After a 20 hours long bus ride, I made it to the city of Embalse, in Argentina; I´ve come to compete on indoor free flight, I´ll be flying two EZB (F1L category) againts seasoned fliers , but since I´ve done some very remarkable flight test I have a chance of making it to the first three positions.
In case you´re wonderingh an EZB plane looks like THIS (It isn´t me on that picture!) Weights 1.2 grames and is powered by a twisted rubber motor; so far my best flight has been 9:20 under 1400 turns, that made the other competitors look concerned.
VunderWife and I spent the morning at the Langley AFB airshow. Lots of cool planes, aerobatics, and the US Army Golden Knights for the girls to drool over.
One of the more unusual displays was an air cushion landing craft from the Little Creek Amphib base across the river. It flies, of course, but it doesn’t have wings. I stuck my head in every possible nook and cranny, and I was asked what I was looking for. Morays and congers, naturally. :dubious:
I was trying to find out the veracity of “My hovercraft is full of eels.”
Umm, excuse my ignorance here, but what actually do you do in these comptetions and how is it judged? Do you build your own plane to weight/dimension specifications then wind it up and let it go? Is there a specific elsatic band you have to use, or can people buy really expensive ones that boost power? Once the plane is airbourne, do you just watch and pray?
Just curious, haven’t ever heard of a competition for these before!
An indoor flight of 9:20? That leads me to think either
A. They fly really, really slowly,
B. They are under some sort of user control, or
C. The competition is held in the world’s longest building.
I can’t seem to figure how one of these babies can stay aloft for 9:20 without banging into a wall. Do they use some sort of system of fans to keep them on some kind of course?
I built a wooden box that has cushioned supports for differennt parts of the model, the box is 50X30X12 centimeters, and two models fit inside; the wing and propeller can be detached, and each part rests in it´s own support. Of course there´s a lot of overlapin´ going on there, the wings go over the stabilizators, the fuselages over the propellers…
Basically the one who flies longer, wins.
There are 6 flights, the seconds of two best ones are added to make the final score.
The F1L category (recognized by the FAI, Federation Aeronautique Internationale, my French ain`t good so forgive any spelling errors) The models should be built under certain limitations:
Maximum wingspan of 18 inches (48 cm)
Maximum wing chord (the width) of 3 inches (7.5cm) Minimum weight of 1.2 grams
Maxiumum stabiliztor surface area of 50% of the wing area.
The model should be built entirely of balsa wood, except for the propeller shaft and support
The model should be covered with a commercially available solid material.
That´s about it, there are some other restrictions.
Yeah, that´s pretty much it
In this category there´s no limit as for the rubber motor, as long as the plane is powered by an elastic motor it´s all fine and dandy. This days almost all rubber comes from a couple providers, one of them produces what is considered after much testing to be the best, and since it´s not more expensive than other types everyone uses the same rubber. However the selection of the appropriate rubber is extraordinarely complicated; if the strand is too thick there will be a powerfull burst of energy and the model will rocket to the ceiling, once there it can either keep bouncing if it´s flat or get tangled on whatever sort of structure hangs from there, in any case that´s an undesirable flight patter. The rubber must have the exact energy storage capacity to make the model climb slowly almost untill it touches the ceiling and then keep turning the propeller all the way down; preferably by the time the model stop on the ground there should be less than 10/5% of the turns still wound on the motor. Then the lenght of the motor affects how fast it´s energy is discharged, a short rubber loop unwinds faster than a long one, but the long one provides (all other things equal) less energy, so a longer motor may run for a long time, but that´s no use if it´s so weak that the plane comes down while it still has 50% or more of the turns unused.
Even more, a longer, thicker motor can store more energy than a smaller one, but it weights more, so it´s a delicate balance between having a strong enough motors yet a light enough one.
Now, the differences in thickness on the rubber are in the order of tenths of a milimeter, a 1.2 mm motor may be too much, but a 1mm one can yield a sluggish performance, so there´s an exact and precise thickness and lenght with which the model should perform at it´s top everytime… not…
Air temperature can affect the performance of the rubber, plus the overall performance depends on very small adjustments of the structure; so an optimum performance requires a very complex combination of tweaks that are quite hard to achive for every flight.
Well, I have to trust that all the adjustments and calculations work as planned… but divine intervention is always welcome!
Or… they fly in circles…
That´s another can of worms if you want to know the myriad adjustments needed for a precise flight orbit. Suffice to say that after the planes leaves my hand there´s not much that can be done. The rules allow to touch and correct the trajectory of the model with a fishing rod or whatever long object to avoid a collision, but only once per minute at most, and if a competitor abuses of that allowance the flight can be sanctioned. In any case it´s just a very small nod in the wing or tail to make a minute correction. However I don`t do that myself and I rather let the plane go unassisted.
If there´s a single thing that can describe the flight site is “Close that bloody door!!!”. The models are extremely sensitive to any wind draft, so sensitive that if a model flies over a person the heated air rising from the body makes the model jump up 10 or 15 cm!
So, no, no fans are allowed for any purpose.
OK, tomorrow is the big day, I´ll post the results here.
That makes sense. So much sense, in fact, that I think I’ll give myself one of these dealies: :smack:, wish you the best of luck tomorrow, and slink away unnoticed.
Competition day, six flights, the best two add for the final score:
First flight, mostly for checking the trimming is OK, flies flawlessly right under 7 minutes, I know that for every other hundred extra turns I wind I´ll get another minute of flight, since the motor can take at least 350/400 more turns I´m sure I can make
After two days of carefull trimming the model I was ready.
My plan was to make two moderate flights, progresively push the envolope a bit further in the next two and for the last two bet my shirt on it.
The first two flights worked out exactly as expected, the plane was working like a clock.
In the third flight disaster, for some reason after a few minutes the plane started to spiral dive, it came down quickly; at first I thought that the problem was that the plane caught a wind draft. this models are so flimsy that if for some reason they pitch down too much there´s a good chance that they won´t recover, the plane pics up speed and the structure begins to twist, it´s a vicious circle. So that´s what I thought…
Fourth “flight”, the model barely stays airborne for 10 seconds, it spirals sickly to the ground. Obviously there´s something wrong here, I make a quick inspection of the model and I find that the front wing post support is loose! :smack: Don´t ask me how it broke, I haven´t got a clue, I fixed it but then I kissed good bye to the two days of trimming.
Fifth flight, quite good until the model gets tangled on a f*cking wire hanging off the ceiling!, at this moment I should start to Pit the organization for that, it´s quite difficult to make this models fly without the addition of booby-traps. :mad: They should have removed those wires to begin with.
Sixth flight, seems that the ride on the wire threw whatever trimming still remaining right out of the window, the plane is a wreck, 30 seconds and thank-you-very-much.
sigh
In the end, out of 14 participants I placed 8th, it was very frustrating but not all that bad, considering that I got there with just the warm-up flights. Next year I´ll make sure to do a complete inspection of the airframe after each flight, a lesson learned I guess.
As a side note, my team mate and I are going to write a letter of complaint to the organization, apart from the wire thing and a general unfitness of the flying site there was a serious violation of the rules by the winner of the competition, the rules allow the flier to use a long rod to correct the course of the model in case of an imnent collision, and then only touching the leading edge of the wings; but that man kept touching and moving the plane all the time, not only controlling it´s direction, but also it´s altitude, wich is completely forbidden and a cause for disqualification; but the judge couldn´t be bothered by our complaints. :mad:
Ale, I’m sorry it did not work out as planned/hoped. Thank you very much for sharing your story though. It was a fascinating look into a hobby I have never had exposure to before. Very cool.
Good job with fighting ignorance (of hobbies). And good luck with your complaint.
What type of building was the competition held in? I don’t know about schools in Argentina, but I’d think a US high school gym would be a little small. A basketball arena, perhaps?
Not much, actually it´s a dirt cheap hobby, as for the materials needed anyway; we´re talking about 1.2 grams worth of balsa wood and covering material (mylar), even if the plane would be made of solid gold it wouldn´t be expensive.
All in all, on a single model there is, I guess, 10 or 15 dollars worth of materials. The most expensive is the wood for the proppeler blades, it´s a very special and specific cut of very light balsa wood.
We´re talking about densities of around 4, 41/2 pounds per cubic feet here; the cut is called quarter grain or C cut. If you look at a log from one end you´ll see the growth rings, if you cut a board perpendicular to those rings you obtain an A cut board, the growth rings will cross the board vertically and that will give it a high lengthwise tensional strength but poor widthwise (?) one. The C cut consists on a board cut tangentialy to the growth rings, that yields a board that can handle loads across the wood grain much better, which is more suitable for a propeller.
So, this light C cut wood, comes, for example on packs of 4 sheets, 1 inch wide and 12 inches long, enough for two propellers and costs around 6 dollars.
The covering (2 micron thickness Mylar) comes in rolls 1 feet wide per 15 feet long, about 4 dollars.
Other types of light balsa wood can amount for 4 or 5 more dollars and there´s lumber for many models; some steel wire (electric guitar strings) and finally the rubber that is sold by weight, for example a pound costs $ 22 which is enough for several years.
So… it ain´t expensive at all, one can then add costs buying tools and other stuff, but the basic materials are very inexpensive.
Of course there´s the time factor, this things take time; a good indoor plane may not cost much, but it´s worth a lot, it is a large investment of time, dedication and love for the art; I´ve been asked many times if I would sell one of my planes and I´ve always said no, they´re very personal creations.
It was a large sports building, four basketball courts side by side, the ceiling was about 12, or 13 meters at the center of the dome, but as I said there were many obstacles there, lights, cables and the roof truss structure… heck, it was a bloody geodetic structure! the thing was like bloody flypaper, the models got stuck all the time on the trusses!. It was a good site, but not very suitable for a competition.
