P-38 Fowler Flaps

by FliteTest | May 6, 2016 | (15) Posted in How To

Community member Andres joined Josh to discuss his gigantic 8-foot-wingspan P-38 Fowler Flaps build.

The P-38 was made primarily with Dollar Tree Foam Board, with some wood in places to add shape and support.

Andres has put over 160 hours into building the P-38. The plane now has functioning inboard and outboard flaps set up. 

For the Fowler Flaps, Andres made it so one servo controls both the forward/backward movement and the up/down movement of the flap. 

 

Two arms on the outside come off of the servo on a torque rod and control the forward/backward motion. The shoulder arm in the middle controls the forward/backward motion.

Andres used music wire and servo arms that he cut off of servos combined with heat shrink to set up the complex arms.

 

 

The foam flap slides on a rail that is attached to the foam board to prevent it from binding. There’s also a small rod that allows for some flex in the flap movement to help prevent damage.
 

Andres put V bends in his servo wires so they would still work well even if they weren’t cut to the exact length. He also soldered the arms to the torque tube.

The outboard flap servos are hooked up with a servo arm and a large Z bend that matches the center of the servo arm and the outermost hole. There’s another torque rod CA’d and threaded to the servo arm that controls the outboard flap.


Andres created an algorithm for his Fowler Flaps, which you can download here!
 

Materials:

  • Foam board
  • Music wire
  • Carbon fiber tube or very thick music wire
  • Servo arms
  • Heat shrink
  • CA
  • Thread
  • Wood or other material to space the rails apart 

See more of Andres' airplane in the previous episode linked below.
Here's another clip of his plane flying at the indoor event:

Share your own big builds in the comments, or create an article!

COMMENTS

Turtles110 on May 10, 2016
Its mini peter and mini alex
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bruin12 on May 11, 2016
Great stuff, Anders. I am interested in learning more about the techniques you use to work with foam board and building model airplanes in general. As a dad of a child fascinated by all things aviation, I am also interested in how your parents helped foster your interests and skills. I see a very bright future for you and your pals.
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kkmalu on May 9, 2016
Very cool!!
Does Andres already have PDF plans for this?
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joker24458 on May 9, 2016
Are you referring to the P-38 or the fowler flaps? I do not have digital plans for the P-38 (or the BF-109, for that matter), only rough physical plans which would be difficult to make into digital copies, and even if that were done, the builder would still have to figure out a lot for themselves. The fowler flaps can be built at any size with the equations in this article. I will, however, try my best to make plans for my future projects.
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Turtles110 on May 10, 2016
what kind of motor are you running on the p-38
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joker24458 on May 10, 2016
Two Emax XA2212-820kv motors swinging Emax 13x4 carbon fiber props. Has enough power to fly and that's about it. :D
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kkmalu on May 9, 2016
I was referring to P-38 plans... Flower flaps math-calculation notes are very cool! Thanks for sharing this - you are very talented!!
I am sure a lot of people are interested (as I am) in building this so digital plans for your projects would be fantastic!
Great work! I am subscribed on your channel so will be following your updates...
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joker24458 on May 9, 2016
Thanks for the kind words. I don't post a lot on my YouTube channel, the best way to be updated on this particular build is on my build thread here: http://forum.flitetest.com/showthread.php?23097-Scale-Build-Off-Scratchbuilt-96-quot-P-38-Lightning
I will post pictures and info in the build thread as I continue to work on the build.
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Planiac01 on May 9, 2016
Dude that's awesome! How old are you and what math are you taking? Calc?
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joker24458 on May 9, 2016
15, freshman in high school. Currently taking Algebra 2, but we learned sin/cos/tan last year in Geometry which is really all the fowler flap equations use.
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Planiac01 on May 9, 2016
Oh ok. I am the same age. Out curriculums must be different b cause I am taking an Algebra 2 equivalent and we are only doing that stuff now.
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Turtles110 on May 10, 2016
Did you make your fowler flaps algorithm before or after you made the fowler flaps.
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joker24458 on May 10, 2016
After P-38, before mock-up model.
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Imbecilliac on December 1, 2016
I'm in awe. There is some real brilliance in that design and a bright future ahead of you. Thank you for sharing. Beautifully executed Lightning, too!
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Cozmacozmy on May 9, 2016
Excellent job!
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ValHolla on May 10, 2016
If anyone is interested, I took the awesome hand written equations and transferred them to MS Word and PDF... Link to the google drive share below.

https://drive.google.com/folderview?id=0B3QSs5yLORmRLUNMNEIxaW9YN1E&usp=sharing#sthash.Ljh723TF.dpuf
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joker24458 on May 10, 2016
I looked at your typed version, there is one thing that I spotted that is incorrect. The first term of the denominator of the equation to solve for L2 should be 2 sin(c-90), not 2 sin(c-40). Looking at the formula paper it is a bit difficult to distinguish from a 4 and a 9, sorry about that. Anyways, thanks for taking the time to type it up and share it with the community. :)
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ValHolla on May 10, 2016
The correction has been made, Thank you for the wonderful job you did on the equations!... I am happy to help in a small way.

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PropSpinner on May 9, 2016
Very good. This is the kind of story I enjoy. Then everybody flies together. 😄
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MeSoLost on May 14, 2016
any way to get a still picture with each rod labeled with it's variable -.-
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ValHolla on May 11, 2016
ok, I think I have the issue resolved, my "Known" numbers didn't work. I just put numbers in from what I thought was good... for the formulas to work proper the following formula must be true in your known numbers... f2 = f1 + d I am sure I knew that, before, I just didn't think ;-)

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Robbutler1977 on May 24, 2016
I have been thinking of making a simple park flyer with curved hallow wings like this but I have not seen any plans that are like that. I was trying to figure out the cg or how much more curve I would need? I was thinking curve it enough to have the 9 gram flush with the bottom and just have carbon fiber Arrow shaft and 4-6 suports off that. Also I've been having lots of trouble trying to get my flap rods even right and left so I have used the zbind pliers to Make them fine tuned. perfect just a little pinch in the middle.

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abieex on May 9, 2016
Amazing article! Very impressive young man and a beautiful project. Great episode.
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Rajazo on June 21, 2016
I had to register because I needed to congratulate you on your excellent work. It's perfect, clean and really clever. .. a excellent use of math and geometry...I hope to use your system soon... congratulation
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The Dodger on May 10, 2016
Andres,
I am extremely impressed. That is a truly beautiful design. You will go far in aeronautical engineering. Josh commented about how simple your design is. I think that's a huge understatement. The most genius designs use the minimum amount of material to leverage the strength of all the various pieces used. You really did a great job here! Please keep sharing your talent here on Flitetest.
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joker24458 on May 10, 2016
Thank you so much for the kind words. Yes, I tried to make the fowler flaps as simplistic as possible to be easy to make with common materials and easily recreatable by anyone who has a calculator. I may try to create a more complex, compact slotted version sometime though.
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tblake3 on May 11, 2016
Using ValHolla's typed version to confirm my reading of the original scan of the formula sheet, I created an excel spread sheet: https://drive.google.com/file/d/0B30eQUyNZGGXa3Q1aTBUcFd4aXhZV2RqQUl6ZG8tcGp4WXUw/view?usp=drivesdk
Enter your known dimensions in the corresponding green boxes. The calculated values come out at the bottom.
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ValHolla on May 11, 2016
Awesome! I love how this community comes together!

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karl.rueckert@gmail.com on May 9, 2016
Excellent, instructive video describing methods to improve flight characteristics on foam board planes. Great explanation of the Fowler Flap design and construction. This bright young man's aircraft are also beautifully built. I would be very interested other videos detailing his construction methods. I hope Andres will become a flight test regular.
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ValHolla on May 11, 2016
Playing with the Excel Spreadsheet, the numbers don't seem to be coming out right.. the P2 calculations are not coming out the same. I will try to dig into the spreadsheet equations and see if where the issue lies. Excel is weird about how it handles some complex math.
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CaptBill on December 5, 2016
Andres.
I am completly blown away by your work.
As a grandfather, and two of my grandsons are about your age, I am doing my best to keep introducing them, and their 8 younger siblings, and cousins, to projects which I hope will fuel theor inrerests in math and science
Ill be passing this along to them.
I hope that in some way we all stay a bit connected, I anxiois to see what excoting things are uet to come from you and your friends.
Alos, a Vary big shout of "well dome" to your parents, and others, who Im guessing have helped to nurture your ambitions

Blessings,
Bill

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tblake3 on May 10, 2016
Can we get a better scan of that formula sheet? I'd like to convert it to an Excel spreadsheet to make it easier for others to do the calculations.
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Balu on May 10, 2016
I'm on it.
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tblake3 on May 10, 2016
I got the spreadsheet done but it's not balancing out. I think I wasn't able to read the formulas correctly.
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Balu on May 10, 2016
I'm having the same problem :) I have asked Andres for some test values with results so I might be able to identify problematic formulas :)
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tblake3 on May 10, 2016
I got a little closer... Excel sin(x) is in radians.
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Balu on May 10, 2016
Goodle Spreadsheets too ;). I had to use DEGREES() everywhere...
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joker24458 on May 10, 2016
Hey guys sorry for the issues with reading the formulas. I can get a typed version together ASAP and post it here. I will also try doing an excel spreadsheet, never even thought about it but that is a great idea!
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P-38 Fowler Flaps