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:
- Get Adobe Reader
- Download all of the files (right-click > Save link as... or Save target as...)
- Opening the PDF file in Adobe Reader
- When you print, in the print dialog, choose "actual size" or turn off all "fit to page" options.
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.
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
Misc. Updates
- Added note on motor choice in Materials
- Added adverse yaw/coordination note in Throws, Expo
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steve
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steve, Viet Nam Vet
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Going great so far! Thank you for the fantastic plans!
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Thank you for awesome build :)
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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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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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http://help.sketchup.com/en/article/114292
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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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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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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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-Nice job, Keep up the great work!
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Thanks Paul
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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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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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Very nice model, I want to build one.
I do not see Plan to engine mounts
Thanks
eitan
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Thank you very much.
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1 - elevator
1 - rudder
2 - ailerons
2 - flaps
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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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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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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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Brian
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Will post pics after it's done.
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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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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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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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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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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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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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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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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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Cheers,
Peter
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Fantastic!
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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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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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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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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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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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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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Please check your Flite Test private messages.
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Great job, please keep the great ideas comming. 5-Stars for sure!
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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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