2011-2012 Rules

User avatar
smartkid222
Exalted Member
Exalted Member
Posts: 774
Joined: June 22nd, 2008, 8:12 am
Division: C
State: NY
Location: Western Long Island
Contact:

Re: 2011-2012 Rules

Postby smartkid222 » April 11th, 2011, 7:31 pm

I agree with wlsguy. In addition to his points I'd like to mention that the no touch bonus is a poor idea becaue it depends too much on the flying site.
1. The relative importance of the bonus would depend on the flying site. For example, if the bonus is set at 2.5*flight time, the effect is very different if the venue is an 80ft armory or a 20ft gym.
2. In order to get the no touch flight to work work the teams are going to have to do a lot of testing. In order to get it right at the competition they need to know the height of the venue which is often not given. Basically, you need to make certain adjustments to optimize the helicopter for a certain height. Without knowledge of the height then the best adjustments can't be made. Yes, it can be argued that if a team did a lot of testing they may be prepared for all heights but i would say that a lot of luck would come into play in that situation.
Image 2008 NY BLG Champ
2010 NY Helicopter Champ

calgoddard
Member
Member
Posts: 214
Joined: February 25th, 2007, 9:54 pm
Contact:

Re: 2011-2012 Rules

Postby calgoddard » April 12th, 2011, 8:48 am

I agree with wisguy and smartkid222.

More specifically, it would be very difficult to get a rubber powered helicopter to hover (cruise) for any significant aount of time. The ascent could be slowed, but only at the expense of shortening both cruise and descent. In addition, to keep the Helicpters event competitive across the country, any bonus for a no-touch fight would have to vary depending on the ceilng height of the flying site.

Friction, cannot suspend the weight of the helicopter from the ceiling. Unless the helicpter is stuck, only the lift of the rotor(s) can do this. Timing in such situations is easily accomplished by using two stop watches, as wisguy explains. There has always been a luck factor in flying competitions where the aircraft are designed for free flight.

The Helicopters event has only been official for one year. Next year, the rule changes should be minimal, e.g. change the max rotor dimension, miniumum helicopter weight, and/or max rubber weight to prevent students from handing down their 2011 helicopters. This would still allow returning students to build on their knowledge base in the Helicopters event.

If the National SciOly organization wants to encourage experimentation in the Helicopters event, try a bonus of doubling the flight time of a tandem rotor helicopter, i.e. one that has a pair of separate rotors that spin about different axes spaced apart at least the max allowed rotor dimension. Imagaine the challenges in building and trimming a balsa wood stick version of the Chinook helicopter.

chalker7
Member
Member
Posts: 610
Joined: September 27th, 2010, 5:31 pm
Division: Grad
State: CA
Contact:

Re: 2011-2012 Rules

Postby chalker7 » April 12th, 2011, 9:10 am

calgoddard wrote:
If the National SciOly organization wants to encourage experimentation in the Helicopters event, try a bonus of doubling the flight time of a tandem rotor helicopter, i.e. one that has a pair of separate rotors that spin about different axes spaced apart at least the max allowed rotor dimension. Imagaine the challenges in building and trimming a balsa wood stick version of the Chinook helicopter.


Now that's an interesting idea. However, I suspect that we would have to more than double the time in order to make it an effective incentive. Has anyone built an actual, flying, chinook style, rubber powered helicopter? I've seen a couple at competitions, but they didn't fly particularly well.
I'm very curious about what the theoretical max time on one of those would be (within the current rules)...
National event supervisor - Wright Stuff, Helicopters

wlsguy
Member
Member
Posts: 366
Joined: March 23rd, 2009, 9:08 am
Division: Grad
State: OH
Location: Ohio

Re: 2011-2012 Rules

Postby wlsguy » April 12th, 2011, 2:33 pm

The tandem rotor idea sounds very interesting.
This would require either 2 motors or some type of mechanism to use 1 motor. In any case, it's quite a challenge....

I haven't made one yet but will try and get something in the next couple of weeks. My understanding is the rules are finalized until sometime at or after Natls.
Hopefully this gives enough time to add a bonus if it works out.

chalker7
Member
Member
Posts: 610
Joined: September 27th, 2010, 5:31 pm
Division: Grad
State: CA
Contact:

Re: 2011-2012 Rules

Postby chalker7 » April 12th, 2011, 4:38 pm

Normally, yes, rules aren't finalized until after nationals.
National event supervisor - Wright Stuff, Helicopters

calgoddard
Member
Member
Posts: 214
Joined: February 25th, 2007, 9:54 pm
Contact:

Re: 2011-2012 Rules

Postby calgoddard » April 12th, 2011, 5:03 pm

Try using two separate six inch motor sticks, each supporting one rotor at the top and a rubber motor of about 0.98 grams. Connect the two motor sticks with a long balsa (fuselage) stick that extends perpendicular so that the motor sticks extend vertically and parallel to each other.

new horizon
Member
Member
Posts: 175
Joined: March 7th, 2010, 6:46 am
Division: C
State: NJ
Location: on pluto.
Contact:

Re: 2011-2012 Rules

Postby new horizon » April 12th, 2011, 5:13 pm

However, unless you used super light balsa it'd be very difficult to be at 4 grams with such a device. I wonder if the benefits of such a design, or the theoretical bonus would outweigh the added weight.
Chalker, you said you saw a few quadrotors last year at nationals. Were they coaxial or were they tandem and similar to chinook helicopters? I'd think a tandem quadrotor would be extremely stable but also extremely heavy.

User avatar
illusionist
Member
Member
Posts: 942
Joined: March 20th, 2010, 4:13 pm
Division: C
State: MI
Contact:

Re: 2011-2012 Rules

Postby illusionist » April 12th, 2011, 5:17 pm

The weight will be Very hard to achieve in my opinion, however it does seem kinda interesting (like a pusher Wright Stuff). Maybe I'll build one after States is over. Can Jeff, or anyone with knowledge of aeronautics explain the advantages of using a tandem design?
2012-2013 Building Event Captain
Rule 7d. "Event Supervisors are allowed to break any competitors' devices" -bearasauras

chalker7
Member
Member
Posts: 610
Joined: September 27th, 2010, 5:31 pm
Division: Grad
State: CA
Contact:

Re: 2011-2012 Rules

Postby chalker7 » April 12th, 2011, 5:21 pm

They weren't quadrotors, they were dual rotors (duorotors?). Quadrotors have 4 seperate rotors (and are currently a popular electronic helicopter design with a lot of pretty amazing autonomous videos on youtube).

Nevertheless, the helicopters I was specifically referring to were tandems and non-coaxial (like a chinook). They were extremely heavy and not at all optimized, so I don't think they are necessarily good representatives of a fully developed solution. I am curious to see if it is even possible for a rubber powered event. My main concern would be equalizing thrust from both rotors for the full flight. If one side gets even a little bit off of the other, the whole thing will start tumbling end over end. However, this is also what would make seeing one legitimately fly so impressive.
National event supervisor - Wright Stuff, Helicopters

chalker7
Member
Member
Posts: 610
Joined: September 27th, 2010, 5:31 pm
Division: Grad
State: CA
Contact:

Re: 2011-2012 Rules

Postby chalker7 » April 12th, 2011, 5:24 pm

illusionist wrote:The weight will be Very hard to achieve in my opinion, however it does seem kinda interesting (like a pusher Wright Stuff). Maybe I'll build one after States is over. Can Jeff, or anyone with knowledge of aeronautics explain the advantages of using a tandem design?


Maybe Jeff can expand more on this, but I don't think there would be any benefit to doing this in a model-based scenario like SO (I could be 100% wrong there though, since I don't think it's ever really been done). In full-scale applications, dual rotors allow for much greater lifting capacity (effectively double that of a single rotor) and also don't require a yaw-adjusting tail rotor to keep from spiraling out of control.
National event supervisor - Wright Stuff, Helicopters

new horizon
Member
Member
Posts: 175
Joined: March 7th, 2010, 6:46 am
Division: C
State: NJ
Location: on pluto.
Contact:

Re: 2011-2012 Rules

Postby new horizon » April 12th, 2011, 5:35 pm

Oh they weren't quadrotors, must have misread, sorry. Yeah I've seen the video of the quadrotor UAV built by UPenn, it's really amazing.
Is it the differences in lift/thrust generated that accounts for the instability in two free rotors (tandem or coaxial)? I always thought it was the torque of the rotors that caused such a thing, you'd need them to be exactly perfect to cancel each other out, or it wouldn't be balanced. It is really difficult to do that on a power system like rubber bands so maybe that would account for the lack of experimentation on two free rotors, coaxial or tandem.

chalker7
Member
Member
Posts: 610
Joined: September 27th, 2010, 5:31 pm
Division: Grad
State: CA
Contact:

Re: 2011-2012 Rules

Postby chalker7 » April 12th, 2011, 5:42 pm

The actual forces acting on tandem helicopters would end up being very complicated. I believe (but am not certain) that if the torque on the two rotors was different, but somehow the thrust remained the same (unlikely), that the helicopter would experience a rotational force that would cause it to yaw (spin around like a top). The more likely scenario is a difference in torque causes a difference in thrust. If one rotor is pulling harder than the other and they are side by side, it will cause the helicopter to tumble end over end (rotate on the pitch axis).

FYI, there seems to be some confusion about coaxial vs tandem. Coaxial means sharing the same center of rotation, which describes pretty much every SO helicopter. In this case, tandem means side by side (http://en.wikipedia.org/wiki/CH-47_Chinook)
National event supervisor - Wright Stuff, Helicopters

fleet130
Staff Emeritus
Staff Emeritus
Posts: 433
Joined: November 10th, 2001, 3:06 pm
State: -
Location: Mare Tranquillitatis
Contact:

Re: 2011-2012 Rules

Postby fleet130 » April 12th, 2011, 5:48 pm

Stability could be improved by adding "dihedral" to the rotors at the cost of some lift. Not sure, but I believe some real-world helicopters use this principle for greater stability.
Image

In today's world, stability is often less, since computer "reaction" times can make up for it.
More info.
Information expressed here is solely the opinion of the author. Any similarity to that of the management or any official instrument is purely coincidental! Doing Science Olympiad since 1987!

new horizon
Member
Member
Posts: 175
Joined: March 7th, 2010, 6:46 am
Division: C
State: NJ
Location: on pluto.
Contact:

Re: 2011-2012 Rules

Postby new horizon » April 12th, 2011, 6:27 pm

Thanks for explaining dihedrals to me, I never understood them from wright stuff last year nor do I really understand how on a physics standpoint that increases stability.
Though computer control does make these practical for real world applications, it's difficult to keep these constant with a rubber band model so perhaps tandem rotors is a bit of a stretch but I'll definitely try to build a model or two next year :D

fleet130
Staff Emeritus
Staff Emeritus
Posts: 433
Joined: November 10th, 2001, 3:06 pm
State: -
Location: Mare Tranquillitatis
Contact:

Re: 2011-2012 Rules

Postby fleet130 » April 12th, 2011, 6:34 pm

When the aircraft/heli tilts the vertical component of the lift vector decreases on one wing/rotor and increases on the other, causing the aircraft to tilt in the opposite direction and return to "level".
Information expressed here is solely the opinion of the author. Any similarity to that of the management or any official instrument is purely coincidental! Doing Science Olympiad since 1987!


Return to “Helicopters C”

Who is online

Users browsing this forum: No registered users and 1 guest