FTCC'18 WWII Vought V-173 "Flying Pancake"

[Sir Fly]

FTFC'18 WWII Vought V-173 "Flying Pancake" by Sir Fly



DTFB Flying Pancake Mk. I



DTFB Flying Pancake Mk. II



History:
The Vought V- 173 was a prototype fighter designed during the second world war. The aircraft was developed for the XF5U "Flying Flapjack" program. The plane was developed very slowly during the war and unfortunately was shelved as the war came to a close and jet fighters stole the show in the Research and Development community. However, the concepts and theories that were incorporated into the design were proven and the plane was essentially revolutionary. Without wings the airframe was so stable and structurally secure that it could handle much higher g loads and heavier armament.

Aircraft Specs:
Crew: 1
Propulsion: 2x Continental A-80 4 cylinder (80 hp each); 2x 16.5 ft diameter, 3 bladed wooden propellers
"Wing"-span: 23' 4"
Length: 27'
Max speed: 138 mph (about as slow as a biplane)
Rate of Climb: 5,000 ft per minute
Armament: None (prototype)

 

[Sir Fly]

Introduction:

The Vought V- 173 was a prototype fighter designed during the second world war. The aircraft was developed for the XF5U "Flying Flapjack" program. How these names were developed truly bewilders me!



The plane was developed very slowly during the war and unfortunately was shelved as the war came to a close and jet fighters stole the show in the Research and Development community. However, the concepts and theories that were incorporated into the design were proven and the plane was essentially revolutionary. Without wings the airframe was so stable and structurally secure that it could handle much higher g loads and heavier armament.

It also was incredibly forgiving in a crash scenario. The Wikipedia page recalls one story of an unfortunate test pilot:

On one occasion, the V-173 was forced to make an emergency landing on a beach. As the pilot made his final approach, he noticed two bathers directly in his path. The pilot locked the aircraft's brakes on landing, causing the aircraft to flip over onto its back. Remarkably, the airframe proved so strong that neither the plane nor the pilot sustained any significant damage.

I encourage you to check out the rest of the article here: https://en.m.wikipedia.org/wiki/Vought_V-173

I hope you enjoy this build thread!

- Sir Fly

 

[cvdmaverick]

I'm interested to see how you end up designing this!

 

[rockyboy]

Awesome! It'll be great to see this progress! I think there are some balsa plans for this design on Outerzone if you need inspiration on the airfoil too...

 

[Sir Fly]

I'm interested to see how you end up designing this!

Hehe, me too!

 

[Sir Fly]

Awesome! It'll be great to see this progress! I think there are some balsa plans for this design on Outerzone if you need inspiration on the airfoil too...

Okay cool thanks, I'll check it out. I am waiting to begin formulating designs until I hear back from wilmracer and localfiend.

 

[Tench745]

The size of the props and direction they rotate is key to making the pancake fly.

 

[PsyBorg]

I was interested in this particular plane a year or so ago. I could have sworn that I read somewhere that it was used on a reconnaissance mission but I may be remembering something else.

Anyway there are also these models in here if someone is thinking along the same lines but wants different planes to try.

 

[Sir Fly]

First Designs!

So I haven't heard anything back from wilmracer and localfiend yet, but in the meantime I figured I would start drawing the basic design of the "Foamboard Flying Pancake" on graph paper.

Here is the basic design below (please excuse my drawing ability; probably not everything will be to scale ).



The 3-View illustration I used for reference.


The entire aircraft can be constructed with only ~10 pieces of DTFB! I originally thought I would have to use the cross-section plans and then skin the airframe, leading to a much more complex build. However, by using an extremely simple airfoil - like the ones on most FT planes - I don't need to; most of the airplane can be made from one piece of foamboard! Even though the plane does not have a symmetrical airfoil like the original prototype, I think that can be sacrificed for easier construction and possibly better performance.

Without a doubt my biggest concern is the engine nacelles ripping off of the lifting body. I want to construct the engine mounts separately and then glue them to the leading edge of the wing, but this means that the whole force from thrust is being translated right to the glue joint and will be pulling the nacelle directly away from the wing. I will have to add a few tabs to slot into the wing because the last thing I want to happen on the maiden is for the engine nacelle to pop off!

My only other large concern is balance and making the props and motors look decently to scale. I want to keep the main body constructed out of one piece of foamboard, but this means the size of the sheet (30 in x 20 in) is limiting the size. I am using two Emax 2204 motors (power pack E I believe) and 5x4 tri-blade props. Hopefully this will look appropriate.

I haven't bothered designing any landing gear yet, but it shouldn't be too hard. I will probably just use pushrod wire/coat hanger wire. But, I'll leave that till when I finish prototyping.

Let me know what you guys think, and if you have any suggestions or questions please feel free to voice them!

- Sir Fly

 

[Kunphushun]

What the what?!!! I've never even seen or heard of this craft. In for pics!

 

[Sir Fly]

What the what?!!! I've never even seen or heard of this craft. In for pics!

Haha lol! I agree, it's very....unusual. I hadn't heard of it either before I saw a YouTube video about it. Also check out the XF5U Flying Flapjack, it's older brother.

Also, subscribe to the thread and hopefully I will have plans out before the next Flite Fest. Then it's "Pancakes for Everyone!"

 

[PsyBorg]

I see your initial drawing shows a flat bottom. Are you going that way for ease of build or are you planning symmetrical airfoil like the original? Flat bottom could really change handling I would think.

 

[mrjdstewart]

2 x 2204's seems like it may be a bit overkill. might be able to keep it more scale using 1806's and the mini power pod set up kinda design.

just from your graph paper drawing i was able to calculate (assuming 1 sq=1 inch) that the plane had a wing surface area of roughly 154 in/sq. and guessed at a weight of roughly 260g.

i then went to ecalc and plugged in this info;

using 2x1806-2300kv (power pod a), a 30A ESC, 3S-850mah, and a 5x4x3 prop. the plane was almost perfect. i then switched it to 2x2204 and there wasn't much diff. i would highly encourage you to play with the numbers @ ecalc and see what you think is best. when i was playing with it i was getting almost 4-1 thrust/weight numbers, and speeds upward of 64mph.

i think this plane will be cool. add in some differential thrust and it will be crazy fun.

good luck,

jason

 

[Sir Fly]

I see your initial drawing shows a flat bottom. Are you going that way for ease of build or are you planning symmetrical airfoil like the original? Flat bottom could really change handling I would think.

I am planning on using a flat bottom, asymmetrical airfoil to make it easier to build. At the later stages of prototyping I may change to a symmetrical airfoil if I don't like it's flight characteristics. I have to do more research to figure out what flight characteristics the original prototype had to make it decently "scale."

 

[Sir Fly]

2 x 2204's seems like it may be a bit overkill. might be able to keep it more scale using 1806's and the mini power pod set up kinda design.

Well, I have been using the 2204s for my other mighty minis. To be honest I don't have any other motors. I am relatively new to the hobby and just made my first electronics purchases a few months ago in the spring. I wasn't planning on purchasing a new power plant, so I plan on sticking with this one. I appreciate that you took the time to calculate the numbers on ecalc. 64 mph is pretty fast! And yes, you were correct that 1 square=1 in. I'll have to look at that calculator myself. Thanks!

 

[JimCR120]

Mmmm pancakes. I'll bring the syrup.

Oh, got it. I'm glad this one is being done.

 

[Sir Fly]

Mmmm pancakes. I'll bring the syrup.

Oh, got it. I'm glad this one is being done.

Lol thanks. That is definitely going to be one of the final paint schemes!

 

[F106DeltaDart]

Lol thanks. That is definitely going to be one of the final paint schemes!

The nose art should be the Ms. Butterworth, haha

 

[rockyboy]

The nose art should be the Ms. Butterworth, haha

That would be epic! :applause:

 

[Sir Fly]

The nose art should be the Ms. Butterworth, haha

Lol that would actually be awesome!