SEN 1304<
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Table of Contents - SEN 1304
Latest LH Update
More on Al
Larry Conover
F1Q and A
Pain is temporary, Quitting is forever
Latest LH Update
Hi Roger,
Would you kindly post this update to the SCAT ANNUAL Results?
Yesterday morning, May 24, 2009, at Lost Hills the postponed
F1H Flyoff between Jim Parker & Brian Van Nest was completed.
It was windy & Brian won it with a 128 sec RDTed flight, after
Jim had a poor launch for only a 44 sec flight.
Regards,
Lee Hines,
SCAT ANNUAL Contest Director
To report on Sunday's Bissonette Memorial Mini events,
about 830AM the wind dropped sufficiently, to allow CD Walt Ghio
to announce the contest would be for 5 non-round flights between
9 and noon, then FO decision would be forthcoming.
That went well for those that had stayed the day, as few DTed
flights went to the east dune or pits.
Jon Davis was extremely lucky to get his M&K F1H back when he
forgot to switch timer on and it landed near Holloway Gypsum HQ
after 20-some minutes.
Flyoffs started about 1PM.
Tiffaney O'Dell won the Coupe FO, Hal Cover won F1Q, I won A1
Glider FO and I am not sure who won F1J...Dave Parsons, I think.
On Saturday, the ABCP events were bothered by wind to the
extent that Walt cut the max to 120sec for some of the rounds
to keep from the big dune & pits to the east.
It was unfortunate that flight lines were placed in the hollow, as
the higher ridge to the east caused some to lose valuable time
OOS, when going a few hundred feet west would have given easy
line of sight for the timekeepers.
Ciao,
Leeper
More Al
I'm sure that Walt will send us the full results soon - But Jim Parker won F1A and Mike Roberts C and there is a 5 way tie for B to be flown off real soon now.
As you may have gather from Lee whinging, Walt moved the flight line south west and it was better and we did not go over the ridge and down the hole. Most people liked the new place but agreed that to keep the Leeper and friends happy we should try a a little further south. back in fact to close tot where we first flew from at Lost Hills. We need too rumble around a bit on the bikes - thanks moto flapper Mike - to chase the snakes away.
But a great contest organized by the Walt, a few new and semi new people. Great to see John, son of FAI flyer Pete Buskell, down from Canada with his vintage FAI Night Train
Larry Conover
Roger:
Tammie Walker, Larry Conover's granddaughter wrote me this morning to let me know that he passed away last week, 5/21/2009 Thursday morning at 12:30 am. 'He was an amazing man and there will never be another like him' she said. Very true.
He will be sorely missed.
Bob Beecroft
F1Q and A:
I read with interest comments on F1Q, a very controversial topic. I was interested in F1Q when the rules first came out in 2005, so I spoke with some of the US R/C electric team flyers to understand what performance might be possible (and as a result, immediately decided never to pursue F1Q !).
Comments in SEN have made interesting comparisons with F1B, so here are my observations, based on current R/C technology:
Electric propulsion is similar to rubber power: batteries store energy like rubber; and motors release energy like prop hubs. Performance is limited by the specific rules. Competitors try to maximize performance of every possible aspect. So let's compare F1B and F1Q:
F1B Comparison:
Q: Do you think Alex Andriukov uses good rubber ?
A: yes / no
Q: Does he use the very best ?
A: yes / no
Q: Does he spend a lot of time and resources to make sure it is the very, very best ?
A: yes / no
Q: Does he worry about the cost of this rubber, relative to his model, travel etc ?
A: yes / no
Q: Does he try to preserve this precious rubber by being really, really nice to it and only winding on a few turns, so as not to harm it in any way ?
A: yes / no
Q: What then does he do with this wonderful rubber after he has made a contest flight ?
A: a) He carefully saves it in cotton wool so that it can rest for the next contest
b) He stores it in a cold dark room for several months for the next contest
c) Having wound it mercilessly to the limits of destruction, he doesn't think twice
about throwing it away immediately
F1Q Comparison:
Q: Will you use a good battery ?
A: yes / no
Q: Will you use the very best ?
A: yes / no
Q: Will you spend a lot of time and resources to make sure you have the very very best ?
A: yes / no
Q: Will you worry about the cost of a battery, relative to the model, travel etc
A: yes / no
Q: Will you try to preserve your precious battery by being nice to it and only charging / discharging it very slowly so as not to damage it in any way.
A: yes / no
Q: What will you do with this wonderful battery after you make a contest flight ?
A: Did you learn anything yet ? If not, re-read the F1B questions.
In Luddite terms: Rubber quality is measured by its capacity to store energy by weight (energy density). Battery quality is also measured by its capacity to store energy by weight (C Amp hours = energy density), and by its ability to release energy over time (Watt hours = power density). The standard manufacturer's capacity "C" rating is based on a 1 hour, or 60 minute discharge rate (ie 1C x 60 minute = 60 C minutes). As this discharge rate is increased, (ie 2C x 30 minutes = 60 C minutes, or 4C x 15 minutes = 60 C minutes, etc) battery performance suffers (= efficiency loss, ie actually less than the theoretical 60 C Amp minutes output is achieved) but often a more useful power output can be obtained. Currently, a 20C maximum discharge rate is typical for good quality Lithium based batteries (ie 3 minutes x 20 C = 60 C Amp minutes theoretical). So a 1 A/hr Lithium cell can be discharged at 20A for 3 minutes (lets say 3 volts per cell) = 60 Amp minutes x 3V = 180 Watts. But when the motor shuts off at 25 seconds (say _ minute, allowing for spooling up the motor before launch) it has only used up 1/6 of its stored energy ! So you could make 6 flights back to back without re-charging !
Would this be a winning strategy for F1B ? Let's see: Wind up 600 turns in round 1 and have the prop stop work after the first 100 turns have run down. Then save the remaining 500 turns for the second flight (another 100 turns used) and third, forth, fifth, sixth etc. Will this put you at a disadvantage compared to Alex ? But wait, there's another way. Only wind up 5 grams of rubber for the first flight, and save 25 gms unused for later flights, then use another 5 gms in the second round, etc. But don't forget to carry the extra 25 gms as ballast, because of course you cannot cut a battery up into smaller pieces, like you can with rubber motors ! Is it likely this approach will be any more competitive ? So how do you get all of the energy from a Lithium battery in just 25 seconds (or shorter in a reduced motor run fly-off). That's easy, just set fire to the battery. You will get all the energy, all at once, but instead of an electric motor you will need a rocket nozzle ! Do you understand yet that Lithium batteries are never going to work for this competition. They are nice and lightweight, but that is all they have going for them. You simply cannot get the power out of them in a short time. All the other models will be 6 times higher than you when the propeller folds ! Shorter motor runs in the fly-off make this even worse !
But wait, the rules already allow for this conclusion, you are permitted to use another type of battery ! So what competition class discharges batteries very quickly? No, not R/C electric model airplanes. I mean really quickly ? How about R/C car drag racing. Does it take them 60 minutes (1C) to finish the course ? How about 1 minute (60C) ? How about 30 seconds (120C) ! No such times will still come in last place. Do they use 20C Lithium batteries ? (Did we learn anything yet ?) What is the discharge rate for R/C car drag racing - try 200+ C ! Do they ever use this battery again (re-read F1B Questions !). What type of wonder-battery is this ? Very low internal resistance Ni-Cd or Ni-MH cells. Ahh yes, we can use 125 gms of these in F1Q !
So, how do you size the battery pack ? Cells are only available is finite step size increments. So a 125 gm battery = 12 x 10 gm cells, or 11 x 11 gm cells, or 10 x 12 gm cells, or 8 x 15 gm cells or 6 x 20 gm cells or 4 x 30 gm cells, etc (unless you make your own cells !). You will want to remove all of the battery insulation, connect cells directly end-to-end with no wiring, and mount connectors directly to the battery end terminals without any wires (so that the processing weight of the "battery" is at the absolute minimum, ie all battery with no extras wires or insulation). If you are really serious, you will want to chemically-etch the cells to minimize wall thickness and reduce unwanted mass. Then get an electric motor custom wound to provide peak available power / efficiency for the available electrical energy and (big) propeller size you want to use. Of course you will want to pre-heat the battery cells before launch (F1Q is more like F1B than you thought !) to momentarily boost their voltage just before launch, which will last throughout the climb, before you completely destroy them in flight anyway and hope they do not catch fire half way up the climb.
http://www.cheapbatterypacks.com
International model drag racing association
80 mph in 2 seconds
rc model car drag racing batteries
132 ft track in 1.5 sec
Lithium batteries provide very good energy density (storage capacity by weight) but comparatively limited power density (ability to quickly release that energy for their weight). Hence they are good for long duration, slow drain applications (cell phones and laptops - note there is no FAI class for 25 second laptop duration events, and for good reason) but not so well suited for short duration high drain rate applications (monster power tools). A 25 second motor run (or less !) definitely constitutes a short-time, high rate, discharge.
Ni-Cd and Ni-MH cells are not very impressive for energy density compared to Li-Po cells, however, they can provide very high power density, during extremely high discharge rates, over very short periods of time, which is simply unattainable with Li-Po cells.
The present Li-Po cells are typically restricted to 20C discharge rates (although getting slightly better), whereas Ni-Cd, and some of the new Ni-MH, can be discharged at literally TEN TIMES higher rates. Note, you will never see such discharge rates quoted by manufacturers, but modelers routinely void the warranty and exceed the advertised limits to get the best performance (remember these batteries will go in the trash after 1 flight, just like your F1B motors).
There are drawbacks with high rates of discharge, because the total energy content of the cell (the manufacturers rating) will not be fully obtained at these quick rates. Generally, Li-Po cells suffer a rapid decline of discharge efficiency (ie reduction in effective capacity) as the rate increases, whereas, Ni-Cd and Ni-MH cells, which have lower energy content to start with, can maintain a more consistent discharge efficiency (ie a lesser reduction in effective capacity). Therefore at very high discharge rates, the relative comparison of these different types of cells is reversed. The important factor is to select cells with the lowest possible internal resistance, so that heat buildup during very high rate discharge is at least minimized, or delayed, either way the cells will be ruined, you just don't want to set the model on fire as well, if it can be avoided ! Although, this could help improve visibility in fading daylight during a fly-off !
If you think F1B is challenging now, imagine what F1Q will be like with 4,000 different manufacturers of rubber ! Now it is not just like trying to choose from the April batch of Super Sport Tan versus the September batch. So with 4,000 different batteries to choose from, as previously reported in SEN, this is the equivalent of having a new batch of rubber for every day of the year for 11 years ! Add to that, not just two or three manufacturers of propeller hubs, but instead 400 electric motor manufacturers, plus the available propeller combinations and speed controllers, and you have quite a test program on your hands ! Here at last we have some good news, because now we may have a permanent solution to our age old problem of lack of flying sites ! Not only will electric Free Flight solve the noise problem, but competitors will be spending so much time in their workshops (laboratories ?) testing battery discharge rates, and testing motor and propeller combinations, that they will never actually get to the flying field ! Instead they can email each other their results, in a kind of global internet challenge to see who has the greatest potential for success in F1Q. This will also help solve Global Warming, because no longer will you need to jet around the planet to travel to contests, and this will also help solve the timekeeper, eyesight, binocular and retrieval problems in one fell swoop. Contests can be held completely by computer.
Taken to its logical conclusion, this electrification of Free Flight power model flying will ultimately be performed only with electrons. No balsa will be involved. In fact models will become redundant.
The conclusion is that F1Q rules permit considerably better than F1C-on-steroids performance (approaching a 1 KW destructive discharge) with 5 times the motor run. Let us see, 200m climb multiplied by 5, should reach around 1 km on climb, if you can still see it (the battery smoke trail will certainly help), with a duration of around 8 minutes multiplied by 5, yes that's 40 minutes (if your stopwatch batteries have not gone dead by then).
Last question:
Q: Do you plan to fly F1Q anytime soon ?
A: yes / no
- Biqqles
Pain is temporary, Quitting is forever*
My first observation is that's just as well that the guys from AV :
Alex focusses on F1B
and he's got Dave Saks to do that too,
Biggles confines his FF activities to writing,
Jim L .. well it's, ... Jim!
So the rest of the semi-normal sometimes swaydoe-FAI flyer who work on Q can enjoy themselves.
I need to go to the local R/C drag strip because I've never found the high discharge NiMH Biggles talks about, my battery quests with NiMH have been stumped by a very low c-rate. Maybe the NICAD are better or there is a plot with the AMA that protects us simple modelers from finding those batteries?
I do agree with the group captain that the evolution of F1Q is going quite slowly and people are so far having trouble harnessing all the power available. It is still possible to be competative with quite a modestly performing but reliable airplane. While there is not question that F1Q could smoke its way to 1000' at the current rate of development we are aways from that today - so what is there to fly , lets just stop FF now because the same argument could be applied to every class.. There's no way that Don Zink can run around the field like Rene Limberger even Grandfather Brian, nor can le launch as high, so why does he come out and fly and do well, I guess no one's told him that yet?
*Lance Armstrong, cyclist
........................... ...
Roger Morrell