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Author Topic: New type of wing construction  (Read 4612 times)

Offline TDM

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New type of wing construction
« on: August 04, 2021, 09:27:15 AM »
Has anyone thought or used 1/64 plywood for skins in order to build a wing?
I have used this technique in the past to build a DLG glider wing that required to be built up strong and very stiff in torsion and most important it had to be light. The wing had to be built with washout in order to maximize the performance plus the bottom of the wing was not flat.

This is how I made this work: All that was in place to make that wing can be applied to build any other wing including wings for control line. It can be applied with geodesic construction too.
1  I made a frame that simulates the underside of the wing.
2 Using double stick tape I taped the lower wing skin on the top of the frame.

3 ribs were glued in place

4 put in the sheer webs

5 some sanding and blending followed by the top skin

The result was a wing that has a wing panel 30in long that weigh in at 77grams.
Some advantages are: first I think we can achieve wings built with this technique in the 140g without breaking a sweat, second since the outer layer is a continuous piece of ply much harder than a balsa surface it might also be easier to finish, third it will be more durable, and forth it will be a lot stiffer too. 



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Offline Brent Williams

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Re: New type of wing construction
« Reply #1 on: August 04, 2021, 05:21:24 PM »
Eric Rule posted a few years ago about his experiments, (or intention to experiment) with using paper backed wood veneer as a sheeting material. 
It is less expensive and less heavy than 1/64 ply. 
It would exhibit some of the desirable qualities of 1/64 ply, ie. less finishing effort required, strength in torsion/tension, ect.
It just requires a rethink of construction methods and materials.
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Offline Howard Rush

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Re: New type of wing construction
« Reply #2 on: August 05, 2021, 06:26:51 PM »
I had some paper-backed teak veneer, thinking it might be useful for something.  It didn't spark joy.

I like Traian's idea.  1/64" plywood has become some of my favorite stuff, now that I found out how nicely it lasers. One could lay up a sheet from several balsa pieces with grain oriented as needed, smear Z Poxy on if you like, then laser the layup.
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Offline Brent Williams

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Re: New type of wing construction
« Reply #3 on: August 06, 2021, 12:46:58 AM »
If only there was a way to make a plane from a thin shell of carbon fiber.

Motorman 8)

There is a way, however it takes an entire new set of skills and the desire and drive to use them....
Carboweave.  https://alofthobbies.com/carboweave-cw-30-600mm-x-3100mm-245.html

 
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Online katana

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Re: New type of wing construction
« Reply #4 on: August 06, 2021, 03:37:22 AM »
..and now the manufacturer ( www.mahogany.fi ) has a new "indoor" variant of thin plywood, that lasers even better. The original phenolic resin they use can be quite nasty. They have a nice web shop, worldwide shipping.

Interesting website and as I suspected the thinnest veneers they listed at 0.55mm is almost twice as thick as their thinnest plywood at 0.4mm ( 1/64" = 0.396mm)
So, I can't imagine the addition of a paper backing will reduce a veneers thickness nor its weight.
Mind you plywood airplanes do have precedence - the De Havilland Mosquito, one of the fastest and most versatile multi role aircraft of WW2!

Offline Larry Renger

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Re: New type of wing construction
« Reply #5 on: August 06, 2021, 02:27:18 PM »
The German Albatross of WW1 has a wood monocoque fuselage. Don’t know if it was ply or not. Beautiful plane. A friend has a park flyer version that flies really well. Fully aerobatic.
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Offline Avaiojet

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Re: New type of wing construction
« Reply #6 on: August 07, 2021, 08:27:50 AM »
The German Albatross of WW1 has a wood monocoque fuselage. Don’t know if it was ply or not. Beautiful plane. A friend has a park flyer version that flies really well. Fully aerobatic.

Lockheed Vega Winnie Mae,

Two layers of ply for the fuselage construction.

Mig-3 also has plywood fuselage sides.

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Offline FLOYD CARTER

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Re: New type of wing construction
« Reply #7 on: August 07, 2021, 05:59:32 PM »
I have always avoided balsa sheeted wings.  My first effort had ripples and uneven surface.

I shudder to think of the cost using 1/64 ply on a 650 sq,in, wing.  That's 1300 sq.in. of very expensive material..  Also, that can't be very light.
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Online Brett Buck

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Re: New type of wing construction
« Reply #8 on: August 07, 2021, 10:34:02 PM »
I have always avoided balsa sheeted wings.  My first effort had ripples and uneven surface.

I shudder to think of the cost using 1/64 ply on a 650 sq,in, wing.  That's 1300 sq.in. of very expensive material..  Also, that can't be very light.

  He said it was 77 grams/panel, which does not sound too bad to me. A foam/balsa Imitation wing panel is 102 grams +-5 (i've build A LOT of them).

   It's also probably cheaper than the graphite and epoxy he was using before.

    Brett

Offline pmackenzie

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Re: New type of wing construction
« Reply #9 on: August 08, 2021, 04:43:59 AM »
77 grams was for the DLG wing panel. He is estimating 140 grams for an F2B panel
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Offline TDM

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Re: New type of wing construction
« Reply #10 on: August 08, 2021, 10:06:17 AM »
The DLG wing has the same span but half the cord. So if you double the size of the skins I thin you end up with roughly double the weight. the span is the same as what we are using now around 5ft. So a good guess is, you have an 150-160g wing panel with flaps.
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Happiness is the harmony between what you think and what you do. Mahatma Gandhi

Offline TDM

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Re: New type of wing construction
« Reply #11 on: August 08, 2021, 10:11:27 AM »
There is a way, however it takes an entire new set of skills and the desire and drive to use them....
Carboweave.  https://alofthobbies.com/carboweave-cw-30-600mm-x-3100mm-245.html

 

https://stunthanger.com/smf/gettin-all-amp'ed-up!/revolutions/
I use that everywhere in the plane.
Each goal you meet is a moment of happiness
Happiness is the harmony between what you think and what you do. Mahatma Gandhi

Online Brett Buck

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Re: New type of wing construction
« Reply #12 on: August 08, 2021, 04:21:13 PM »
The DLG wing has the same span but half the cord. So if you double the size of the skins I thin you end up with roughly double the weight. the span is the same as what we are using now around 5ft. So a good guess is, you have an 150-160g wing panel with flaps.

  My mistake, I just misread it. 160 is pretty heavy for a stunt wing panel.  How much were the carbon/epoxy wings?

    Brett

Offline MikeyPratt

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Re: New type of wing construction
« Reply #13 on: August 24, 2021, 04:11:24 PM »
Gentleman,
It seems that I went through this same thing every two years during my 20 years at Sig as a designer and engineer.  Almost every time there is a balsa (supposedly) shortage people want to find something cheaper and easier to use,  in that time I’ve tried countless types of verniers from pre-preg glass sheets, to paper backed mystery wood with the same results, heavy as hell, nothing works as good as balsa.  At Sig we even had a product called “Rino Skin” but that stuff didn’t turn out so well at all.  When the sun was on the wing it would srink and add warps and other things you didn’t want   

I’ve even tried the foam sheets from art supplies stores, I did find the that stuff can be vaccine formed that works pretty good.  But my opinion hasn’t changed, I found it difficult to use as a wing skin unless you you built a structure under the skin.  It did get heavy just like everything else we tried.  The molded carbon fiber maybe the way to go, but it will be very costly if you don’t have the equipment and/or mills for the molds.  Finding a good process is the key here, or use heavy wood until the shortage ends.  Im always open for good ideas so let’s hear it from those that have tried something different and it worked?

Mike Pratt

Offline phil c

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Re: New type of wing construction
« Reply #14 on: September 01, 2021, 06:17:21 PM »
Gentlemen:  always open for good ideas so let’s hear it from those that have tried something different and it worked?
Mike Pratt

Hi Mike.  There is an affordable method that fill the bill.  To well in fact.  If a warp gets in it's hard to get it out.
I built an eyeball ready profile built with foam core on all the major parts: wing panels, fuselage, and tail surfaces.  740 square. 49 oz RTF with an LA 46.  It flew very nicely, could do a full pattern in my unpracticed hand.

The only foible was sharp square corners tended to make it yaw and roll at the same time.  Igor Burger somewhat later developed a fix- usinf a low profile, in the range of fuselage height with a wider chord and a Rabe rudder.

I've still got the original plane despite crashes.  I'm trying a chopped rudder on it, and an LA46 with a three bladed prop.

Cheers!
phil Cartier

Offline Dennis Toth

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Re: New type of wing construction
« Reply #15 on: September 02, 2021, 06:41:35 AM »
It seems the one thing that would be needed to use the 1/64" ply for light weight wing sheeting is to design the frame structure to take full advantage of the plywood's strength and stiffness. The plywood would require less internal structure or at least use of thinner material for this structure. They used 1/64 ply for wing skins in RC way back over foam cores. It was applied with heavy glue and no effort was made to save weight, just fast assembly.

1/64" ply is very close to medium 1/16" balsa in weight but has many time the strength. If the wing was designed with thin internals say 1/32" ribs, maybe geodetic layout and creative spar construction you could get the weight down to match straight balsa but would be stronger. Would work well with MonoKote type coverings or if painted the ply takes less to fill and the total weight of the finished wing might be very competitive.

Maybe some of the design Wizards can work on this and suggest a few approaches.

Best,   DennisT

Online jerry v

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Re: New type of wing construction
« Reply #16 on: September 02, 2021, 08:30:33 PM »
One sheet of 1/64 plywood size 48x12 inches is 5.29 oz or 150 grams.

Jerry
Variety is the spice of life.

Offline Fred Underwood

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Re: New type of wing construction
« Reply #17 on: September 02, 2021, 08:43:55 PM »
Just curious, what does that 1/64 actually measure.  My last couple sheets are 0.019 and 0.020" so more like 1/50.
Fred
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Online jerry v

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Re: New type of wing construction
« Reply #18 on: September 03, 2021, 06:25:18 AM »
It's sold as 0,4mm (1/64") but you're right, more often it's closer to 0,5mm thickness. It's a natural fibre product, maybe it swells back a little after processing?
but still, it's pretty darn impressive for a 3-ply plywood.
Made in Finland, by the way.
L
The 150 gram sheet of 1/64 plywood is .019 inches or .4826 mm thick and is a pretty consistent. It’s a very useful material to build profile fuselage with balsa criss-cross sticks and 1/64 ply sides. It’s stronger than a foam core and 1/16 balsa.

Jerry
Variety is the spice of life.

Offline TDM

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Re: New type of wing construction
« Reply #19 on: September 03, 2021, 09:16:51 AM »
So initially I was going off some previous made wings that I made for a glider and out of curiosity I made a CAD drawing of a typical SV wing geodesic construction with .5in cap strips included and full flaps with no lightening holes in it. I ended up with a surface area of 131.5 square inches for the wing and 59square inches for the flaps. Double that for top and bottom 381square inches that is a budget of 99g of 1/64ply per panel for each wing including fully sheeted flaps. Add some ribs 1/8 square balsa sticks and wing tips should yield a very reasonable weight for a wing.

You don't really need the half ribs or big spars because the ply is the spar so other than 1/8x1/8 balsa to keep the ply flat there is not a big need for anything else than the minimum structure.

This is not heavy at all for our standards.
https://www.aircraftspruce.com/catalog/wppages/finnishbirch.php  75$ plus shipping will yield a full plane worth of wings and tails and then some.

I based my numbers on the 150g for a 48x12in ply surface ifo from Jerry.
Each goal you meet is a moment of happiness
Happiness is the harmony between what you think and what you do. Mahatma Gandhi

Offline michaely

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Re: New type of wing construction
« Reply #20 on: April 02, 2022, 11:59:03 AM »
In my experience 1/64" ply is about twice the weight as medium weight balsa.

I once cut the sheeting for .60 size pattern plane out of 1/64".   After cutting out the ply sheeting they seemed heavy in my hands.   So I took the trouble to figure out the total square inches of 1/64" ply sheeting, consulted Sig charts for balsa weights, did the math and the ply sheeting would have been twice the weight of medium weight balsa.

There may be some applications where the extra weight issue is not significant but for almost all the models I can think of balsa is significantly lighter.

Online Ken Culbertson

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Re: New type of wing construction
« Reply #21 on: April 02, 2022, 01:41:27 PM »
I concur that 1/64 plywood is heavier than medium balsa.  We used to use that for sailplane skins.  Much stronger to take the stress of the zoom launch.  When you are carrying a couple of pounds of lead in a tube at the cg, it makes sense to beef up the construction and carry less lead, but not for our wings.

Ken
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Offline Avaiojet

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Re: New type of wing construction
« Reply #22 on: April 02, 2022, 02:02:22 PM »
I concur that 1/64 plywood is heavier than medium balsa.  We used to use that for sailplane skins.  Much stronger to take the stress of the zoom launch.  When you are carrying a couple of pounds of lead in a tube at the cg, it makes sense to beef up the construction and carry less lead, but not for our wings.

Ken

Back in the day, pattern ships, those which came in kits, fiberglass fuselage, foam wings and generally 1/64 ply wing sheeting.

The guys I knew would toss the sheeting and use 1/16" balsa. I never gave it a thought, I did what they did.

Charles
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