The building process of an Hot Air Balloon, from A to Z |
Some people ask why and how to build a hot air balloon. You will find here, in few lines the beginning of an answer.
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In French, we do not say "homebuilding" but "amateur building". First, two word definition :
Let's split up the building of a hot air balloon in several phases :
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We all are guided by different reasons when we realize something. So I shall describe several reasons to build I have heard in the homebuilding context :
Caution ! If saving money is your only reason for building, it does not seem to be enough to make a good work, and your security is perhaps compromised.
Note : in France, homebuild balloons can not be used in a lucrative way. But it is not a problem to use an homebuild balloon to organize "first flights" within a non-lucrative balloon club.
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Few words about the necessary competences in building. A lot of persons ask themselves if they are able to build a balloon. And inflated balloon is very impressive and it looks enormous, but when the enveloppe is in the bag, it seems very small.
You will need a several hours to build, between 100 and 200, depending on your quickness and your skills. To build a balloon, it is not necessary to be a perfect seemstress (but after having sewn a kilometer, you will become one !). Necessary qualifications to build are :!
100 to 200 hours take easily place on 6 monthes. Do not believe some balloon sellers who say "at last 5 years, with heavy constraints". These sellers do not want you to build ! It is an evidence that some balloon sellers did have understood that there is space for everybody, and not only for themselves.
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It is difficult to rush headlong into a building project, taking a decision in few hours. Before beginning a building project, you will need to mature the project. Firstly, you just open the ears, taking some informations because homebuilding seems to be an interesting thing. Then, day after day, the project grows in your head. You see the homebuilds balloons of others pilots. After speaking with builders, your project become more concise and real. When you will be convinced that building is not very difficult, and that you can do it, you will take part in the cutting process of a balloon a friend is building... Cutting a balloon doest not seems to be very difficult, and sewing is fast to understand.
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As the idea matures in your mind, you will surprise yourself making hypothesis about the fabric manufacturer, the shape of the balloon ... This step of "maturation" can last two monthes to five years. The most important is that you do it and that you feel yourself confident to begin the process of building. |
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Will your ballon have a sharp or flat top ? What use and size do you project ? How much gores ? Flat or bulbous gores ? A lot of existential questions you have to find an answer during the process of maturation we have just spoken before. |
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It is one of the most important step. If it is easy for tapes, thread, cables ... It is another problem to select a good fabric : the coating must be good enough to last a lot of time, and the price must be affordable. The seeking step can last long. To buy with other pilots to make tests and lower the prices can be interesting. If others builder are in the process to buy, take advantage of this order to save your time. Elsewhere, you will have to start your own order.
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When you have the fabric (you know the exact width), it is possible to calculate and draw the patterns you will use to cut the panels. You can make the calculation with a software designed for this purpose or with an "Excel" table. Yan can copy an existing balloon to (by measuring the existing panels) copy it.
Depending on how you want to cut the panels (manually or with a cutting machine), you must cut the panels in a strong paper (like brown wrapping paper, at least 150g/m2) or put the files on a disk for the cutting machine.
Generally, it is a stressful step, because you want to avoid mistakes. You will perhaps awake during the night, asking yourself : "Do I have count the margin for sewing ?"...
During the project of my first balloon, I have done a model of 2 cu.m with my new (and first) software for panel calculation. The model had 24 gores et 11 panels per gore, it makes 264 panels and I have spent 50 hours to build this model ! I was very satisfied when I finished the model and I can see that it was perfect (but this checking took me a lot of time, to much time). After that, the real balloon (a 1600 cu.m one) showed a small default : the panels are a bit "flat".
To build my second balloon (a 3000 cu.m which has 20 gores), I made some small changes in my software and the result is very good.
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It is the first big building, which requires about 50 hours. A small advice : do the cutting with some friends or you, during a whole week-end. It is possible to cut 200 to 450 panels in two days (we have done that !). For an efficient cutting, the best and the fastest is to organize two teams of three persons and to swap the teams every hour. Then the job go fast and has a good quality : it is a real pleasure.
With the cutted fabric, you must tidy the pannels in big bags. The same panels are in the same bag (same : same shape, the color can be other). This tidying up step is very important to save time during the sewing step.
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Automatic cutting. It does not mean that you have nothing to do ! picture : 21k |
Otherwise, it is possible to ask a company (specialisezed in cutting fabric for sails) to cut the panels.
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Welcome in the world of sewing. You have for 50 to 150 hours of work, depending on your skill and the size of the balloon. A 1600 cu.m/12 gores/160cm width fabric balloon require less time than a 3000 cu.m/24 gores/110cm width fabric ! For this step, it is essential to have an help for your beginnings in sewing with a sewing guide. You will save time and fabric. After the beginning, your speed will depend on the setting of the sewing machine. So it is essential to spent several hours to adjust the sewing machine (to the size of thread, to the thickness of fabrics). Depending on the troubles you have with the machine, you can save more than 10 or 20 or 30 hours. |
Sewing the enveloppe, we feel alone sometimesnbsp;! picture : 117k |
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If you do not own a basket, or if you want to renew a basket, it is possible. You will have to work wicker, rattan, wood, or for experimental baskets, fabric, aluminium, composite ...
| The five following pictures have been provided by Sebastien Rolland, homebuilder. | ||||
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Aluminium basket, with plywood,
seen without the fabric own building. |
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The building of a burner is technical and requires some skills we do not all own. The easiest solution is to buy a second hand burner (you can easily find one at an affordable price). For the purist, or the "technician" who want to build everything out his hands, it is possible to design and build a burner. It will be investissement supplémentaire (en temps comme en argent, mais il est très rentable financièrement de fabriquer son brûleur). |
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Picture from Philippe Lusley,
builder of this burner. |
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For the homebuilder, the easiest way to get cylinders is to buy second hand cylinders. However, if you want to make Stainless Stell cylinders at an affordable price, it is possible. A french builder is on the subject for now. |
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| Study from P Lusley for the cylinder building. |
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As I describe the administrative step, I only write about french administrative. The whole process of administrative is easy. During the building process, you open a file to ask a CNRA. A CNRA is the name for the "C of A" for homebuilt aircraft. In this file, you put a description of the balloon, of the materials, a stress calculation, how you built... The file is simplified if you build from a "plans bundle" (which is already certified). When the balloon is built, the GSAC (Groupement Sécurité pour l'Aviation Civile) has to inspect it (this inspection lasts one hour). During the inspection, the GSAC inspector will ask you additional questions The GSAC inspector put forward an opinion to the DGAC (Direction Générale de l'Aviation Civile), which then delivers a temporary "laissez-passer". With this "laissez-passer", you can make the trial flights. This administrative step requires about 15 hours. |
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This is the D Day ! With your "laissez-passer" in your hand, you can finally try the balloon. In France, the test program requires 5 hours of flight and 15 landings. This is fast to do ! But you are free to go on with the tests if you believe it is necessary.
To begin the trial tests, you must have an insurance. First flights are a bit particular. Will the balloon have a nominal behaviour ?
Flying a new balloon is a bit particular. During the trial flights of my first balloon, this one was so airtight that I had to pilot at the end of the flight with the parachute lightly open. Otherwise, I was unable to land it.
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When the trial flights are finished, you just have to fill the "test" form and to send it to the DGAC, which will give you a final "laissez-passer" and the CNRA just after. The CNRA is valid for 3 years in France (if you sell the balloon, the CNRA is valid 1 year). Then, you have to flight and wear out the balloon until the next building ! |
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