a Greek Foam-Composite Airchair attempt

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DeltaMan

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Aug 21, 2009
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61
Location
Trikala / Thessaly / Greece
Hello All.

I've decided to use the Naca 4514 airfoil. I've transferred it to 4 mm poplar plywood to use it as a pattern for further cuts on foam...
Chord at the root of the wing will be 101 cm or 39,7 inches.
 

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DeltaMan

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Aug 21, 2009
Messages
61
Location
Trikala / Thessaly / Greece
Hello All and I'm sorry for the delayed continuation on my project but other, smaller planes must be made first... :)

I've attached the fin and rudder on the end of my boom with two 8 mm (0,3 inches) in diameter screws. Those simple nuts are just there for maiden assembly. Later on everything will be disassembled and reinforced and I'll be using safety nuts of course...
Rudder needs 2 x 4mm screws on every hinge as the hinges are only glued on the Fin side...
It's a work in progress. I'm back on it from time to time and let's see where this journey will take us guys... :)
 

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Victor Bravo

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Jul 30, 2014
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KWHP, Los Angeles CA, USA
The teleflex controls, as well as inside/outside tubes ("Bowden Cable") like R/C model controls are heavier and not as precise as regular "old style" cables. Since you are building from scratch and have the capability to do laminations, it is not much extra effort to install mounting blocks or mounting points for pulleys, and use cables for control. Now that there are synthetic fibers that are equal or better than steel cable, you can save even more weight and still have fairly precise control. Kevlar string may well be more than strong enough for your lightly loaded controls.
 

DeltaMan

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Aug 21, 2009
Messages
61
Location
Trikala / Thessaly / Greece
Victor, Yes.

Besides using Bowden cables which was a thought, I'm also leaning towards regular steel cables. I had never thought I could purchase kevlar string on a fair price. I know they are used on glider winches and parachutes but I didn't know a fair price is on the market... If you have a link for that it would be great! It's easy for me to make composite L or U shapes too, right...
I'm also thinking of running pulleys and cables outside the body (like in the pic), 'cause I'm a bit scared to cut access doors for maintenance... :(
Don't want to interfere with the structural integrity of the body, not for now at least... At the end maybe I'll make extra cowlings to cover all that.
 

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Victor Bravo

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Please consider the fact that this will be a slow speed, high drag aircraft... the opposite of the AS-G29 and other racing class gliders. So having the pulleys and strings outside the stucture provides several benefits with very few disadvantages. Ease of construction, ease of adjustment, ease of maintenance, no holes in the carbon. Also, the majority of the cables or strings will be parallel to the airflow, reducing their drag a little.
 

DeltaMan

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Aug 21, 2009
Messages
61
Location
Trikala / Thessaly / Greece
Yes, Victor. My thoughts exactly... :)

I'm currently building a 1-meter rectangular box out of carbon and wood for the insertion of the wing's "tongues" (main spars). When I've made some progress I'll post pics... :)
 

DeltaMan

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Aug 21, 2009
Messages
61
Location
Trikala / Thessaly / Greece
Some progress...

> I made a carbon sheet that consists of six (6) layers of 160 gramms/sq.m. fabric. Dimension was 27x100 cm and thickness is about 1,6 mm. The next day I cut that piece in two. Sandpapered the inside edges of the one and glued 9 mm plywood strips with epoxy. Next day the other "wall" was glued also on top of those wooden strips and that rectangular shape you can see in the pics was formed...

It's really stiff like a box structure but heavy I think at 712 gramms. Maybe I overdid it, but my wing will be supported on that! It won't be alone of course. Imagine the first one meter on the wing formed around that piece and everything wrapped around with fabrics + epoxy...
 

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DeltaMan

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Aug 21, 2009
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61
Location
Trikala / Thessaly / Greece
I cut a hole on the fuselage with a three (3) degrees positive angle of attack because I think those classical NaCa airfoils need that. After all, my horizontal stab will be all-moving so it should be easy to trim correct incidence angle between wing and tail at the end... :)
Made a "special" tool to help me with the sanding to get it right (pic 139)... ! After I felt happy with the fit, I sandpapered both sides of the box on the center plus 6 cm on each side to glue it permanently of the fus. Later I will add extra cloth of course from the four outside "corners"...
 

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DeltaMan

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Aug 21, 2009
Messages
61
Location
Trikala / Thessaly / Greece
Hello All.

I used my vertical hot wire to cut some airfoil foam, after I've made two identical airfoils out of 4 mm plywood. I put some aluminum tape over the edges of the airfoil shaped plywood so that hot wire will run smoothly on it while it's hot...

That's a black foam I find on the local market and they sell it as light but "graphite" reinforced. I've measured it at 15,5 kg/sq.m. I wanted something light but a bit stonger on the center of my wing joining... :)
 

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DeltaMan

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Aug 21, 2009
Messages
61
Location
Trikala / Thessaly / Greece
I removed a slice of foam from the spar area (1/3 chord length), exactly at the width of my spar pocket and glued the four airfoil pieces in place.

Before attaching the foamy airfoils, I reinforced the inside corners (red lines) where the spar pocket meets the fuselage. That was done with 4 layers of 160 gramms/sq.m. carbon cloth on each corner.

I've also decided on the shape and size of my wing. Each panel will be tapered at 5,5 meters span! My total wingspan will be 12 meters this way. Chord length at the wing tip will be 56 cm. Pictures on that as I progress. I'm currently setting on building the main spar. Thank God I have that nice big space at work and I've built a 5,82 meters flat table to work on... :)
 

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pwood66889

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Feb 10, 2007
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Sopchoppy, Florida, USA
Your nickname in that forum feels like you're having Greek routes. Do you?

Do you know, have you heard of people using flexible control linkages for full size like the ones we use in airmodelling? .
My only Greek route, Apostolos, is that I was in an American fraternity in college, and had to learn the Greek Alphabet (alpha, beta, gamma...). Don't know it that was ancient or modern.
Your English is Much Better than my Greek. English has only two sticking points; the spelling and the verb structure. Greek is inflected, which means (like the Russian I learned starting high school) that the word endings establish place in the sentence.

As to flexible control linkages, Airbus Helicopter uses them; EC-145, etc. They call them "Flex Ball" controls, and use them for collective, pitch and peddles.

Percy in NW FL, USA
 

DeltaMan

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Joined
Aug 21, 2009
Messages
61
Location
Trikala / Thessaly / Greece
Hello lurker, hello all.

That project will never cease. I'm just having some temporary trouble with space to built it and money for materials. Family needs all my attention.
Sorry, but hopefully I'll continue working on it in spring '19...

Best wishes for a Happy New Year to all._

:)
 

DeltaMan

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Joined
Aug 21, 2009
Messages
61
Location
Trikala / Thessaly / Greece
Hello All.

Lately I had to make some wings for a friend's uav, using the Lost Foam technique. I was quite happy with the result.
Styrofoam is a bit hard to be burned out, but lighter foams just... dissapear when they get in touch with paint thinners and such liquids.
If I knew this technique, I would have made my fuselage with simple, coarse grain foam, cover it with simple clear tape, skin it with epoxy and carbon and then loose the inside foam... !!
I'm thinking of producing my wings like that and a basic plan is already written on my notebook :)
On the photo I'm posting, I couldn't lay the textreme fabric on a +-45 angle 'cause I didn't had enough fabric! I made six pieces of that 75 cm panel... Root chord is 35 cm.
Center small foam section which has the female spar carbon tubes inside is also wrapped with fiberglass around the tube! The result is Very Strong but not so light for it's size.
Moving flying surface had to be detachable for transportation. That flap or aileron fits inside the hollow wing!
 

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pictsidhe

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North Carolina

pictsidhe

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Jul 15, 2014
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North Carolina
No Sir, I haven't.

I don't know how to do that and I'm pretty confident that nobody will help me without a serious amount of money.
It's necessary to build a successful flying machine. It may even be a legal requirement there. No requirement for any calculations in the USA for ultralights, but I'm following FAR 21.

Look up CS 22 for Europe.
 

litespeed

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May 21, 2008
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1,557
Location
Sydney
Lovely looking wing panel for the rc/uav.

Just remember as stated before the importance of having the spar transfer its loads into the skins when doing a man carrying aircraft. The skin must directly connect to the spar, a spar to foam to skin load path is not sufficient for a human carrying flight. With foam to transfer loads - it is only the foam holding it all together. The carbon must take the loads.
 
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