Constructing Mini Hot Air Balloon for Physics Olympics

[jangag]

First , i am sorry if i posted on a wrong section because I am just new here .
We , as a group of four ,need some ideas on constructing a hot air balloon with maximum diameter of 50cm (for balloon) and it should be powered only by candle (made or bought) with maximum of 3 wicks for our Physics Olympics (school competition). My problem is , i don't know what is the best material for the whole hot air balloon so it can lift up with weights on it ,and also how to construct a balloon (currently i am searching for guides on how to make) so i am here asking for some help . Thank you

 

[Jobrag]

A quick calculation shows that you aren't going to do this with a spherical balloon think cylinder.

 

[Spinnor]

Buy one and study? Play the video of the following link (how to light a lantern) to see a very nice design.

https://www.theskylantern.com/shop/index.php?osCsid=1d007d858263bbae80885804b6630f98

https://www.google.com/search?q=sky+lanterns&tbm=shop&hl=en&aq=0&oq=sky+la