FT Explorer ... Depron style.

Discussion in 'Scratchbuilding!' started by TomMonton, Feb 21, 2016.

  1. TomMonton

    TomMonton Administrator

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    Yeah...I'm with you on that one. The 9x is a little to close for comfort. I would hate to suggest raising the motor more because it has a "top heavy" quality to it already.

    9" is the right prop for displacement but it just fits a little too tight. I'm right behind you
     
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  2. TomMonton

    TomMonton Administrator

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    ....ugh. all I have is an 8x4x3 EP and the rest are 8x4 slofly. I hate to wait out a parts order it's going to be pleasant wind finally this weekend and....

    .....now where's that ply.
     
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  3. TomMonton

    TomMonton Administrator

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    Some outpatient surgery over night. I had always felt that the tail boom was just a little too short for this plane.

    My first clue was after adding the camera and video tx, that i was now stuffing the battery way back into the fuselage .... then the light come on.

    Let's make her a stretch


    After a short conference with Malukk, he suggested 2 inches. I just sort of eyeball'd it and ended up at almost 2.5 inches longer. I still have ply reinforcement to add to stiffen things up. [​IMG]
     
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  4. TomMonton

    TomMonton Administrator

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    ..and ready to go. I just outboard'd some ply on the outside.

    I used an old paper business card and tac'd that into the little slice left by the propeller.

    [​IMG][​IMG]
     
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  5. I hope it doesnt bend at the junction of fuselage, is it stiff now?
     
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  6. TomMonton

    TomMonton Administrator

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    She fits nice and snug and yes. Very little twist if at all and lots less waggle up and down.
     
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  7. TomMonton

    TomMonton Administrator

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    ...and done. One more touch of ply wedged inside the track. Now it feels right...this should fix that weird porpoising effect and keep the propeller nicely away from the boom.

    The boom will still slide out again if I need to change something up later.

    [​IMG]
     
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  8. So cool :)

     
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  9. TomMonton

    TomMonton Administrator

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    Today was 8mph steady wind gusting to like 14 or something ... ideal for a stress test.

    She took it MUCH better this time. I could actually watch the frame flex buffeting against the wind on low passes. The flex is even now across the length of the entire plane as it bounced around. The added ply made all the difference that way.

    My final suggestion on this is make it an even 3 inches longer. You "will" need reinforcement but I am finally pleased with how it will manage a glide.

    I'll cut up another tail/boom using MPF next, but I'll need to get some more ply laminate first. Now I can move onto video linking and flight control.

    Turnigy D2830/11 1000kv
    EMP 9x4.7R (pusher)
    SkyWalker 40a ESC
    4 each 5g Servos
    4+ Channel Radio
    3-axis Stabilizer
    1600 - 2200 ma Battery
     
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  10. Will you go with brown paper this time on tail?
    That would make it stiff in all directions... The twist and the tilt...
     
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  11. TomMonton

    TomMonton Administrator

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    Probably not...I'm leaving that one for you

    I'll go with a ply laminate again....go with I know works ? The side bracing I'll lay on the inside of the foam so it looks a little nicer but the top skin, I'll leave on the outside with about a inch+ to slide inside that channel for boom support. I really liked how that worked.
     
    Last edited: Jun 26, 2016
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  12. TomMonton

    TomMonton Administrator

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    No kidding....it's been June since our last visit with the fpv explorer.

    I've put some mileage on her this season and have had enough time to formulate what this aircraft really needs to fly a little more pleasantly.

    Where to restart right ?

    [​IMG]

    Faults: She tends to fly nose heavy. I was never entirely happy with balance. I've had to shove the battery as far back as possible to glide right.

    She liked to porpoise big time.

    She doesn't stall well. At stall it will tend to nose down and curl if you do a throttle punch coming out.
     
    Last edited: Oct 16, 2016
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  13. TomMonton

    TomMonton Administrator

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    What I've done thus far:

    To settle down the porpoise effect I stretched the boom 2.5" longer. You can see where the previous boom was getting hit and is where I started from.
    [​IMG]
    I got busy with some ply and tightened up the fuse cavity where the boom rests inside. [​IMG]

    The center of gravity.... it's too narrow a balence to plan on a consistent feel everytime out. This tells me we need to move center mass back just a little more yet....giving up some slack for battery placement.

    My marks where gauged against a whimpy little 650mah 3s battery.

    [​IMG]
     
    Last edited: Oct 16, 2016
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  14. TomMonton

    TomMonton Administrator

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    Next step...okay let's move it back some more. I've moved the motor mount back 9mm more and as a bonus will give back a little better prop clearance.
    [​IMG]

    I've lengthened the elevator looking for a little more authority approaching a stall. I'd say i have a touch more control surface than really needed but I can dial that back easy enough down the road.
    [​IMG]
    [​IMG]

    ...and I still have some hinge work to sort out but you can see where I am going with all this. I shouldn't have to lengthen the rudder... only lift it higher into the wing.
     
    Last edited: Oct 16, 2016
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  15. Nakul

    Nakul Ace Pilot

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    Hey guys! Had built the FT 3D last month out of 5mm depron. Turned out to be pretty sweet. Please pay attention to Tom's advice on having ur excess glue all cleaned up on the slide in to fit parts. I didn't have to do any mods and everything fit just perfect. [​IMG][​IMG][​IMG]


    Sent from my iPhone using Tapatalk
     
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  16. Nakul

    Nakul Ace Pilot

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    oh btw would like to add with the 1400 kv emax motor x hobbyking 9x4.7 slowfly prop this becomes a multirole plane. you can fly it slow, it wont stall at all. you can have it fly fast with apc 8x6, hover,inverted, do some basic 3D, Just love how this one flies. :)
     
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  17. Nice! Yeah, I feel like I could use more horizontal and vertical stabilizer surface...

    Here are a couple of mods that I did to strengthen overall:

    First of all, I added CF strips to either side of the tail, so that it doesnt flex as bad and pitch up as I powered up...

    IMG_4528.JPG

    Next, to get rid of the bad characteristics in flying, I had to take care of few things mechanically...
    When I first flew I felt like this plane had a mind of its own... so fixed a couple more areas such as wing flex...
    Simply made struts out of 1.2mm CF rods and connected wings and fuselage - super light weight solution!

    IMG_1052.JPG

    This took care of almost ~60% of the bad characteristics...

    Next, I had to fix the horizontal and vertical stabilizer flex/twist - "mind of its own" issue
    I simply attached bbq skewers towards the edges of both stabilizers.

    IMG_6845.JPG

    Finally, I also moved the tail section ~1.5" outwards and kept the CG at same spot and this improved its performance dramatically! You can see in the picture below how much I pulled out...

    IMG_6737.JPG

    Even without the CF rods in tail, I never really had the grinding issue which tells me that I have the motor placed tad bit higher than that of Tom's setup...


    One more thing to try before I add more foam to the rear stabilizers is to move the tail even more inwards while keeping CG the same - My hypothesis is that both surfaces will see a little more air as they'll be closer to prop (therefore elevator and rudder would become more responsive) and "cleaner air" as well - I think as the air (from prop) travels further back, it get more and more turbulent.. Along with this, the turbulent air coming off of wings also is hitting these surfaces?
    Therefore, moving it further inside will hopefully get rid of the turbulent air hitting the elevator and rudder in the back, make it more responsive and hopefully more stable? Guess we'll find out...
     
    Last edited: Oct 16, 2016
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  18. TomMonton

    TomMonton Administrator

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    Yes.... the next wing I build will have a 6mm cf tube down the spine (part way because of the added pitch). With any weight I was seriously reluctant to yank it around too much. Point that into a gusty wind and I might snap it in two.
     
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  19. Yeah, I was so close to a wing snap given that I dont even have a wooden spar in it, lol
    Now however, I feel more responsible. :p
     
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  20. TomMonton

    TomMonton Administrator

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    I did some more homework on this plane and think I have a sweet spot finally and here is what I've done.

    I leveled the motor mount. I wanted to omit that porpoise effect it was so fond of. Even when balanced it would lurch and want to climb with most any amount of throttle up. I also moved the motor further back about 12-15 mm. You can see from the photo how far the motor sticks out as compared to before.
    2016103120440300.jpg
    The tail ... and this has been the single biggest issue with this plane. First I had extended it 2.5 inches and braced the boom better to scrub out that flex it had when fighting with it porpoising all the time. I over sized the Vertical stabilizer up about 1.5 inches and the elevator out about an inch. You can see where I had added white foam there.
    2016103120441200.jpg
    COG for me worked best around this area. (1800mah 35c 3s battery) Getting to this point I already have the battery shoved as far back as it can go into the fuse. Still not a good placement given this fuselage. My next suggestion is move the tail back even more. I went 2.5 inches and a final recommendation would be add one more. Make to 3.5"
    2016103120443000.jpg
    Last recommendation would be to widen the fuse itself. It's just simply a too narrow inside to work nicely for parts placement. The inside should be large enough to accommodate a 36x36mm flight controller and cables. Widening the fuse will also allow to widen the tail boom for more support and may be the difference in weight distribution to make up for that difference in the COG ?

    In closing ... nice. It really does fly nicely and I like how this wing shape can cup so much soft air and lift. She soars soft and easy now and is what it was intended for anyway. Nice plane Malukk and you're right on the edge of something very nice here. Keep up the good work
     
    Last edited: Oct 31, 2016
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