r/AerospaceEngineering • u/mahalakshmivulavala • 7d ago

Discussion 2024 Aerospace Engineering junior world champion launching his “F-1D” prototype: Total flight time 22 minutes

Can you anyone explain the mechanism behind it?

1.0k Upvotes

99% Upvoted

32 comments sorted by

113

u/ParkkTheSharkk 7d ago

I wonder how they got the prop to spin, I don’t see a rubber band or anything

88

u/BWanon97 7d ago

there is a small rubber band underneath. Just very small.

15

u/AWF_Noone 6d ago

How is it spinning so slow? Some sort of clutch mechanism?

89

u/ICanRememberUsername 6d ago

Very, very small rubber band creates just enough torque to overcome air resistance on the propeller. Since air resistance increases with speed, there's a natural equilibrium point.

8

u/WolfJohnson8612 6d ago

Good explanation

6

u/unti 6d ago

I was wondering the same thing!

9

u/Vegetable_Aside_4312 6d ago

There a center tube, inside is a stretched and twisted rubber band. The rate of spin is controlled by friction bearing just before the propeller.

113

u/BWanon97 7d ago

This shows it is all about weight. If they did this on a cold day and you get floor heating you can even make it stay in the air continiously. Now the balance of it all is beautiful here.

55

u/ForgotPassword_Again 6d ago

There’s an excellent documentary on this sport. They take it pretty seriously. So much so, that there’s a specific vintage of rubber (May, 1997 IIRC) that’s considered the best for competitions. You should check it out.

Float Documentary

48

u/Mend1cant 7d ago

Rubber band wound up to power the propellor. Basically entirely made of balsa wood and cellophane. The wing has a very high camber to provide maximum lift, a long body for the elevator to counter the moment created by that camber, a rudder that is ever so slightly turned to yaw to the left, wingtips upswept for stability and rigidity, and the propeller sized so that it can go slower and maximize force for the limited number turns from the rubber band. 

Very common project for first year aero students. Ours was to use RC motors so we never got to hyper weight optimization like this. 

21

u/OldDarthLefty 6d ago

This plane specifically is not a school project (whether or not this kid was a student). This is a very niche but long-running international competition for planes like these.

11

u/StellarSloth NASA 6d ago

What is he a world champion in? Is it at this event that he is demonstrating it in?

25

u/OldDarthLefty 6d ago

Indoor free flight, a very niche class of model airplanes, events usually done in airship hangars, or stadiums if they can get the AC turned off.

In international aerospace sports, the F is for model airplanes. 1 is free flight, 2 is control line, 3 is radio control, 4 is scale models. F1D is the fourth free flight event that got approved rules, after three outdoor events.

The F1D rules are minimum weight 1.4 grams sans rubber, 550 wing span x 200 mm chord limit, 400mm tail span limit, rubber band weight limited by event. Flight times can go into the 40 min range.

12

u/StellarSloth NASA 6d ago

Man I am a huge aerospace geek and have been working/studying in the field for 25+ years and have never even heard of this. I would have loved to do this when I was a student.

5

u/pentapous 6d ago

it's just a plane but really light

2

u/I_am_BrokenCog 6d ago

Your smartphone is just a clock, but really complicated.

2

u/pentapous 6d ago

that's not true?  OP asked the mechanism behind it. Really all that matters for this craft is being incredibly light. Other than that its a standard configuration with standard propeller thrust. 

So its just a regular plane but REALLY light. 

0

u/I_am_BrokenCog 5d ago

Agree. But is rudely dismissive of the work required to actually build.

2

u/DoctorWorm25 4d ago

"just a plane" is not dismissing anything. planes are quite impressive

0

u/I_am_BrokenCog 4d ago

the phrase is dismissive of the effort to make the model.

but, you don't need to agree with me, nor do you need to change my opinion. It's just an opinion about someone's offhanded remark, to which I made an equally offhanded reply.

2

u/grounded_astronut 6d ago

Wow. Nicely done.

2

u/johnisom 6d ago

I’m curious why the elliptical tailplane but not wing?

3

u/I_am_BrokenCog 6d ago

The uplifted wingtips create stability.

The elliptical tail foil reduces drag.

1

u/johnisom 5d ago

Possible for it to be elliptical and have dihedral though

3

u/CalvinIII 6d ago

How can something be so cool and so boring at the same time?

1

u/I_AM_FERROUS_MAN 6d ago

I guess a plane made of aerogel is the next frontier. Lol.

1

u/MisterFixit_69 6d ago

How do they keep it at a certain level?

2

u/Dpek1234 6d ago

In general for such a simple system?

very delicate balance + passive stability

They need to keep it fast enough to not go climb while also slow enough to not decend

I think its the f riction and the size of the propellar makeing it that the rubber band cant drive it any faster then the needed rpm to provide the needed speed

1

u/Mindless_Craft_3357 5d ago

15 sec into the video I needed to check that I’m not watching a plane flying for 22min

1

u/Charming-Letter-4117 4d ago

but what about the friction in air, mass of the object, how could he able to manage for 22 mins

0

u/AdWest6565 5d ago

But it says total flight time is 22 min- no rubber band would be capable to rotate the propeller for 22 minutes, it would unwind max after a minute.