40" Swappable Specter - an IBCrazy design

by spencer | April 7, 2013 | (9) Posted in Projects

After building the last specter and getting quite a few requests for more information on how I did a few things, I decided to build a smaller version for my father.  I used a few different techniques that are outlined.

Everything he flies is swappable.  I did a 3/4 scale down so that we could get the weight down on if for smaller motor/esc combo.  The wing span measures 40" and the tale is a perfectly scaled 3/4 from the my original design (minus the rudders, I made them a little larger for good vertical stabilization).

This should be quite a bit lighter than the previous.  The wing is much stiffer and the fuse is permanently attached to the wing, and accepts the swappable fuse (in pusher mode).  The fuse inside dimensions is exactly 2x2".

As you can see we are about 8" shorter than the first edition.  We still haven't gotten this 100%, but the purpose of this was to show the construction of the forward sweep.

 

So here it goes...

I put the wing on a flat square surface.  Measuring 1.25" back (1.75" on the 48') from the front edge of the wing at the root, I marked the bottom of the wing and cut the excess off.  Note: for the wing spar, I used a 3/4" foam spar, one sheet thick all the way through and 2 sheets thick on the root side 8" long.  This made a much better taper than on the previous wing.  The connecting spar was 2 sheets thick, 10" long and glued on the front edge of the wing.

This is what you should be left with.  I did the same thing on the other side of the wing to keep the wing tip parallel.

A closer look at the measurements.

 

For a closer look at the fuse for the swappable, I've added the pictures below.  The fuse is built to snugly accept the swappable fuse, being that it is a swappable, we probably wont even be adding the BBQ skewers or tabs. It was a super snug fit.

Back of fuse.

The tail measures as follows:  Elevator - 11x3 3/4" , Vertical Stabs - 6x3 3/4"

The tail sections were spliced together with a 1.5" overlap on bother sides.

We used 2 carbon rods for the tail (my dad had some broken fishing poles lying around).

 

The nose was brought together and kicked up a little on the bottom (mostly for looks).

The tail spars continue through the center of the wing through both wing spars, and continue clear to the back of the tail.  The distance between the tail and the wing at the spar is 6". Total length of the spars were 14", and the distance between the spars are 9 1/4".  The fuse extends 8 1/2" from the leading edge of the wing making the fuse a total length of about 15 1/2".

All in all, we used 2 sheets of foam for this build (closer to 1 1/2), 2 carbon shafts from some old fishing poles, hot glue and extreme packing tape.  Stay tuned for a build video on this one.  I will be doing a fast-forward style video on this to show how it is constructed and what steps I took.

A big thanks goes out to IBCrazy and Experimental Airlines for the plane design and the Arman Wing design. Without all their expertise and experimenting, I would have this design to play with.

Also a big thanks to Flitetest!  These swappable series have opened doors to friends an family members to the hobby.  It's truly and inspired idea.

Click here for dimension on the 40" version.

 

 

 

COMMENTS

Jaxx on April 9, 2013
I'm very interested in seeing how you built the wing. Did you remove the paper on the upper side of the wing before doing the fold (the way ExAir does)? Are you still going to post plans for this build? This is going to be my next build(the smaller version). Keep up the great work!
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spencer on April 11, 2013
I'm in the middle of putting together a video on how I put together the wing. I should be able to get it posted in the next couple days. Stay tuned...
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EZ Air on April 8, 2013
what kind of electronics did you use

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spencer on April 8, 2013
I'll be using 9 gram servo's, and we'll be trying a couple different motors. I'd like to start out with a standard 24gr with a 3 cell pack. We're hoping that will be enough motor, but it may not be. In which case we'll be installing a 2208 turnigy on there. That should be more than enough for this bird. Hoping to keep the weight down on this. The 48" came out to 28oz, this should be just over a pound.
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EZ Air on April 8, 2013
is this the first scratch build plane you've built
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spencer on April 8, 2013
It's not. I've done quite a few of the swappable series, both with plans and without. I've got a few articles on here of some of my other builds.
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johanjonker on July 18, 2013
I build my Specter with no foward swept wings, made the cord a lot less. and have mine on a bigger motor, and its a real floater even with all my FPV gear on it, extra battery's it still fly's so smooth.. I build a smaller version with a wing from my Baby Blender. and on a 24g motor and 2200 2S battery (no FPV gear) its a lot of fun.. with 750mah 3S and FPV gear I manage to get 110km/h
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wolfpackt99 on March 5, 2014
Here is some video of my swappable 40". Thanks Spencer. http://www.youtube.com/watch?v=WApMOKdzF2I
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spencer on March 5, 2014
Looks good man.
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Gargoil on September 25, 2014
if you want a LOOOOOOOOOng flight try the emax cf2822 with a 7*5 apc E prop i have runtimes of 15-22 min with full fpv on 1*2200 mha 3s I love this plane
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FOX on June 18, 2014
Hi again Spencer.

I've just finish building the 40" version... gona stick to the ntm 2826 1200 kv from my ft spitfire and some 9x4.7 prop to try out.
I have a question...what kind of angle should the motor have on this pusher model? At this moment is just strait with the fuse. ( same case on the spitfire)

Thanks and best regards,

Afonso. (Fox)

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spencer on July 18, 2014
I haven't put any thrust angle in. It could probably use some, but it all depends on your power system. My 9g setup was fine without it.
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wga22 on October 16, 2014
what is the purpose of the forward swept wings? do the contribute to stability, or just aerodynamics?
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RMW16 on November 27, 2014
Sorry, I'm a noob. I want to build this plane but don't really understand how to cut the wing? thanks
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spencer on November 28, 2014
I use the measure and cut method. No printable plans, just measure from the edges and cut it out.
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Brock on April 21, 2016
I built one of these, but am having problems launching it, due to thrust angle and/or elevator authority. I wrote some information at RC Groups - http://www.rcgroups.com/forums/showthread.php?t=2649223#post34577730

The rudders broke on the last launch/crash, so I need to rebuilt that. I wanted to have the motor set up high, but I think I can place it inline with the CG, which will make things easier.

Any tips?
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mistik1 on September 28, 2017
Thanks a lot for sharing the build.
I've built one of these lately but I used a Ex Air folded tube for the fuse and increased the width of the elevator to be flush with the end of the vertical stabs.
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40" Swappable Specter - an IBCrazy design