or lap time and line length, if you prefer. 

    And the weight, which is actually a critical point.

    Brett

[proparc]

I think lap times are EXTREMELY IMPORTANT when you are either thinking about, or actually flying for other people,i.e. a contest. Other than that-screw it!!

[Bill Little]

Wow, almost 5 years later and this thread reappears.

Maybe I am still out in right field, but I have always believed that a particular model will need to fly at a certain "speed" (be it airspeed which was what I was lead to understand, or ground speed, I guess ) to maneuver properly, such as generating lift and cornering ability, etc..  Get the needle set where the engine likes to run, get a prop to fly the plane at the speed it needs to fly properly, then adjust line length to get where "you" are comfortable.  Of course, all the necessary trimming has to take place regardless.  It seems from talking with the big guys (a term of endearment! ) that a model will have a speed where anything slower and it just doesn't perform, but it "can" fly faster with no loss of performance if you can fly it there.

Around the time this thread started, we had a model (Aaron's Ares) which was an excellent plane and originally powered with an OS .32F.  On .015s which were about 60' eye to eye, it flew best at 4.9-5.0.  A relatively thin airfoil, but fairly light (37 oz. RTF)   We got a Magnum XLS .36 compact case like PTG was touting.  This engine allowed the model to slow down to 5.2-5.3 (3 tenths of a second on the same length lines is a decent difference I would think) on the same lines with more authority.  The extra power with different props let the model fly slower and not lose performance. 

Personally, it seems that I am most comfortable (and I have actually been flying regularly) when the laps times on lines in the 63'-65' E-E length is about 5.3-5.4.  But the plane is flying at different "speeds" when the line length changes, and we are getting a touch more room to maneuver in by using the longer lines (yet isn't closing speed also at a higher rate?).  All bets are off when I fly the Tomahawk with the OS .20FP BBTU, it is usually around 4.8-4.9 on 58'-60' E-E but doesn't feel "fast".

Ted, if you see this (since you did chime in on the factors), how much does line length come into play?  A 5.2 lap on 63' E-E versus a 5.2 on 66' E-E is a significant difference in aircraft speed, right?  Or not?

Thanks!
Bill

[Russell Bond]

It's almost 2.5mph difference, which is quite noticable.

[Serge_Krauss]

  A 5.2 lap on 63' E-E versus a 5.2 on 66' E-E is a significant difference in aircraft speed, right?  Or not?

Thanks!Biill

Hey, I'm not Ted! But...

It's not just faster, but it generates higher line tension, which for equal lap times turns out to be proportional to the flight radius.

For the example given (I'll leave out the dreaded 9th grade math), assuming that 66' eye-to-eye is about 70' of flying radius, that's an increase of about 4.5% in line tension.

...FWIW.

SK

[john e. holliday]

I am surprised that this has been brought up again.  A fellow flyer I used to fly with a lot, used to say a plane should fly some where around 60-65 MPH.   I am in the old school of if the plane is finally trimmed to my saticfaction,  The only thing I reach for is the tach and see what the engine is turning while still warm.   Some times I let the engine cool out and then start it and check it in the first 30 or so seconds.  Don't touch the needle and fly.