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Thread: Ideas to build an ultralight...

  1. #1

    Ideas to build an ultralight...

    I'm planning on designing my own small ultralight aircraft, witch i plan on constructing my self.

    I'm thinking of making it a full metal body aircraft, made of aluminum, with a lawnmower engine. I live in the United States also.... I know I'll need a rivet gun and a TIG welder, and other various tools for aluminum. So could anyone give me any suggestions on what to do exactly?

  2. #2

    Re: Ideas to build an ultralight...

    Also, in order for an ultralight to be an ultralight in the U.S., it must weigh 254 pounds (115 kg). Any one know how powerful of an engine that would be needed to power this....?

  3. #3
    New Member
    Join Date
    Apr 2010
    Lake Charles,Louisiana(USA)

    Re: Ideas to build an ultralight...

    Hi, Michael!

    The first thing to do that helps most inventors or design engineers is to research the problem. Look up other
    Ultralights using the various search engines such as google, Bing or try going to for information,
    evaluate your findings as how or what type of similar designs you will select after viewing other ultralights,
    make sketches(preliminary or conceptual). Look up info on drag, rpm's, wind speeds and Bernoulli equations
    related to ultralight design. Look up books on aeroneutical design or ultralight aircraft design at your public library
    or go to Amazon books etc. I realize this is general info for a complex subject but one that is possible to accomplish,
    however don't neglect quality and safety which should also be concurently in your design and hopefully your finished prototype.


  4. #4

    Re: Ideas to build an ultralight...

    firstly, be careful - many of the founders of ultralight companies are now dead from crashing their products.
    power depends on speed and drag
    drag depends on form drag and induced drag (drag by caused lift) and increases as the square of speed
    lift depends on wing area, speed squared, and lift coefficient (basically proportional to camber)
    ultralights also have a maximum stall speed requirement.

    The tricky part is stability and control, and if you get it wrong it can be fatal. so make sure you understand it, and get a ballistic chute
    I could tell you, but then I would have to kill you

  5. #5

    Re: Ideas to build an ultralight...

    Well.....i knew aircraft were always picky on stability and stuff like that....but that's quite awesome to know that most people die who embark on their own ultralight (being sarcastic.....)

  6. #6

    Re: Ideas to build an ultralight...

    not most people - just most ultra-light manufacturing company presidents.
    minimize if you wish, my condolences to your family if you do. The fact that you have to ask such basic questions means you need to take care. the fact that I know the answers to your questions, even after a few years of not using it, means that I really don't need the attitude.
    I could tell you, but then I would have to kill you

  7. #7

    Re: Ideas to build an ultralight...

    This can be a bad idea real quick. If you do decide to go through with it, I suggest you get someone that has some qualification to at least look at it before test drive.

    I've seen manufactured kits that you can buy off the shelf go so terribly wrong. You have to make sure that everything is done correctly and all calculations are triple checked.

    Keep us posted on what you come up with.

  8. #8

    Re: Ideas to build an ultralight...

    Ultralights are very cool but...
    and so on and so forth. Read and understand these so you can know what to watch out for. Test everything several times. Do lots of practice pieces.

    Good luck
    I could tell you, but then I would have to kill you

  9. #9

    Re: Ideas to build an ultralight...

    Having designed and flown ultralights I would have to say there is a lot of incorrect information or guessing (shooting from the hip) on this thread but also some good advice. My advice to you is to study basic aerodynamics first of all. If I were you, I would take a college level course in aerodynamics and aircraft design before you begin anything. Next, do a search of all existing ultralights that are similar to the one you have in mind to build. In particular, pay attention to the usefull load, payload, gross weight, construction method & materials. I would also forget about powering it with a lawnmower engine. Not enough power, and the power to weight ratio is not good. There are a few four-cycle engines used in ultralight aircraft; one very capable and promising is a surplus engine the military used at one time in a ground generator application. Interestingly enough, it is or was made by the Teledyne Continental corporation (the same company that still makes many aircraft engines for GA aircraft). It is a horizontally-opposed four cylinder engine that is capable of around 40 HP (just right for an ultralight) it is affaectionately call a "Baby Continental". Anyway, I digress.... Most ultralight engines are two-cycle due to weight and the better power to weight ratio. Rotax being the most prominent. Rotax makes engines for the Skidoo snowmobiles also. The snowmobile and aircraft engines are made in the same facility, the difference is the aircraft engines are held to tighter tolerances and quality control. At one point in their history, certain Rotax engines were physically interchangeable between snowcraft and aircraft. However, this is not the case anymore since most of the latest snowmobiles use a different model of engine.
    More later.......

  10. #10

    Re: Ideas to build an ultralight...

    Now, about the "many of the founders of ultralight companies are now dead from crashing their products" quote posted earlier;

    First of all, there was a time (early 1980's) or period called the "Ultralight Apocalypse". During this period in the age of the ultralight there were over 100 manufactureres of ultralight aircraft. Many of these companies popped up seemingly over night in an effort to take advantage of the potential profits associated with these somewhat new aerial recreational vehicles. Many of the aircraft at the time were cop-cats of proven and safe designs but not complete clones for obvious reasons. So there was a lot of airplanes out there on the market that looked suspiciously similar. The danger was in the details; small things that a non-engineer type might not be aware of that could be critical. There were a lot of the airplanes designed to meet a certain LOOK for public appeal. These "disasters waiting to happen" along with the generaly un-trained public (no piloting skills or experience) led to a mounting pile of statisics.

    Most of the manufacturers of ultralights that actually employed engineering into the development, production, and business equation are still with us today. I can't count on two hands the number of manufacturers from the early days that are retired or have passed on due to natural causes. This is not to say that none of them, even the smart ones haven't been killed in their creations. However, ultralights are not inherently dangerous. They do have limitations and they have to be flown withing those bounds to be safe. Get educated, be thorough, be smart, learn from others, measure twice and cut once. You get the idea...

  11. #11

    Re: Ideas to build an ultralight...

    Hi Michael,

    First, don't let the naysayers get to you. Time was, ultralights were quite dangerous. Nowadays, they're somewhat safer than riding a motorcycle on public roads, though still more dangerous than driving a car.

    As flydude said, a lawnmower engine probably won't cut it. The typical ultralight engine is 25-55HP, and is most often a 2-stroke as few 4-stroke engines are light enough. Rotax engines are the most common; while they originated in that company's snowmobile engines they've diverged and now the aircraft versions are purpose built.

    You probably won't need the TIG. Aluminum aircraft structures are rarely welded; the welding destroys the heat treat and few amateur builders have the facilities to properly reheat treat an assembled structure. Steel tube you can weld; aluminum you rivet.

    There are few all aluminum ultralights. One is the Hummel Ultracruiser.

    The fact that you are asking such basic questions in a forum like this leads me to believe you aren't very familiar with ultralights. Rather than jumping into a new design, you'd be better advised to learn to fly an ultralight first (the fact that no pilot certificate is required does NOT mean no training is required!). Flying around for awhile in a used ultralight (which will almost certainly cost far less than a new original design) will put you in a much better position to start working on a new design.

    An excellent online resource for homebuilt aircraft is

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