That's when I decided to try the true composite formula: two layers of light glass cloth with a thin layer of foam in between.  (I will be detailing everything later).  This worked out great, and soon enough we had cheeks that were light and rigid -- and required absolutely no balsa!  This was the missing link.  The reincarnated airplane was named Education (for all the lessons we learned during 2019 and 2020), and eventually came to earn Luca his first Senior trophy at the 2021 Nats.  Gabe, flying a different design called Skittles, also used the composite cheeks from the same molds, and took the Junior trophy alongside his brother.

As the season was nearing its end, it became obvious that the boys will need more and better equipment going forward.  Each one of them wanted to have the primary competition airplane, a backup plane (just in case... ya know), and a "beater" - i.e. a practice plane that could be taken to the field and back, inevitably develop hangar rash, dings and dents, and yet fly the same as the primary airplanes.  I'll do the math for you: that's at least 5 identical airplanes, all to be built in one winter!  My mind starts racing.  Kits? ARCs?  Which design should we build? How long will it take us? How much will it cost? finally, will we be able to build and finish everything so quickly? 
Going the kit, ARC, or foam wing route would cost us at least $1000.  (as of this writing, Brodak is out of SV-11 ARCs, and foam wings from Robin's View Productions are no longer available). 
But here we were: 21 years into the 21st century, trying to find exotic wood imported from Equador, smelly lacquer called dope (?!), and something that looked like doctor's exam tissue paper.  And then hundreds of hours of rubbing the surface with a small piece of sandpaper.  I knew that it was not going to happen. More importantly, it was becoming clear that putting a decent finish on those planes would make this plan an impossible dream.
Let's do quick math here.  A typical full-size stunter has about 2 sq.yds of surface area.  During a typical dope finishing process, bare wood to clear rub-out, a plane gets completely sanded by hand at least 10 times (in reality, much more, but let's be conservative).  So that's 20 sq.yds of area to be sanded.  Times 5 airplanes = 100 sq. yards = 900 sq. feet, that's about the area of my driveway!  By hand. With wet 600 paper.  Now add the number of times it needs to be coated by dope, whether that's brush or spray (not to mention toxic load of this stuff, no matter how good we think it smells).  I think we're looking at about 1500 working hours.  Considering that my boys maintain very good grades and participate in sports and band during the school year, they have maybe 4-8 hours per week left for airplanes.  End of discussion; mission impossible.  Where do we go from now?

That's when I floated the idea of an all-composite plane.  Luca said that it's not going to happen, and started to build another profile.  Gabe was intrigued and excited, but had no idea how everything was going to work. Neither did I.  I always thought that all-composite airplanes were only possible if made in an undisclosed location near some Ukrainian aircraft factory, using CNC-milled molds and a sprinkle of fairy dust.  Mortals like myself should not apply, I was told.

Desperation makes people do desperate things. 
Over the winter of 2020-2021, we made bucks (plugs), molds, and learned how to make composite parts.  On the Labor Day weekend of 2021, those parts were assembled into the prototype airplane, and first test flights were made.  At 660 square inches of wing, it weighed 62 oz ready to fly, did not use any carbon fiber (except pushrod), and a total of 2 sheets of balsa (will be replaced later).
Gabe entered the plane in Advanced at Cleveland and Before the Snow Flies, and won both times.  Every Advanced and Expert level flier that was given an opportunity to fly the airplane immediately went to put a complete pattern on it, with very positive feedback.  Some guy named Bob Hunt flew the plane and declared "I could fly this every day!" (maybe he hasn't flown any decent planes before?).

In the next installment, I will start detailing the building process.  Believe it or not, but the first step in making a 21st century electric all-composite take apart stunter was... a trip by my good friend Joe to an Amish wood supply store somewhere in Geagua county, Ohio.
Stay tuned.

Haha, too late.  The composite plane prototype got named "Ripslinger".  Watch the Disney animated movie Planes - it has an evil character (looks like a Reno racer) named Ripslinger; the boys liked the looks of it, and that's what was put down on paper for fuselage outline...

I am just posting to get you on my threads list.  You are a very lucky man to have sons that share your passion for the hobby and from what I can gather, you may be actually sharing theirs!

Post a lot.  I go through the build threads a lot, especially when it is new ideas!

Ken

Mike, I'm lovin' it just as much as I loved judging your guys at the FCM.  (There, now I'm on the thread.)

Step 2: Carve the block per the top view, and finish to a 220 grit level.  No need for surface perfection at this time, but it needs to be accurate to within a pencil line thickness.  Having a benchtop sander helps immensely, as having the part on the table guarantees that your sides are sanded 90 degrees (plumb, or square) to the top and bottom surface.

Step 4: Using a carving knife, carve the piece until desired shape is obtained, and finish with file and sandpaper.

Step 6.  Turn on the vacuum.  As the air gets evacuated from the bag, make sure there is enough slack in the bag to allow all the remote corners to get properly pressed in.  Leave overnight and hope for the best.

Step 8 (final).
This is the scariest and most rewarding (or frustrating) step.  Pry the two mold halves apart and extract the piece.  Do not damage the mold or the piece in the process!  I've never done that... er... well, anyway, it's possible to get overly anxious to see the result and damage things in the process.  Don't use sharp tools at this stage.
Extract the piece - some recommend a quick shot of compressed air to help. Can't really hurt anything with that.  I haven't tried that yet, but I intend to next time.
The part will have a very thin layer of flashing.  This is the extra epoxy that oozed out after the two parts got pressed together.  A small amount of flashing is a good thing: it means your epoxy has fully connected the outer layer of the layup.  Too much flashing means you put too much epoxy.  No flashing is worse: you won't know how much epoxy is holding the two halves together, if any.  According to Murphy's Law (in which I am a firm believer), you will find that out when the wing pops apart at the seam on the 4th corner of the hourglass in your best flight of the Nats qualifying rounds.
Flashing can be removed carefully using a simple file.  Voila!  Molded wheelpants.

With the whole process debugged using wheelpants, it was time now to gather courage and begin the real work. 
We will start with the fuselage mold, arguably the most difficult part of the airplane.  My reasoning was this: if we can make molded fuselage, everything else is easier.  If not, we are only lost a couple of months' worth of work, and a Plan B is in order.

There are two methods of making two part negative molds: using a single piece or two-piece buck/plug.  The wheelpant plug I showed earlier was made as a single piece - it's small and simple enough.  The fuselage, on the other hand, is a much larger and complex piece, so I decided to try a two-piece approach.

With Joe's help, the two larger pieces of basswood were planed to the target thickness (each one half the final width of the fuselage, with parting plane vertical).  (Not shown here): mark and drill blind holes in each half of the block in matching locations, so that the halves could be joined and separated any time using pieces of 3/4" wood dowel.  Once done, pull the pieces together so that they form a single block.  Using a band saw, cut to a top view, and then a side view outline.  The final piece should look like this.

Your goal is to arrive at two identical mirror copies of the fuselage halves.  To make them as close as possible, I bought a profile gage at Lowes to compare curvature from one half to another at marked stations (every 2" or so along the fuselage).

Once satisfied, final sand to 320-400 grit, and go through the same process (Minwax poly, apply and dry, sand, repeat).  Your goal is to get rid of the wood texture.  This is where I really appreciated Joe's advice to go with basswood - it doesn't have annular ring texture near I could tell, just the fine grain of the wood itself.  I did not have any need to use any fillers or primers; several layers of Minwax provide a good enough surface - but should you feel a need to use those other materials, this is the time to do it.  In the end, the surface quality you achieve at this stage is what will be imprinted into EVERY layup you pull out of the molds.  If you are unhappy with the surface, fix it now, don't count on fixing it later.  I'm talking about any surface texture rougher than 400 grit and any surface imperfections that can be seen with a naked eye in oblique light.  Don't worry about shine, it will come later.

Once the parting board has been waxed several times, go ahead and install the first finished buck onto the board, using some wood screws driven from the back side.  Be careful to plan the screw lengths so that they don't protrude through the finished surface or split the grain.  Since the thickness gets much smaller towards the rudder, you will need to go to much smaller screws, like #2.

Once the buck has been pulled firmly towards, the parting board, force thin beads of modeling clay to completely close the remaining gaps (which should be no larger than 1/32", more like 1/64" and less).  Once satisfied, wax the entire surface with Partall wax several times, buffing out with towel in between each layer. 
Make and install smaller parting boards to cap the nose and (in our case) the future separation line for fuselage take apart.  If you are not making a take apart fuselage, leave out the parting board in the middle of the fuselage.
Do not forget to install at least a couple of peanut-sized indexing pins (I shape mine out of modeling clay) and a few wedge-shaped pieces (also clay) to serve as future prybar pockets for separating molds.
The final step is the application of the PVA release layer.  I found that the most cost effective tool to apply PVA are pieces of Magic Eraser sponge cut into a wedge shape.  Do not reuse those - once PVA dries, throw them away.

I did not take pictures of the following steps - it's kind of hard to do when your hands are covered in epoxy and fiberglass (you are wearing nitrile gloves, right?).  Start mixing epoxy in 2 oz batches and applying layers of heavy fiberglass, rotating grain direction 45 degrees on each layer (which means that they should have been cut "on the bias" during prep stage).  After 4-6 layers, apply core material called Lantor Soric XF (a flexible honeycomb foam core fabric), and then 4-6 layers of fiberglass again.  The core material serves to build up the layup thickness to the target 3/16"-1/4", instead of the heavy and expensive glass and epoxy layers.
Once cured, use an oscillating cutter to trim the edges neatly.  Do NOT remove the mold from the buck at this time!  Prepare the front section of the buck with release materials, indexing pins, etc, and repeat the process.  Once done, you should have a mold that looks like this.

Once done, wash away the remnants of the PVA layer with water and inspect for defects (hopefully, none).  I'm talking about cavities and other serious defects. 
Assuming you did a good job, now is the time to put some real shine on the mold surface.  Starting with 600 wet and going progressively finer to 3000 wet, sand the inside surface of the mold, being careful not to round off the sharp edges of the parting line.
Buff, wax, and admire.

Once again, avoid the temptation to pull out the shells out of the molds - until assembled, the edges are extremely vulnerable.  Instead, dispense the bead of epoxy+Cabosil+cotton flocks, and close the molds until full cure.

If everything is done right, you will be rewarded with a shiny, strong, and light part.

A quick note on cutting composite fabrics.
I highly recommend doing so on a cutting mat, and using a rotary tool (we like Olfa brand) found at any fabric supply stores like Jo-Ann fabrics.  Do not use scissors.
Fiberglass cuts cleanly and easily.  Use cardboard templates prepared according to the mold size and shape.
Carbon fabric will fray very easily.  Before cutting carbon fabric, run a narrow piece of masking tape along the cardboard template positioned over the fabric, and then cut in the middle of the masking tape. The tape will hold the fibers from fraying.
Eventually, the masked edges will spill onto the parting board outside of the finished part, and will be cut away during the trimming process.

Mike, the old DOC is going to follow this to the end. Reminds me of when I was trying to compete in F2C and we were supposed to make our own air planes.   We had fibre glas fuselages with no balsa in them.  Another secret, what ever your boys do don't raise your voice to them.  I can see they are doing great work.

Excellent, excellent work.

CB

Part III.  BOTH FEET IN THE 21st CENTURY

You might be reading this and thinking to yourself, "Wood from Amish store?  Carving?  How is that 21st century technology?" 
And you might be right.  So read on.

It was right around January when the fuselage molds were finished, and the first successful fuselage was produced.  It had good glossy finish, and was stiff and light enough to give us hope that this technology is viable enough to continue working on.

The next large part of the airplane, of course, is a wing.  Some would say it is the most important part, because that's what is carrying the plane through the air.  After all, that was the foundation of the sheeted foam wing cottage industry: consistently straight, dimensionally stable wings.  Everything else can be built.

So I breached this subject with Gabe.  My thinking was that we could hotwire the wing bucks out of blue foam, cover them in fiberglass, sand and finish, and then pull the mold off that.  There was one limitation, though...
Gabe's ears perked up. 
- What is that?
- Well, I can only hotwire a straight tapered wing...
There was some silence for a moment, and then I heard:
- No.  It has to be elliptical, just like Skittles.
"- Gabe", objected I, "how am I supposed to hotwire an elliptical wing? It's impossible. The wire is straight."
Again, silence, and then "No".
  Have you ever had a 4-year old stop in his tracks at the sight of an ice cream shop on a stroll through town, and refuse to leave until he got a cone?  "Johnny, you can have a popsicle when we get home..."  -- "No!"
That was Gabe at this moment.  He dug his heels in and would not budge, which is not very typical of him.  Usually my technical arguments are convincing enough, but this was not the case that day. 
In retrospect, I'm glad he stood firm.  The composite elliptical wing turned out to behave very well (something that we actually knew from the original, built up Skittles), but I'm skipping too far forward.

We started brainstorming how to make a buck for an elliptical wing.  The only method that I knew of was learned by me from an RC boat modeler about 30 years ago; he was making bucks for racing boat hulls.  Not too long ago I came across Bob Hunt's TruForm molding method description, and it is very similar.  The idea is to install several plywood bulkhead-like templates at predetermined stations along some sort of a building reference board, fill the spaces in between with a material that can be carved (blue foam, basswood, etc), and carve until the surface reaches the bulkheads.  This way the cross sections are both known and guaranteed (as opposed to me eyeballing the fuselage cross sections when carving from a single block). 
I outlined the process to Gabe, and warned that something this involved could cause our build schedule to slip severely, but it did not seem to move him.  You know, this generation of kids just doesn't understand what it's like to operate within constraints (technical, budgetary, etc) - they reach for the sky and worry about the costs later. Maybe it's a good thing, I don't know.

And then he said something that almost made me laugh: 
"I'll 3D print the wing buck".
It is true, he just got a shiny new 3D printer for Christmas, a $500 Creality CR-10 Pro V2.  But wait, kid... It will take you up to a year to learn how to use it!  And then you need to learn CAD, which is probably another year.  I took CAD in graduate school.
"Nah", was Gabe's response, "it won't take that long. I'll have the buck printed before you can make your foam wing. Bet!"

The word "bet" was a challenge thrown my way, and in such a cocky tone, that I just had to teach this kid a lesson.
I said the following:
"If you can produce a useable elliptical wing buck before I make mine, you will get a fast gaming laptop for your birthday".
Needless to say, I was absolutely confident that I'll win this bet.  After all, how long does it take to hotwire a wing!  Piece of cake, huh?

Instead of cake, I ended up eating crow.  Before I had my templates made out of formica (again, thanks Joe!), Gabe presented a fully rendered 3D model of the Skittles wing, done in Fusion 360 (and Autodesk product).  He downloaded the Fusion 360 hobby version (free), watched a 10-minute tutorial on Youtube, and declared, "I got it".  At that time, I chuckled to myself, thinking "good luck, kid".  By the end of the day, he was lofting straight wing sections.  Next day, he had a crude prototype of an elliptical wing, which got refined better and better every day.  Things were looking both promising and more sour for me.
Here's a 30-second animation of his design process in CAD:

In order to fit within the printing volume limits, Gabe split the wing model in half spanwise, and inserted two cylindrical tubes in the middle of the wing, such that the halves could be joined over two short sections of a cheap fiberglass tube we had laying around. 
A mere 104 printing hours later (!), which took about a week, we were holding two 3d printed wing sections, which matched with each other perfectly, and were more accurate than what a human hand could produce out of wood.

The halves were joined using epoxy, seam patched using Aeropoxy Light (I just had lots of it), and it was looking very, very real. 

Wing molds are produced using the exact same method as was described earlier. The picture shows the molds when they just got separated from the buck for the first time. They had to be washed of PVA, wet sanded and buffed to achieve high gloss surface.

Finally, the first composite wing was produced, and came out right around 6 oz.  You may notice a patch of 6oz carbon cloth around the spar at the root.  In all subsequent wings, this was replaced with several layers of 2oz glass, and proved to be adequately strong, easier to work with, and substantially less expensive.

Well, you know the rest of the story.  The prototype trimmed out on the first day, flew well, and gave us hope that the next batch of airplanes we will be building this winter will fly just as well.

Well, one thing, once the prototypes are done it should be easy to reproduce the new planes.

Mike, this is a wonderful thread that I have read with great interest and satisfaction. It's just captivating and lucidly laid out for us. You have done wonderful work with more than just your modeling; your boys are much more than a usual source of pride, and I'm amazed at their abilities and dedication. Thanks so much for sharing this with us. Would you also care to share with us your findings relative to the wings' stiffness and any internal structure they might - or might not - have?

Thanks for telling us the trick of leaving parts to be joined in their molds. I wondered how people joined parts like that, but I never knew until now.

 Steve, the completed airframe is shown in Reply #3 of this thread. A fully painted version is yet to be built.

I have not thought about ARF yet, but a question back to those who might be potentially interested would be: what price would you be willing to pay for a composite ARF?
I need to know whether it's a viable thing for me to spend my time on.

It is now time to plan the actual layup.  Here's what we currently use, in the order of the layup in the mold:
Two layers of 1.4 oz plain weave (aka "E glass") - one layer along the axis, another on the bias (45 degrees), then a 1/16" thick sheet of blue foam (from Lowes) - more on how to prep the foam later - followed by a single layer of 1.4 oz E-glass.

Did you ever detail this step?  I read though the thread a few times, but didn't spot it.

Thanks,

Pat MacKenzie