CriCri Composite

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BoKu

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@BoKu:
There is a new sandwich material called "3d core" (www.3d-core.com). You can get it in either XPS or PET and it can be easily infusioned (so done in one step). The honeycomb is adding significant weight, yet it is still way lighter than Soric. Another upside: the Epoxy within the structure is protecting against core failure. We want to test it for a safety cell which can be manufactured in a single step.

I thought this may be the solution for your fuselages if used in 3mm thickness.
Thanks for that information, but the cost/benefit ratio comes down deep in the red. My fuselage shell is primarily bounded by the torsional and bending stiffness between the wing and the root of the vertical fin, for which any kind of core is pretty much immaterial. What little panel stiffness we need back there is easily provided by the ring stiffeners we apply in a secondary operation.

As I've written before, my fuselage is optimized to meet its structural requirements when fabricated by one leader and a crew of total amateurs on their second day of composites experience. That demands a simplified layup schedule with lots of margin for minor inconsistencies in techniques and processes. And as it turns out, for a female-molded carbon fiber part, the weight penalties for doing it that way are rather modest. That, among other things, is why I still firmly believe that molded carbon fiber is among the most cost-effective way of fabricating even modest-performance airframes. Once you accept the value of collective action (or reject the exorbitant cost of rugged individualism) the necessary molds and infrastructure amortize themselves very quickly.

Going OT, we generally make our fuselages at our Akaflieg build sessions, and it takes a newbie crew of three a five-day week:

Monday: Cut carbon, consumables, and fin foam core. Wax and prep the mold, safety briefing for the crew.

Tuesday: Fabricate fuselage right half (the easy one) and the turtledeck.

Wednesday: Fabricate fuselage left half (the hard one because it has the bonding joggle).

Thursday: Install ring stiffeners and elevator push-pull tube guides.

Friday: Install plumbing, wires, and rudder cable tunnels. Prep all bondlines. Install bondline pressure rails. Mix and apply bonding paste, bond halves together.

Saturday morning: Separate fuselage molds, demold finished fuselage shell.

For a crew with two or more experienced members, we can lay up both fuselage shells on the same day, compressing the schedule by one day to catch up for a lost day or advance the demolding to Friday.

For a Canadian fuselage shell, we would omit the bonding operation, and instead temporarily join the shells with aluminum pop rivets 6" OC. The builder would then drill thru the rivets, have the shell interior inspected by TC, then field-close the shell using more pop rivets or clecos for bondline clamping.
 

Victor Bravo

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The Akaflieg serving as both an income stream and a slave labor camp is a fantastic idea Bob ! ( :) ).

You might think, to expand that revenue/labor model out to small Luciole- and KR-2-sized powerplanes, composite kit cars, canoes and watercraft, Minibat or Monarch sized low-dollar gliders, ultralights, etc. as well.

Almost as good as free prison labor on the Rockwell Lark Commander :)
 

BoKu

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The Akaflieg serving as both an income stream and a slave labor camp is a fantastic idea Bob ! ( :) ).
Just so.

Cue "butts thatsez elitist!!! eleventyone!!!" :)

George Applebay built most of the Zuni sailplanes using as near actual prison labor as you can get without having demolding wedges carved into shivs. He had a contract with some New Mexico corrections bureau that subsidized wages for recent parolees. The legend goes that he picked out the biggest, meanest-looking one to run the toolroom and make sure everything got checked back in at the end of the day. I just get most of that stuff from Harbor Freight, and the Akafliegers generally leave more and better tools behind than they take away.
 

Victor Bravo

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I'm sure you could make one out of wood and carbon strips, but I'm not sure it would be any lighter or better than the original. You would have to do the whole structural design over, and I am not sure what you would gain. Maybe something, maybe nothing.
 

Speedboat100

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I'm sure you could make one out of wood and carbon strips, but I'm not sure it would be any lighter or better than the original. You would have to do the whole structural design over, and I am not sure what you would gain. Maybe something, maybe nothing.
The wing spar arrangement looks challenging with wood...possibly steel could be used there ?
 

Tiger Tim

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Apr 26, 2013
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Full size outdoor Cri Cri is neat, but I like that someone was crazy enough to make one to fly indoors!
 

stanislavz

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And as it turns out, for a female-molded carbon fiber part, the weight penalties for doing it that way are rather modest.
Hi, you are taking about this one :

I originally designed the HP-24 fuselage to be made of fiberglass, with a base layup of 5 plies of 7725, three at 0/90 and two +/-45. That was what George Applebay recommended. When we switched to carbon, I decided to simplify the layup at the expense of weight. Now we just use three plies of 11oz carbon, first and last at 0/90 and the middle one at +/-45. Plus reinforcements at the wing side of body and cockpit rail. The total thickness and fiber distribution is similar to what the Europeans are doing. After the shell cures, we add five or six ring stiffeners inside the aft fuselage, and the kit builder installs a bunch of bulkheads and longerons in the mid and forward fuselage areas. The only core foam is in the vertical fin; we put it down under the last 0/90 ply. The primary optimization here is getting a 22-foot long thing with 42 square feet of area laid up and bagged inside of two hours using relatively unskilled labor.
How worse/better it was on weight compared to more high tech solution ?
 

Scheny

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Who knows about the electric carbon CriCri from Magicraft? They finished it end of 2019 and I read in some YouTube comments that the test pilot died during test flights around Vancouver.

Guy claimed a battery failed. This is the problem when you use oversized RC gear.
 
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MadRocketScientist

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Canterbury, New Zealand, Earth, Milky Way Galaxy.
Who knows about the electric carbon CriCri from Magicraft? They finished it end of 2019 and I read in some YouTube comments that the test pilot died during test flights around Vancouver.

Guy claimed a battery failed. This is the problem when you use oversized RC gear.
I think that is an internet rumor, Last I heard (on another forum) it still exists and no fatalities.
 
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