The construction of a helium balloon, is similar to a balloon and in some ways easier, cause we will not have to put special attention to anti-flame protection and burner management.
To avoid having to realize one by one the gores you should develop one "mother gore" which allows you to quickly create more gores at a time.
In our case will be 28 semi-gores, 14 for the upper part and 14 for the lower, then when combined will give us 14 whole gores.
To realize the mother gore I used the corrugated plastic sheets bought at brico, but you can also achieve it in cardboard or other material a bit hard.
When you have decided and you have purchased the material, equip yourself with a ruler, set square and marker to begin to draw the gore shape, using the data that you have previously obtained.
Begin drawing the base of the half-gore, its length should be taken from the Gore Base value that we calculated before.
Now, starting from the middle of the Gore Base line we draw the height line equal to hss, also calculated before.
In the images below, to be able to explain better, I'll do it on paper, but of course you'll have to do it in real size on the material chosen.
The next step is going to apply the points H and L previously calculated.
The H points represent the distance of the respective L points from the base of the gore.
When all the points are in place, the mother gore is complete, so it's time to make the real gores.
To do this we will have to overlap and secure with the weights, more layers of material that we decided to use for the balloon, so in our case the cellophane.
I have bought a cellophane roll to paint, light and which is already folded into 4 and then I just have to unroll it and place the weights to hold it in place.
When the cellophane will be positioned then we can lean over the mother gore and go over the outlines with a fine tip marker. The type of marker is important, because if we use the usual pointy thick and wide, solvent, melt cellophane ruining it, I recommend so the thin tipped markers and if possible, DO NOT solvent or at least that it is not aggressive.
Now that we have rehearsed the contours, gently so as not to move the cellophane we remove the weights and the mother gore, and with a sharp knife cut carefully along the lines outlined above.
Repeat the drawing and cropping operations until all 28 semi-gores that we need, are complete
When we have all 28 semi-gores, we will have to put them together in pairs to the base so you get a 14 complete gores.
To unite them we will use the common transparent tape, it is important to be careful not to form strange folds during this phase.
Obtained the full 14 gores, the next step is to merge them laterally so that the envelope beginning to form.
We start place side by side two gores, and then we will start from a end to join them. When we do this, it is good to leave a few centimeters (2-3 cm) without adhesive tape, because in this way, at the end of construction, will remain a hole from which enter the helium.
We continue to join up to the other end.
When the previous operation is complete, repeat it with for all the gores, until you get, when the work is finished, the complete envelope!!! 😀