Aluminum Dragon

Discussion in 'Member Project Logs' started by proppastie, Mar 29, 2016.

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  1. Jun 19, 2018 #141

    proppastie

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    Finding the CG. First picture balance on the edge of the table for the fore and aft location. Second picture for the span location. Assumption the actual location is close to the center for the Z direction. This includes the ballast weight on the tip. Stay tuned for the load test. (not today though)

    IMG_20180619_132027.jpg IMG_20180619_133516.jpg
     
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  2. Jun 23, 2018 #142

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    LEARNING EXPERIENCE:....You think you know what you are doing and something happens....sort of like life......better here on the ground than in the air.
    FAILED LOAD TEST:....end bottles are water... had to put sandbags in box because they wanted to spread out more than where I wanted to put them. Started at the tip with the light loads. and worked inboard. The failure was lightning quick no warning as I was laying on the sand bag over the failed rib.
    Only one rib failed and after the weights were removed the aileron still rotated freely...had it happened in the air I would have been able to still fly, although if the limit load was on the unloaded ribs too, perhaps more would have failed and I would not have been able to fly.

    See discussion: https://www.homebuiltairplanes.com/forums/showthread.php?t=30073&p=431974#post431974

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    Last edited: Jun 23, 2018
  3. Jul 3, 2018 #143

    proppastie

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    Rib fix done...better than new....really....the trailing edge ended up better.

    IMG_20180701_141936.jpg fix Copy.jpg
     
    Last edited: Jul 3, 2018
  4. Jul 20, 2018 #144

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    I have started another load test. The plan is to use the bottle jack per Bill's suggestion (see discussion) and hang the weights with the load distributed over the verticals per BB suggestions. I also refined the plates the load was on so the load was distributed over the vertical of the angle element. The plan is to load in increments at 33% 50% 75% 90% and full limit load of 9 PSF. I tried to stabilize the ribs with filament tape and duct tape.

    The 33% came out great. Deflection was very close to the model and I thought everything would be alright.

    At 50% about 1/2 way bottle jack expected extension... I noticed a rib ready to fail/cripple/twist etc.

    Thanks for the help BB, Mcrae, Bill, your suggestions were incorporated in the test.

    Apparently I do not know how to predict instability, I am not sure I saw any analytical methods.....This method of incremental load testing should help but I wounder if there is other methods.

    To be fair the model and the part are always different....the model is welded beams or meshed surfaces, and the real part is certainly different.

    I have tested another vertical member and it looks like at 50% loading more of the same will work.....

    IMG_20180716_102225.jpg IMG_20180719_095240.jpg IMG_20180718_135317.jpg IMG_20180719_102209.jpg
     

    Attached Files:

  5. Jul 20, 2018 #145

    proppastie

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    Finished 50% test.....shown the reinforcement example typ. of ribs 2-6

    IMG_20180720_155508.jpg
     
  6. Oct 21, 2018 #146

    proppastie

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    Still working, just not posting…..till now….I had second failure 8/2/18 after reinforcement to .050 thickness of ribs. I decided that my stress analysis was all screwed up. I have done lots of dancing around with different designs and have attempted to make sense of what is happening.
    The second failure was done after a more careful load test as from suggestions from the list. The failure was between 50% and 75% of limit load, which gave me a rough allowable for the .050 x .025 angle structure of the rib.
    It was also suggested that rather than just crippling strength of the angle I should also look at Euler of the rib.
    The failure was at approximately 4578 PSI at 75% limit.
    I had designed the structure to withstand a calculated 18,000 PSI crippling at design ultimate load. Not a very good initial stress analysis. Or in other words big mistake and bad design.

    What I think happened is:

    1. Given the geometry of the ribs and load path…. the least “Moment of Inertia” “I” for an angle is in the 45 degree direction rather than parallel to the legs of the angle. The “I” of the .050 angle in the X and Y is .00126,….the least “I” in the 45 deg. Direction is .00044.
    When I plug that “Least I” into my FEA at the approximate 75% limit failure load the axial stress is 4578 PSI.

    2. When checking Euler for a 24” long rib, I get 4761 PSI failure. The rib failed at 12 “ on the 24 “ rib. Bingo, least wise if I am wrong it sure makes sense anyway.

    The new design is lots stronger in terms of the “Least Moment” .00721 vs. .00044, and in terms of Euler in the failure direction Inbord-Outbord, or Aircraft Y the failure PSI is 36243 vs. 4578.

    Shown pictures of added .063 caps and .04 gussets, added .063 angles and .040 doubler to ribs 1-7.
     

    Attached Files:

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  7. Nov 9, 2018 #147

    proppastie

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    Passed the "Limit Load Test"....9 psf per FAA Glider Criteria....that number includes gust loads.....243 lb on a 17 lb full span aileron. I had estimated the aileron might weigh 12 lb so I have taken somewhat of a hit on weight all aft of the CG...but 10 lb more total weight is better than an in-flight failure.

    IMG_20181109_160525.jpg IMG_20181109_160541.jpg IMG_20181109_160350.jpg IMG_20181109_155305.jpg IMG_20181109_140850.jpg
     
  8. Nov 10, 2018 #148

    proppastie

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    Re-did the CG of the aileron.....I think this way was easier than the last way I posted. Balanced on rollers....used what I had laying around.

    IMG_20181110_105145.jpg IMG_20181110_105129.jpg IMG_20181110_104932.jpg
     
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  9. Nov 10, 2018 #149

    proppastie

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    Deflections did not match my FEA,...it does not do torque very well for not-round parts. The deflection from the actuator to the tip at 3 psf was 3/4 "...The wing loading for my version is perhaps 2.5 psf.
     
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  10. Nov 11, 2018 #150

    proppastie

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    Started the assembly of the LH aileron. I had plotted the RH on Mylar because the vellum was not stable at that length. All I had to do was turn it over for the LH, which was nice. There are reinforcements that I did not make drawings for, so I have the RH part there to refer to.

    IMG_20181111_181735.jpg
     
  11. Dec 5, 2018 #151

    proppastie

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    Still working....line up of the hinge line with laser.

    IMG_20181130_165544.jpg IMG_20181204_095907.jpg
     
  12. Dec 21, 2018 #152

    proppastie

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    look hard and might see the stretched line

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  13. Jan 13, 2019 #153

    proppastie

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    almost done with this other aileron

    IMG_20190109_144643.jpg IMG_20190111_141747.jpg
     
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  14. Jan 14, 2019 #154

    proppastie

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    done LH aileron ....take a break and plan the next battle. This one is about 1.1 lb lighter because the RH had much re-work and this one the changes were incorporated from scratch.

    IMG_20190114_101944.jpg IMG_20190114_105354.jpg
     
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  15. Feb 4, 2019 #155

    proppastie

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    #1 rib, that is a 12 inch ruler (304.8mm)

    IMG_20190202_140400.jpg
     
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  16. Feb 23, 2019 #156

    proppastie

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    All the ribs for the wing.

    IMG_20190222_200509.jpg
     
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  17. Feb 26, 2019 #157

    proppastie

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    Decided I need to be able to remove the aileron so now the hinge is crimped one side and has safety wire on the other.

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  18. Mar 26, 2019 #158

    proppastie

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    IMG_20190325_163210.jpg IMG_20190325_163158.jpg Working on the Spoiler.....looked good on paper....what you see here is Revision 2 of the linkage. I plan on load testing it and may have more revisions if it fails. It is not as stiff as I think it might need to be, but the Never Excede 60 mph limit load on this panel is 15 lb. which it should carry without bending. The problem is the linkage has to move and the play in the linkage causes it to perhaps move too much and I need to see if it will bind up at that load.
     
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  19. Mar 27, 2019 #159

    proppastie

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    60 MPH Never Exceed Speed Limit Load test per FAA Glider Criteria..... IMG_20190327_135207.jpg IMG_20190327_135213.jpg IMG_20190327_135249.jpg IMG_20190327_135558.jpg IMG_20190327_140228.jpg
     
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  20. May 11, 2019 #160

    proppastie

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    One of the problems with this is remembering what I designed maybe a year ago......the drawings are not complete with much left to "at assembly" or "when I get there".....

    I have been reviewing my rear spar and designing a rear spar attach fitting, which required a slight re-design of the rear spar caps, nothing major.

    I needed a "taper attachment tool" for to saw the taper in the caps....trying to follow a scribed line just was not very good.

    I made the fixture which allows a .11 degree taper of the cut. I have to flip the sheet every time I do the next cut....it worked out much better.

    IMG_20190510_103644.jpg IMG_20190510_131030.jpg
     
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