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General control line discussion => Open Forum => Topic started by: Nova Joe on August 19, 2019, 12:10:51 PM


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Title: Lap times
Post by: Nova Joe on August 19, 2019, 12:10:51 PM
Why is there an effort to have a specific lap time. 5.2 seems to be very popular in my area but I donít understand why. If a 5.5 lap time maintains line tension and allows the maneuvers to be completed, why would I want to increase angular velocity to reduce the lap time. Conversely, if a 5.0 lap time accomplishes the pattern, iwould there be a valid reason to increase lap time?
Title: Re: Lap times
Post by: Howard Rush on August 19, 2019, 12:39:08 PM
It would be what scores best, which I figure is the speed your airplane flies best. My Impacts vary from 5.18 to 5.4. Dallas airplanes fly well at 5.6 or so.
Title: Re: Lap times
Post by: Tim Wescott on August 19, 2019, 12:58:03 PM
5.2 is a pretty good number for a newbie pilot flying on 60 foot lines.  The better the plane is trimmed, the slower it can go and maintain tension.  To a degree, longer lines let it fly at a bit higher airspeed while getting longer lap times and maintaining line tension -- but there's tradeoffs (which I don't understand -- I build porky planes that like to fly on really long lines, and I don't experiment with line length as much as I should).

Dialing down the speed and refining the trim is a good thing to work on, but make sure you do at least some of the work in the wind -- on a nice calm morning you can go a lot slower than on days when part of your stunt pattern is to dodge lawn chairs and small children that are getting blown across the circle.
Title: Re: Lap times
Post by: SteveMoon on August 20, 2019, 06:35:24 AM
I'm not really sure why 5.1-5.2 lap times seems all the rage now.
Looks too fast and herky-jerky to me. Bob G always told my brother
and I that the slower the better, of course with good line tension. He
usually tried to be in the 5.6 range. The first time Doug made the Top 5
he flew the whole week at 5.95.

My current plane performs best at 5.7-5.8. If it flies good at that speed
I don't see any reason to speed it up. I think the best way to think of
it is to fly as slow as possible while still maintaining proper line tension.

Steve
Title: Re: Lap times
Post by: peabody on August 20, 2019, 07:43:56 AM
Windy always suggested that 40 sized planes fly at around 5.0 and larger at 5.2
Title: Re: Lap times
Post by: Ken Culbertson on August 20, 2019, 07:54:00 AM
I'm not really sure why 5.1-5.2 lap times seems all the rage now.
Looks too fast and herky-jerky to me. Bob G always told my brother
and I that the slower the better, of course with good line tension. He
usually tried to be in the 5.6 range. The first time Doug made the Top 5
he flew the whole week at 5.95.

My current plane performs best at 5.7-5.8. If it flies good at that speed
I don't see any reason to speed it up. I think the best way to think of
it is to fly as slow as possible while still maintaining proper line tension.

Steve
y1 y1 y1
At my age I would fly at 10.0 if I could get a plane to stay out on the lines at that speed.  Maybe a hovercraft, wonder if that would be legal?  I still do not know why the pressure to conform.  It is a compromise between the flier and what is being flown and each one is going to be different.

Ken
Title: Re: Lap times
Post by: Steve Helmick on August 23, 2019, 08:10:27 PM
Seems to me that on the west coast, there may be more emphasis on a "blinding corner" than elsewhere. I'd like to offer proof, but I haven't watched stunt being flown elsewhere.

Personally, being the slacker and low-life local yokel stunt grunt that I am, I don't pay any attention to lap times, but adjust the speed until the airplane wants to fly and keep the lines fairly reliably snug. I really don't know what that lap time is and don't really care. Usually somewhere around 10k rpm, tho.  #^   Steve
Title: Re: Lap times
Post by: Dwayne on August 24, 2019, 05:02:59 AM
Seems to me that on the west coast, there may be more emphasis on a "blinding corner" than elsewhere. I'd like to offer proof, but I haven't watched stunt being flown elsewhere.

Personally, being the slacker and low-life local yokel stunt grunt that I am, I don't pay any attention to lap times, but adjust the speed until the airplane wants to fly and keep the lines fairly reliably snug. I really don't know what that lap time is and don't really care. Usually somewhere around 10k rpm, tho.  #^   Steve

^^^This^^^, I haven't used a stopwatch in years, I set my planes up to where I feel comfortable flying the pattern with good line tension.
Title: Re: Lap times
Post by: john e. holliday on August 24, 2019, 11:02:06 AM
As I have stated in the past, lap times are good to know after you have the plane flying comfortably.   As you travel to different parts of this great country of ours you may have to adjust the air speed or line length.   There are so many things to get a plane flying to your satisfaction and then it is up to you to impress the judges.

Also don't forget fuel and props figure into the equation. D>K
Title: Re: Lap times
Post by: Nova Joe on August 24, 2019, 09:53:09 PM
Thanks to all for the replies. From what Iím reading, a specific lap time is not necessarily a goal. You donít score more points with one time over another. Keep the plane out there with good control, be comfortable and let the time be what it is.
Title: Re: Lap times
Post by: Crist Rigotti on August 24, 2019, 10:41:29 PM
Thanks to all for the replies. From what Iím reading, a specific lap time is not necessarily a goal. You donít score more points with one time over another. Keep the plane out there with good control, be comfortable and let the time be what it is.

Right!
Title: Lap times
Post by: Dennis Moritz on August 25, 2019, 01:56:39 AM
If the planes falls out of the air when hitting the vertical in many cases itís necessary to go faster. Fly a reverse wingover. Enter the vertical with a moderate corner. If the plane comes in on you it probably needs to go faster and/or lines need to be shorter. Fiddling with leadout position might help some. Aim is to adjust lead outs so that plane flies tangent to circle. If this doesnít do it plane is flying too slow. Probably. Iíve flown many overweight stunters. I was BOM, buyer of the model. Necessary lap times have hit ďmanly speeds.Ē Quoting Steve Fitton. If the trim is on, even close, and your dog falls in at the top of the vertical increasing speed often is the only option. Not optimum, a definite liability, at times itís the only solution that works.


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Title: Re: Lap times
Post by: John Lindberg on August 25, 2019, 06:36:07 AM
I'd say an hour and a half per lap at my age! Gives me time to look for ticks!  :!
Title: Re: Lap times
Post by: Nova Joe on August 27, 2019, 12:52:11 PM
Methinks Ken, John and me are in agreement...time the lap with the minute hand😊
Title: Re: Lap times
Post by: Tim Wescott on August 27, 2019, 01:05:35 PM
Methinks Ken, John and me are in agreement...time the lap with the minute hand😊

You might be erring too far the other way.

While it's a mistake to try to rigidly set lap time to someone else's ideal, there is still a best speed (and, hence, lap time) for a plane in any given state of trim.  So if you're really serious about this stuff you should measure your lap time and know it, and you should deliberately adjust it along with the other parameters.  And then, you should check it, as an indication that your power package is doing its job properly and consistently.
Title: Re: Lap times
Post by: Frank Wadle on August 28, 2019, 12:57:44 AM
It is interesting to read the different thoughts on laptime.
Iím flying in Europe and get to see people like Igor Burger fly almost every contest I go to.
He and his followers are usually in the 5-5.2 sec./lap range.
In general it seems to me that (with some exceptions) electric planes need faster laptimes.
Iím flying IC and I usually aim at 5.25 sec. But since an IC-Engine responds to a change of temperature it is always difficult to achieve this laptime exactly.
Last contest I flew for example we were only able to practice early in the morning at nippy temperatures or in the evening. This made it difficult to set the needle for the contest flights at higher temperatures. The result was a 5.0 in first round, a 5.4 in second round and a 5.2 in third round.  (Please donít mention a tachÖ. Doesnít work on my engine since it doesnít respond on the ground)
One thing that wasnít mentioned so far is the effect such variations have on the pilot. It messes with the timing. And the plane responds differently for each laptime (rudder response, tracking,Ö.). I think this is the big advantage of electric vs. IC. The laptime is much more consistent and much less affected by weather changes.
Title: Re: Lap times
Post by: Peter in Fairfax, VA on August 28, 2019, 07:33:01 AM
For what it's worth, measuring lap times is popular in my area, especially for those using IC engines.  Just last weekend, my lap times were high, with reduced tension.  I was running a new fuel and had set the needle rich.
 When I adjusted the needle for lap times around 5.2, the plane was easier to fly in the overheads (wingover, overhead eights) plus gave better top corners in the hourglass.

For an IC engine, probably a tach combined with lap times is the best quantitative measuring technique to get a consistent starting point.

On a somewhat related point, has anyone experimented with using a handheld IR thermometer to measure head temp?

https://www.amazon.com/Infrared-Thermometer%EF%BC%8CDigital-Thermometer%EF%BC%8C-50-380c-Pyrometer-Temperature/dp/B07M5GRPX2/ref=asc_df_B07M5GRPX2/?tag=hyprod-20&linkCode=df0&hvadid=343868117984&hvpos=1o1&hvnetw=g&hvrand=9393451670710323369&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=1027116&hvtargid=aud-801381245258:pla-751853204353&psc=1&tag=&ref=&adgrpid=68767445426&hvpone=&hvptwo=&hvadid=343868117984&hvpos=1o1&hvnetw=g&hvrand=9393451670710323369&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=1027116&hvtargid=aud-801381245258:pla-751853204353 (https://www.amazon.com/Infrared-Thermometer%EF%BC%8CDigital-Thermometer%EF%BC%8C-50-380c-Pyrometer-Temperature/dp/B07M5GRPX2/ref=asc_df_B07M5GRPX2/?tag=hyprod-20&linkCode=df0&hvadid=343868117984&hvpos=1o1&hvnetw=g&hvrand=9393451670710323369&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=1027116&hvtargid=aud-801381245258:pla-751853204353&psc=1&tag=&ref=&adgrpid=68767445426&hvpone=&hvptwo=&hvadid=343868117984&hvpos=1o1&hvnetw=g&hvrand=9393451670710323369&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=1027116&hvtargid=aud-801381245258:pla-751853204353)

Peter
Title: Re: Lap times
Post by: Steve Helmick on September 03, 2019, 06:50:42 PM
You might be erring too far the other way.

While it's a mistake to try to rigidly set lap time to someone else's ideal, there is still a best speed (and, hence, lap time) for a plane in any given state of trim.  So if you're really serious about this stuff you should measure your lap time and know it, and you should deliberately adjust it along with the other parameters.  And then, you should check it, as an indication that your power package is doing its job properly and consistently.

The more "POWER" (thrust or potential for more thrust, I'd say would be more proper description for the engineers and physicists) you stick into your model, the slower lap time you can fly with it. With weight remaining constant, along with CG and all those other trim factors, of course. This is why folks are sticking bigger engines into smaller airplanes and liking it...a LOT!  y1 Steve