Rotor Egg Drop B

[sophie2220]

Does the top side (rounder) or bottom side (pointier) of the egg break easier

[sophie2220]

I'm coaching the rotor egg drop, and my team is currently confused on how to attach our blades to the hub. Any suggestions? We're currently using carbon fiber rods that are bent into tear drop shaped blades with the veggie bagging covering them. We followed the instructions on http://fc.niskyschools.org/~psherman/03 ... gDropNotes but all they say is to use fixtures to attach the blades at the pitch angle and we have no idea how to do that. Any suggestions?

On mine, I made 8 blades and connected them by a rod. Something like + with a X in it overlapping. Basically an X and a + on it. Worked pretty good. You could use that as a starting point.

Did you keep all the blades flat? If not, how did you make the blades all connected at certain pitch angle? Btw, what is the best pitch angle to provide the maximum lifting power?

[saurabhg47]

Be very careful with laminated rotors that they are not arched, or at least have a solid bottom. A curved rotor will act like a parachute and can get you DQ'd.

That's the second time I've heard that, but I still don't understand it. Nothing in the rules about a curved bottom.

MANY airfoil shapes have curved bottoms but certainly don't act as a parachute. The key would seem to be rotary movement, NOT shape. A flat plat that doesn't rotate acts the same as a parachute.

Where is this statement coming from?

Jeff Anderson
Livonia, MI

Jeff,

We just came back from Wright State invitational. Our device has rotors spinning and had space between rotors to let air move. one of the official decided to call it a parachute because the covering on the rotor gets raised a little bit when rotating and coming down. That surprised us as it does not meet definition of parachute and looks like very subjective point of view. This makes us wonder what constitutes a parachute so when kids are building the device they can make sure they build something that will not get them either disqualified or downgraded to teared category. Kids were very disappointed and couldn't understand why their device was downgraded to tear even the device was not a parachute.

[Skink]

Unfortunately, we do have word at the National level as to what constitutes a parachute. Actually, it's a bit unclear because it leaves the question up to the supervisor's discretion. That said, it seems being as conservative as you can in your definition of 'parachute' is your best option, and design your next device with that in mind, whatever the most unreasonable supervisor would DQ or Tier ? you over.

[jander14indoor]

First, usual comment about this NOT being the place for clarifications, anything I say is ONLY opinion.

You REALLY need to submit a question to the NSO website for helicopter egg drop to get this clarified. My opinion is that's not a good call, but while I'm considered by some to be an 'expert' on the flying events, I'm not the Rotor Egg Drop national event supervisor and my opinion isn't worth a thing (well, maybe not that bad, but certainly not the last word) in a rules discussion or appeal.

Hmm, thinking on this some, I think you could demonstrate that the loose skin does not act as a parachute. Look at the wings for WS, they also ballooned in flight and I don't think anyone could argue they acted as a parachute in ANY way. The key is relatively high forward speed (or relative wind), and if your rotors are spinning at a decent rate, they have that. Shouldn't be too hard to do the velocity diagrams to show the rotor is certainly NOT acting as a parachute. You'd need to know decent rate and rpm, then you could do some geometry to get the airflow over any given section of the rotor blade.

As writing this, Skink posted the current clarification. (Biting tongue as opposed to offering opinion on that answer)

Note, if you ask and get an e-mail reply, but nothing goes on the website, let me know. Sometimes if only one person asks, or question is considered trivial nothing is publically posted.

Sorry,

Jeff Anderson
Livonia, MI

[saurabhg47]

First, usual comment about this NOT being the place for clarifications, anything I say is ONLY opinion.

You REALLY need to submit a question to the NSO website for helicopter egg drop to get this clarified. My opinion is that's not a good call, but while I'm considered by some to be an 'expert' on the flying events, I'm not the Rotor Egg Drop national event supervisor and my opinion isn't worth a thing (well, maybe not that bad, but certainly not the last word) in a rules discussion or appeal.

Hmm, thinking on this some, I think you could demonstrate that the loose skin does not act as a parachute. Look at the wings for WS, they also ballooned in flight and I don't think anyone could argue they acted as a parachute in ANY way. The key is relatively high forward speed (or relative wind), and if your rotors are spinning at a decent rate, they have that. Shouldn't be too hard to do the velocity diagrams to show the rotor is certainly NOT acting as a parachute. You'd need to know decent rate and rpm, then you could do some geometry to get the airflow over any given section of the rotor blade.

As writing this, Skink posted the current clarification. (Biting tongue as opposed to offering opinion on that answer)

Note, if you ask and get an e-mail reply, but nothing goes on the website, let me know. Sometimes if only one person asks, or question is considered trivial nothing is publically posted.

Sorry,

Jeff Anderson
Livonia, MI

Skink and Jeff,

Thanks for prompt response and guidance. Even though I understand the onsite supervisor has discretion, and Science Olympiad site states, "The event supervisor will use his/her best judgement as to whether the rotor captures air and/or is acting as a parachute" it doesn't give a clear, data based measurable specifications to come as close as you can to build the device. and I thought it is an engineering event where only specific measurable data rules. However, we will certainly follow Jeff Anderson's guidance and submit our clarifying request to NSO. Hopefully asking measurable requirement will not be discarded as Trivial, because only one person is asking.

With warmest regards,

[jander14indoor]

We can fix the only one person asking, power of the internet and all.

Hmm, specific and measurable. Be nice, but not sure how to do it in the SO environment. Suggestions might help.

Unfortunately the word 'parachute' isn't really well defined in engineering terms. I spent some time looking it up.

Keep in mind, in common AND technical usage the older round dome and modern inflated flying wing designs both come under the term parachute when made of cloth and used to pigeon a person (and many other objects) falling from the sky. But they work in VERY different ways.
- That dome mostly (simple ones, not the more complex more recent designs with slots everywhere) slowed the object down by DRAG directly opposite the direction of motion.
- The inflated wing designs slow descent almost completely by LIFT perpendicular (mostly) to the direction of motion. You can see this by the significant forward speed of these designs and note that to prevent smearing the parachutist across the ground on landing, they learn to kill forward speed and stall them in at the last moment or land into the wind.

Keep us apprised of what you get.

Jeff Anderson
Livonia, MI

[saurabhg47]

We can fix the only one person asking, power of the internet and all.

Hmm, specific and measurable. Be nice, but not sure how to do it in the SO environment. Suggestions might help.

Unfortunately the word 'parachute' isn't really well defined in engineering terms. I spent some time looking it up.

Keep in mind, in common AND technical usage the older round dome and modern inflated flying wing designs both come under the term parachute when made of cloth and used to pigeon a person (and many other objects) falling from the sky. But they work in VERY different ways.
- That dome mostly (simple ones, not the more complex more recent designs with slots everywhere) slowed the object down by DRAG directly opposite the direction of motion.
- The inflated wing designs slow descent almost completely by LIFT perpendicular (mostly) to the direction of motion. You can see this by the significant forward speed of these designs and note that to prevent smearing the parachutist across the ground on landing, they learn to kill forward speed and stall them in at the last moment or land into the wind.

Keep us apprised of what you get.

Jeff Anderson
Livonia, MI

I agree that definition of Parachute could be lengthy and tricky, but measurable specifications for a rotor device could be simple, just like what we have today (51cmx51cmx51cm device, Use wings/blades that rotate around a central axis to slow decent) now keeping these directives in mind, the device met all of these qualifications to the point and some.

But since it was downgraded, on undefined criterion of how a cover should behave during descent, how about adding that (and only a suggestion), device must have spaces (how much length, width, height) between each rotor. Covering on rotor must not be raised more that X-cm when descending. Should two covered rotors be attached with each other or should they be completely free of next rotor? but once it is defined, then the discretion of supervisor should be limited to look for these specs only and not add their own undefined criterion. It can make the judgement process very un-predictable.

My point is that this is a very basic device built by middle schoolers who are only starting out their journey in trying their interest in engineering. the device is covered by a plastic or paper, kids have spent a good amount of time to build and have broken few in the process of having too tight of covering or too lose, a little bit of raised covering during descent shouldn't degrade an otherwise good device that actually meets all defined specs except supervisory discretion.

There must be some basic criterion, if it rotates, and have space between rotors to not restrict air, and if the covering doesn't just balloon to the sky while in descent, it should be OK. the whole intent of these activities is to encourage kids not discourage, which regrettably these kind of decisions may lead to. Just my two cents.

With warm regards.

[Skink]

I could be off base here, but I suspect the reasoning behind the FAQ answer linked is that whatever definition that would theoretically be provided Nationally for 'parachute' would be up to scrutiny and further interpretation just like the original rules. Leaving it up to the supervisor is, practically speaking, easier because it stops that chain of further questions from coming in. It also goes without saying that writing the clarification you're seeking is difficult to enforce Nationally. At this point, such an addition to the rules would surely lead to confusions at the local level meaning the default answer that supervisors will resolve the issue of what a parachute is is ultimately the best option despite possible upsets.

That said, I loaded up a slideshow prepared by the National event supervisor. He put several pictures of devices and annotated their legality. The ones that were considered illegal on the grounds of being a parachute included rotors that raised some distance upwards, as you noted in your proposed definition. Two similar designs that came up (both deemed illegal due to having a parachute) had primarily flat rotors far as I could tell except a part in the center that elevated some distance. So, avoiding such designs is certainly possible; it's not as though it is completely unknown to folks what a 'parachute' could be (yes, I understand your frustration with the fact that the criteria change supervisor to supervisor). Like I said before, instead of trying to change the definition of 'parachute', I would construct a device that errs on the side of caution.

My point is that this is a very basic device built by middle schoolers who are only starting out their journey in trying their interest in engineering. the device is covered by a plastic or paper, kids have spent a good amount of time to build and have broken few in the process of having too tight of covering or too lose, a little bit of raised covering during descent shouldn't degrade an otherwise good device that actually meets all defined specs except supervisory discretion.

That is very true; however, understand this is not limited to this event. Way back when, when I was in your kids' shoes, I had a first place device that was DQ'd on grounds analogous to how your kids were stung here. We went through arbitration and lost. I'll admit, I'm still bitter about that, but my point is this is neither the first nor last time that a team could be argued as being slighted by a legalistic supervisor (and at an invitational, no less!).

[saurabhg47]

I could be off base here, but I suspect the reasoning behind the FAQ answer linked is that whatever definition that would theoretically be provided Nationally for 'parachute' would be up to scrutiny and further interpretation just like the original rules. Leaving it up to the supervisor is, practically speaking, easier because it stops that chain of further questions from coming in. It also goes without saying that writing the clarification you're seeking is difficult to enforce Nationally. At this point, such an addition to the rules would surely lead to confusions at the local level meaning the default answer that supervisors will resolve the issue of what a parachute is is ultimately the best option despite possible upsets.

That said, I loaded up a slideshow prepared by the National event supervisor. He put several pictures of devices and annotated their legality. The ones that were considered illegal on the grounds of being a parachute included rotors that raised some distance upwards, as you noted in your proposed definition. Two similar designs that came up (both deemed illegal due to having a parachute) had primarily flat rotors far as I could tell except a part in the center that elevated some distance. So, avoiding such designs is certainly possible; it's not as though it is completely unknown to folks what a 'parachute' could be (yes, I understand your frustration with the fact that the criteria change supervisor to supervisor). Like I said before, instead of trying to change the definition of 'parachute', I would construct a device that errs on the side of caution.

My point is that this is a very basic device built by middle schoolers who are only starting out their journey in trying their interest in engineering. the device is covered by a plastic or paper, kids have spent a good amount of time to build and have broken few in the process of having too tight of covering or too lose, a little bit of raised covering during descent shouldn't degrade an otherwise good device that actually meets all defined specs except supervisory discretion.

That is very true; however, understand this is not limited to this event. Way back when, when I was in your kids' shoes, I had a first place device that was DQ'd on grounds analogous to how your kids were stung here. We went through arbitration and lost. I'll admit, I'm still bitter about that, but my point is this is neither the first nor last time that a team could be argued as being slighted by a legalistic supervisor (and at an invitational, no less!).

I do agree with your point and the authority of the supervising official. That's why even though we did not agree to his decision, we didn't contest it and have no intention contesting it either. What I am trying to get is could there be a possibility of further tightening specs to help build, test, compete and judge. And if it is not, or rather not policy then we will abide by it. And if the kids continue to experience these variabilities, then it is up to them and their parents to either show positive side or chose another line that interests them.

I was not trying to come to this forum to argue, just trying to get clarifications with logical reasoning and POV. If it has offended anyone, I sincerely apologize.

With warm regards,