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About CoClimber

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CoClimber's Activity

  1. CoClimber added a post in a topic Model 2/912   

    There is a 912 in front of my KF2 but I am still a long way from flying it so I can't tell you much.  I hope to fix that situation as soon as possible!
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  2. CoClimber added a post in a topic AOA   

    Details here:
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  3. CoClimber added a post in a topic AOA   

    With my build, I bought a Dwyer differential pressure gauge to use as a lift reserve indicator.  You add a second pitot tube angled down ~45 degrees and this gauge reads the difference between the pitot pressure and this tube.  Costs ~$50.  I am also working on a DIY glass screen that will have an electronic pressure sensor to give me the same info and could also sound an alarm but first I want to get the airplane flying...
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  4. CoClimber added a post in a topic Near miss with fuel line.   

    Thanks 109jb.  Aluminum for me then.  Now where can I borrow a flaring tool? 
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  5. CoClimber added a post in a topic Near miss with fuel line.   

    I have a question regarding fuel lines.  Why do we use aluminum tubing between the header tank and the firewall?
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  6. CoClimber added a post in a topic New Flaperon Mixer system   

    Well done!  I kept it simple in my conversion and just copied the Model 4 mixer.  Meant that I had to modify my fuselage to attach it.
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  7. CoClimber added a post in a topic Rudder/Elevator   

    I believe that the 2 uses smaller diameter tubing than the 4.  I made the mistake of not going to a larger tubing when I added 12" to my rudder/vertical stab.  It now flexes more than I'm happy with so I will be adding braces to the vertical stab to prevent flutter, which will add drag.
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  8. CoClimber added a topic in Kitfox IV   

    Flaperon horn dimensions
    I managed to find two new flaperons for my model 4 wings that I am building.  However, they don't have the horns.  I would like to fabricate my own.  Can anyone measure the length of the tube that slides over the tube that runs down the length of the flaperons, and also the distance from the tube to the linkage attachment hole?  

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  9. CoClimber added a post in a topic Getting started/setup for Welding?   

    I have very little welding experience but I welded up a bunch of expansion chambers a few years ago out of 20 gauge steel using a tig welder where I work.  Spent half the time filling in the holes I created.  When I started working on my Kitfox, I looked into using a torch welder I had at home. I didn't want to have to haul the fuselage in to work so wanted to get the gas welder going.  I soon learned that the stock tip was way too big for our thin wall 4130 steel.  I bought a Smith AW1A torch handle and absolutely love it.  I personally find it much easier to use than a tig. Heat control is just a matter of moving the torch further or closer to the weld.  The tig is much brighter, making it hard for me to see both the puddle and the adjacent seam.  Regardless of what you choose, practice a bunch.  Cut the welds in half to examine the penetration, and break a bunch of them.  The weld itself should never break.
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  10. CoClimber added a post in a topic Structural analysis on spars   

    I went through three DARs and this is the best I could do.  I don't really mind because I am enjoying the process and I will have the airplane I want.  I will also be able to get a repairmans certificate.
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  11. CoClimber added a post in a topic Structural analysis on spars   

    The reason I am going to all this effort is because I couldn't get an airworthiness certificate unless I could prove it was 51% homebuilt.  I figured that if I was going to tear it down and build it back up, I might as well build in the Model 4 improvements.  It has a 12" taller rudder, differential controls, model 4 ribs and flaperons, 5" wider fuselage, wing tanks allowing me to have a full size panel and no be limited to the space provided in the 9 gallon tank that came with it.  I also switched to nose wheel because I am a student pilot, insurance is cheaper, and I don't expect to ever fly somewhere without a proper runway.  I can always convert it back.
    I also love to fabricate so I'm really enjoying the process.  I thought I could have the left wing assembled today but I can't find my box of latex gloves. It's the little things that get you.
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  12. CoClimber added a post in a topic Structural analysis on spars   

    I took 17" of of each wing, from 174" to 157".  Lift is a function of wing area, coefficient of lift, and airspeed squared.  It is that last bit that is important.  Not counting the effects of lift from the fuselage,  I reduced my wing area by 10%.  If the lift was a linear function of speed, we would have to go 10% faster to get the same lift.  If the stall is at 40, we would now have to go 44.  However, because it is the square of the speed,  the stall goes to 42.
    Remember too that I am going from 65 to 80hp. 
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  13. CoClimber added a post in a topic Structural analysis on spars   

    To answer some of the comments, on the carry throughs, I cut and drilled out the small vertical tubes that connect the spars to the carry throughs, welded in smaller tubes inside the carry throughs, then welded in new vertical tubes.  Hope that makes sense.  On the strut carry through, I welded a 1" strap below the existing tube.  It is in tensiion so a strap works well therre.  The landing gear has been completely replaced with cabane mains and a nose wheel.  The 65Hp 582 is swapped with a 912UL.  With the 912, nose wheel, and 26 gallon wing tanks vs the 9 gallon fuselage tank, the airplane needs a boost in GW to remain useful.
    Happy New Year everyone.  I think I'm going to go make my wife some coffee.   Then clip those wings. 
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  14. CoClimber added a post in a topic Structural analysis on spars   

    Interesting point but I don't know if the angle change is significant enough.  The angle will change from 23.8 degrees to 21.6 if I move the attachment out 10 inches.  Ithink the reason the attachment point was moved out was to reduce the amount of cantilevered wing.  It was moved out 10 inches and I will move my tip in 18".
    Another consideration is that the fuel load has been moved from in front of the panel to the wings themselves.  That is 156 pounds that don't have to be supported by the fuselage.
    I sat down with a mechanical engineer today and we looked at the loads through the wing struts.  I think I should go ahead and get beefier struts. We calculated that there is a 1500 pound tensile load on the struts and that each strut has a yeild strength of 5000 pounds, conservatively.  This load changes to 1337 pounds if I clip the wings.  I don't know where the center of lift is on these wings but if the load is distributed equally between the tubes, They would fail at 5Gs with a 1.5x safety factor (actual failure at 7.5Gs).  
    All this math is fun but, ultimately, unforgiving.
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  15. CoClimber added a topic in Avidfoxflyers General Hangar   

    Structural analysis on spars
    I have a Kitfox 2 that is seeing extensive modifications.  Today's discussion is about the wings and struts.  I want to increase the gross weight from 950 to 1200 pounds when I apply for my airworthiness certificate.  The fuselage has been modified and I am now considering the wings.  I have the old spar that has the web extruded right into the tube.  The model 4 1200 has the strut moved out 10" but I am reluctant to drill out the strut attachment ant move it out.  
    I understand that the load on the strut is a function of the square of the cantilevered section of the spar.  Currently the distance is 88" from the strut to the wing tip.  If I remove one rib bay that goes to 70".  88 squared / 70 squared =  1.58.  So, 1.58 times 950 pounds = 1500 pounds.
    Is my logic correct?  If I remove the outermost bay and leave everything else the same, the wing that was rated for 950 pounds should see the same forces at the strut brace when loaded to 1500 pounds.
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