First build advice.

Discussion in 'The light stuff area' started by Flying dachshund, Jan 8, 2011.

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  1. Jan 8, 2011 #1

    Flying dachshund

    Flying dachshund

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    Howdy. I'm working on my first plane build right now, and have a couple questions. First off, the material is 4130 tube, but what diameter should be used for the fuselage? Wing? For the engine I'm thinking of the 30hp Briggs unit. I saw the 22 horse version on a similar plane, and the guy said he'd never go back to the Rotax. Any thoughts on that? Any other tips or advice for tube and fabric builds?
    Thanks.
     
  2. Jan 8, 2011 #2

    Jman

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    First off, welcome to the group.

    Secondly, we are going to need to know a LOT more about your situation and design.

    Good luck,
     
  3. Jan 8, 2011 #3

    WonderousMountain

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    First advice-don't buy materials yet.

    There are some things we need to know.

    Are you building a Far 103 ultralight?

    Chromoly is a swell building material, but it gets heavy fast. Wise attachment points and clever triangulation will minimize fuselage weight. The diameter can be as little as 1/2" , or a quiet large in a pod & boom arrangement.

    The wing spar should be nearly as deep as the wing, generally.

    There's whole lengthy discussions about engines, tube and fabric even has it's own category.

    Try and give as good a description of what you have in mind as possible. That's the best way to get good advice.

    Wonderous Mountain
     
  4. Jan 9, 2011 #4

    Flying dachshund

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    Thanks for the responses, you guys posted sooner than I expected. I want to do something very similar to the Spacek SD-1, only I don't have any working experience with wood, so I'm much more comfortable with steel. I realize they sell the easy kits, but that's far out of reach in terms of funds, whereas doing the build from scratch will take much longer, but most of the materials can be collected a few dollars at a time. An ultralight is nice due to the fairly open regs, but I wonder if I may be better served with a light experimental? Then I could carry more fuel, have a larger engine, the whole nine yards. What do you think?
     
  5. Jan 9, 2011 #5

    Flying dachshund

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    Oh, I have a chance at some cheap tubing, specs at 3/4" X .080, is that a suitable material or should I pass?
     
  6. Jan 9, 2011 #6

    Dana

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    Whether you should go UL or not depends on the kind of flying you want to do. Ultralights can be about as much fun as you can have in the sky, but they're limited, both in weather and how far you can go. Although a few people have complete coast to coast flights (with many stops, naturally), for most people they're "around the patch on a nice day" kind of machines. A larger, faster plane with more fuel expands the possibilities significantly, but also brings the added hassle of regulations, inspections, etc.

    Obviously you will also need to take flying lessons. Just because they aren't legally required to fly an ultralight doesn't mean they're not necessary.

    The Spacek looks like a very attractive airplane, but it's not an ultralight under the US definition... too heavy and too fast for Part 103.

    It's impossible to talk tubing sizes without knowing what the structure looks like, but 3/4 x .080 steel tubing is almost certainly too heavy for nearly anything in a light aircraft structure. A more likely size (this is not a recommendation, only an example!) would something like 1/2" x .035.

    -Dana

    A child of five could understand this! Fetch me a child of five.
     
  7. Jan 9, 2011 #7

    Flying dachshund

    Flying dachshund

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    The speed and distance capabilities of a larger craft are certainly appealing, as I would love to do touring with the plane. Hmm, if it looks like I can't get the plane in under weight and speed, maybe I should just start mocking up a scaled down p38, complete with twin 100's. I guess I have some pondering to do...
     
  8. Jan 12, 2011 #8

    Catocala

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    Hello everybody!

    I know that it is very difficult for a french person to sell blueprints in US due to laws in your country.
    However, it should be interesting to have a look to that website: Bienvenue sur le site du Spratt 103 (in french, sorry, but things are very intuitive)

    In my view it will be e x t r e m l y c h a l l e n g i n g to produce a ULM for less money than that design.
    Flying dachshund will be pleased likely with that design. It relies essentially on a metal structure and foam/fabric wings. Pictures related to fabrication are presented on the site.
    In my view, the main problem is the fact that the metal pieces of the chassis m u s t be welded whith inert gaz by a certified specialist.

    Price is assessed to be somewhere between 2000 and 3500 €, depending of the engine used, as follow:

    Chassis: 500€ for the material + 500 € for the certified welding;
    Wings: 500€ for the material
    Engine: modified brand new engine like Brigg and Stratton, or other aero engine: 2000€ something. But solutions exist with second-hand old engines from small cars (I know...I know, there are more small cars in France than in US, but things can be found likely in the area of agriculture, pumps, industry or something). Exemple: here, an old engine used on citroen: 200€ (+ some weeks of works to adapt it). THat limit the price to 1500 -2000 €.

    Hope this help!
     
  9. Jan 12, 2011 #9

    Flying dachshund

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    Thanks Catocala, that is a nice little craft. It looks like that would be a pretty good design for my kid and nephews to start working with.
     
  10. Jan 12, 2011 #10

    djschwartz

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    That is very heavy tubing. FWIW the tubing in my Stephens Acro, a 200 MPH, 1600 lb gross weight unlimited aerobatic ship is 3/4" x .035. The entire steel fuselage frame, which includes the vertical fin, weighs approximately 70 lbs. The fuselage frame of a Pitts S-1, if built to the original plans, weighs something like 27 lbs. So chrome moly steel can be very light and strong if the design is done properly.
     
  11. Jan 12, 2011 #11

    Flying dachshund

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    Okay, looks like I can get away with thinner steel than I had originally thought, which is good. My local steel yard doesn't stock thin metals, but I can order it without much hassle. Does anybody know which which is stronger/lighter, thin walled larger diameter tube, or smaller, thicker material?
     
  12. Jan 12, 2011 #12

    kent Ashton

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  13. Jan 12, 2011 #13

    djschwartz

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    I would STRONGLY recommend you do some studying on basic structural engineering before you proceed any further. The question you ask is a very basic one but has some if's to its answer, and it is one of many subjects you'll need to understand in order to safely and effectively design an aircraft. If you're actually serious about design the time and money spent studying will be well worth the effort and expense.
     
  14. Jan 12, 2011 #14

    Dana

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    Actually it's not difficult at all. You can sell nearly anything here. Unfortunately, lawyers can also do nearly anything too, and the fear of lawsuits has scared many people off (like Michel Colomban. designer of the Cri-Cri). I don't think it's as bad as that, but I can understand the concern.

    -Dana

    Bismark said God looks after fools, drunks, and the United States.
    He didn't say how long the Almighty's patience might endure.
     
  15. Jan 12, 2011 #15

    Flying dachshund

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    That's the whole idea behind this, learning a new area of interest, such as the practical application of the basic engineering knowledge required to build a plane. Odds are good that I'll never finish the project, because once I have a strong grasp of what I need to do and know how to do it, the challenge will be gone and I'll lose interest. But for now, I'm enjoying the experience and learning new things:)
     
  16. Jan 21, 2011 #16

    PONCH

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    Larger pipe with a thinner wall is stronger. Chromoly is very rigid metal. Generally a chromoly structure is much lighter than a steel tube structure because of thinner wall thickness, you might be suprized. It's not so simple to work with, dificult to bend thin wall chromoly, when you weld it it moves and it has to be TIG welded. If you are familiar with it that's great, you could build anything better out of chromoly.
     
  17. Jan 21, 2011 #17

    Hot Wings

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    It's not so simple to work with,

    This kind of depends on your definition of simple.

    dificult to bend thin wall chromoly,

    Not with the proper tools and methods. And these are not necessarily so expensive or complex that the average home builder can't do the job.

    when you weld it it moves and it has to be TIG welded.

    Nope, you don't have to T.I.G. it. In fact there are quite a few very successful welders that can make a very convincing case that 4130 should NOT be welded with T.I.G., but that's a subject for a whole different thread.

    If you are familiar with it that's great, you could build anything better out of chromoly.

    This is an over simplification. There are many situations where 1026, or similar, may be a better choice than 4130.
     

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