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Pumpkin drop event

1 Sheet Plane

Mad_Mechanic

Well-known member
#1
Yes, you read the title correctly. I'm sure this has been done, but I wanted to challenge myself to design a plane that only needs 1 sheet of dollar tree/store foam board to make the airframe, thus making the airframe 1$.

I created a list of design constraints:
> Bottom Wing
> 3 or 4 channel
> No flying wing design (I know FliteTest already has a flying wing from 1 sheet)
> All structural components must be included in the 1 sheet, no using scraps from another left over board!
> Utilize an FT Firewall
> DO NOT use an FT swappable power pod as this would add foamboard and weight.

Here is what I've designed thus far:
Wingspan: 27 in
Elevator width: 8 in
Rudder Height: 4in
Overall length (no motor): 21.6in

Iso view.jpg

Top View.jpg

Bottom View.jpg

Front View.jpg

Side View.jpg

Here is the board layout thus far:

Board Layout.PNG

My concerns at this time are the tail surfaces, I fear they might be a bit small.

Thoughts? Concerns? Ideas?

Once I finalize my version 1 design I plan to have this printed at a local staples office supply print center for ~$3 (they can print up to a 24"x36" sheet of paper).

I currently do not have an motor, propeller or battery spec'd, any thoughts on those? Perhaps a 6in prop?
 

Mad_Mechanic

Well-known member
#3
Looks good!!
The FT A or F pack would work for that.
Thanks!

I was wondering if a Power Pack A would be a good fit. I'll plan for that pack and move ahead on the design.

Regardless of how my prototype goes, I'll try to get plans posted up here for anyone who is interested in trying the plane or tinkering with the design.
 

CapnBry

Well-known member
#4
Cool idea! I was thinking, "how hard can that be?" when I clicked into the thread, but doing it without being a flying wing or a nutball or a having everything be just a profile is a real challenge. Look forward to seeing it fly because I am always looking for more fun planes to fly on 2S with my A Pack motor.

You might consider cutting a little more off the top wing cutout to allow a little dihedral, and it would be great if there was a way to use one servo for both ailerons since I am betting the 4x servos are going to be like a quarter of the weight.
 

Mad_Mechanic

Well-known member
#5
Cool idea! I was thinking, "how hard can that be?" when I clicked into the thread, but doing it without being a flying wing or a nutball or a having everything be just a profile is a real challenge. Look forward to seeing it fly because I am always looking for more fun planes to fly on 2S with my A Pack motor.

You might consider cutting a little more off the top wing cutout to allow a little dihedral, and it would be great if there was a way to use one servo for both ailerons since I am betting the 4x servos are going to be like a quarter of the weight.
I actually intend for the wing to have some dihedral, it's just a bit tricky to model this in SolidWorks.

Your idea of using 1 servo for ailerons is interesting, and I think I recall seeing someone on the forum do this for a custom build they were working on, I just don't recall exactly how they accomplished it.
 

CapnBry

Well-known member
#6
Your idea of using 1 servo for ailerons is interesting, and I think I recall seeing someone on the forum do this for a custom build they were working on, I just don't recall exactly how they accomplished it.
haha I was hoping you were going to show me how to do it, because I can't figure out how it would be possible either but I've heard of it being done! EDIT: I suppose the way to do it is with a pair of pushrods in a giant modified Z bend that are inserted into coffee straws and the straws are glued to the wing. I'm thinking that's not much weight savings since the rods will weigh a few of grams as well.
 
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Mad_Mechanic

Well-known member
#9
Cool idea! I was thinking, "how hard can that be?" when I clicked into the thread, but doing it without being a flying wing or a nutball or a having everything be just a profile is a real challenge. Look forward to seeing it fly because I am always looking for more fun planes to fly on 2S with my A Pack motor.

You might consider cutting a little more off the top wing cutout to allow a little dihedral, and it would be great if there was a way to use one servo for both ailerons since I am betting the 4x servos are going to be like a quarter of the weight.
So I applied foam board density to my model (and I'm using a set known weight for the servos) and right now I've got ~110 grams of airframe and servos. On that note, you are not far off with your estimate that 4 servos would be ~25% of the airframe weight. The servos I'm planning ot use are HobbyKing HXT500 servos which are ~6.2 grams a piece, so I'm at ~25 grams of servos weight. 25/110 is 22.7%.

I still need to add a Motor, ESC and battery. For the motor I'm thinking a Cobra C-2203/34 which is ~18 grams, but can swing a GWs 6x3-DD prop with a rated thrust of 308 grams @6.9A.

For the ESC I'm thinking a a PowerUp 20A ESC with SBEC, this will add ~15g.

So now I'm at ~150g total weight.

For a battery, I have on hand a 460mAh 2S which weighs in ~31g.

For the Receiver, I use an FrSky radio so I'm looking at an RX6R receiver. This is a 6-channel receiver which will be enough for 4 servos + ESC. I prefer to do the ailerons in the radio instead of using a y-cable as I can trim each aileron servo individually. The RX6R weighs ~3g.

So that puts my all up weight to ~184g, which is well below the ~308g thrust rating of the motor/prop combo. Should work.

Thoughts?
 
#11
You might think about eliminating the rudder servo and make the plane a bank and yank flyer. This would lower the weight in the rear which is usually an issue with most planes.
 

CapnBry

Well-known member
#12
Yeah I need to find some smaller super cheap servos. Junk 9g servos are like $1.50 each so I use them in everything. I see $3.50 for a 6g servo and I think how rich other people must be to afford such extravagant servos! :LOL: They definitely make sense here though, where the difference adds up.

Gotta have a rudder though, for FPV through the trees flying!
 

Mad_Mechanic

Well-known member
#13
You might think about eliminating the rudder servo and make the plane a bank and yank flyer. This would lower the weight in the rear which is usually an issue with most planes.
I hadn't thought about this. Eliminating the rudder and going Bank-n-Yank would give you weight savings in several areas. First is the elimination of a 6g servo, then there is the weight of the foam board of the rudder itself. Lastly is a minor weight savings in going to a 4-channel receiver instead of a 6-channel. I could then increase the size of the elevator a little too as it frees up some space on the foam board sheet.

It would not be difficult to make two designs based on this, one with rudder and one without. I'll make a note to tweak the design into a bank-n-yank rudder-less design and upload both designs.
 

Mad_Mechanic

Well-known member
#14
Did some more work last night and this morning and modeled the wing dihedral. I've also added things like the battery, motor, esc and receiver with weights which allows me to add a CG marker. I adjusted where the wing is siting on the fuselage and played with 2S battery sizes/weights to get the CG approximately on the wing spar.

Something I should mention is that the front top cover is designed to hinge for battery access, hence the rectangular cutout.

See Through Iso View.PNG

Update Front View.PNG

Update Side View.PNG
 

Matagami Designs

Well-known member
#17
SolidWorks is how I earn my money daily, so it's what I know how to use. I also know how to run AutoCAD, but I prefer working in 3D space.
I am considered a bit of a Solidworks guru at work myself. :) I spent a few weeks modeling up an F-14 which turned out, well TBD... 3-D space is nice but i eventually had to just build since it feels more rewarding when you can throw it in the air and see what happens. :p
 

Fallegon

Active member
#18
Heres my 1 piece foamer.
20190226_212944.jpg
A tip with the under wing design is that the wing mount is super weak. I doubled up on mine and have bbq skewers running on the inside. Also If you want to save on foam kf airfoils are great for these smaller projects.

Also I would advise you to switch to swapable aswell. With these designs the noses get beat up a lot whether you are dumping it or going for a nice landing. Crumpled up foamboard only lasts so long with super glue before you have to make a new airframe. Replacing just a power pod is simple.
 
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Mad_Mechanic

Well-known member
#19
Good looking plane @Fallegon , here is a more detailed cutaway of my wing as designed:

Wing cutaway.PNG

I'm planning on a folded wing design like many of the FT wings. I'm also planning for a double foamboard thick spar that will run from servo to servo. This spar will also run through the fuselage. Hopefully that will give me ample strength.

I'm also planning for the wing to be permanently attached to the fuselage instead of a rubber band design. Again, hopefully this will give me adequate strength.
 

Fallegon

Active member
#20
In my experience keeping it simple is ideal.. Aerodynamics tends to get less picky as you scale down. Your wing dimentions look fine I would suggest getting rid of the double break and just make it a single break dihedral. When joining two wings together its the top and lowers portion that gives it strengths. The spar adds a bit of strength but the key factor is keeping the wing from squishing flat and losing the dihedral. I would argue that packing tape is the key ingredient for a strong wing.
20190807_121400.jpg
Just realized I didnt even put a spar in mine.
 
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