Rotor Egg Drop B

[TrueshotBarrage]

I'm pretty sure you have to drop it the same way you put it in the box. However, since a 51 cm cube is a cube, you can use 45-45-90 degree triangles and their properties to roughly figure out if you need to reduce the size.

[Bozongle]

I'm pretty sure you have to drop it the same way you put it in the box. However, since a 51 cm cube is a cube, you can use 45-45-90 degree triangles and their properties to roughly figure out if you need to reduce the size.

Yeah I used that to figure out it can be a max of 70cm, but still confused about the "flying configuration"

According to the soinc website:
"Students will be the ones who choose the orientation of their device in the cube and place it in the cube for verification. Students must be the only ones to touch their device. As long as it fits into the allowed dimensions of the cube,in flying configuration which means with the cup attached, then it passes."

So it seems like it only has to fit with the cup attached rather than having to be dropped in the same orientation that you put it in the box

[jander14indoor]

As per usual, opinion, not official, etc.

I suspect that if they'd meant drop configuration they'd have said drop configuration. By flying configuration I suspect they mean as it flies, not as held in some orientation when dropped.

For most rotors I've seen (it is possible to design otherwise) that would mean with the rotor in horizontal plane.

I believe (wait, checks FAQs on the soinc.org website, yes I'm correct) there is a FAQ that says the rotor does not have to rotate in the box.

So yes, you can have a four bladed rotor stretching from corner to corner of the 51 by 51 cm box horizontal cross section. Note, the corners are pointy, you won't fit broad round tips out there at the extreme.

Regards,

Jeff Anderson
Livonia, MI

[Bozongle]

Ok, sounds good. I currently have a makeshift box which is roughly 51x51x51 and my rotor fits pretty well. Hopefully I don't run into any problems with the event supervisor having conflicted views at State this weekend.

I also finally tested my rotor at a good height today, and from a height of 4.75m it averaged a time of 3.6s. This is a lot better than my older rotors, however I still don't know how this will fare competitively. Good/Bad? Thanks

[Somicvs]

Can someone give me some times for egg drop for this year?

[TrueshotBarrage]

@Bozongle
Doesn't seem bad. I got slightly longer time at regionals but still got 5th. However, our regionals is pretty competitive, so there's that.

[demoso]

Is there a minimum height for this event? The rules say "It is recommended that the drop height be the maximum that the site will accommodate with a minimum of five meters."

Is the minimum a recommendation or a rule?

[JustDroobles]

Is there a minimum height for this event? The rules say "It is recommended that the drop height be the maximum that the site will accommodate with a minimum of five meters."

Is the minimum a recommendation or a rule?

My best and most succinct advice is: Don't worry about it.

To me it seems like a "rule", but even if it isn't, you should just have faith that the tournament will pick the best site available. I would prepare counting on the location having at least a 5 meter drop.

If there is a rare case where this requirement isn't fulfilled just keep in mind:

• The tournament has done their best to determine the best drop site.
• If they can't run it above 5 meters, it is better to run the event at a short height than to not run it at all.
• You shouldn't know the drop height until tournament day, and at that point it is a near logistic impossibility to change the site.
• What is equally unfair to all is fair to all.
• If you have a superior device at 5 meters, it has a good chance of being superior at a shorter distance.

[Somicvs]

Does the outer edge of the rotor need to be fixed/closed with balsa? Can it be open ended?

[Toms_42]

Does the outer edge of the rotor need to be fixed/closed with balsa? Can it be open ended?

It can be, but it tends to reduce the tension at the end, resulting in the film "flapping" and reducing your ability to slice the air as well. I recommend keeping the outer piece.

From 2 years of experience, I have found that to make a good rotor there are several factors:

1)weight doesn't matter as much as you think. The variance in the weight of the egg renders any changes less than 3-5 grams ineffective.

2) its about surface area. higher SA means more drag, obviously, but it also increases your risk of stability issues, and if using few, large blades pitch can be affected a lot by widening the blades.

3)and number of blades. I have found that against all predictions, my best rotors are the ones with 2 blades. 4 blades in a rectangle shape causes pitch inconsistency.

4)AND pitch. low pitch=falls fast initially, then very slowly after a meter or two. good for long drops. high pitch = moderate fall rate the whole way down, spins up fast. good for short drops. As always, build a lot of different rotors and test this empirically.

5)simplicity is key. make a design you can build fast and constantly, with commonly available materials. I can build one in a couple of hours, including frame, filming, stringing, and calibration.

6)String arrangement matters. do you tie your strings to the center? the tips? he middle of the spars? do you even use strings? How the weight of your egg is distributed makes a big difference. build multiple identical rotors, and try stringing them differently until you get something that works well.

7) calibrate your strings! they need to be of equal length, so the egg hangs centered. otherwise you get what I call "orbiting."

Any competitive wing takes all of these factors into account. Most are tradeoffs, such as stability vs drag, and some designs are better for low drops or high drops.

Pro Tip: pick a good egg. do some experiments with different eggs to see what I mean.
Pro Tip 2: the person dropping the wing should be tall with long arms, and a steady hold. Lift it as far up and away from the wall as possible. hitting the wall early on can ruin your drop.