Glider

And it weighs? You're sure it is not your mother in law?

weight is optional .... it should be light enough to reach 20 metres

Only 20 meters? You don't need a glider for that. You can catapult a fall'er that far.

98*98*33 cm glider is big i think .. can a rubber catapult can project it to 20 metres easily ???

Just take 2 inner tubes of a bicycle, make a launch stand and pull hard. Then let it go. If your glider glides, and you do it against the wind and under the right angle, it will fly much further.

so two inner tubes should be tied to the launch stand ... approximately combined length of the tubes will be how much ???? can you give rough length

The place that sold you the glider should have 'launching rubber' bands, or lengths.

It is very commonly used for larger gliders than yours.

And it's higher airspeed that gives altitude, not catapult elevation - so the lightness and elasticity of the rubber are most important properties.

Modern inner tube 'rubber synthetics' have nothing like 'pure rubber' properties.

An alternate is tubular silicone rubber, such as used in slingshots and hand spears, but it would have to be much smaller diameter, or you may rip off your wings.

I agree that there are more elegant rubbers to get, although I tried to stretch tubes from smaller wheels to fit on larger diameters and they still come back to the original size. I am referring to the classic tubes, like a thin tire 28" wheel. Just not the racing tubes without inner tire tubes. We used to cut them for rubber bands and they last longer than commercial rubber bands for our purposes. 100 years ago when I was young, I used to catapult a 1 kg rock 100 meters far with it. It is like 34.5 says: the lift of the wings and the airspeed makes your glider glide. A tilted launch stand will affect your climb.

Yes, it can.

The catapult should be 20 meters long and pointed downhill.

You can't help but get the prize.

20 metres catapult ? so much big ???? what kind of catapult ??? rubber doesnnt work i think

If well designed and suitably launched, it should do much better than that. See previous version of the thread.

previous version of thread ??

Yeah, the one with 20cm.

but what kind of catapult a 20 metre rubber catapult is needed for that ???

A pretty good glider can be made from a corrugated paper carton. Laminate two thickness to make the fuselage, including the tail. Below the tail, cut a horizontal slot and insert a small stabilizer. Near the center of gravity, toward the top, cut a cambered slot and insert a wing formed to match. Try a few times, adjusting as appropriate. Such a glider can be hand lanched and can easily attain 20m of flight, and quite likely 200m or more. Good luck, and enjoy!

You can Google "cardboard glider plans" to get some neat ideas.