Tuesday, 8 July 2014

1.3m Twin-boom Pusher

Also called the Depron Spectre.

This was inspired by Alex Greve's (IBCrazy) EPP Specter designed for proximity and obstacle course FPV.

The twin boom configuration means the motor doesn't need to sit up high, which means the fuselage can be slimmer.

The forward swept wings give amazing anti-stall characteristics and increased grip in the turns. I suspect when the wing tips flex upward they give positive feedback to the turn, similar to snap flaps. A swept back wing would do the opposite. It also looks very cool in the air.

This plane can fly slow or fast and is crazy manoeuvrable even without movable rudders, and it can balance in it's tail.










The wing build is slightly different to my previous style, with cut out ailerons rather than full span. Wingspan is 1.3m or 53" compared to IBCrazy's 40" and 48" versions.

I made a 200mm (8") x 20mm flat bottomed airfoil in two 700mm halves, then cut a wedge from each inner end to make the forward sweep when glued and taped together. The tips are about 45mm forward of the root. I also cut wedges off the wingtips so they were parallel. Naturally I cut them the wrong way first.

I removed some of the forward former in the spar channel either side of the join so the Skyshark P4X spar had a wider bend curve.




Here it is in the air with 10-15kn wind


Wingspan - 1.3m (53")
Length - 80cm (32")
Airframe weight - 660g
Flying weight (2200mAh LiPo) - 850g
Motor - Turnigy 2822/14 1450kV (160W)
30A ESC
Prop - 7 x 4.5"
Ailerons
Elevator
TGY 9018MG servos x 3

Depron Spectre plans and dimensions





Build overview video


UPDATE: Here are a two more recent Depron Spectre videos. Some aerobatics on a rare calm 13th Beach day and some slope soaring at Beacon Point in a lovely 10-15kn NW wind.





45 comments:

  1. Awesome job. Is there any chance of you posting some dimensions of the tail construction - or even better - a build video ; ) I'd really like to have a go at building this beauty. Keep up the great work.

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    1. I've done an overview video here - https://www.youtube.com/watch?v=Uk7n0xJMaUg&list=UU2QTy9BHei7SbeBRq59V66Q

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  2. I was wondering if you could post some dimensions of your wings and tail. It doesn't have to be anything fancy just some hand drawn dimensions. Wonderful looking a flying plane. It is next on my list of scratch builds and will be my first fpv platform

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    1. Unknown? Introduce yourself and I'll post some dimensions for you.

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  4. Sorry about that my name is Chad. I have been flying RC airplanes for almost a year now. I am currently flying a Radian and a scratch built FT storch. I wish i had the money to buy prebuilt aircraft but since i don't i am building scratch builds for the most part. The one thing nice about scratch builds it doesn't hurt as much when you crash which is always nice. When i first started in the hobby i bought a finnwing penguin from rmrc. I completely destroyed it first time i flew it. Some guys at the local club suggested a Radian. Best 160 bucks i ever spent the thing flys like a dream and i have learned a lot. Thanks for posting the dimensions i am going start building your spectra next week.

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    1. Greetings Chad, and thanks for prompting me to to whip up some plans, have been meaning to do that for ages. I have had a Radian for 2 weeks now and I agree, it's a ripper. The Spectre is such a great design, you will love I'm sure. Can go fast, slow, do aerobatics, carry weight and rip around wherever you point it. Good luck, I'll be interested to see how it goes.

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  5. I will be sure to post some pics and an update when it is done. I will probably start it next week. I need to order a motor and esc for it.

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  6. Hi! Thanks for the plan.lets say i build w/o swep is my cg will be around 85mm?im planning to build x1.2 bigger than yours so that i could glide more and stay up in air a bit longer with 1600mah batt only and rewound d2836 1100kv motor

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    1. CG will be about 30% back or at the thickest part or your airfoil, so it will depend on your wing chord. Sounds like a nice project, something I have been pondering too.

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    2. hi sir andrew, just wondering how you calculated the CG for forward swept wing, mind to share the computation, thanks.

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    3. Trial and error. I watched ibcrazy videos on his Specter and started with the same CG then adjusted from there. Mine ended up 1" back at the wing join.

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  7. Hi Andrew, this looks like a great plane :) I was just watching your overview for probably the third time to try and see if I could gleen all the information I need. Thinking to myself 'it would really be useful for some more detailed dimensions' only to notice the link to this! :)

    I don't have any Depron right now but do have some foam board, do you think it would be ok to build in that? Will be a bit heavier I guess.

    I can't see details of how you've fixed the horizontal and vertical stabilizer together anywhere. Did you just cut a slot in each then push them together? Keep up the good work, thanks Dave

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  8. I have a question about prop selection for the specter. I built a diy v2 specter. I have a fairly large motor it is a 3530 1400kv with a 40amp esc. I have tried several props a 7x45 and an 8x45. When go full throttle the prop makes a hollow noise. Can someone tell me why this may be happening. The prop is definately on correctly because it pushes the plane forward but not very well. In fact while testing holding the plane when i ran full throttle one of the props broke. I am thinking i need better props but i dont know for sure. Any advice would be helpful.

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  9. I have noticed the same effect sometimes, lots of noise but no thrust, with a setup that works correctly most of the time. It's just an uneducated guess but maybe the prop is stalling or cavitating at high speed.

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  11. Andrew,
    Thank you for sharing your experiance with us/me.
    I just finished up the "Spectre" some days ago and hade the first flight yesterday.
    The plane is a great performer and a stable camera platform.
    https://vimeo.com/113849286

    Thank you.

    UWE

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  12. Hello Andrew, I have been following your videos and am in the process of building your design Spectre and the twin boom pusher. The Aluminum you use to hold the motor on, how thick is it and how did you get the 90 degree angle formed. This has been an obstacle for me. Thanks.

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    1. Aluminium is 20mm x 1.6mm and bent by hand while clamped in a vice.

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  13. Sir I can use this to learn flying?
    Never flown an rc before.
    Thank you.

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    1. There would be easier planes to learn on but this one can crash a lot and keep on flying. If you're a fast learner and have some simulator time it would be OK.

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  14. Hello Andrew
    Thanks for your interesting Tube Channel
    I just build the Specter and it flies too agile for my two years rc experience
    Do you have any suggestions for the expos on ailerons an elevator for this plane?
    regards from Chile

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    1. Hi Pablo,
      The Spectre is quite an agile flyer but it should be smooth once you have it balanced and setup well.
      My setup is like this...
      Aileron throws 10mm up and down no expo
      Elevator throw 18mm up and down no expo
      You could certainly reduce the throws and add lots of expo to calm it down.
      Good luck

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  15. Hi Andrew,
    Where can i download "depron spectre plans and dimensions"(http://anewton.net.spectre.skp/)? The link is not working.
    And love your videos, builds and those kite are so awesome. im planing to make my own kite in the Philippines and doing KAP. hihi
    thanks
    -Richard

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    1. Hi Richard. Did you try a right click and Downoad linked file? I'll can email it to you if that doesn't work

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  16. Hi again,
    yes, it works thanks. did think of that hihi

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  17. Hi Andrew,
    I built your Spectre and have been having some fun with it. But would like to solve a problem where my plane oscillates in yaw. My FPV image swings slightly from side to side. Did you encounter any problems like this during your Spectre flights and are there any known cures?
    Larry

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    1. Yes I did notice the wobble occasionally. But I don't know the cure for this plane I'm sorry.

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    2. I am experimenting with reducing the size of the tail vertical stabs. Making them larger does not help.

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    3. I experienced it too - in my case the fuselage was too long and my battery hatch was too big so so there was not enough reinforcement to keep it stable.

      Great plane btw - thx! i've installed a old multiwii board (crius AIO pro) with RTH etc and works great. It doesn't really need stabilisation but RTH is great.

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    4. Hi Andrew, Finally got an aerial video. Inverted v tail and built up wing.
      https://www.youtube.com/watch?v=t4RdjdYU1Zs
      regards
      Bob Wells

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  18. Hello Andrew , like your blog , congratulations on project Spectre.Link video my Twin boom with small modificações.Meu name and Jose Airton , live inside Sao Paulo Brasil.Facebook: https://www.facebook.com/joseairton.mattos?ref=tn_tnmn Link video: https://youtu.be/ts23bEfj0eU

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  19. Dear Maigo parabens for its buildings and contributions. QUuero get this model , if you have problem with straight wings, will have much difference ?

    thank you

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  20. Swept forward gives better slow flying performance with less stall tendency. Straight wing would work well also.

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    1. Thank your videos are very good congratulations penalty could not understand their language my English is bad

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  21. Dear Maigo parabens for its buildings and contributions. QUuero get this model , if you have problem with straight wings, will have much difference ?

    thank you

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  22. Hi to everyone. My name is Denis, I'm italian.
    Sorry for my bad english.
    First of all many thanks to Newtonairlines for his beautiful job on this famous plane.
    I have built my version with landing gears. I've made this plane for fpv purpose.
    Here is a short video of my depron Spectre:

    https://youtu.be/d3oYpKPZJZo

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  23. Hi to everybody.
    I'm italian. Sorry for my bad english.
    First of all many thanks to NewtonAirlines for his beautiful job with this famous plane.
    I have built my version with the landing gear. I've made this plane for FPV purpose.
    Here is a short video of my plane:

    https://youtu.be/d3oYpKPZJZo

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    1. Hi Denis,
      Looks damn good!!! Where do you fly?

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  24. hi Andrew,
    is experimental airline airfoil the same as clark-y airfoil? or any airfoil. im planning to make mine fully xps foam, wont use depron.

    thanks
    richard

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    1. Good question Richard. I think Ed's Adams foam board wings turn out more like a fat Clark Z (flatter bottom) and my depron versions were more like a thin Clark Y. But you cant go wrong with a Clark Y for a normal plane. I'd thin it down to 10% if you want a faster flyer.

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  25. looks like an interesting build ....gathering parts for a foam board model.... depron latter on ........ or hot wire foil ........
    any suggestions for slower, close to the ground FPV modifications ??????????
    keep up good work............

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  26. Hi Andrew, Firstly congrats on the site and the youtube channel. I've spent that last few late nights reading and watching your content which is absolutely great. You've inspired me to have a goal of building the spectre and flying over a couple locations to capture the scenery. I have a question in regards to materials. Would I need to increase the motor if I was to build this from foam board purchased from Riot Craft stores ?

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    1. Thanks. Yes I would use a bigger motor for a heavier build.

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  27. Finally, got round to building the plane. I used a 2830 1300kv motor and 8x6 prop, I did a test glide and seemed ok. In the since it glided level so I thought I had the CG about right. However when I launched it the pitch was quite radical. Ailerons throws were set 10mm and Elevator set 18mm both with 30% Expo. Here is a link to the video, the day was quite still. https://www.youtube.com/watch?v=GaHdfEeLwIs Does the CG look wrong or am I flying it to slow ?
    Thanks in advance. BTW AUW is around 1200 grams as it's built from Riot foam board.

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