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Old Mar 19, 2012, 05:00 AM
Registered User
Germany, BY, Munich
Joined Jul 2004
26 Posts
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free flight aircraft made only of steel

There's a university-based free flight contest held every year in Germany. This year the task is indoor endurance launched from about 20 feet high carrying an M8 nut (4.54 g 0.1 g).

The catch is that the aircraft must be made entirely of steel!

The rules are attached for you German speakers, but the highlights are:
  • Materials must all be steel alloys with minumum 70% iron content
  • Max weight 400 g
  • Must fit inside a 1m x 1m x 1m cube
  • Energy storage in the form of steel spring(s) or RUBBER is allowed (no pressure vessels, though)
  • Adhesives allowed on contest day only for repairs

I hope this has given some of you free flight fans (or metallurgists?) out there something to think about while trying to fall asleep.

Googling "Stahl Fliegt" will give you some videos from past contests.

The amount of rubber, and therefore the energy storage allowed, is unlimited, so one thing I'd like to know from you experts is, would it be a good idea to suggest to contest organizers a limit on the amount of rubber to avoid a 2-tier contest? What should that limit be?

What else do you guys foresee being an issue for this contest?
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Old Mar 19, 2012, 05:21 PM
B for Bruce
BMatthews's Avatar
The 'Wack, BC, Canada
Joined Oct 2002
11,352 Posts
Not really needed. Rubber flyers have found over many decades of trying to beat everyone at this game that there is an optimum rubber to model weight ratio. And that is 1:1 or less. If they try to stuff more than the model's 400 gms into the thing they'll soon find out that it glides like a duck with a belly o' birdshot.

And for indoors with a limited cieling they are going to find that the ideal ratio for duration is even a lower rubber to model ratio of more like 0.7 or 0.8:1 so that the model can have a longer powered cruise portion.

The metal spring idea is a whole other issue. I won't even begin to try to figure out how they'll do that and what the optimum ratio might be or even if it's at all suitable.

Looking at the past years competition videos I see a LOT of thin shim stock covering and what appears to be thin small section tubing. And a lot of troubles keeping things straight and together. But when it works well the models can be seen to fly VERY nicely.
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