+ Reply to Thread
Results 1 to 8 of 8

Thread: Ultralight aluminum tube size questions

  1. #1
    Registered User
    Join Date
    May 2011
    Location
    Lubbock, Texas, USA
    Posts
    5

    Ultralight aluminum tube size questions

    I have recently become fascinated with ultralight aircraft and now I want to build one of my very own. I have built a 1.5:1 scale cg-4a stick and rag glider before that still flies today [a WWII cg pilot bought it from me one day when I was out flying! it was pretty cool to actually meet one of the original pilots]

    Anyways this isn't my first aircraft, it is however my first ultralight so I have a few questions about materials:

    First What size and thickness of tubes should I use for the craft? I would like to use 6061-T6 aluminum tubing because a supplier near me carries it pretty affoardably. plus I'm pretty sure its the metal used in the affoardaplane designs, so I trust it for aircraft use.

    The aircraft will have around a 30' wingspan with a 4' chord including flaps and slats, weigh less than 254 lbs empty [in order to classify as an ultralight] but be able to carry 550 lbs of pilot+cargo+fuel+chute+etc... I weigh 200lbs suited up, a full tank of fuel weighs 40lbs, the chute weighs another 50 mounted, I would like to carry an additional 40 lbs of fuel as cargo to meet the ultralight limitation while still giving more usable range] so I can fly further, fuel up, then fly back if I choose. 2 gallons of fresh water adds 15lbs, guns and ammunition [for hunting] are probably 30lbs bringing me to 425lbs fully loaded

    I would LOVE to put floats on so that I could land on the lake and fish, then dock and hunt. So I would add the weight of whatever I hunt [I would dress and pack it to save on weight] and the weight of the floats themselves [I dont actually know how much floats weigh but I'm pretty handy with fiberglass and foam so I could just fabricate them and they shouldn't weigh terribly much but to be on the safe side it would probably be around 550lbs total

    Is this even possible? Am I dreaming too much with how much I could carry?

    second would be a different scenario where I wouldn't add the floats but instead add a power transfer system to transfer power from the prop to the wheels so that I could fold up the wings and drive off the landing strip to my destination. Has anyone heard of such a system? would it be possible to replace the last gear in a motorcycle transmission to a 3:1 ratio so that I could spin the prop, but keep the first through fifth gears intact [1986, honda cmx 450] so that I could drive with them and fly with the last?

    I know this sounds crazy but I think its possible, using a chain between the engine and the propeller with a movable second sprocket that could be swung into contact with the chain and locked in place to be started back up and driven away.

    if you have a better Idea or can explain why this will not work please tell me, I don't want to build the craft, then get out to the runway and not be able to takeoff because of some problem somewhere that I didn't think of. So hit me with everything you've got to help design a better aircraft.

    I am working on getting a 3d rendering up so I can better show you but my cad program is being buggy so I am working on getting it fixed for now.
    Last edited by MisterInnovation; May 16th, 2011 at 11:10 PM. Reason: 5 gallons of fuel is more like 40 pounds than 64

  2. #2
    Moderator Dana's Avatar
    Join Date
    Apr 2007
    Posts
    5,376

    Re: Ultralight aluminum tube size questions

    Tube sizes for ultralights can be anywhere from 1/2" diameter to 6" diameter. It all depends on the load that particular tube is carrying. 6061 is most common, though 2024 is also used where the extra strength is needed.

    But what you're describing isn't an ultralight. Not with the mission you describe. Furthermore ultralights are limited to 5 gallons of fuel.

    As for powering the wheels and taking to the road, people have been trying to build flying cars for years. You end up with a lousy airplane and a lousy car.

    -Dana

    Things should be made as simple as possible, but not any simpler.-- Albert Einstein
    Fisher FP-404
    ParaFan PPG
    Kolb Ultrastar

  3. #3
    Registered User
    Join Date
    May 2011
    Location
    Lubbock, Texas, USA
    Posts
    5

    Re: Ultralight aluminum tube size questions

    oops! I completely messed up my math for the fuel, its only 40 pounds of fuel [5 gallons] it needs to be single place, and under 254 pounds, it is for recreational use with a max speed of 60 mph airspeed in level flight, what about this makes it not an ultralight?

  4. #4
    Registered User
    Join Date
    May 2011
    Location
    Lubbock, Texas, USA
    Posts
    5

    Re: Ultralight aluminum tube size questions

    also, Im not looking for an amazing aerobatic plane, I'm looking for something to tow [or drive] out to my local farm field, fly out to the lake or woods for the weekend, then pack up and fly back. I don't need to fly fast or high, I don't even need doors or a windshield to save on weight. What diameter/thickness tube would be best for the spars in the wing? would square tubing be better I beam?? Is there some formula I can use? Thanks.

  5. #5
    Moderator Dana's Avatar
    Join Date
    Apr 2007
    Posts
    5,376

    Re: Ultralight aluminum tube size questions

    There is a "formula". There are hundreds of "formulas". One of those formulas says that 5 gallons of fuel weighs 30 lbs, not 40 lbs. Not to brush you off, but there is a lot more to aircraft deign than sizing a wing spar.

    The reason I say it's not an ultralight is that there is no way a legal ultralight will do what you want it do do (i.e. carry). An aircraft that can safely carry 550 lbs load won't be an ultralight. Half that is more realistic.

    -Dana

    If at first you don't succeed, skydiving is not for you.
    Fisher FP-404
    ParaFan PPG
    Kolb Ultrastar

  6. #6
    Registered User
    Join Date
    May 2011
    Location
    Lubbock, Texas, USA
    Posts
    5

    Re: Ultralight aluminum tube size questions

    sorry, I didn't know. My cg4 could carry a willys jeep so I figured a smaller plane could carry at least 500 lbs, but I was very wrong! also in terms of weight I always over estimate to be on the safe side, an extra 10 lbs of fuel could actually be seat padding or better suspension.

    Would 2" square tubing be sufficient to support the wing, with 1" square tubing for the fuselage and the empennage?
    also using your 250lb mark, could I install floats and have it fly or will I not have enough power to take off from the water/lift the extra weight of the floats? I don't know much about seaplanes, but I do know a fair amount about boats and seaplanes. should I just play it safe and build a land craft with wheelbarrow wheels, no extra roadable drive system and a direct drive from the engine to the prop? Then once the craft flies I can start experimenting with different options such as floats?

  7. #7
    Moderator Topaz's Avatar
    Join Date
    Jul 2005
    Location
    Orange County, California
    Posts
    8,856

    Re: Ultralight aluminum tube size questions

    If you're serious about designing your own airplane, then it's time to hit the books. The type of questions you're asking here simply cannot be answered without a lot more information about the design - information you don't have yet.

    As a start, I would suggest Simplified Aircraft Design for Homebuilders by Dan Raymer. You can find here on Amazon.com. This is a beginning. It will get you to a point where you can start asking some of the questions you have here - and there are other books where you'll learn to find the answers and ways to ask even more detailed questions. Aircraft design is something you can learn, but it's a lot of information and study. There is no shortcut, even for a "simple" airplane. If you're not really interested in taking on that task, I recommend you go find a used airplane that you can purchase outright. Also, check the local regulations in your area regarding using a seaplane on the area lakes and waterways. Many states prohibit such activities except in certain pre-defined areas.
    "If you have built castles in the air, your work need not be lost; that is where they should be. Now put the foundations under them." - Henry James Thoreau

    Design Project: Conceptual Design of an "Inexpensive" Single-Seat Motorglider
    Discussion Thread for the Project: Discussion: Conceptual Design of an "Inexpensive" Single-Seat Motorglider

  8. #8
    Registered User
    Join Date
    May 2011
    Location
    Lubbock, Texas, USA
    Posts
    5

    Re: Ultralight aluminum tube size questions

    cool beans, its on order! thanks!

+ Reply to Thread

Similar Threads

  1. Carbon instead of aluminum tube
    By ultralajt in forum Composites
    Replies: 23
    Last Post: December 7th, 2013, 07:05 PM
  2. Attaching Aluminum Skin to Steel Tube
    By GESchwarz in forum Tube and Fabric
    Replies: 6
    Last Post: January 22nd, 2010, 12:25 PM
  3. Bending aluminum tube
    By BAILEIGH INC in forum Tube and Fabric
    Replies: 2
    Last Post: July 12th, 2009, 06:09 AM
  4. Bending Aluminum Tube. Need Advice
    By Tom Kay in forum Tube and Fabric
    Replies: 10
    Last Post: June 17th, 2008, 02:22 PM
  5. Aluminum tube spars
    By lake_harley in forum Aircraft Design / Aerodynamics / New Technology
    Replies: 37
    Last Post: May 9th, 2007, 08:12 AM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts