Self-designed Carbon U/L

Discussion in 'The light stuff area' started by mstull, Jun 23, 2005.

Help Support HomeBuiltAirplanes Forum by donating:

  1. Jun 23, 2005 #1

    mstull

    mstull

    mstull

    Well-Known Member

    Joined:
    Jun 23, 2005
    Messages:
    1,263
    Likes Received:
    12
    Location:
    West Texas
    I was encouraged to start a new thread, to introduce y'all to my self-designed, scratch built, carbon, legal U/L. Here's some specs:
    Dry weight: 229#, including the BRS chute
    Maximum gross weight: 460#
    Engine: CorsAir M25Y, recoil start, with float/slide carb, about 21Hp tuned for silent running.
    Prop: PowerFin E-2, 50"
    Cruise: 40 to 55 mph. I usually cruise at 50 mph
    Fuel consumption: 1.2 gph
    Vne: 70 mph
    Stall speed: 27 mph
    Controls: 3 axis. Right stick controls ailerons and stabilator. Left stick controls throttle and rudders. Foot controled nose wheel steering.
    Design loads: +5 and -2 Gs This plane has been looped.
    Rate of climb: 300 to 400 fpm (in standard conditions) depending on engine tuning.
    Maximum crosswind component: 15 mph.
    Covering: Stitts Poly Fiber, fully silvered.
    Main Gear: Swing arm, with bungee shock absorbers.
    Fuel capacity: 4.7 gal
    Construction materials: Mostly carbon fiber, some 2024 aluminum, very little wood and 4130 steel.
    Control surfaces: Fully counterballanced rudders and stabilator. Dropped ailerons. Dual vertical stabilizers and rudders.
    Wing construction: Single, tubular, carbon spar. Carbon/styrofoam sandwich ribs. Carbon leading edge. Carbon reinforced, aluminum trailing edge.

    I have about 700 landings on my Mantis so far. I fly about 4 hours a week. The plane is super easy to fly and land.
     

    Attached Files:

    • 15.gif
      15.gif
      File size:
      80.7 KB
      Views:
      2,033
  2. Jun 24, 2005 #2

    mstull

    mstull

    mstull

    Well-Known Member

    Joined:
    Jun 23, 2005
    Messages:
    1,263
    Likes Received:
    12
    Location:
    West Texas
    Here's a photo of my carbon wing, ready for covering.
     

    Attached Files:

    • nw1.gif
      nw1.gif
      File size:
      238.8 KB
      Views:
      2,581
  3. Jun 24, 2005 #3

    mstull

    mstull

    mstull

    Well-Known Member

    Joined:
    Jun 23, 2005
    Messages:
    1,263
    Likes Received:
    12
    Location:
    West Texas
    Here's an older photo from the rear. The plane has larger ailerons now, and different engine mounting. But you can get a good feel for the configuration, and see the filament wound, carbon, rear fusalage booms.
     

    Attached Files:

    • nov1.gif
      nov1.gif
      File size:
      125.1 KB
      Views:
      1,544
  4. Jun 24, 2005 #4

    Rhino

    Rhino

    Rhino

    Well-Known Member

    Joined:
    Apr 8, 2004
    Messages:
    771
    Likes Received:
    4
    Location:
    SW Ohio
    The dropped ailerons are interesting. In the first picture they make it look like a lightweight crop duster.
     
  5. Jun 24, 2005 #5

    mstull

    mstull

    mstull

    Well-Known Member

    Joined:
    Jun 23, 2005
    Messages:
    1,263
    Likes Received:
    12
    Location:
    West Texas
    Rhino,

    Those dropped ailerons are wonderfully powerful... even when the wing is stalled, I can maintain wings level with just the ailerons... since the ailerons never stall. They also add a lot of lift in slow flight, reducing wing loading and stall speed. They also have very little adverse yaw.

    Here's a very old photo, flying over west central Texas. Coincidentally, my old, Hirth F-33 siezed just a few minutes after this photo was taken. I glided to a safe landing on an abandoned road with no damage... other than the melted engine.
     

    Attached Files:

    • me.jpg
      File size:
      82.8 KB
      Views:
      1,544
  6. Jun 24, 2005 #6

    mstull

    mstull

    mstull

    Well-Known Member

    Joined:
    Jun 23, 2005
    Messages:
    1,263
    Likes Received:
    12
    Location:
    West Texas
    Rhino,

    Those dropped ailerons are wonderfully powerful... even when the wing is stalled, I can maintain wings level with just the ailerons... since the ailerons never stall. They also add a lot of lift in slow flight, reducing wing loading and stall speed. They also have very little adverse yaw.

    Here's a very old photo, flying over west central Texas. Coincidentally, my old, Hirth F-33 siezed just a few minutes after this photo was taken. I glided to a safe landing on an abandoned road with no damage... other than the melted engine.
     

    Attached Files:

    • me.gif
      me.gif
      File size:
      183.4 KB
      Views:
      1,179
  7. Jun 24, 2005 #7

    Bob Kelly

    Bob Kelly

    Bob Kelly

    Well-Known Member

    Joined:
    Aug 19, 2004
    Messages:
    373
    Likes Received:
    0
    Location:
    N.Calif Mountians
    Ok now for a stupid question... i am used to Gyros so my knowledge on fixwings is limited.... do you do a haing test with something like this to find the center of gravity or something ? or do you have to figure that out mathimatically ?

    My dad's Robenson's B1RD originally had the Flying ailerons but a upgrade kit was put on it to get the ailerons on the main wing...
    it has a Rotex 503 with a belt reduction drive and is a tractor configuration
    the bad thing about the B1RD is that it has like 30 cables to hookup ! once you have removed the wings ! we did that so we could transport it to and from the landing strip and not have to disessimble it each time even as it is ...its a royal pain to set up ...
    takes about 30 minutes , which is better than the original 1hr 30 min
    but.. I am spoild with my gyro ... 5 min and its off the trailer and ready to go !
    Your Aircraft sure makes me think about my lack of knowledge on carbon fiber !!!! because I sure like that clean UN-cabled Wing ! <GRIN>

    again ...Congradulations on a very nice aircraft !
    ...
    Bob.
     
  8. Jun 24, 2005 #8

    mstull

    mstull

    mstull

    Well-Known Member

    Joined:
    Jun 23, 2005
    Messages:
    1,263
    Likes Received:
    12
    Location:
    West Texas
    Yes I did "hang" the plane to find its CG. I supported it with a pointed board on each wing tip, with me sitting in it and all. You can also calculate the CG by weighing the weight on each gear, then use a plumb bob to carry that point up to where it intersects the wing. I did a lot of fiddling with the CG after I started flying the plane. The whole cockpit part can be moved fore and aft to move the CG.

    The center of lift moves quite a bit, depending on the angle of attack... forward in slow flight... aft at Vne. I was surprised how far aft I could go, and still be stable in stalls, and all modes of flight. My CG is about 25% of chord now, but the dropped ailerons move the effective CL back a lot in slow flight.

    The only disadvantage to having full flying ailerons is: they add a bit more drag. But that is insignificant on a slow flying craft, like an U/L. My wing doesn't have any dihedral or washout. So it needs good, powerful ailerons to keep the wing level.

    Actually my wing is only semi-cantelevered. The spar is designed to withstad at least + or - 2 Gs on its own. There is a single flying wire on each side, connected to the landing gear for +5 Gs. The spar/plane would have come out 10# heavier if I had layed up enough unidirectional carbon on its top and bottom (spar caps) to withstand the at least +4.5 Gs I felt was necessary for safety. That carbon is expensive too. I like flying in the heat of the day, when I can fly in shorts and sandals {%->} So my wing strength and aileron power is well tested in the bumps.

    My wing is all one, long 26.2' part. So my plane doesn't fold or transport easily. Everything does quickly unbolt off the wing. So it can be transported on an open trailer.
     
  9. Jun 24, 2005 #9

    Bob Kelly

    Bob Kelly

    Bob Kelly

    Well-Known Member

    Joined:
    Aug 19, 2004
    Messages:
    373
    Likes Received:
    0
    Location:
    N.Calif Mountians
    thats neet ! being able to move the weight front to back like that , add a bit bigger engine and some floats and you could easily land on the water too

    do you have any idea on how long your take off roll is ? with such a small engine i would amagon its a good distance eh ?

    I was just finishing up on my gyro this morning , if i can find some 2x6" boards to use as ramps I think I'll go taxie test her , and perhaps get in a few crow hops
    ....I can alwayse hope heheheheh

    c ya !

    Bob...
     
  10. Jun 24, 2005 #10

    mstull

    mstull

    mstull

    Well-Known Member

    Joined:
    Jun 23, 2005
    Messages:
    1,263
    Likes Received:
    12
    Location:
    West Texas
    Bob,

    I've never actually measured the take off roll. But I'd guestimate in the 100' to 200' range at sea level in standard conditions with no wind. The plane picks up speed pretty quickly since it's so light. The new wing I'm making for it should cut that in half.
     
  11. Jun 25, 2005 #11

    M51

    M51

    M51

    Active Member

    Joined:
    Apr 14, 2005
    Messages:
    27
    Likes Received:
    0
    Location:
    MI
    Very interesting design. Nice work Mark.
     
    Last edited: Jun 25, 2005
  12. Jun 25, 2005 #12

    Bob Kelly

    Bob Kelly

    Bob Kelly

    Well-Known Member

    Joined:
    Aug 19, 2004
    Messages:
    373
    Likes Received:
    0
    Location:
    N.Calif Mountians
    Mark :

    Somethings been nagging me why didn't you put a dehidril in the wing ? a 6 degree dehidral realy stablizes a wing a great deal ... was it the construction ? being easier to build a flat wing over one with a dehidril ? just courious ,
    nothing wrong with what ya have and if it flys as good as you say theirs no need for a dehidril ... but i got a feeling
    there was other considerations that i'm missing ???? hehehehehe

    I am wondering what the same bird built strictly out of alumimium would weigh ?
    or even if it could be built strong enough heheheheh
    .... I often woundered how a twin tail ....tail dragger would handle the tail wheel ... I see you have skids on both tails .... interesting ! i bet it only skids for about 10 to 15 feet before the tail lifts off the ground uh ? hehehehe pirty cool !
    I thank you for all the info you are shareing with us about your creation !
    You do indeed have a one of a kind craft there .... to fly at 50 mph with only 21hp is a true breakthrough !
    at least I've never hurd of it being done before ! great work !

    Bob....
     
  13. Jun 25, 2005 #13

    mstull

    mstull

    mstull

    Well-Known Member

    Joined:
    Jun 23, 2005
    Messages:
    1,263
    Likes Received:
    12
    Location:
    West Texas
    Wow... a lot of good questions, Bob.

    Dihedral doesn't add as much roll stability as most people think. Compared to the bumps, flying in the heat of the day, a slight dihedral would be pretty insignificant. You'd still have to use the ailerons to keep the wings level. But the main reason I chose no dihedral was for light weight. Making the wings in two halves would add about 10# to this design... 20# if the two halves were able to be taken apart for transport. A flat wing flys great and is slightly more efficient than a dihedraled one. The biggest difference dihedral adds, is the ability to steer with the rudders. With a flat wing, the plane just skids when you use the rudders, eventually rolling very gradually. This actually makes cross wind landings easier. When you use the rudders to straighten the plane with the runway, it doesn't roll (the wrong way). The flat wing aslo saved weeks of work, because I was able to assemble it all on a very long, level work bench.

    I designed this plane specifically for composite construction. I'm sure you could use some of my ideas on an aluminum plane.

    My plane is tricycle geared. It only rests on the tail skids when you're not sitting in it. You can touch the skids down if you try to take off or land near stall speed. Normally, the only time the tail skids touch ground is when I'm starting the engine. I originally designed the plane to be convertable from tricycle to conventional. Making the rear gear legs a little longer would move the main gear forward and turn it into a tail dragger. I've never flown it that way though. Those carbon rear fusalage booms can flex quite a bit, so it does need a skid on both tails.

    Actually, getting good cruise speed from a small engine isn't that hard. Most U/Ls get a lot of drag from their tubular trailing edges. I found a way to make standard, preformed, aluminum, trailing edge strong enough to support the fabric tension and lift: You assemble the wing with the aluminum trailing edge. Then support the wing with the trailing edge down. Then pour some "wet micro" (micro filled epoxy) into the trailing edges. Then lay a single 1/8" diameter carbon rod into the micro. That carbon rod is unbreakable. You can pound my trailing edges with your fist, they're so strong. The ribs have to be structural to use this technique. It wouldn't work if the aluminum trailing edge was used as a spar, like most U/Ls have. My wing has just the one, super strong, tubular carbon spar. I put a photo of it in the composites chat section.
     
  14. Jun 27, 2005 #14

    Rhino

    Rhino

    Rhino

    Well-Known Member

    Joined:
    Apr 8, 2004
    Messages:
    771
    Likes Received:
    4
    Location:
    SW Ohio
    That can't be west central Texas. There's green vegetation! LOL!

    I used to live in Lubbock and spent a year in San Angelo (courtesy of the Air Force). Greenery was hard to come by, except in someone's yard.
     
  15. Jun 27, 2005 #15

    mstull

    mstull

    mstull

    Well-Known Member

    Joined:
    Jun 23, 2005
    Messages:
    1,263
    Likes Received:
    12
    Location:
    West Texas
    Rhino,

    The drought ended. Yes, all my photos are from the San Angelo area. Everything is totally green here now. But we're worried about grass fires now that it stopped raining for the last month or so... with no rain in sight. San Angelo's reservoirs are still very low, from the many year drought that ended a year ago.
     
  16. Jun 28, 2005 #16

    Rhino

    Rhino

    Rhino

    Well-Known Member

    Joined:
    Apr 8, 2004
    Messages:
    771
    Likes Received:
    4
    Location:
    SW Ohio
    I was just joking, Mark. I was at Goodfellow in 1982-1983 and have some very fond memories of San Angelo. Great flying weather there too.
     
  17. Jun 28, 2005 #17

    Sonnyj

    Sonnyj

    Sonnyj

    Well-Known Member

    Joined:
    Feb 13, 2005
    Messages:
    135
    Likes Received:
    0
    Location:
    Rosman NC USA
    Very nice I haven't seen a U\L that I liked till now.
    Please keep on writing about yor work, I learn more from each post.
    I thought that looked like the San Angelo area,I used to build Texas rocking chairs and sold a lot at the Concho River fesival,I had a lot of fun ther.
    Thanx again
    Sonny
     
  18. Jun 28, 2005 #18

    mstull

    mstull

    mstull

    Well-Known Member

    Joined:
    Jun 23, 2005
    Messages:
    1,263
    Likes Received:
    12
    Location:
    West Texas
    I'm attaching a photo of my engine installation. You'll notice quite a few changes from the stock CorsAir M25Y: I rotated the engine 90 degrees to the right, just because it worked out better with the center of thrust and my engine mount. Note that the engine is mounted to the wing, not the fusalage. My plane doesn't really have a fusalge.

    You can see my float/slide carb that replaces the tiny diaphram carb that came with the engine... and the intake duct to the custom air cleaner and intake silencer that are inside the wing behind the fuel tank. The intake manafold is all custom fabricated of aluminum and a piece of radiator hose.

    I couldn't abide with the stock, transverse muffler set up... too much drag. So I changed the bend on the exhaust headder, to bring the muffler closer to the engine, with my fore and aft muffler allignment. That allowed me to mount the muffler to the engine. You can also see my home made, all aluminum, exhaust silencer. That took a lot of trial and error to perfect... and it's really only slightly better than the stock one. I think it's a tiny bit quieter, and doesn't leak oil all over itself. I used kevlar cloth for the packing material for unlimited life. If the kevlar ever gets saturated with two stroke oil, it can be washed in solvent or soap and water. Glass packing tends to gradually disintegrate.

    My engine is solid mounted to an 11' long steel bar that is rubber mounted to 6 ribs inside the wing. I had to do that to quell the tremendous vibration of my old Hirth F-33. The mounting on my new wing will be different to save weight.

    I'm using the 2.6 to 1 re'drive ratio. So the drive pulley is pretty small, with not quite enough contact area with the belt. The new engines come with an upgraded, 15 groove belt. I got 60 hours from my first, 12 groove belt. If the drive pulley ever wears out, I'll probably invest in the upgrade. But belts are very inexpensive.

    I found an accurate way to tension the belts that works with any belt re'drive: You put a torque wrench on the drive pulley nut, and hold that still. Then turn the prop till the belt slips. Too little tension, and the belt slips. Too much can overload the crankshaft and prop pulley bearings. I keep mine between 15 and 20 pound feet. As the belt wears, you have to tighten it more to keep the same slipping torque. So replace the belt before you overload the bearings.
     

    Attached Files:

    • june.gif
      june.gif
      File size:
      97.8 KB
      Views:
      645
  19. Jun 29, 2005 #19

    mstull

    mstull

    mstull

    Well-Known Member

    Joined:
    Jun 23, 2005
    Messages:
    1,263
    Likes Received:
    12
    Location:
    West Texas
    I'm fabricating the ribs for my new wing. I finished cutting them out with the bandsaw, and sanding them. The scrimmed, 1/4" thick, balsa, non-structural ribs came out perfect... both strong and light weight. The carbon-balsa and carbon-styrofoam sandwich, structural ribs are perfect too... plenty strong and stiff. I'm almost finished fabricating the new landing gear that will go on the new wing.
     

    Attached Files:

  20. Jul 4, 2005 #20

    mstull

    mstull

    mstull

    Well-Known Member

    Joined:
    Jun 23, 2005
    Messages:
    1,263
    Likes Received:
    12
    Location:
    West Texas
    I just added a windshield to my plane, so I don't have to wear a helmet.
     

    Attached Files:

    • ws1.gif
      ws1.gif
      File size:
      106 KB
      Views:
      501

Share This Page



arrow_white