Twin Boom • Depron • Easy Build • Easy Fly • KFm Wing - RC Groups
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This thread is privately moderated by BlueFielder, who may elect to delete unwanted replies.
Feb 29, 2012, 04:44 PM
BlueFielder's Avatar
Build Log

Twin Boom • Depron • Easy Build • Easy Fly • KFm Wing

  • 48" Wingspan / Kline-Fogleman Airfoils
  • Axi 2208/34 Brushless Motor
  • 2S 2200 LiPo (use anything that fits the balance)
  • 10x4.7 slow fly prop
Plan (version 0.94b) : March 12, 2012
Work on the Fuselage begins!
March 11, 2012
Changed the tail to an inverted V with working Ruddervators.
Much easier build... and gives full tail control. It's also MUCH sturdier.
I've always dreaded building v-tails. They are a pain to align and they are usually flimsy.
My latest change to this is quite slick if I may say so
Everything just falls into place. No fiddly measuring or complicated clamping!
Hint: Notice the sq. channel aluminum that slides into the end of the arrow shaft at the tail end in Image 1.


I am posting this BUILD to demonstrate how easy it is to build a top quality RC aircraft.
While you can go to the store and buy an 'out of the box flyer'.... there is nothing more satisfying in this sport than building and flying your own plane.

The materials and techniques that I use take advantage of modern materials/technology and afford a plane that you will be proud to own and enjoy flying. The build is relatively fast. I've gone through a lot of trial and error on this one .. and discovered quite a few techniques that will make this very easy ... If you follow Step by Step!

I have designed and built many planes. Some were very detailed.
But I now find that engineering SIMPLE designs and discovering/using readily available materials adds a bucket of reward to this sport. Everyday.... I look at 'things' laying around the house or 'shapes' in a product (bottles of cleaners, Plastic packaging , soda cans ..... or just materials in the trash all in different ways.

With this build.... you'll learn a bit about aerodynamics... build tricks.... materials... glues.... style.... motors and props ...creative thinking... scavenger hunting.... and you'll also learn about pride in what you have accomplished.

There is NOTHING set in stone in this build and I'll most likely change things along the way. Pipe in if you have ideas!
I can draw out templates if you think it is necessary ... but really they are not needed except for the fuselage ... which I will post soon.

Image 1
The wings are laminated and folded panels of 3mm Depronฎ - utilizing experimental Kline-Fogleman (KFm) airfoils.
There is much about the thinking and use of such here: Kline-Fogleman

Tools and Materials Need
  • 3mm Depron - 1 sheet*
  • 1 Carbon Fiber Arrow/shaft ($6 @ Walmart)
  • 1/16" Balsa
  • 2" Packing Tape
  • EPP foam - a scrap chunk for the nose ... or use a piece of styro that you can carve.
  • 3/16" aluminum square tube - 12"
  • Wall Paper Seam Adhesive - 1 Tube *
  • Gorilla Glue
  • #11 Xatco blades - get a big pack - CHANGE blades often!
  • 24" framing square
  • 1 straight edge --- 3ft is what I use
  • 2 liter plastic pop bottle (canopy)

* I'll use gray Depron for wing except for the 'wrap leading edge layer' which will be white.
Also.... if you have some scrapes of 6mm , use that for the fuselage bulkheads or just laminate 3mm

*A note on glue: For Depronฎ you really can't beat 'Wall Paper Seam Adhesive'. (Lowes / HomeDepot / Canadian Tire). It's less than $2 and you get a lot. AND it dries CLEAR. This is a must if you are going to use grey Depronฎ.

I'll use it on 90% of this plane. Yes.... it needs to dry overnight. But I've laid out the steps so that there won't be much wait time.
For the tail.... I used Elmer's (or 3M) stay adhesive. I usually stay away from this stuff as it's a nightmare to clean off of areas where you don't want it ... as it remains tacky for days. But in this case.... the entire interior of the tail surface gets 'folded' and covered ... so there's nothing left in the open to cleanup. The tail completion... from start to finish took less than 1 hr.

Cutting out the KFM panels - fast and easy w/ limited cuts ... and easy measuring.
Plus.... MINIMAL waste. You'll use less than 1 sheet of Depronฎ !

Main Wing Panels:

Suggestion: Cut the 2nd pair of main wing panels out of WHITE Depron for the bottom of the wings for flying/visual orientation.

The Mid and Top Panels are cut out of a slight slightly oversized rectangle.
This will aid in the cutting and layup.
IMPORTANT: Measure and mark ALL cut lines before cutting.

You'll use the lower/main panels as cutting templates To trim everything evenly after assembly.

Leading Edge 'Wrap' Panel

For the leading edge 'wrap' panel, I'll use some 3mm white Depron for design/contrast.
The panels are cut OVERSIZED to aid in proper fit and alignment.
Keep in mind the orientation of each panel. Left & Right wings.

Inverted V-Tail
I changed this design last night and I must say...
What a HUGE improvement in how it looks and how well it goes together.
So much sturdier . Better looking... Adds FULL tail controls now.
Plus.... aligning things up in assembly will be so much easier.
I'll get to all that soon. Almost there.

The tail fabrication might look complicated... but it really isn't.
I just made my 3rd prototype ... took just a few minutes.

The fuselage (a start)

Last edited by BlueFielder; Mar 22, 2012 at 08:43 AM.
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Mar 08, 2012, 02:00 PM
Vertical approach specialist
potshot's Avatar
Great start, KnotEye. Are you planing to continue? Are you going to include landing gear?
Mar 08, 2012, 02:45 PM
BlueFielder's Avatar
Originally Posted by potshot
Great start, KnotEye. Are you planing to continue? Are you going to include landing gear?
Thank you .... Yes I work on the design most everyday. You'll note the version # at the top changing. Small tweaks ... usually just trying to make the build simpler... through tricks/shortcuts/the order of events.

No plans for Landing gear at the moment.... but I don't see why not.
I have 300 acres of wheat, hay and soybeans around me.
Makes any landing .... 'cushy' .
Mar 08, 2012, 02:58 PM
Vertical approach specialist
potshot's Avatar
Originally Posted by KnotEye

...I have 300 acres of wheat, hay and soybeans around me.
Makes any landing .... 'cushy' .
You just made thousands of city-bound fliers jealous. Fortunately I'm in a semi-rural area and can fly within steps of my door. Are we lucky, or what?

Our club has a small runway, hence the question about gear. I'm thinking tricycle with a steerable nose wheel.
Mar 08, 2012, 09:11 PM
BlueFielder's Avatar
Hey PotShot.... yes we are lucky - While I've lived in London, NY and San Francisco ... I could not image returning to live in 'the city'.

I'll look into some ideas for landing gear. I should point out that this design does NOT incorporate a Rudder. Hence the LONG ailerons. So... a steerable nose gear would be needed. Heck ... you could add a rudder..... but the weight to the tail might be excessive ... on first thinking.

If you have ideas/thoughts for either the rudder and a nose gear.... please chime in!
Mar 09, 2012, 11:36 AM
Vertical approach specialist
potshot's Avatar
Originally Posted by KnotEye
...If you have ideas/thoughts for either the rudder and a nose gear.... please chime in!
Actually, I have a 44" foam wing that I want to use with your planform. It has dihedral, so I'm thinking it might need a rudder to deal with adverse yaw. I guess one servo can operate the rudder and nose gear - a buddy in our club set up a twin boom FPV drone with that setup so I have something to clone.

I made a CAD version based on your image and I'm going to widen the fuse to about 3", too, to allow some flexibility for gear. I will keep you posted, but it will be a while - there are a couple of projects ahead of it.

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