This is my first blog for our hot air balloon project. We've done some at home experimenting. We constructed some geodesic domes out of different materials (printing paper, parchment, and tissue paper) and used clear tape to hold them together. Through this process we have determined that we need to make the paper portion fire-retardant, and figure out some other way to attach the pieces of paper together. The paper becomes too hot and will catch fire without a "fire proofing" method. The heat causes the tape to melt and loose its cohesion even before the paper starts to scorch. Also the melting tape seems to concentrate the heat onto the paper, contributing to the paper catching on fire.
Today in class we did some experimenting with Alum (used in picking, clothes dying, and paper marbling). We found that soaking paper in an alum-water solution does in fact make the paper much more fire resistant. We made some sheets of fire-retardant alum paper out of tissue paper and some newsprint.
We did some experimenting with wax and cotton for the fuel source. From the various examples of functioning balloons I have seen, this could be an effective method for heating the air inside our balloon. This method does create quite a bit of heat. Also, it stinks and produces some soot and smoke. The other method I have seen for heating small scale balloons is birthday candles. This might be a good method because the formula we found on the Internet for lift used birthday candle count for the heat source (number of candles per amount of cubic space for amount of lift in weight).
Our group is leaning away from using the geodesic dome design. The math is much more complicated than I had anticipated for figuring out lift. There is a much larger amount of surface area to contend with (in terms of connecting the many pieces together) for the dome than some of the other shapes I have seen used. We can try some different shapes once we have a dry supply of alum-paper. The tetragon shape might be the simplest to construct, but we should look for some kind of pattern to determine the length of the sides of the triangles. The other idea would be to make a cylinder, yet attaching a top to this shape might prove challenging.
We still need to address attaching the fuel source to the balloon. This would be in part dependant on the fuel source we decide to go with (wax-cotton wrapped in foil or birthday candle). I'm waiting on pictures to post for the experimenting we've done, please look forward to them in a future post.
I think that when the cotton has a better suply of wax it is much less inclined to create somke & soot. I think that the 2nd one made in class today probably has a much better suply of wax, and that using the foil will help force the wax to burn more so then the cotton. & I may be secretly working on another dome shape @ the moment ;-)
ReplyDelete