Hovercraft B/C

[zebraruns]

Where can we get fans powerful enough to levitate a hovercraft?

[windu34]

So what you're saying is that the "mass of the vehicle" should be defined as the heaviest mass of the two successful runs. I find 6a to be ambiguous. The top of the fraction is just "mass of the vehicle," and no where is this defined. Even though the bottom says "mass of the heaviest successful vehicle of all teams," I didn't think that implied anything about how I selected the "mass of the vehicle." I interpreted the rules as saying use the mass of the vehicle during the run with the best Time Score.

I think this can be misinterpreted and I will submit an FAQ tonight.

Hmm...

so let's say you have a run with a low MS and high TS, and a second run with high MS and low TS

You would be able to use the high MS and the high TS in your final score?

Interesting.

Nowhere in the rules does it associate MS with particular runs. You simply have a MS associated with your vehicle. If the mass changes during the competition, the MS goes up as long as you have a successful run with it.

Note we've posted an official scoring sheet (per rule 6) on the website, which per general rule #3 (https://www.soinc.org/ethics_rules) should be treated as if they are part of the rules. You can play around with it to see how the scoring works.

I really dislike this component of the event. I doubt many teams interpretted it that way and I feel manyh event supervisors will get confused by the wording and not follow it correctly because logically, it doesnt make the most sense without knowing the intention of the writers. Additionally, it takes away from the challenge of hovercrafts in the real world: trying to create the most efficient levitation system that can carry large mass.
I suppose a high mass can be advantageous for runs bacause inertia increases greatly which will help woth consistency, but the entire principle and challenge of the event in my mind is ruined.
After determining the best fans to use for this event (took maybe 20-30 hours of research and experimentation), it took me about 2 hours to build and test a craft sufficiently in that I was able to handle the full mass and placed 1st at the recent Cornell Invite. Once you remove the challenge of trying to minimize the friction so that you can propel a 2 kg craft, the event is no longer a challenge and i'd be suprised if the upper half of nationals teams dont have full mass.

Was Maglev like this as well?

[CaptainJackSparrow]

If the mass changes during the competition, the MS goes up as long as you have a successful run with it.

chalker: It sounds like you are involved in the rules committee. Thanks for that and for your contributions to this forum.

If the approach of making the the mass score independent from the time score is intentionally sanctioned by the rules committee, I would strongly suggest that it be spelled out in the rules, rather than inferred from the scoring sheet. I think it is a stretch for a reasonable judge, coach, or student to come to that conclusion without some official guidance.

Now for my soapbox.... I will admit I was very surprised to see this rule interpretation. This is only my second season as a coach, but my experience at our first regional was that clever applications of the rules to gain an advantage are frowned upon by the judges/organizers. Clever applications of science are the objectives. Given that there is a top level ethics rule to not "violate the spirit of the problem", I would not have reasonably considered separating mass and time scores as a strategy (I would have considered it a loophole, or an oversight by organizers). I see the spirit of Hovercraft event as having the kids understand the principals kinematics, how force affects acceleration, and how acceleration affects the time you need to cover a fixed distance. In fact I think this event is a GREAT way to convey how time, distance, and acceleration are related. If you decouple the time score and the mass score, you are potentially decoupling the best scores from the best application and understanding of the physics behind the hovercraft. Regardless, I think there may be controversy and disappointment unless this scoring implementation is well communicated to the teams and judges.

[hovercraft_dude19]

scioly.org/rules
Hello.
I just wanted to clarify that in the Hovercraft rules for 2017, for the target time, it says from 5 - 25 seconds, and that the event supervisor must announce the time. It also says that this is only for Division C. However, in the score section, it says that you get a time score which is the target time - the run time and that thing. I just wanted to confirm that we do not need to make our hovercraft adjustable for division B.
Thanks,

Hovercraft_Dude19

[Unome]

If the mass changes during the competition, the MS goes up as long as you have a successful run with it.

chalker: It sounds like you are involved in the rules committee. Thanks for that and for your contributions to this forum.

chalker is in fact the chair of the Physical Science Rules Committee (seeing as signatures are still invisible on posts)

[Adi1008]

scioly.org/rules
Hello.
I just wanted to clarify that in the Hovercraft rules for 2017, for the target time, it says from 5 - 25 seconds, and that the event supervisor must announce the time. It also says that this is only for Division C. However, in the score section, it says that you get a time score which is the target time - the run time and that thing. I just wanted to confirm that we do not need to make our hovercraft adjustable for division B.
Thanks,

Hovercraft_Dude19

I could be wrong, but I think you could be misinterpreting the rules.

5.II.e says that Division C is the only division with a variable length (any distance between 100.0 and 195.0 cm), but B is fixed at 135 cm.
5.II.f says 'the target time is between 5 and 25 seconds. The event supervisor must announce the exact length (Division C only) and time after impound, which must be the same for all teams.

5.II.f makes me think that Division C has variable length and time, while Division B has a variable time and a fixed length

Based on this, you would have to make your hovercraft adjustable so that it could go the 130cm in whatever time the ES tells you

[Unome]

scioly.org/rules
Hello.
I just wanted to clarify that in the Hovercraft rules for 2017, for the target time, it says from 5 - 25 seconds, and that the event supervisor must announce the time. It also says that this is only for Division C. However, in the score section, it says that you get a time score which is the target time - the run time and that thing. I just wanted to confirm that we do not need to make our hovercraft adjustable for division B.
Thanks,

Hovercraft_Dude19

I could be wrong, but I think you could be misinterpreting the rules.

5.II.e says that Division C is the only division with a variable length (any distance between 100.0 and 195.0 cm), but B is fixed at 135 cm.
5.II.f says 'the target time is between 5 and 25 seconds. The event supervisor must announce the exact length (Division C only) and time after impound, which must be the same for all teams.

5.II.f makes me think that Division C has variable length and time, while Division B has a variable time and a fixed length

Based on this, you would have to make your hovercraft adjustable so that it could go the 130cm in whatever time the ES tells you

This was my interpretation as well. There's not much precedent for a fixed time in either division; variable is far more common.

[chalker]

If the approach of making the the mass score independent from the time score is intentionally sanctioned by the rules committee, I would strongly suggest that it be spelled out in the rules, rather than inferred from the scoring sheet. I think it is a stretch for a reasonable judge, coach, or student to come to that conclusion without some official guidance.

Now for my soapbox.... I will admit I was very surprised to see this rule interpretation. This is only my second season as a coach, but my experience at our first regional was that clever applications of the rules to gain an advantage are frowned upon by the judges/organizers. Clever applications of science are the objectives. Given that there is a top level ethics rule to not "violate the spirit of the problem", I would not have reasonably considered separating mass and time scores as a strategy (I would have considered it a loophole, or an oversight by organizers). I see the spirit of Hovercraft event as having the kids understand the principals kinematics, how force affects acceleration, and how acceleration affects the time you need to cover a fixed distance. In fact I think this event is a GREAT way to convey how time, distance, and acceleration are related. If you decouple the time score and the mass score, you are potentially decoupling the best scores from the best application and understanding of the physics behind the hovercraft. Regardless, I think there may be controversy and disappointment unless this scoring implementation is well communicated to the teams and judges.

As usual, this is not the place for official statements - the FAQ process on soinc.org is for that. That said, I'll point out a few things about how nowhere in the rules does it say nor imply the mass score is directly tied to the time score or on a per run basis, but rather the exact opposite of that:

-5.g. explicitly states that the supervisors might remeasure the mass of the vehicle after a successful run.
-5.h. and i. state teams may adjust and modify their vehicles (from which can naturally be inferred that includes changing the mass)
-6.d. describes how to penalize the mass score and references actions during the testing period (and doesn't mention runs at all), whereas 6.e. describes how to penalize the time score on an individual run basis
-6.g. shows the final score includes the mass score and the best run time score. Note it doesn't say the best run mass score.

From a philosophical standpoint, this is exactly the kind of thing we often do in SO events. We try to make then as low a barrier to entry as possible, so the majority of teams will be able to compete in some form or fashion. But we also try to craft the rules or incorporate something that will allow teams at the highest level of competition to be differentiated without having to go to tie breakers. The spirit of many of the engineering events is to try to not over-optimize a design for one particular scenario, but rather to provide a solution that can be adapted to a variety of scenarios. Being able to adjust independently for both max mass and precise timing as I've described is a great example of that.

[chalker]

5.II.f says 'the target time is between 5 and 25 seconds. The event supervisor must announce the exact length (Division C only) and time after impound, which must be the same for all teams.

The exact way to word this in the minimum amount of space was something we struggled with.

Compare these various sentences:

"The event supervisor must announce the exact length (Division C only) and time after impound."
"The event supervisor must announce the exact time and length (Division C only) after impound."
"The event supervisor must announce the exact time after impound. In Division C they must also announce the exact length."

The first one seemed to us to be most obvious the the length portion is only relevant to Division C, whereas the second one could be ambiguous and the third one is a much longer sentence that might require an extra line in the already space constrained rules.

[windu34]

From a philosophical standpoint, this is exactly the kind of thing we often do in SO events. We try to make then as low a barrier to entry as possible, so the majority of teams will be able to compete in some form or fashion. But we also try to craft the rules or incorporate something that will allow teams at the highest level of competition to be differentiated without having to go to tie breakers. The spirit of many of the engineering events is to try to not over-optimize a design for one particular scenario, but rather to provide a solution that can be adapted to a variety of scenarios. Being able to adjust independently for both max mass and precise timing as I've described is a great example of that.

Teams aren't adjusting their timing for different masses though, they will be testing their crafts with a low mass and ensuring their craft can move with a large mass so that they can score the mass score. This "superscoring loophole" does not force students to learn how to adapt to different situations and it does not make the scores at higher levels of competition less differentiated, it does the opposite. The biggest challenge of this event is figuring out how to minimize pressure losses so a large mass can be moved at relatively high speeds. Once you eliminate that challenge, the event becomes very simple and all the top teams will have full mass score regardless of if they actually figure out how to levitate a large mass and the entire build portion of the event will come down to who can get tenths of a second closer to the target time.