1.3m twin boom pusher

by apnewton | September 25, 2014 | (15) Posted in How To

Also called the Depron Spectre. Inspired by Alex Greve's (ibcrazy) Specter, designed for proximity and obstacle course FPV.

This is a great design. It can fly fast and aerobatically, slow and smooth, can carry weight like cameras and FPV gear and it looks unique in the air. It can really take a beating too. Might be a bit too nimble for a first plane but excellent once you're over that first learning stage.

Materials

6mm depron covered with packing tape

Skyshark P4X wrapped carbon fibre spars from kitesandfunthings.com

Motor ESC and servos from HobbyKing

Hot glue, double sided tape, plastic ID cards, velcro, gaffer tape.

Design features

The twin boom configuration means the motor doesn't need to sit up high, so 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 on it's tail.  

The wing buildis 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.

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

 

  

Download Sketchup file


Depron Spectre videos

Build tips and overview

 

Early test flights

Aerobatics on 13th Beach 

Slope soaring at Beacon Point 

 

 Give it a go, it's a ripper!

 Andrew Newton - anewton.net

Newton Airlines blog

My YouTube Channel

My Flickr photos

 

 

 

 

- Find this article & others like it at www.FliteTest.com -

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COMMENTS

The Flying Dutchman on October 5, 2014
Great project!
Do you have any plans that you could post, so that I can build your amazing plane?
Nice video!
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apnewton on October 5, 2014
Yes they are in the article above!?
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apnewton on October 7, 2014
I have progressively shortened the nose, doesn't need to be that long. Maybe a spar in the horizontal stabiliser for a bit more stiffness. Otherwise it's good as is.
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Chamika on October 2, 2014
Great ! this will be my next build..
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apnewton on October 2, 2014
Excellent, you won't regret it.
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udo789 on October 2, 2014
Nice job! What is the advantage of the Skyshark P4X over standard carbon tube?
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apnewton on October 2, 2014
Thanks. Not sure what your standard tubes are but Skysharks are wrapped CF spars. Lighter than "pull-truded" CF spars. and more resistant to splitting.
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Beetlebeetle on October 7, 2014
Thanks, very much.

In retrospect, what would you change about this model? What would you add/modify?
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N222NY on October 7, 2014
I'm attempting this build, but slightly modified, in that I'm using a 60 inch wingspan. I noticed your wingspan is 53 inches with an 18 inch fuselage. Would you recommend that I scale up my fuselage length to around 25 inches (relative proportions)? Thanks for your great design and input.

Shawn

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apnewton on October 7, 2014
Shawn, 25" seems a bit too long but it doesn't really matter. Maybe start there and chop off the excess nose once you work out the CG. It depends how heavy your battery and other gear in the nose will be.


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Beetlebeetle on October 6, 2014
This is a great airplane! This will be my next build.

Would you be able to post the Sketchup file here? The link on your site doesn't work.

Thank you!
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apnewton on October 6, 2014
No problem. Link to Sketchup file added to the article.
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mjmccarron on October 2, 2014
Nice. Looks like a fun plane. Very nicely presented.

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apnewton on October 2, 2014
Thanks, fun is a good word to describe it.
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butch.bohrer on October 3, 2014
This planes wing style is like my father real sailplane that he & some friends scratch built when I was a younger teenager & where he died my mother sold it ! Now with your plans you shared I'll be able recreate one like it. Thank you for sharing your plans !! Now to my foam boards & start building one !! Thanks Walerus
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apnewton on October 5, 2014
Nice story Walerus, go to it.
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stormboy on October 7, 2014
Nice plans. So detailed. Another great article from you.
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Beetlebeetle on October 24, 2014
Hi Andrew,

Why do you (and others) put FPV cameras on top of the fuselage and not inside the nose, poking out? Inside would seem to be more aerodynamic, no?

Cheers.
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apnewton on October 24, 2014
Yes it would Beetle. But my FPV setup is an all in one backpack so I can easily mount it on any plane, just tucks under the wing rubber bands. In a dedicated FPV plane I would mount the camera in the nose.
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ginger on December 13, 2014
What kind of flight time are you able to get with this plane? Im still trying to work out a prop motor combination that will give a good range for it.
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apnewton on January 2, 2015
Finally did a power consumption test today.
Used 1500mAh in 27min (2200mAh 3S battery) cruising around continuously on just under half throttle.
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apnewton on December 13, 2014
20 to 30 min on a 2200 I think. I now have a current sensor and telemetry so I'll test it and get back to you.
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ginger on December 13, 2014
I just built one. I won't be getting around to putting electronics in until next month. I had some free time so decided why not. I was thinking a 3000 to 5000 battery. Im also going to put fpv gear on. You made really excellent videos and they are probably the only reason it turned out so well.
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matjey on April 25, 2016
Nice plane there. I have a fella friend build it too. Just didn't have a chance to ask him regarding the wing airfoil. Is it going to be reliable if i'm building it using KFM wing instead?
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apnewton on April 27, 2016
I don't have any experience with KFM airfoils but I believe it will work fine, may lose some gliding performance
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treetopflyer on September 17, 2016
I just finished one of these, but inadvertently cut my wing to 48". All the other dimensions are to spec. Can't wait to try it out. Will be using the recommended motor, esc and prop. With a 3s 35c 2200 mah battery. Thx for sharing the info. Great videos.
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1.3m twin boom pusher