GumbyJ's scratchbuilt 167% Hydrofoam
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  1. #1
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    GumbyJ's scratchbuilt 167% Hydrofoam

    I nearly bought a Hydrofoam about 6 or 7 years ago when they first came out. In hindsight it was probably a wise move not too as it would have ended in tears and a bag full of foam.

    After seeing B-Money's RC Powers hydro 150 my interest was sparked once again, the extra size and the dual motors with the counter rotating props to eliminate torque roll, I was sold.

    However I wasn't too fussed on the boxy look of the spontoons and the tall single fin of the RC Powers design.

    So I've taken the free plans from Parkjets.com done up by Prop-er and scaled them up to 167% so that they take up a whole 1000x700 sheet of Depron.

    I went with these plans for a few reasons,
    1. The fact that the scaled up size gives approx 44cm betweens the spontoons which should allow me to fit 2 6x4 props and a cockpit of sorts.
    2. The width to length ratio is higher which should be more stable.
    3. The length of the spontoons is slightly shorter which will get the motors further forward which should help me get the cg right, I hope.
    4. These plans have a lot more keyed notches which I hope will add to the strength of the joints.

    So the cutting of foam begins.

    Traxxas Revo 3.3, Gumbyj Electric conversion in progress, Spektrum DX3R
    Traxxas E-Revo Brushless Edition, RPM arms, Summit CVD's, Turnigy 2S 5200mah (#1 MT in Aus)
    Traxxas Stampede, Mamba Max 5700, Turnigy 3S 3500mah
    Traxxas Mini E-Revo, 2 & 3S rhino lipos

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  3. #2
    R/C God RogerDaShrubber's Avatar
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    I just watched a video on one of these, looked pretty cool cruising around a lake, i tell you what thought, i almost **** when it took off from the water and started flying, i did not expect that at all. Freaken cool.
    Spec-R S1 - Hobao GPX4 - TT EB4 S3 - Kyosho Inferno EP - LRP S10 BX - Serpent LX - 3Racing FGX F1

  4. #3
    R/C God B-Money's Avatar
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    Can't wait to see how this compares to the RCP one when finished.
    My Youtube Channel


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  6. #4
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    There is a lot more cutting to do on this than the f117!!

    I have finally gotten the bulk of the pieces cut and it is starting to come together

    Got too keen to get gluing and forgot to add the carbon before gluing one of the side pod pieces



    Forming up spontoons, lots of trimming and shaping to get it all to come together nicely.



    Starting to take shape



    One spontoon nearly finished, glue went off too fast, had to scramble to get it together.



    I still need to source some ply for motor mounts but havn't yet found what I need. Motors, props, esc, servos & batts have all arrived.

    Did some tests on the 6x4 3 blade prop on the 2826 2200kv. Got approx 800g of thrust @ 27amps on 3s, this should give me over 1.5kg of thrust. I hope to pull this build in under 1000g.
    Traxxas Revo 3.3, Gumbyj Electric conversion in progress, Spektrum DX3R
    Traxxas E-Revo Brushless Edition, RPM arms, Summit CVD's, Turnigy 2S 5200mah (#1 MT in Aus)
    Traxxas Stampede, Mamba Max 5700, Turnigy 3S 3500mah
    Traxxas Mini E-Revo, 2 & 3S rhino lipos

  7. #5
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    Did some "glide" tests on the bare airframe today, when I say glide, I more mean fall;-)

    Stated cg of the 100% is around 60mm back from leading edge of wing. Scaled up that's 100mm, quick mock up of parts show about right.

    Need to get more motivation in this cold weather. Over mixing araldite, don't have a good enough hot glue gun tho.

    Have obtained some ply for the motor mounts and solved a few issues that were slowing progress. So looking forward to getting this girl flying.
    Traxxas Revo 3.3, Gumbyj Electric conversion in progress, Spektrum DX3R
    Traxxas E-Revo Brushless Edition, RPM arms, Summit CVD's, Turnigy 2S 5200mah (#1 MT in Aus)
    Traxxas Stampede, Mamba Max 5700, Turnigy 3S 3500mah
    Traxxas Mini E-Revo, 2 & 3S rhino lipos

  8. #6
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    Have gotten a few complicated bits done that were causing me a few problems. Still got a fair bit to do but it's starting to come together nicely.


    Traxxas Revo 3.3, Gumbyj Electric conversion in progress, Spektrum DX3R
    Traxxas E-Revo Brushless Edition, RPM arms, Summit CVD's, Turnigy 2S 5200mah (#1 MT in Aus)
    Traxxas Stampede, Mamba Max 5700, Turnigy 3S 3500mah
    Traxxas Mini E-Revo, 2 & 3S rhino lipos

  9. #7
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    Just the canopy to go, thinking a coke bottle. Still a bit to go, weighing in @ 522g less batt servos esc.

    Traxxas Revo 3.3, Gumbyj Electric conversion in progress, Spektrum DX3R
    Traxxas E-Revo Brushless Edition, RPM arms, Summit CVD's, Turnigy 2S 5200mah (#1 MT in Aus)
    Traxxas Stampede, Mamba Max 5700, Turnigy 3S 3500mah
    Traxxas Mini E-Revo, 2 & 3S rhino lipos

  10. #8
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    The arrival of some much needed hardware has sparked life into this build.

    Control surfaces hinged & control horns fitted, servos fitted, control rods fitted, motors fitted.





    Fired up the motors last night for the first time, they are really loud, they must resonate through the foam and gives out a really loud high pitched squeal. Would hover at about 2/3 to 3/4 throttle.

    Have dialed the roll back to 50%, pitch to 75% and set 50% expos all round to calm things down.

    She's 1100mm long, 700mm wide and stands 280mm high, I've still got to epoxy coat the skidding surfaces but at the moment she's weighs 966grams.

    Hope to at least give her a ground run this weekend if not maiden her.
    Traxxas Revo 3.3, Gumbyj Electric conversion in progress, Spektrum DX3R
    Traxxas E-Revo Brushless Edition, RPM arms, Summit CVD's, Turnigy 2S 5200mah (#1 MT in Aus)
    Traxxas Stampede, Mamba Max 5700, Turnigy 3S 3500mah
    Traxxas Mini E-Revo, 2 & 3S rhino lipos

  11. #9
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    Skids epoxied, added 18 grams, auw 984g rtf

    May maiden her tomorrow

    Traxxas Revo 3.3, Gumbyj Electric conversion in progress, Spektrum DX3R
    Traxxas E-Revo Brushless Edition, RPM arms, Summit CVD's, Turnigy 2S 5200mah (#1 MT in Aus)
    Traxxas Stampede, Mamba Max 5700, Turnigy 3S 3500mah
    Traxxas Mini E-Revo, 2 & 3S rhino lipos

  12. #10
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    Ok, gave this a "maiden" this morning, one thing is very clear, it is way tail heavy. Made for some very interesting "flights" trying to keep it level.

    Had a few rough landings and nearly parked it in some trees but she has come away in mostly one piece. Have cracked one of the sponsons on the top and most likely split the carbon reinforcement inside as well as one of the vertical stabs, also one of the elevon control rods came loose.

    The rudder control is very anemic and it really didn't want to turn right at all.

    I'll undertake some repairs and will likely tape a couple of 20c pieces to the front of the sponsons before the next run. Here is some of the video that my daughter took. http://www.youtube.com/watch?v=ANryc...e_gdata_player
    Traxxas Revo 3.3, Gumbyj Electric conversion in progress, Spektrum DX3R
    Traxxas E-Revo Brushless Edition, RPM arms, Summit CVD's, Turnigy 2S 5200mah (#1 MT in Aus)
    Traxxas Stampede, Mamba Max 5700, Turnigy 3S 3500mah
    Traxxas Mini E-Revo, 2 & 3S rhino lipos

  13. #11
    R/C Guru crisis time's Avatar
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    looks good mate take off didnt look to bad
    i dont think the dog is going to catch it

  14. #12
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    Interesting craft. Thanks for the build thread. May be just what i need for up here. Leigh
    Out flying, boating or driving.

  15. #13
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    Effected some repairs/changes overnight, glued the stab that had cracked and added another carbon spar to support the sponsons. But most importantly added 30g of lead to the very front of each sponson, so 60g on the nose has brought the cg forward by approx an inch making the cg approx 80mm back from the leading edge of the "wing".

    Took her for another "fly" yesterday morning and it was much better to fly, only getting about 5min runtime with the 2 motors so still need a lot more stick time to get familiar with it and start to do more than just takeoffs and landings.

    Thanks for your comments, will keep you updated on how I progress.
    Traxxas Revo 3.3, Gumbyj Electric conversion in progress, Spektrum DX3R
    Traxxas E-Revo Brushless Edition, RPM arms, Summit CVD's, Turnigy 2S 5200mah (#1 MT in Aus)
    Traxxas Stampede, Mamba Max 5700, Turnigy 3S 3500mah
    Traxxas Mini E-Revo, 2 & 3S rhino lipos

  16. #14
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    Had to cover the whole bottom of the front sponsons with araldite to prevent further wear to the foam, this has added another 60g or so, but up front so not too bad. This has meant that I've only got a single 14g mag wheel weight on the front of each sponson and it flies quite nicely. AUW is at thr moment 1070g, Runtime is pretty much 5min if your game to push to the end.

    Finally got out to film some onboard footage, this one an early afternoon run during a break in the rain.
    http://www.youtube.com/watch?v=AGMVv...e_gdata_player

    Tried to push my luck and fly in way too windy conditions, was getting blown away while on the ground! in the end I stalled it about 5ft off the deck resulting in a cartwheel "landing". Check out my other videos for those. A bit more gluing and she's ready to go again.

    Is dipping the right hand side on lift off which is I think due to the glue of the repairs as it was dipping left prior to the cartwheel which damaged the right spontoon. Gonna try the camera up on the left spontoon tomorrow morn see if that changes it.

    Is also pulling left on high Alfa, this requires full right aileron, d/r only @ 70% tho, and it still won't go right. I have upped the d/r & added a little shim under the motor to move the thrust line right a little. Will also see if this makes a difference in the morning.
    Traxxas Revo 3.3, Gumbyj Electric conversion in progress, Spektrum DX3R
    Traxxas E-Revo Brushless Edition, RPM arms, Summit CVD's, Turnigy 2S 5200mah (#1 MT in Aus)
    Traxxas Stampede, Mamba Max 5700, Turnigy 3S 3500mah
    Traxxas Mini E-Revo, 2 & 3S rhino lipos

  17. #15
    Senior Moderator little_drifter's Avatar
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    That onboard video is awesome mate. Well done looks very cool indeed.




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  18. #16
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    Thanks LD, is quite a funky thing to fly. Put 4 packs through it yesterday morning, here is some video of the first 2 packs.
    http://www.youtube.com/watch?v=uhelK...e_gdata_player

    The right thrust I added made a little bit of difference, I was able to at least stop the left turn tendancy in high alpha but this still required a lot of right aileron. I'll try putting a bit more in and see if that makes it any better.
    Traxxas Revo 3.3, Gumbyj Electric conversion in progress, Spektrum DX3R
    Traxxas E-Revo Brushless Edition, RPM arms, Summit CVD's, Turnigy 2S 5200mah (#1 MT in Aus)
    Traxxas Stampede, Mamba Max 5700, Turnigy 3S 3500mah
    Traxxas Mini E-Revo, 2 & 3S rhino lipos

  19. #17
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    So gave this girl her "paint" job today, care of the trusty sharpie;-)



    Still havn't given it a run on water but she is flying nice, well as nice as you'd expect.
    Traxxas Revo 3.3, Gumbyj Electric conversion in progress, Spektrum DX3R
    Traxxas E-Revo Brushless Edition, RPM arms, Summit CVD's, Turnigy 2S 5200mah (#1 MT in Aus)
    Traxxas Stampede, Mamba Max 5700, Turnigy 3S 3500mah
    Traxxas Mini E-Revo, 2 & 3S rhino lipos

  20. #18
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    Traxxas Revo 3.3, Gumbyj Electric conversion in progress, Spektrum DX3R
    Traxxas E-Revo Brushless Edition, RPM arms, Summit CVD's, Turnigy 2S 5200mah (#1 MT in Aus)
    Traxxas Stampede, Mamba Max 5700, Turnigy 3S 3500mah
    Traxxas Mini E-Revo, 2 & 3S rhino lipos

  21. #19
    AUSRC Legend PC WIZ's Avatar
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    That's really interesting to watch. I like how well it turns and powers on when it's on the ground. Could be a new type of land craft for racing, even without the abillity to fly. Thanks for that!
    Come to Lake Centenary in Temora to run your RC boat. Free BBQ's, power points, great amenities with hot showers, a childs sandpit/play area and lots of shade sails around the lake edge. It's 2km out of town, fresh water and gas boats are welcome.

  22. #20
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    That is one cool video!

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