Swappable FoamCub - Build and Demo

by ShaunMartin | April 15, 2014 | (75) Posted in Projects

UPDATED 5/14/2014 (See below.)

Designed in 3D in Sketchup after the Multiplex FunCub, the Swappable FoamCub is a versatile airplane.  It flies slow or fast, has STOL capabilites, climbs vertically, has plenty of aerobatic capability and prefers a rough landing surface to a smooth one.  It's one fun airplane.

If you build one, please tell us how it went! (The forum thread is a good place to do that.)

Flight Video

Swappable FoamCub Flight (YouTube)

Forum Thread

Share your photos, tips, build experiences, mods, etc. on the FoamCub Swappable forum thread. I'd love to see them and I suspect others would too!

Specs

Wingspan: 55"
Length: 41"
All-up weight with 2200mah 3S lipo: 53 oz. (using Elmer's foam board which is heavier than others)

Plans

Left Wing
Right Wing
Dihedral Instructions
Fuselage Version 2
Horizontal Stabilizer
Vertical Stabilizer
Small Foam Board Parts
Plywood and Poster Board Parts
Landing Gear
Power Pod Thrust Angle Modification
Standard FliteTest Swappable Power Pod

Printing Instructions

All of these PDF files are a single page, so you'll need your PDF reader and printer to do the tiling - I think most printers can do this.  Here's what I recommend:

  1. Get Adobe Reader
  2. Download all of the files (right-click > Save link as... or Save target as...)
  3. Opening the PDF file in Adobe Reader
  4. When you print, in the print dialog, choose "actual size" or turn off all "fit to page" options.
  5. Print

What you want is to print at 100% without any shrinking or auto-sizing and let the PDF reader and printer do the rest.  Printers and PDF readers are different so you might have to do some figuring out.

Materials

  • Elmer's foam board 30"x20", about 4-5 sheets - I find Elmer's to be much higher quality and strength than Dollar Tree. I find it at Walmart for around $1.50 a sheet.  However, Elmer's weighs twice as much as Dollar Tree - you would knock 1lb off the AUW by using Dollar Tree.  If anyone tries Dollar Tree, let us know how it goes!
  • poster board
  • 9-gram servos (6) - I used HobbyKing HXT900's
  • 5-channel receiver
  • 0.047" x 36" music wire (1-2)
  • 3/32" x 36" music wire (1)
  • Firepower Sport 3542-10 brushless motor (550W) from headsuphobby.com (for a Dollar Tree build, a smaller motor could be used - see Motor Choice below)
  • Turnigy Trust 45A ESC from HobbyKing
  • APC 12x6 Composite Propeller
  • Du-Bro 2" Diameter Spinner
  • 50cm servo extensions (4)
  • servo Y (2)
  • Du-Bro E/Z or Mini E/Z connectors(6)
  • plywood 1/32" one small sheet
  • Sullivan Tailwheel Bracket 10-22lbs
  • BBQ skewers, medium diameter and small
  • rubber bands - I use the blue size 125 rubber bands from rubberbandguns.com - they're great!
  • Dave Brown Treaded Lite Flite Wheels 5" (2)
  • Du-Bro 1 3/4" Super Lite Wheels (1)
  • Du-Bro 3/32" Plated Brass Dura-Collars (3)
  • 2200mah 3S lipo

Throws, Expo

Ailerons: 0.75-1" up and down, 35% expo
Elevator: 1.25" up and down, 35% expo
Rudder: 1" both directions
Flaps: 1.5" down and program some down elevator to prevent ballooning

Of course, customize these as desired.

Also, most Cubs (of any type) produce significant adverse yaw, which means you'll want to coordinate turns to turn smoothly.  This means using the rudder along with ailerons in a turn, and if you're not accustomed to using your rudder, you can often program your transmitter to do it for you.  But, I would encourage you to learn how to use your rudder in turns - it's a very helpful skill.

Build Videos 

(Sorry they're so long - I figure too much info is better than not enough...)

Swappable FoamCub Build Part 1 of 4 (YouTube) 
Swappable FoamCub Build Part 2 of 4 (YouTube)
Swappable FoamCub Build Part 3 of 4 (YouTube)
Swappable FoamCub Build Part 4 of 4 (YouTube)  

In Depth

Design - As I mentioned above, I designed this in 3D in SketchUp. I highly recommend the program - the only real downside is that printing designs well is a little tricky.

Foam Board Choice - I used Elmer's foam board, which is very different from Dollar Tree. It has much heavier paper backing and as a result is stronger, looks better (IMHO) but also weighs *twice* as much.  A 30"x20" Elmer's foamboard weighs about 8.4 oz whereas Dollar Tree is about 4.1 oz.  Building this plane out of Dollar Tree foamboard would reduce the AUW by around 1lb, which would be awesome. But, Dollar Tree might not be strong enough, especially where the wing halves join.  The strength of that joint relies on the crush strength of the top surface of the wing - so be careful. If anyone tries this build with Dollar Tree, please let us know how it works out.

Spar Design - This design has no real wing-to-wing spar, relying on only glue and foamboard structure for strength.  I tested the strength by setting the center of the inverted wing on a scale and placing books along the length of each wing. The wing happily supported 120 oz, about 2.5x the weight of the plane.  I have also performed some emergency "pull up quick!" maneuvers which I'm guessing has put the plane through more than 2.5 Gs without trouble.

Flight Characteristics - I've had a FunCub owner fly this plane and he said it flew just like a FunCub, which it should since they are so similar.  This plane is a blast to fly - the motor in the specs has plenty of power, and the flaps allow it to float along beautifully.  The gigantic tires allow it to land almost anywhere.  The plane will fly inverted, but the airfoil shape and weight require a fair amount of speed and down elevator to do so.

Motor Choice, Flight Time - The above motor (550W) works well for an 53oz plane (the weight when building with Elmer's foam board) and allows for 4.5 minutes of hard flying on a 2200mAh 3S lipo.  If you build with Dollar Tree, your weight will be around 37oz which is about 70% of 53oz, and I would scale the motor power accordingly.  For a Dollar Tree buld, I would suggest getting a motor that produces at least 350W.  Remember, a FoamCub is WAY more fun with plenty of power.  It will fly with much less, but it won't be nearly as fun.

A good resource for power system options is FunCubParts.com.  They offer several packages with different power levels.

Photos/Videos Above vs. Build - The plane in the flight video and photos above is the prototype, with small differences with the final design (which is in the build videos).  The main difference is that I abandoned the V-bend control rods and added connectors to the servo arms instead of a Z-bend on each end.  The V-bends and 2 Z-bends resulted in control response that was too sloppy.  The current design fixes that.

Landing Gear - The landing gear stiffener could be done in a number of different ways, such as substituting the second, inner wire with a rubber band across the middle.

Swappable - The term "swappable" is used loosely here.  Technically this is a standard swappable, but the recommended motor for this plane would be overkill for most of the standard FliteTest swappables, so you wouldn't normally swap this power pod to another airplane.  Fortunately the swappable power pod system is a handy design for simply mounting a motor and storing electronics so it still serves a great purpose even if you don't swap.

And finally...

Thank you to my sons Willem and Nels for taking photos and video while dad flies:

 

Bonus!

A behind-the-scenes look at my luxurious basement workshop/studio, recording a build video with an iPhone :)

 

UPDATED 5/14/2014

Added forum link.

UPDATED 5/13/2014

Fuselage Plans Updated

Fuselage plans are now updated to move the ventilation exit point, to increase tail strength (see below).

Version 1 Fuselage Tail Strengthener Retrofit

Both of my FoamCubs developed a small crease in the fuselage just ahead of the tail feathers due to a weak spot in the tail where I left the bottom of the fuselage open for ventilation. This is corrected in the latest plans (above), and if you have already built the plane or are in progress, here are some instructions for an easy retrofit - it only takes a few minutes.  This will be especially important for Dollar Tree builders.

Fuselage Version 1 Retrofit Piece Plans

Retrofit Video (YouTube)

Misc. Updates

  • Added note on motor choice in Materials
  • Added adverse yaw/coordination note in Throws, Expo

COMMENTS

killerD on May 1, 2014
Can you post the dxf's? Thanks.
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ShaunMartin on May 1, 2014
Hmm, I did this in Sketchup and the plans drawings were "printed" to PDF's directly from Sketchup so there were no dxf's involved, sorry. Just curious what you're interested in the dxf's for? That's the AutoCad format, correct?
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killerD on May 2, 2014
Exporting 2D DWG or DXF Files

http://help.sketchup.com/en/article/114292
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ShaunMartin on May 2, 2014
You have a laser cutter...envious! :) The DXF article you posted is for Sketchup Pro which I don't have. BUT, I did see there's a free converter plugin that might do the trick. If I get the Sketchup file cleaned up and posted (see comment above) you could give that a try.
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killerD on May 2, 2014
I have a laser cutter, so I don't have to cut out the plans by hand :) Though it requires the vector files. I may be able to use the sketchup files, thanks
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Kevinjt4 on May 3, 2014
What laser cutter do you have? I use a Epilog Zing 24 50W and am having issues getting the foam to not melt when cutting, depending on the settings. Let me know what you have, I would like to pick your brain on getting mine to work right (regardless what model you have, you may know something i dont.)

As for vector cutting (svg), I open any PDF plan I find on the web into InkScape (free download). When the PDF Import wizard pops up I set the Precision of gradient setting to medium and leave the rest default. Next, from the Path menu use Trace Bitmap and click OK, leaving the default settings as is. Nothing will seam to happen. Immediately go to Save As and the default Save As type will be automatically selected as an SVG file. I change it to plain svg or Inkscape compressed svg. Now I can import it into Adobe Illustrator which is what my Zing Laser cutter is set up to print from. YouTube search for this solution as well. There are times when I've tried to import plans that have lines that are just too thick (my Laser is set to cut at line width of .082" in Illustrator) or are so messed up that they just cannot be used to cut from when in svg format and then I have to basically retrace each and every part in Illustrator... but at least i can cut it out quickly.
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JimmyO on May 5, 2014
Hi, I am trying to do exactly the same thing; to use an Epilog Zing 24 50W to laser cut foam board. Could you please give me an idea of the settings that you use? Thank you!

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JimmyO on May 6, 2014
Thanks Kevin. I haven't tried the laser cutter yet, but I'll let you know how I get on!
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Kevinjt4 on May 5, 2014
First off I would read this review as I started with his settings.

http://www.modelairplanenews.com/blog/2011/05/18/epilog-zing-24-laser-cutter-online-review/

Of course, I wasnt able to get any setting to work regardless, in foam or hobby plywood to cut. I have tried practically the entire spectrum of settings;

Speed 65, pwr15
Sp 50, Pwr 13,
spd 50, Pwr 10
Spd 50, pwr 7
Spd 80, Pwr 10
Spd 75, Pwr 50
Spd 75, Pwr 75
spd 100, Pwr 100

The best laser cut piece was Speed 50, Power 10 but I can cut with an Xacto better than this setting.

All these had a frequency of 500. The manual to me really doesnt clarify or make if easy to understand what Power and Speed number do percentage wise. I know speed of 100 is fast and vice versa so I'm assuming Power 100 is a good amount of energy, but then what does Frequency do?

I've been trying to even cut 3/32" hobby plywood for motor mounts and 1/16" wood for wings but can cut these either on any setting. Have you actually cut wood? what settings do you use.

Doing more reading lately on all this and noticed that when people offer foam kits they say they are CNC cut and not laser cut. I am guessing FlightTest CNC cuts their plans out as well, thus no laser and no melting of the edges.

I think for now I will stick with a knife. Though if I had settings for cutting hobby plywood for motor mounts that would be ideal!


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sokol on May 2, 2014
Do you think you could also upload sketchup source file? In case someone (me including) wants to hack some stuff. It would also come handy if you want to verify any dimensions as you can take them with tape tool when you have sources.
Thank you for awesome build :)
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ShaunMartin on May 2, 2014
I *knew* someone would want the Sketchup file! :) It's kind of a mess, but I'll see if I can clean it up and post it. I'll be out of town this weekend so it'll be next week at the earliest. Thanks for the comment!
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Yogenh on May 1, 2014
I like this a lot. Will have to try it. How about floats for it? Could floats be made from foam board?? I am some what new to this.
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ShaunMartin on May 1, 2014
Floats would be AWESOME! But the problem of paper-backed foam board... I think you generally get a fair amount of water on the plane when flying off water, even if you avoid any mishaps. A good Minwax job or a coat of tape might do the trick. But building floats out of foam board? I'd probably try depron or some other paperless foam first. I'd love to see someone get this thing on floats. Come to think of it, I'm sure there are plenty of Multiplex FunCubs out there on floats - you could see what they do: https://www.google.com/#q=funcub+floats
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ultramicrobe on May 4, 2014
I think I figured out how to do floats with dollar tree foam. I have a couple projects to finish up, but this is next on the list for new jobs. If it works my plan was to do them on a DHC Beaver. I have a FunCub and love it, so I was thinking a swappable version of something that flies like it would be great, so if this really does fly like a fun cub I would highly recommend making one.
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BirdMan9876 on May 1, 2014
yea, I built one similar and covered it with minwax and it resisted water just fine with floats on it. I think I might build yours now that I see it is stronger than the other ones.
-Nice job, Keep up the great work!
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ShaunMartin on May 2, 2014
Excellent - good to know that Minwax works for a foamboard seaplane!
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suvansh on May 1, 2014
awesome work! thanks for posting!
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steve1947 on May 7, 2014
does this come cut out if so where can i purchase kit arf ?
steve
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ShaunMartin on May 7, 2014
Hi steve - This doesn't currently come in a kit, just plans - you'll have to do your own cutting.
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steve1947 on May 7, 2014
ok ill get"rr done....

steve, Viet Nam Vet
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walkerr on May 2, 2014
Thanks for a great high quality article and for putting down the effort! I'm a foam board to depron converter, living in Norway with no foam board access. I might give it a try. Anyhow it looks awsome! ***** Five stars *****
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alibopo on May 2, 2014
Hi walker, I'm surprised you can't get foam board. Ask local architects what they use to make their buildings models. I know UK architects use foam board. Also it might have a different name, my nephew uses it to make Warhammer scenery & vehicles, but he calls it foamcore. Cheers.
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FKreider on May 1, 2014
This is exactly what I have been wanting to design! Amazing work! I cant wait to build this plane!!!
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FTDude on May 20, 2014
Nice job! Looks amazing.
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ShaunMartin on May 1, 2014
Excellent - let us know how it goes!
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FKreider on May 1, 2014
How do you print the plans? I'm not sure if its just the laptop I'm using but I cant figure out how to get them in tiled format. Or did you take them to a print shop and get them printed full size?
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ShaunMartin on May 1, 2014
Hmm, I'm guessing its going to be different based on what PDF reader and printer you're using, but I was hoping that most printers/PDF software would tile automatically if you turn off all "shrink to fit" options and print at 100%. My low-end laser printer that does that (and I'm using Adobe Reader). Can you try to set all the scale options to 100% and turn off any shrink-to-fit options in your print dialog? Also if you're viewing the PDF in your browser it might be helpful to download the PDF files and open them in Adobe Reader. Sorry - I don't have much experience with all the printing options and procedures. Let me know if you get it working.
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FKreider on May 1, 2014
Switched to my desktop computer and the plans printed in tile format from Adobe Reader, time to build!
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ShaunMartin on May 2, 2014
Woohoo! :)
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FKreider on May 10, 2014
Started my build thread: http://forum.flitetest.com/showthread.php?9251-FoamCub-Build&p=102702#post102702

Going great so far! Thank you for the fantastic plans!
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ShaunMartin on May 1, 2014
Thanks everybody, for the kind comments!
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MT Alex on May 2, 2014
Fantastic job! This is definitely on my summer build list. Also, twenty two 5.0 ratings, that has to be pushing a record. I hope some of the low voting trolls don't come around :)
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ShaunMartin on May 2, 2014
Up to 29! Don't jinx it! :)
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bellcrank on May 2, 2014
I coppied all the plans for the super cub The grid squares are different sizes. How do I get the proper dimensions? I really liked the assembly vids and want to build the plane. Thanks for a job well done.
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ShaunMartin on May 2, 2014
Hi bellcrank - I added a Printing Instructions section above - try the things there let me know if you continue to have trouble.
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bellcrank on May 3, 2014
Thanks,ShaunMaartin,somehow in my haste I missed that info.
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andre on May 1, 2014
Great stuff. I flew my 48" wing cub all winter long. Complete hoot.
Takes off and lands on a dime. I've crashed it twice (once fpv and one range issue) with out much damage. My student has even hit a log with it...


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Desert.Rat on May 2, 2014
Part 2 of your build video does not play on YouTube, comes up with an error
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ShaunMartin on May 3, 2014
Ok, another update - uninstalling and reinstalling the YouTube app on my iPhone allowed me to play the video. I definitely recommend watching the videos before building - there are a lot of instructions that are only in the videos. Good luck!
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ShaunMartin on May 2, 2014
Hmm, part 2 won't play on my iPhone, nor my wife's. Plays everywhere else (that I can see). What kind of computer are you on? PC, Mac, phone? Not really sure what to do, but it would be good to know what device you're on.
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Desert.Rat on May 3, 2014
I have an iPad 2 and an iPhone 5C and neither one lets me play it. I also un installed and tried again but still no luck.
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ShaunMartin on May 3, 2014
Ok, thanks for testing - I'll add a note to the article and I'm headed out of town for about 48 hours, but I'll try to find a fix when I get back.
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ShaunMartin on May 2, 2014
Arrg, that's frustrating! Thanks for letting me know. I just tried a couple of different computers and it worked ok for me, but I have seen that video struggle - I think because it's longer than the others. If you clear your browser cache that might help. Unfortunately I think this is YouTube's problem - the only thing I could do is split up the video to make it smaller. If other people report trouble, I'll do that. Sorry! And thanks again for letting me know.
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Desert.Rat on May 2, 2014
Thanks for responding. I ave been watching the others on my iPad and have cleared it out twice. I will try it on my home PC.

I'm excited to build this plane. This is the exact style I have been looking for. I have already downloaded the plans and have them printed out and getting ready to cut the foam. I wanted to see what parts need close fits. Unfortunately part 2 is the body and looks the most complicated. iI would suggest that you cut it up to a part 2A and part 2B just so it's easier to follow.

If I can't get it working, I will just have to be a true engineer.

My Engineering prof told us how you can tell a true engineer, he's the one that pulls out the instructions after the item is smoking to see why it broke!

Thanks again for such a great plane.

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ShaunMartin on May 3, 2014
Ha! I probably qualify as a "true engineer" as well.
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bellcrank on May 10, 2014
Did you use hi temp or low temp hot glue?
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ShaunMartin on May 12, 2014
I believe it's high-temp. It's the only thing available in places like Walmart. I remember somewhere in one of the FT videos, the FT guys said stay away from low-temp - it'll melt in the trunk of your car, or something like that.
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bellcrank on May 12, 2014
Thank you.Will start building soon.
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kms64 on May 1, 2014
Very nice!
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magnatec on May 1, 2014
Thank you for Sharing. Great Job.
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Bob_Curtains on May 5, 2014
Awesome build Shaun, very impressive with your detail and patience with the build videos. I for one am excited to put this one in my hangar this summer. Best of luck and please keep them coming.
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ultramicrobe on May 15, 2014
Great post. I wanted to build it, but I already have an actual fun cub, which is an awesome plane. Even still, I thought your design might be a good basis for a mini-fun cub. I just finished it - it's 60% size, and has about 840mm wingspan. Had to make a few modifications but kept the same overall proportions. I will hopefully test fly it soon and let you know how it goes. If it flies like the big brother, it will be an amazing little plane.
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ShaunMartin on May 15, 2014
Awesome! So cool! Can't wait to see it! That will be intriguing to see how it behaves scaled down.

And your posts/threads are fantastic so you may just do your own, but I wanted to mention that I just started a general thread for this plane (should've done that to start with - noob mistake) - feel free to post anything there.

http://forum.flitetest.com/showthread.php?9343-FoamCub-Swappable
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JasonEricAnderson on May 1, 2014
Amazing! Great work on this.
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RAMartinJr@live.com on May 4, 2014
Nice plane! I like the wing spar design, it makes a nice channel, I hate trying to fish wires through an open wing.

A simple way to strengthen that wing joint would be to sand the dihedral angle on the root of the wings and replace those alignment tabs with some thin plywood spar joiners or you could add these spar joiners to an already built wing with a very thin slot.

You could replace your bottom landing gear strengthener with some plywood, put your springer gear on an angle and strap the gear to the bottom, this would make it handle better on the ground. I put foamboad between the wire on mine to look more scale.
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liemavick on May 13, 2014
Howdy Shaun, Thanks for the effort on the plans.I printed them out tonight and plan on getting started soon. You mentioned you flew the Cub with a different motor then the one listed. Do you remember which one, what size & KV? Im building with DTFB so the plane is going to be lighter, I was hoping to try a motor I already have laying around. Thanks again,
Brian
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ShaunMartin on May 14, 2014
Hi Brian - I just added more motor info to the article. See the "Motor Choice" section above - I think it'll have the info you need (especially the funcubparts.com reference).
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Hookdriver on May 6, 2014
Something I have been doing lately is pulling the paper off the inside of the dollar tree foam. The paper on the outside either gets minwax or tape. It really seems to help spars and formers stay bonded even when they get wet or it is really humid out. Seems like a piece of 3mm carbon tubing would make the wing of this cub plenty stiff enough to use dollar tree foam no problem. I am super stoked about putting one of these together! Thanks for sharing the plans. Josh
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Yogenh on May 1, 2014
Oh and you did a great job on it and keep up the great work!!!
Thanks Paul
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bak2exodus on May 14, 2014
Beautiful Shaun, thanks for sharing! Exactly the summer build I was looking for.
Will post pics after it's done.
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vietphi1411 on May 12, 2014
why 6 servo ? ( 4 ok ?)
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ShaunMartin on May 12, 2014
You could use 4 if you didn't use flaps, but flaps (and STOL) are what this airplane is all about! :)
1 - elevator
1 - rudder
2 - ailerons
2 - flaps


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vietphi1411 on May 13, 2014
very thank you !
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tenpenny_05 on May 13, 2014
Hey! Just finished building this plane. It was a very enjoyable straight forward build. I love the wing, its very strong and easy to assemble. My only worry is the landing gear, I built them as closely to your plan as I could, but they seem very flimsy, maybe they are intended to be springy. There have been high winds in SoCal this week but I'm going to get this plane up as soon as I can! CAN'T WAIT!
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ShaunMartin on May 14, 2014
Thanks for the feedback! Glad to hear the build went smoothly - here's to an equally smooth maiden! I grew up in SoCal, I'm guessing you've got Santa Ana winds right now?

Yes, the gear are intended to be springy, and I think an actual FunCub's are even more springy - I understand that FunCub owners spend a lot of time bending their gear back into shape. But just to make sure, you should've used 1/10" (or 3/32") music wire and the gear is built out of two pieces - the main gear and the reinforcer in the middle. If you did those, you should be good. I still have to tweak my gear back into position every once in a while, but that's life as a Fun/FoamCub owner.

I'd love to see your plane - I'll set up a general forum thread in the next day or two where I hope people will post photos.

Good luck!
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tenpenny_05 on May 15, 2014
Shaun! Just got back from my maiden! It took me exactly a week from printing plans to wheels up, This build was very straight forward even for a ham fisted dude such as myself. I used all the electronics from a dynam biplane that i dumb thumbed into the ground (650kv detrum motor and 50 amp esc, 13x6 prop). Only changes from the plans were smaller wheels (3.5 inch was the biggest the LHS had) and i used a cheaper dubro tailwheel that i glued straight. I also used some unorthodox foam board colors :).

The maiden went so good! Abslutely zero trim needed, I couldn't believe how well it flew. My only high wing airplane currently is an eflite apprentice that has been banged around, and this Cub flew way better than the apprentice ever did. The stall characteristics are a little unpredictable, that may be attributed to the large 3200 mah battery i was using.

I did have two issues: 1) I think i had waaay to much throw in the flaps, i had some undesirable flight characteristics when they were deployed. and 2) the landing gear did not hold up at all, It quickly splayed and eventually bent backwards (despite my honestly good landings) I'm going to try to re-create the gear with some heavier gauge wire and see what happens. Other than that i am more than satified with this plane.

Here is the link to my maiden! (BONUS: smoke from the san diego fires! keep an eye on the right side of the screen!)
https://www.youtube.com/watch?v=KUhi09uNmZk

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ShaunMartin on May 15, 2014
tenpenny_05! This absolutely makes my day. Thanks so much for the report and the video. Love it.

And yes, agreed, this plane stalls sharply - no gradual, mushing stall (I just added a forum thread and a post where I suggest a solution to that http://forum.flitetest.com/showthread.php?9343-FoamCub-Swappable&p=103667&viewfull=1#post103667). It needs washout or leading edge slats or something. And extra weight will definitely make it worse - just an Elmer's build with a 2200mah battery makes for a heavy plane, and a big battery will definitely add to that.

Gear: are you sure you used piano/music wire? That stuff is pretty stiff - it should hold up pretty well. But it sounds like you'll have that remedied soon.

Flaps: yeah, extreme flaps will do odd things (esp. with the extra weight you've got), since they're mostly just air brakes at that point. I've had good luck with the throws I listed in the article - not sure if that's what you went with or not.

Anyway, great update, great video (love the smoke), great foamboad color choice (!) - thanks for posting. (Oh, and if you're inclined, feel free to post your video on the forum thread I mentioned - I think people will find it easier there as opposed to this comment area.)
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alibopo on May 1, 2014
Great design! I really like your 'box-girder' construction inside the wing - very stiff and strong. Plus I think your comments about the Dollar Tree foam board probably not being strong enough are right. I'm sure I saw another article on Flite Test where someone made the same comment on a similar style of build, based on an experience where they had a wing fold. Maybe 'Dollar Tree' builders of this plane could add wing struts to the design. With such a big weight difference between the two foam boards, a bit of extra build material inside the wing for mounting points wouldn't be a problem. Or, (and I know there's a bit of dihedral) a few well-placed popsicle sticks (or tongue depressors) bridging the centre join would go a long way towards protecting the join, they'd also stop the wing elastics from cutting into or deforming the foam board.
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ShaunMartin on May 1, 2014
Good thoughts - I'm sure there are a number of ways to compensate for lower strength of Dollar Tree foam board - I suspect any of the options you mentioned would work well. I like the idea of strengthening the joint internally to keep wing removal easy - struts would do the job, but would require an extra attachment step anytime you want to remove/attach the wing. The trick with internal reinforcements might be keeping the joint simple enough that you can apply hot glue and get the wing halves together before the glue cools. Or maybe that wouldn't be an issue. Either way, thanks for posting your thoughts.
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alibopo on May 2, 2014
Hi, I just had another thought regarding construction without struts - before gluing up, if you make two cuts in the underside panel of the wing, from just behind the front spar to the back edge of the panel - about 4 inches out from the centreline of the wing. Also make a cut in line with and at the back of the spar which allows this little panel to fold open. When you attach the internal spars DONT glue these panels to the rear spar. Finish the assembly of the wing, and join the two wing halves - on the bottom in front of the little panels and all the way across the top. Then flip the wing over - open the two 'access panels' and install as much extra spar material inside the wing as you think you'll need (including poking it into the void beyond the flap opening). Finally close it all up with hot glue, and tape over the butt joints for extra strength. The joins should be almost invisible. I hope that makes sense - bottom line, there's lots of ways to reinforce foam board, it's such a great build material.
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ShaunMartin on May 2, 2014
Excellent ideas - thanks for posting. A Dollar Tree build is looking more and more viable. Also, your designs are great - I like your style - very creative.
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michaelph on June 15, 2014
Hi, I built up the wing this morning out of Adams foam board. I reinforced the spar seams with 1/8" basswood. Instead of completing both halves of the wing and then sliding them together like the build video, I glued the spars onto the bottoms of the wing halves and then joined and glued the wing halves together at the spars and on the bottom of the wing with one wing half laying flat on the table and the other wing tip lifted 2" for the dihedral. Basically, the wing is partially glued together but it is still open (top of the wing is not glued to the tops of the spars) but the spars are glued to the bottom of the wing and at the center seam. The bottom seam of the wing is also glued together.
I made two reinforcing braces out of 1/8" basswood which were 18" long (9" extends into each wing half) and a little lower than the spar height so they wouldn't interfere with attaching the wing top to the tops of the spars. I cut the basswood braces to match the dihedral angle and glued one piece of basswood to each spar across the center seam. You probably could glue two pieces to each spar if you thought it was necessary. I clamped the basswood to the spars with closepins while the glue dried. Then I closed up the wing and glued each half of the wing to the spars, one side at a time like the build video. I glued the center seam together when I glued the second wing's top skin to the spars. It was pretty easy. You could easily reinforce it with something else but I had the basswood on hand and it's light, strong and easy to cut with a utility knife. Strips of foam board might even be enough to reinfoce the spar seam.
I hope this was helpful.
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ShaunMartin on June 16, 2014
Yes, great info - glad to know that technique works - thanks for posting!
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alibopo on May 2, 2014
Hi Shaun, I used struts on my original Velie Monocoupe, which has been rebuilt as the Morphocoupe. I used spare servo arms embedded in the wing as attachment points and bound wire ends onto BBQ skewers for the struts. The wire end fits just like a control horn, and I use swing-in keepers to keep them in place under the wing. I can remove the wing in seconds.
http://www.flitetest.com/articles/1927-velie-monocoupe-swappable
Another strut system I used was on my Pilatus Porter (which never flew!) it involved modified Z-bends and a twisting motion to get the struts installed - not as convenient, but just as workable. (1/2 way through the article.)
http://www.flitetest.com/articles/nobody-s-perfect
Still, I'm amazed how strong a simple butt joint in foam board can be. Cheers!
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bermuge on May 4, 2014
YES! finally a cub. Looks really good
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eitanbin on May 8, 2014
Hi
Very nice model, I want to build one.
I do not see Plan to engine mounts
Thanks
eitan
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ShaunMartin on May 8, 2014
Hi eitan - This model uses the standard FliteTest power pod - I have added a link to the power pod build article at the end of the plans list above. Thanks for the comment - I hope you enjoy the plane!
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eitanbin on May 8, 2014

Thank you very much.

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Hugh Cherkas on June 5, 2014
Hi Shaun. Just built my cub and waiting for a decent weather window to maiden it as I'm fairly new to RC flight. I was wondering what sort of current your motor draws when you're flying about? I've bought a 550W ntm motor from hobbyking, but I'm concerned that will drain my 2200 very quickly, because the specs on HK say it will draw about 46A with the props I'm using, although I'm assuming that is at full throttle, so gentle flying will be much less. I'm just curious if I should expect less flight time than you are getting or not?! Perhaps I'm being over curious but I'd rather know more than less. Thanks for the great plans, hopefully will be in the air very soon
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ShaunMartin on June 6, 2014
Hi Hugh - It sounds like your power setup will be pretty comparable to mine. I get at least 5 minutes of hard flying out of a 2200mah 3S battery (just got back from the flying field - man that plane is fun!), and I suspect you could easily double that with gentler flying. Not sure how familiar you are with electrical calculations but you can get some interesting numbers:

550W / 11.1V = 49.5A

So at your motor's rated max power, you'll have a current draw of around 49A. I've found the power rating is usually higher than reality, so the 46A in the spec sounds about right.

As far as battery life you can calculate how long your battery would last if you drained it completely empty at constant full throttle (neither of which is a good idea!):

2.2Ah / 46A = 0.0478 hours = 2.87 minutes

That lines up with my experience of getting 5 minutes hard flying from a 2200mah battery.

Do you have a battery checker (http://amzn.com/B007WQHX5K)? That's an absolute must - what I would recommend is during your first few batteries, land every couple of minutes to see how much battery you have left to get a feel for how long your battery lasts with your power setup and flying style - I think that's the best way to go. Also a commonly accepted practice is to not go below around 20% capacity with your batteries - lipo's don't like that.

Anyway, hope that helps. Have fun and good luck with the maiden! Also if you're inclined to post photos on the FoamCub forum (linked above) I'd love to see your plane and I suspect others would too!
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Hugh Cherkas on June 6, 2014
thanks for the heads up on the battery life. I think I'm going to be needing some more 2200s! The guy I usually fly with has a battery checker but I'll definitely be getting my own soon. I'll try and get some pictures today or tomorrow and post them on the forum
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vietphi1411 on May 26, 2014
motor Kv ? size ?
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ShaunMartin on May 26, 2014
See the materials list above - the one listed there is very powerful: 3542, 960kv.
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PeterGregory on July 6, 2014
From all the good reviews and comments I will be adding this to my project list. I sounds like it is the "missing" 4 CH swappable entry of high-wing design. The FliteTest guys mentioned in a podcast they will release a Cub swappable - maybe based on your design.
Cheers,
Peter
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ShaunMartin on July 13, 2014
Yeah, I had heard the FT guys mentioned creating a FunCub-style FT plane on the podcast. In a recent YouTube episode (the FAA FPV one with The Two Joshes) there was a high-wing trainer-ish plane in the background, so maybe that's what they've been working on. Anyway, it'll be interesting to see what they come up with.
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pintokitkat on July 7, 2014
Built one.

Fantastic!
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ShaunMartin on July 13, 2014
Excellent - I'd love to hear/see more! Post on the forum thread if you're inclined, of course.
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webbhm on October 9, 2014
I am trying to fly the Storch at the moment, but this looks more interesting (next build after crashing the Storch too often).
I noticed that the ParkZone Sport Cub has vortex generators. Has anyone considered adding them to this model? They are available as a spare part for about $20:
http://www.parkzone.com/Products/Default.aspx?ProdID=PKZ6822
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ultramicrobe on July 18, 2014
I FINALLY got around to flying my mini-version of your fun cub. It was a bit terrifying at first, but I put a smaller motor in (I think a 2622 900kv) and it behaves pretty well now. It is still not as nice as your larger one. It seems to need differential on the ailerons since I was getting that weird drag effect (you push hard right and the plane actually goes left). I have not tried that yet, but with really light throws and a little rudder mixed in it goes just fine. I moved the battery to a hatch on the bottom which also cleared up some balance issues. Anyway, it's a neat little version of your plane and floats along pretty nicely.
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ShaunMartin on August 14, 2014
Interesting! Thanks for the update.
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Sharky on September 21, 2014
Great article , thank you as it is just what I was looking for I started the build last-night out of foamboard. I think the wing will work with the mods I have planed I will order the rest of the parts within the next week or so, any Ideas on a motor for the foamboard build? Just wondering cause I want plenty of power but nothing to absurd does that make any sense? Anyway I will post some pics when I am able n thanks again, cant wait to get this in the air!
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ultramicrobe on May 26, 2014
I got my 60% size version done. Looks great, and I test flew it with a 2826 1200kv motor and 8X4 or 9X6 prop. It was squirrelly in the air, but I think it's because the thrust angle was way too straight for that powerful a set up (it is from my little mustang, and had been bounced off the nose a few times, flattening it out). I am going to wait on a new lower KV motor and try again with a new power pod and a sensible thrust angle. Looks promising though, I would have done all these things anyway if I were less impatient. Great plans by the way - nicely designed and well thought out.
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ShaunMartin on May 26, 2014
Interesting - well, I think you're better suited to diagnose/troubleshoot the squirrelly-ness. I'd love to see a photo, eventually. Thanks for checking in - keep me posted!
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vietphi1411 on May 27, 2014
i can use motor 2215, 1200kv, prop 10x4 ok ???
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ShaunMartin on May 28, 2014
2215/1200kv sounds like a 200-220W motor. If you're building with Elmer's foam board (heavier), I recommend a motor in the 400W-550W range.

If you're building with Dollar Tree foam board, I would recommend a motor in the 300-450W range.

Your plane will probably fly with a 200-220W motor, but it will be a gentle flyer and you'll probably spend a lot of time at full throttle. It just depends on what you're looking for.

Here are some examples:

550W:

http://www.headsuphobby.com/Firepower-15-Sport-3542-10-Outrunner-Brushless-Electric-Motor-E-680.htm

450W:

http://www.headsuphobby.com/Power-Up-480-Plus-Outrunner-Brushless-Motor-E-570.htm

300-350W:

http://www.headsuphobby.com/Emax-BL2810-12-Outrunner-Brushless-Motor-F-580.htm


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Canair on September 16, 2014
I have to build this. Brilliant.

I'm wondering if the fun cub parts power pack would be a good choice for the foam cub: http://www.funcubparts.com/parts/kits/FCP20-101.html
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ShaunMartin on September 17, 2014
Hi Canair - I think that power pack would be fine. The FoamCub is heavier than the Fun Cub, but a 505W motor should still move it along nicely.
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Canair on September 18, 2014
I would hate for it to be underpowered though. Is there any motor available on the Hobby King that would be directly comparable to the Firepower motor that you have? I'd rather just do one order to get everything.

Also, have you built/flown the simple storch? I was wondering how the 2 planes compare. - See more at: http://flitetest.com/articles/swappable-foamcub-build-and-demo#sthash.XsOeXrOK.dpuf
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ShaunMartin on September 19, 2014
Hobby King motor - I would look for one of similar power (~550W) and similar kv (700-1000) - there should be a number of them that would work.

Simple Storch - I was going to suggest that you look at that - it looks great and should have characteristics very similar to this plane. I'm biased but I think the FoamCub with it's Fun Cub lines looks better. ;) And I think the FoamCub landing gear will be more forgiving. But the Simple Storch looks like a great plane - if anyone is interested in the FoamCub, I would encourage them to consider the Storch as well.
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bellcrank on June 11, 2014
HI Shaun.I started my build three weeks ago.I am now waiting for my electronics.The build went well. Thanks for your effort to produce this plane.Hope to maiden soon.
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ShaunMartin on July 13, 2014
Excellent - did you get to maiden it?
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Nose Dive on June 2, 2014
Love the plane, great article, great design and good video's. I already printed the (tiled) plans...worked great! I intend to build it out of 'Dollar_Foam' and I am waiting for some components to arrive. At the moment I am not that interested in speed and agility since this is going to be my trainer. I intend to use the swappable power pod that is used in the FT_Spitfire ( http://flitetest.com/articles/ft-spitfire-build )... Watta ya think?
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ShaunMartin on June 2, 2014
Thanks for the comment!

Yeah, the suggested motor for the FT Spitfire is a 250W motor which, if you're building with Dollar Tree, should result in a good gentle flyer. I haven't built this with Dollar Tree, so I'm just estimating here, but I think you'll be fine with that motor. Of course you can give it a go, and if you find that you're spending too much time at full throttle, you can always upgrade your motor/ESC. But I'd definitely go with what you have for a first try.

Good luck!
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Nose Dive on July 13, 2014
Hi Shaun. I almost have all the components, so I can start building. ;-P
Since I ended up looking at many, many different websites to complete the 'shopping list ' for this plane. Quick question: where did you get the servo extensions, the prop and the DuBro products?
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ShaunMartin on July 13, 2014
Hi nose dive - I tend to buy things from everywhere - wherever I can find just what I want for a decent price.

Prop - headsuphobby.com, Amazon
Servo extensions - eBay, but I think I've got them on Amazon too. You can find good "Buy It Now" deals on eBay with cheap or free shipping.
Dubro products - Amazon, or headsuphobby.com
Sullivan Tailwheel Bracket - Tower Hobbies

Hope that helps - good luck!
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Nose Dive on July 15, 2014
Since I'm new to "this world of RC stuff" that was a great help.
For a dollar foam build, do you think I should go for a 70% size prop (9x6) or stick to the original size of 12x6? I'm using the 'swappable_spitfire_powerpod".
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ShaunMartin on July 15, 2014
Glad to help and welcome to this wonderful world of RC stuff! :)

If you already have a motor, I would choose a prop based on that. Does your motor documentation specify compatible props? If it's the NTM motor specified with the FT Spitfire build, the HobbyKing page for that motor lists info for a few props (http://www.hobbyking.com/hobbyking/store/uh_viewitem.asp?idproduct=26820&aff=247441). If you're using a 3-cell (11.1V) battery, I'd go with the prop with the greatest thrust, which from that page is an 8x6. You might get away with a 9x6, but I would do some brief full-throttle tests and see if the motor gets hot. I think 12x6 would be way too big for this motor and would probably damage it.

Anyway, short answer is go with the manufacturer's recommended prop(s) to be safe.
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Nose Dive on August 14, 2014
Im halfway the build, your video's are straight as an arrow. Question: why poster board for the 'hood' and windscreen? Why not just foam board. Is it because of the curvature or is there another reason?
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ShaunMartin on August 14, 2014
Posterboard - yeah, partly the curvature and relatively complex folding (on the windshield anyway), and partly because that's what the FliteTest guys do for those kinds of curvy parts that don't need strength. Feel free to experiment if you've got other ideas!
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Bayboos on November 3, 2014
I have to admit, it looks like you have lots of fun flying this plane. However I did notice one thing (and I've noticed that only because I recently build the Storch) that completely blew my mind: do you really fly 1,5kg (53 oz) plane with 1,5m (55") wingspan powered by 550W motor?

Holy cow! It sounds much more like an engine with some (in fact: tons of) ballast for stability rather than airplane! ParkZone Cub weights just under 1kg (33 oz, 30% less than your plane); my Storch weights 750g (27 oz) ready to fly! And it flies perfectly fine on 24g HexTronik, with its 80W max output. I've had only one plane in 1kg range: FT 3D, which could hover at less than 50% throttle on 250W motor!

I bet you can have tons of fun with your setup. But: is it reasonable to put it on high wing, high dihedral plane with large flaps just to have it act like stabilization ballast? I believe you would have much more fun using airframe designed specifically for aerobatics. Making Cub-like airframe this heavy, and powering it with 550W motor sounds much more like terrible waste: it would neither perform like aerobatic plane, nor be capable of slow flight of any kind.

Knowing all this, I no longer wonder why you say DTFB is not strong enough for this plane and should be used with caution. For sure your power setup would rip it into million pieces in a matter of seconds :)

If you are interested in seeing how the similar, but much more light airplane perform, please check my article; Perfect trainer: FT Simple Storch LIGHT. On the other side, I think FT Storch looks like "serious plane", while your design is - aestetically - much more pleasant (or even "cute"). I will definitely try this one out, using Depron for water resistance (and because it's more available here). And even though I would not dare to use 550W motor, I hope I'll have at least as much fun as you have.
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Flying Fox on November 11, 2014
Nice Dude one of my favorite Planes
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JohnDH on January 6, 2015
To set the thrust vector, which corner of the power pod front did you cut away? Top, and pilots right?
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ShaunMartin on January 6, 2015
Bottom and pilot's right - you want a down and right thrust angle. Buried in the plans list above is a drawing for adding thrust angle to a standard power pod: http://assets.flitetest.com/article_files/FoamCubPowerPodThrustAngleMod_1397544466.pdf
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DHiggins on February 22, 2015
Does anyone have a tiled version of this they could share please?

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SP0NZ on March 5, 2015
Shaun,

Please check your Flite Test private messages.
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ShaunMartin on April 12, 2015
Got it - thanks SP0NZ.
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BobN4RCs on May 13, 2015
Shaun, you or anyone build the cub with no dihedral in the wing? If so, how did it handle?
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ShaunMartin on May 13, 2015
I have not built the wing without dihedral, but since there is so little, I would suspect that it flies fine without it. I've seen one or two photos or videos of flat wings, so I know it's been done. This guy's version has little-to-no dihedral: https://www.youtube.com/watch?v=euVGBr1w1j4
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saini_boyz on January 16, 2015
Shaun,
Thanks so much for this plane. It's an amazing plane. I made one enjoyed it and due to some receiver problem crashed it in the trees, now just made another one and weather permitting will maiden it this coming weekend.
Thanks again for the plans and the detailed description.
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BobN4RCs on May 14, 2015
Thanks Shaun! Great job on the plans as they are printed & almost ready for foam. Can't wait to get this baby together as it will be my summer build. Nice addition to my hanger . . . I may have to down-size a couple planes to make room for it!!
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DHiggins on February 22, 2015
Anyone have a tiled version they could share?
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BobN4RCs on June 15, 2015
Got her finished with an Army Bird Dog paint scheme. Used Elmer's foam board & omitted wing dihedral. Made it a permanent "swappable". Modified landing gear like Stortch's but no upper strut going under wing. NTM Prop Drive Series 35-36A 910Kv / 350W with 10x4 APC prop9M (may go bigger), 3s 2200 bat, HK 50amp ESC. Since a permanent "swappable", borrowed somebody's idea who built your cub with a detachable cowl. I also made a detachable windshield for easy access to the electronics. Had to add significant weight to nose for CG. Hope to maiden in 2 weeks! Thanks again Shaun for the outstanding plans & videos!!
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clownbrother on June 26, 2015
A Scratch-build with plans and build videos, plus a great flyer, YES Please, Thank you for your time and imagination! I will be adding this build to my collection!!!

Great job, please keep the great ideas comming. 5-Stars for sure!
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airplaneman on June 24, 2015
I maiden my cub this morning and it is a fantastic flying airplane. I took my time added struts on the wing and tail gave it a tail number and it looks very scale. also I don't put any dihedral in any of my models and I bolt the wings on. a great job on the plans and build video!. I took the plans move the scale up to 110% and my next one will have appx. 62.5in wing span. cant wait to finish it
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Nathan_116 on November 12, 2015
Has anyone compared this directly to the Storch when it comes to flight characteristics and ease of flying? It looks sooo much better than the Storch but if it doesn't fly well, since I'm kinda new to 4 channel flight, I would go with the Storch
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Nose Dive on October 19, 2015
Finally, after one year (I got side tracked by other 'simpler' to fly planes) my Dollar Foam Cub is almost finished. In the meantime I build the Simple Storch, Tiny Trainer and the Tiny Scout so my progressing building skills definitely went into the Foam Cub.
Question: do you think I can I start flying the FoamCub with just 3 channels (throttle, rudder and elevator) and 'work my way up' to 4 (ailerons) and 5 (flaps). Also: should I build 3 different wings for this practice?

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ShaunMartin on October 26, 2015
Hi Nose Dive - You may have proceeded by now but if you're doing a 3-channel build, I'd suggest doing ailerons, elevator and throttle, rather than rudder. I don't know if there's enough dihedral for a 3-channel using rudder. This airplane flies like a standard cub which means it turns best with both rudder and ailerons at the same time. Ideally, if you're not yet comfortable with 4 channels, I would suggest doing a 3-channel with ailerons and mix in a little rudder with your ailerons in your radio (so that if you give aileron input, the rudder follows that input and does the same). Hope that makes sense.
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Cozmacozmy on September 27, 2016
Nice looking Cub!
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Air-headed Aviator on September 27, 2016
It just looks right.
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Adamblack09 on March 2, 2017
I used the landing gear from a 1.5m timber. It comes with a tail wheel assembly that you could make work with some slight modifications. Old hotel keys or gift cards work as well as plywood, might add just a tiny bit of weight though. The timber landing gear fits pretty well and looks like a supercub landing gear so I like it a lot. Plus it makes it pretty easy to through some floats on from the timber too. I'll let you know how it holds up.
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winglet on January 15, 2017
Just finished mine. Thank you ShaunMartin for such a great design, plans and of course your build videos. The project was really fun to produce. Photos of it are in the forums under Mad Scratch Builders heading if anyone is interested in seeing it.
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ShaunMartin on January 17, 2017
@winglet - looks great! Thanks for posting! (Here's the forum link for anyone else looking: http://forum.flitetest.com/showthread.php?31537-FoamCub-Winter-Project-Follow-my-build-makes-suggestions )
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Swappable FoamCub - Build and Demo