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Thread: Sphinx 27" build

  1. #1
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    Sphinx 27" build

    So after building and quickly destroying a FT Mighty Mini Arrow, I started looking for a similar size EPP wing and lo and behold, there was this!
    http://www.stoneblueairlines.com/air...x-27-wing.html

    (Note, the kit does not come with the skids/bumpers).

    I immediately ordered and less than a week later, I got a box!


    And inside that box was a Sphinx (!), some laminate and a fresh ESC.


    For some reason, it's supplied with 2 tubes of Welders..but you'll barely need an 1/8 of one and about 45 minutes later it now looked like this:


    I now have to wait for the glue to dry, so I can sand and prep for paint...if you're not painting it, you can easily finish this in 1 evening.

    The rest of the setup with be:
    RCX 2205-2950kv motor.
    Emax 20A BLHeli ESC. On the Arrow, I was using a YEP ESC, but it simply couldn't handle the high RPM. For the same reason, I'm not 100% sure what prop I'll use, as I think the old ESC put the motor under more stress than needed, but some 4" variation.
    Taranis D4R-II RX
    HS1177
    Hawkeye 600mw 5.8ghz VTX
    Power will come from 1000mAh 4S lipos as that's what I use on my quads.

    To be continued....

  2. #2
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    I hate painting planes...but I also want them to look good?. With this being just a wing, I'm putting in some effort, as it's simple and probably wont get to fly it until next weekend anyway.
    The VAS EPP foam is pretty coarse and it took a lot of work on my Banshee with 220grit (and didn't get that flat anyway), so this time, I made an 80 grit sanding board and went to work:

    It's a bit fuzzy, but definitely flatter than I got with the Banshee.

    Then some masking tape and first layer of paint.


    Since I have to mask on top of that, I want it to dry completely before continuing...

  3. #3
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    12 hour work days slowed down progress, but I managed to get a little done every day:

    2nd coat


    The decided I needed an additional white stripe, which required a 3rd coat and then finally the black numbering and leading edge:




    Some pin striping and it's ready for laminate!

    Bottom:

    Top:




    I should mention that before the pinstriping, I added a coat of 3M 77, which should help both the pinstriping and the laminate adhering.
    Laminating should get done tomorrow and are still aiming for a weekend maiden.

  4. #4
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    Well, it's ready:



    Except...it wont balance out. Even with a 20g piece of lead in front of the lipo, it balances at 6" and not 5.75".
    I'm using Paragon 1000mAh 65C 4S which comes in at 116grams.
    I guess I can expand the battery bay forward by another 1/2", but I'll buy some lead first and get it maidened before I start chopping.

  5. #5
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    Add 3 layers of laminate to the wing leading edge. This will seriously increase the strength and give you the nose weight you need. You also should use a lighter prop. Try an APC 4.1X4.1.

    Also toe in your winglets 1/4". This plane will wag at low speed if you don't.

    Mine flies on a 4S 1050mAh Tattu pack. I run a lighter 5X5 APC prop which really helps with the tail weight issue. The plane was really intended for a 3S 1400 pack or a 4S 1100 pack in the 60C variety as these are what multirotor pilots use and are much heavier than their lower C counterparts. Before you go adding dead weight, add battery

    -Alex
    If it is broken, fix it. if it isn't broken, I'll soon fix that.

    [url]videoaerialsystems.com[/url] - Performance video piloting

  6. #6
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    Also, feel free to cut some coroplast skids if you like. Please be aware that at this size they act as side rails and thus shift the CG of the airplane when it is on edge and the nose-drop you expect from a banked turn with a flying wing will not happen.

    Once you place another 3 strips of laminate (3" wide is perfect) over the leading edge of the wing, the plane will be completely INDESTRUCTIBLE! I have hit poles, posts, walls, other airplanes, trees, ect and have yet to repair mine other than a broken camera or prop. It is tough as nails! So please, fly this as hard as you can and enjoy the adrenaline rush!

    -Alex
    If it is broken, fix it. if it isn't broken, I'll soon fix that.

    [url]videoaerialsystems.com[/url] - Performance video piloting

  7. #7
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    The Paragons *are* my multirotor batteries and are high C...and only 10 grams lighter than the Tattu 1050s. The whole point with buying this was that I could use my multirotor gear.
    I have a Graupner Speed 4.75x4.75 lying around somewhere...but I suspect it wont be enough to make any real difference. In any case, I will add some lead and get it flying before I start modifying.

    Skids will be added the moment I can find some black coroplast. The local stores only seem to carry white?

  8. #8
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    I had to add 55grams of lead in the nose...and now have an AUW of 477grams.

  9. #9
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    Quote Originally Posted by Implicit View Post
    I had to add 55grams of lead in the nose...and now have an AUW of 477grams.
    You might actually be nose-heavy. Better to be nose heavy than tail heavy, though. Once you get it flying, start pulling weight out of the nose. I think you might be able to drop down to 20 grams of lead and it will fly correctly.

    -Alex
    If it is broken, fix it. if it isn't broken, I'll soon fix that.

    [url]videoaerialsystems.com[/url] - Performance video piloting

  10. #10
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    So, yeah..clearly too nose heavy. Also, for some reason I haven't quite figured out yet, the trim on my Taranis worked in reverse, only making the nose-heaviness feel worse!. Took some weight out, got better, but still a bit heavy. Next landing was a bit hard, took some more weight out, but didn't notice that one winglet had gotten loose and it fell off in the next flight!. From the brief moment it did fly, it was probably a tad tail heavy (about 20grams of lead). Could not find the missing winglet, but at least I have one as a template. Never FPV'd it, but it's not slow!.

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