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Thread: Ultralight

  1. #1

    Join Date
    Aug 2018
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    1

    Ultralight

    Hello....my first post here.I am asking if there is a weight,wing span and engine power ratio for designing a ultralight.

  2. #2

    Join Date
    Jul 2011
    Location
    Clarklake, MI
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    2,245
    In the US, applicable rules for wt. speed and other parameters are under Part 103 of the regulations. https://www.eaa.org/en/eaa/aviation-...or-ultralights

  3. #3

    Join Date
    Jan 2012
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    269
    Include AC 103-7 in addition to FAR 103 in your study material. Hope I remember the dash number correctly. It is old and has never been revised.

  4. #4

    Join Date
    Aug 2018
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    2
    Hi Kibet,

    To answer your question directly, I'm not aware of any design ratios that are specific to Part 103 ultralights. The combination of 254 lb empty weight and 28mph max stall speed (from the Part 103 regulation) tend to force most designs to some similar design values. I would say that the most common design value that you will find is a main wing surface area S = b x c ~= 115 ft^2 where b is wing span and c is wing chord. This value can vary based on flap type/size or flaperon usage.

    Engine power can vary widely. Common values range from 27HP to 50HP. Generally designers will put the largest engine they can on the ultralight but still remain below the 254 lb empty weight limit.

    Hope this helps.

  5. #5
    Hi--- I'm new to the whole forum world, but am very interested in ultralight aircraft. I have a private pilot's license, but since retirement, I can't afford rental rates. Seems my only option to get back in the air is to build and fly an ultralight plane. I was a product engineer before retiring, and have been a model builder/designer since third grade or so. I use my TurboCAD 3-D program now primarily for designing ultralights. I have many designs developed to various degrees of completion, but two of them to the point that I could start building. One is a very utilitarian design and would be the obvious choice with minimal build time in mind. The other design was developed with a bit of cuteness in mind and has an enclosed (pretty much) cockpit. I guess what I would primarily like from the forum is an exchange of ideas on ultralight design in general, keeping designs simple and light, structural options, and some general encouragement to keep working at it. I live a hundred miles from the nearest EAA chapter, and communication with them indicates very little action and no ultralights, so I'm pretty much on my own. I'll try to figure out how to include pictures with these messages.

    EDIT: Added picture
    Attached Images Attached Images  
    Last edited by luftbuggy; 08-24-2018 at 06:45 PM. Reason: Added picture

  6. #6

    Join Date
    Oct 2011
    Location
    WA
    Posts
    901
    Welcome to the forum luftbuggy. May want to start another thread with your thoughts and a few specific questions to get started.
    Always fun to discuss design. Sadly, only 20 Ultralight Chapters left now.

  7. #7

    Join Date
    Jan 2012
    Posts
    269
    Quote Originally Posted by luftbuggy View Post
    Hi--- I'm new to the whole forum world, but am very interested in ultralight aircraft. I have a private pilot's license, but since retirement, I can't afford rental rates. Seems my only option to get back in the air is to build and fly an ultralight plane. I was a product engineer before retiring, and have been a model builder/designer since third grade or so. I use my TurboCAD 3-D program now primarily for designing ultralights. I have many designs developed to various degrees of completion, but two of them to the point that I could start building. One is a very utilitarian design and would be the obvious choice with minimal build time in mind. The other design was developed with a bit of cuteness in mind and has an enclosed (pretty much) cockpit. I guess what I would primarily like from the forum is an exchange of ideas on ultralight design in general, keeping designs simple and light, structural options, and some general encouragement to keep working at it. I live a hundred miles from the nearest EAA chapter, and communication with them indicates very little action and no ultralights, so I'm pretty much on my own. I'll try to figure out how to include pictures with these messages.

    EDIT: Added picture
    Nice drawing.

    Looks like wood construction. First order of business is likely to decide on building materials. All airplane type ULs struggle with the 254 # limit. The newer engine options help that to some degree.

    To make the weight limit you will likely need a fabric cover over wood or metal tubular frame. Oratex is the lightest fabric cover http://www.betteraircraftfabric.com/. Aluminum or 4130 steel tube are durable structure. Woodworking is the choice for many and is light and strong. There are several UL plans of wooden aircraft similar to your drawing. They would be useful for comparison.

    Belite sells kits of a very similar metal design that would more or less assure success.

    Let us follow your thought process.

    The used market can be an economical way to get started if you are careful and seek advice from others. Most are somewhat of a project or work in progress so you will still get some building experience.

  8. #8

    Join Date
    Aug 2016
    Location
    Chicago
    Posts
    359
    Would you consider simply buying a proven design ultralight kit or plans for same? A whole lot of options going that route.
    Last edited by CHICAGORANDY; 08-29-2018 at 05:10 PM.

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