Flight B/C

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coachchuckaahs
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Re: Flight B/C

Post by coachchuckaahs »

A-guy:

Your report of being tiered is an important reminder to all that preparation is absolute key. Checking in with only one piece of rubber is a substantial mistake!

While you point to issues with the ES and check-in process, the fact is that nothing they approved in check-in was over-ridden. Had they tiered you on a re-weigh of your plane, with a different scale, you would have an argument for appeal or refly. However, your approved plane was not recategorized, nor was your approved rubber. While there were changes by the ES during your window, these changes made no material change to the result. The ONLY thing that impacted your result was the introduction of an unmeasured piece of rubber. while your "initial impound had everything legal", your flight rubber was introduced afterwards, which was not legal even if it massed properly.

The rules allow you to check up to 6 pieces of rubber prior to flight. This rubber is held by the ES until the start of your flight window, ensuring heavier rubber is not substituted. The rules do NOT allow you to further introduce new rubber during the event. Had you properly sized the rubber, it appears they would have improperly allowed it. But in fact the rubber was 35% over the allowable mass, a considerable deviation.

As far as test flights it is certainly at the ES's discretion. When I ES I try to allow test flights, but depending on the gym size, most often this is only if no official flight is in progress. While this may allow someone to test in one timeslot and disallow another later, it is not fair to a competing team to have to dodge a tester who may run out onto the flor to retrieve, significantly disturbing the air. At many larger events, testing in the venue prior to teh event starting (sneaking in early) is strictly forbidden.

Note also, in the general rules, "Once judging has started", if you leave the competition area you cannot return. Thus, once you were checking in (plane being judged), you could potentially pull out and tie more rubber if you remained in the competition area, but if you left to get more supplies, you could not return.

So, lessons learned (and taught to others by posting here):
  • Know your rulebook, and be ready to defend what you do. OTOH, now it such that you do not violate and get tiered
  • Do not count on testing outside your 10-minute window. Have yo plane fully assembled and tested prior to arrival. Do not disassemble plane after final testing. If there is a substantial change, say you normally fly at 6000 feet elevation and the event is at sea level, consider renting a test facility upon arrival. Not always easy, but far safer than any "official practice" allowed in the venue
  • Always, always, always check 6 pieces of rubber. If you have great confidence in your winding, check in two nominal pieces, two slightly longer, and two slightly shorter, so that upon "reading" your first flight you have an ability to adjust to a different width for your second flight.
  • Have a record in your log on on your rubber motor packets of the number of flights. Do not compete with rubber that is already well used. I would not plan on competing with rubber with more than 3 flights. Generally we compete with new rubber, wound twice for consistent break-in
  • Prepare a "game plan" for the day of competition. This will include your table setup (what items to have available including glue, ribs, tape, etc.), check-in items (box, plane, rubber), your rubber plans (what size rubber, winds, and torque to use for each flight), and planned adjustments based on observations. It is far better to think this through beforehand than on the clock.
  • Bring everything you may need to repair or modify the plane/box, so that you do not have to leave the competition area, Including knives, glues, parts, etc. We always bring our own table because you cannot count on the event to supply competitor tables
  • Always run through a mock competition with team mates acting as ES, including all aspects of check-in. This will reveal flaws in your preparation.
  • IN your mock competition, have a knowledgeable person question you about the plane, its construction, and flying. This is a KEY ELEMENT in the ES's check in process, that perhaps is often shortchanged. An ES, if they suspect the student did not build the plane, may drill in pretty deep here to determine the builder of the model.
Competition brings in new dynamics that are not there during practice. A well-planned approach, rehearsed, can calm nerves and keep you from making unforced errors.

The ES and his support staff are volunteers, giving up a Saturday to support you. Often they are given little time to prep, or put in insufficient time. Just as often, the ED provides inadequate supplies (the 1g scale), which may not be discovered until the morning of the event. I have ES'd enough to know what questions to ask to avert these issues, but many volunteers are not as prepared. We always bring a quality scale with us in case of issues, and our own measuring templates, again in case of issues. Often I have met the ES the morning of, and if I saw a scale that was insufficient, I would offer my (labelled) scale for his use, along with a calibration check weight.

In this case, I believe the ES acted properly, and protected the remainder of the contestants.

Coach Chuck
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Re: Flight B/C

Post by randomdogonapc »

Wow, real quiet around here now. Anyways, I have more of an arbitrary question that I was thinking about. Everyone says that rubber density is the biggest part of the characteristics of the rubber. Has anybody studied how rubber density affects the rubber? Of course if all of the other variables like weight were constant. Although length would also be an unavoidable difference…
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Re: Flight B/C

Post by pumptato-cat »

Still here, still flying! :)
Just nothing worth posting about, as my plane's being very funky right now.
What do you mean by how rubber density affects rubber? Are you referring to flight characteristics? I'm pretty sure people have studied that but I don't know too much on the subject.
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Re: Flight B/C

Post by randomdogonapc »

Yeah, sorry for being vague. I meant in terms of how flight characteristics would change.
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Re: Flight B/C

Post by jander14indoor »

By rubber density, do you mean mass per length, which is a more accurate way of defining the cross section? Or actual density in mass per volume?

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Re: Flight B/C

Post by randomdogonapc »

I meant mass over length.
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Re: Flight B/C

Post by randomdogonapc »

Oh, also, I got some new rubber of 0.094” width. The other rubber of this width that I have tested have come around to about 0.07g/in, but this stuff comes around to about 0.078g/in. Is this in a normal range, or should I steer away from it?
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Re: Flight B/C

Post by pumptato-cat »

Whoa, you doing your calculations right?
My 0.094" comes to 0.066 g/in max. Never had anything remotely close to the 0.07 range...
Or maybe I've messed up somewhere... I'm definitely not a math person :(
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Re: Flight B/C

Post by coachchuckaahs »

randomdogonapc wrote: April 10th, 2023, 5:15 pm Oh, also, I got some new rubber of 0.094” width. The other rubber of this width that I have tested have come around to about 0.07g/in, but this stuff comes around to about 0.078g/in. Is this in a normal range, or should I steer away from it?
And this is exactly why we talk about g/in. While we may call it at times "linear density", it combines all the variations of thickness, width, and density. If we assume the true density is fairly stable, and cutting is consistent, that leaves thickness as the unknown.

But as Jeff says, this method, g/in essentially measures the cross sectional area.

I'll have to look at my 3/32" stock notes. While that is definitely heavy for 3/32, it is not it of the question. But it will perform substantially different from your 070.

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2016 C WS 8th place
2018 B WS 2nd place
2018 C Heli Champion
2019 B ELG 3rd place
2019 C WS Champion
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Re: Flight B/C

Post by jander14indoor »

And the reason we measure linear density is because it is notoriously DIFFICULT to measure the width and thickness of a piece of rubber. Rubber is so soft you have to have consistent pressure on it to get consistent compression and allow consistent dimensional results.
Even more difficult when comparing numbers between you and me. My measurement device probably doesn't exert the same pressure as yours. So a piece of rubber I measure as 0.096 wide you might measure as 0.09 or 0.105. And flyers seldom measure the thickness of their rubber, assuming it is constant. But it isn't all that constant.

On the other hand, it is relatively EASY to measure length consistently. Just lay a piece of rubber along a ruler with no tension.
And it is easy to measure the mass of that now known length of rubber.
And again, easy/accurate to calculate the linear density.

Finally, for our purposes, it is that cross section, or linear density, that defines the characteristic performance of a piece of rubber, thus its importance. To all intents and purposes it doesn't matter if you have a square or rectangular cross section. If the linear density is the same, the performance will be the same (at least to a high degree).

A nice side benefit for SO, since you typically fly with defined rubber motor mass, knowing the linear density of your pre-cut motors makes it easy to make up a new motor close to the correct mass. Just back calculate from linear density to length for say 2.0 g and cut your motor accordingly. Maybe slightly long, but not much, and then trim to exact weight. Saves a lot of wasted rubber, and a lot of time.

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