F5J as an official FAI event? - RC Groups
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Nov 04, 2009, 08:32 PM
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sneu's Avatar

F5J as an official FAI event?

Here is a question for the people that fly LMR type sailplanes --if the FAI created a new class along the lines of F3J would fliers in the US be interested? Such an event is in the works and has a good chance of replacing F5F in the rule book.

It would be a duration event with a spot landing with the motor run limited by an energy limiting device similar to that used in F5B and F5D. When the watt-minutes are reached the signal to the controller is set to the off condition.

The subject will be up for a vote at the next FAI meeting in March 2010, I think it could prove to be a popular event and could be added as a WC event in the future.

If you have comments pro or con now is your chance to have a say.

Steve Neu
F5 SC Representative, USA
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Nov 04, 2009, 08:53 PM
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Ralph Weaver's Avatar
Great idea. There are others using altitude limiters, but I think energy limiting would be more reliable and easy to verify. It's another way to solve the horsepower race.
Initially there would be an advantage to those would could come up with a more efficient system, but after a couple of years I think everyone would settle on similar systems and the focus would be on flying.

Any thoughts on how long the motor run could be? Can you run 10A for the entire flight?
Nov 04, 2009, 09:03 PM
Jesper Frickmann
jfrickmann's Avatar
It really depends on the actual limits defined by the class. On one hand, if it is going to be another over-powered, out-of-sight contest (like I find the AMA rules of today are) then I am not interested. On the other hand, if it's going to be Speed 400 like, then I am not interested either. To me, a good balance is something around the popular 3S 2100mAh range. And if the Watt*minutes is the limiting factor, then hopefully we can choose cell count and battery size more freely, without e.g. a 8.4V limit like in AMA class A.

I think it is really important to find a reasonable balance, if we want people to join the fun. Around here, there are no one competing in e-gliders, as far as I know. I sometimes fly TD with my club using a reasonable motor run that compares to the winch launch.

Thanks for giving this heads-up here on RCGroups and asking for our input. I really appreciate that! Now, the next 20 people will probably give you 30-40 other views on how it should be done

Nov 04, 2009, 10:37 PM
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AndrewBurns's Avatar
How would timing be accomplished? I assume you'd be allowed one motor run, motor must be running before the glider leaves the hand and the power limiter turns off the motor after the specified watt-minutes. Does the timing start as soon as the motor turns off? That could be hard to see if the glider is very high up when the motor cuts. However if the timing starts as soon as the motor starts then people will just attempt to fly the full task doing laps at low level with the motor on...

10 minute task? 6 minutes? 5?

How about the power level. I'm making a glider for Australian LEG rules and it will use a 1110/1Y/6.7 with a 14x10 prop and a 3S1P 1600mAh lipo. For an amp draw of about 80A and a battery voltage of about 10V that gives an instantaneous power draw of about 800W. I anticipate I'll be using climbs of maybe 5 seconds at most for the aussie comp, would this setup still be competitive under new rules I wonder?
Nov 04, 2009, 10:57 PM
Registered User

Like the idea, but there are so many items to address.

1 define the task; thermaling with a spot landing as a tie breaker or not. What will be the winning element

2 keeping the power train advancements;ie not limiting the power in such a way as to take all technology out of the event

Love to see a world class event.

Nov 04, 2009, 11:11 PM
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AndrewBurns's Avatar
As a bit of a tangent to what Ric said, I would like to see the power perhaps VERY limited. When I watch F3J/thermal duration compeitions it seems to all boil down to a landing comp. Most of the new F3X gliders can easily do 10 minutes in dead air from a good winch launch, at a competition I went to recently the difference between first and second was something like a single bad landing over 3 days of flying, there were also numerous 'perfect flights', the better fliers had many many perfect flights. I don't fly the big winch gliders but it seems to me they're just making it a landing competition in a lot of ways, as evidenced by the new F3J landing tape rules.

I would prefer to see the amount of power available so low that the gliders really have to thermal or else they have no chance at making the time, that way pilot skill will play a larger role than spot landings. Perhaps a 100 watt-minute limit or something, the glider power-train I described in my previous post would use about 67 watt-minutes for a single 5 second motor run which would probably get it to a good thermal height.
Nov 04, 2009, 11:50 PM
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Lenny970's Avatar
Sounds great Steve........I'd be interested!

I think what has been holding back F5J type competition so far has been the lack of consistant rules and having an FAI defined event would go a long way toward resolving that.

FAI events are generally about high performance flying, so I'd like to see a power level adequate for a strong climb in an F3J (~3.5M) type airframe. Many of the F3J models are already available with an electric fuselage, so the foundation is already in place.

This shouldn't be an eyesight contest, so the rules should provide some incentive to encourage the pilots to keep the climb short. This keeps things interesting and makes it a thermal contest.

Nov 05, 2009, 04:31 AM
Registered User
I agree completely that some form of energy or height limited comp format is the way to go. Here in the UK we've been trying out a 200m height-limited eSoaring format - and it has been a great success from club level right up through to national level in both 2m and open classes.

Everyone launches to 200m (665ft) within a possible 30s motor run before it's cut automatically. The height limiters have proven very reliable indeed and even contain an anti-zoom feature for those running hotter motor setups - not that they're any real advantage in this format. As the units also contain a logger it is extremely easy to verify the launch altitude (ie cut-off). However, this has rarely been called for, either by the comp CD or other competitors.

An additional unlooked-for benefit has been that most competitors can now run a whole comp of 7 rounds on only 2 batteries (1 each for morning and afternoon rounds), which has become popular at club/regional level.

Slightly off the main point, you may be interested to know that we also run a slot time of 11mins within which you have to complete a 10min target time. You're also allowed a re-launch, so that in poor conditions if it looks as if the flight might not extend beyond 5mins it's an interesting tactical decision to relaunch or not. (Remember, our UK weather doesn't always give decent flying conditions!!)

Hope you find my 2 cents' worth helpful.

Nov 05, 2009, 06:40 AM
turn, turn, turn.
Originally Posted by sneu

It would be a duration event with a spot landing with the motor run limited by an energy limiting device similar to that used in F5B and F5D. When the watt-minutes are reached the signal to the controller is set to the off condition.

Steve Neu
F5 SC Representative, USA
Are multiple motor runs allowed?...If, of course, you still have some energy left.
I think the answer should be "yes"....with no penalty besides motor run time deducted.

I also think that motor run time should be subtracted from the task time.....as per F3J (tow time substituted by motor run time).

Regarding the amount of energy allowed, I fly the AEFA Postal, and I like the Aussie rules a lot.....It seems that the energy is limited to around 1000 watts, given the 6600 mah rule.
Most guys use from 3-5 seconds of motor run to get to a few hundred feet. Relights are Ok......
Flight time task is 5 minutes.
I would say that 12-15 seconds of availiable motor run time would be good for a 10 minute task.

So....I would say around 250-300 watt-minutes would be a good solution.
Nov 05, 2009, 06:54 AM
around Colombia
ShredAir's Avatar
Good idea. Keep the FAI landing, no spot dorks.
If the limiter could record total energy used, how about subtracting points for every watt-minute used (or something like that). This means the less energy you use, the better off you are. If you hand-lauch your model power-off into a thermal and complete the task without motor-run, no points are deducted. But maybe then this would become a F3K contest...

Dieter Mahlein, ShredAir
Nov 05, 2009, 07:49 AM
Registered User
AndrewBurns's Avatar
Yeah if that were the case I'd just put a 2 gram brushless motor into an e-blaster 2 and have at it :P Although you'd never get 10 minutes with one unless there were decent thermals about.
Nov 05, 2009, 09:18 AM
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Ralph Weaver's Avatar
I'm encouraged to see the possitive nature of this thread, some of these discussions get a little crazy.

I'd like to repeat what's been said above... We should have power limitations that will get a current F3J plane to roughly the same height as current F3J launches in about the same time.

I think the limit should be somewhere near 1000W for 10-15 seconds. I dont' have a 'calc here, but I think that should get a 70oz, 3m plane to about 600'. To be competative you'd need to be able to climb at 3000-3500 fpm. I have a plane with 2S and a $60 motor that will do 2600fpm, so that's not that hard.

I assume that motor run would somehow be penalized or deducted from the score? That would result in a power race which most of us would like to avoid. The only way I can see to solve this is to allow an open motor run of 10-15 seconds, then start to penalize for extra motor time.

There will be complaints that "My Radian can't climb to 600' in 10-15 seconds...", but this is to be a world class event, then you'd have to expect that you'd need good equipment (but not crazy) to win.

I'd hope that something like an E-Supra running 4S at about 75A would be more than good enough to win at the world level. If we have to do 250A to win, then I don't think it has a chance.

I'd hope that as people comment on this topic that they are thinking of the future and not just "will my current plane and strategy win".
Nov 05, 2009, 09:52 AM
turn, turn, turn.
Originally Posted by Ralph Weaver
I'd like to repeat what's been said above... We should have power limitations that will get a current F3J plane to roughly the same height as current F3J launches in about the same time.
I have to say that I disagree with this basic strategy.

I say this because it tends to promote a strategy that starts everybody at the same height.
I believe that to keep the contest more of a thermal type of contest, then low level thermaling should be encouraged, as well as low motor run times.

As Dieter has suggested, a sub second motor run would be awesome.
Ray Pike had just such a flight, in last months' postal.....It was recorded on a gas box.

Further, if multiple motor runs were allowed (with the run time deducted), then poor thermaling or air reading skills, would be reflected in the scores.
Nov 05, 2009, 10:28 AM
Flying = Falling (Slowly)
dharban's Avatar
Originally Posted by Ralph Weaver

I think the limit should be somewhere near 1000W for 10-15 seconds. I dont' have a 'calc here, but I think that should get a 70oz, 3m plane to about 600'. To be competative you'd need to be able to climb at 3000-3500 fpm. I have a plane with 2S and a $60 motor that will do 2600fpm, so that's not that hard.

I would very much like to see movement toward some type of FAI rule for these planes. But any such move should be very, very thoughtful. It is clear that F3J did not exactly end up being the sedate, tow line launched event that was originally envisioned. There is an important principal here:

"Except in the case of some sort of "one-design" rule (which I would not advocate) the rule designs the plane and not the other way around."

To explain -- I currently fly two different "competition capable" planes. An E-Ava and an Electron F5J. They are both very capable planes. And they both have measured climb rates in excess of 3000 fpm. While I couldn't put my hands on the exact recorded values, the E-Ava runs at around 750 watts and the Electron runs at around 175 watts. (Both are using outrunner motors). If the event were limited to some value consistent with your 1000 watts for 10 seconds (10,000 watt-seconds) the E-Ava would launch to 666 feet and the Electron would launch to 2857 feet. This disparity would suggest that a power limited event would tend to move planes away from the 70 oz., 3 meter plane to something smaller and lighter. There is a point of diminishing returns which would likely fall short of the Electron's extreme light weight and small size, but I suspect that a rule designed to lift a 70 oz. plane to 600 feet would quickly morph to smaller, lighter planes. I love the Electron, but frankly, when it gets to 1200 feet it is very small and when the wind is blowing 10 kts or so, keeping it at the field is problematic. But my experience with it suggests that plane somewhere between the E-Ava and the Electron could use it's 10,000 watt-seconds to get to 1200 feet or so -- an altitude from which 10 minute flights are pretty easy.

Simply put, a rule designed to provide power to lift a 70 oz., 3 meter plane to 600 feet will more likely result in smaller, lighter planes. After all every 100 feet of altitude is the equivalent of about 1 minute of dead air flying time. A power rule without other restricting parameters may not result in the kinds of planes and competitions which will be interesting or which will attract competition

Clearly, a power limiting rule with a minimum flying weight parameter could quickly move the event into a regime where the rule resulted in something approaching the 600 foot "equivalent launch height" which is being sought to emulate F3J.

Or, in the alternative, a rule incorporating a simple altitude cut-off switch would come closer to achieving more-or-less equal launch heights. I have flown my planes extensively with such a device and find it to be quite effective in emulating TD flying. (Even here, it should be understood that the "rule will design the plane". And in the end the planes which compete under it may bear little resemblance to the planes which we currently fly. That's the way human ingenuity works.

Happy Landings,

Nov 05, 2009, 11:17 AM
You looking at me?
Ed Franz's Avatar
I would tend to agree with Don. A altitude limiting device opens up the contests to a bunch of different planes and motor/batteries all starting at pretty much the altitude. I am not saying a energy limiting device would not work as well, I just think a altitude limiter is a simpler way to go.


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