Aircraft construction from furniture plywood

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hopeless_dreamer

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Feb 11, 2013
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Delhi, India
Hi everyone,

I had a question about plywood construction:
Is it possible to build a structurally sound airframe from furniture grade plywood.
(by that, i mean non-marine, non-aircraft grade plywood you can access in any carpenter or furniture store.)
Has anyone built a functional light airplane/glider using this material?
What would be the tradeoffs with regards to weight and strength.
These are the specs I had in mind:
Size and weight in the same class as the Volksplane or Flybaby or Legal Eagle.
never exceed speed: 100 kts
Is it also possible to use aluminum for spar material and wood for the ribs at the same time?
Please forgive me if these are stupid questions.
 

Aerowerx

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Yes, you could use furniture grade plywood, but would it be safe? You have no way of knowing.

With aircraft grade plywood one of the things you are paying for is a guarantee of the quality and strength, and that there are no defects in the inner layers.

I see no reason why you could not use wood ribs and an aluminum spar.
 

Topaz

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This is not at all my area of expertise, but you could conceivably use "furniture grade" plywood that meets the requirements of aircraft grade ply. That means you'll be sorting through piles of wood and grading it yourself, using (I believe) ANC-18 as your guide to requirements. We've had members here say that they've done exactly this.

You'll be trading cost for peace of mind. Aircraft grade plywood has been manufactured and graded for you, so you know the work has been done right. Making that judgement yourself saves you money, but it's only as good as you are.

Me, I'd save up a few more months and spend the extra money on the genuine aircraft grade stuff, and so have some peace of mind when my soft and fragile body is a couple of miles up in that airframe. Your mileage may vary, of course.
 

FritzW

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I think it's one of those things you're going to have to decide for yourself. So much depends on what constitutes "furniture grade" plywood in Delhi, India and the cost of proper aircraft grade ply.

Where I live a sheet of 1/8" aircraft is about $100 US and $20 or $30 shipping. A sheet of Home Depot 1/8" Lauan ply is about $15 with no shipping. For my kind of airplane you'd be talking about maybe $200 difference in the cost of the airplane. That' a no brainer, go with aircraft ply.

If it cost me $600 or $800 and 3 months of hassle and red tape to ship in proper aircraft ply, I'd be redesigning the airplane to use what was locally available.

Keeping in mind, for the first half of modern aviation history there was no such thing as "certified aircraft plywood". A lot of great airplanes were built before they ever wrote ANC-18.
 

davidb

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Vacaville, CA
"Furniture grade" plywood only indicates that it looks pretty on one or both faces. The core can be anything from MDF to some brash inferior wood. The pretty surface veneer is often paper-thin and the core plies have poor mechanical properties. It's not water-proof and certainly won't survive a boil test. That's not to say there isn't some plywood available (short of aircraft or marine grade) that would prove suitable after close examination and testing. Some Baltic birch plywood manufactured in Russia has fairly consistent quality with all plies made of void-free birch and it is somewhat moisture resistant.

I wonder what is readily available in India. Do they have marine grade plywood?

Are you familiar with this company? welcome to The Western India Plywoods. Ltd (Depots and Agents)

Seems they manufacture marine and aircraft grade plywood in India?
 
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ultralajt

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If middle ply of the plywood is discontinued (a small gap..air only) and you dont know it is there, the structural member made of that part of your plywood will certainly fail at this "invisible" gap at very lower load than expected.

So in the past plywood was observed in the dark using a box where a very strong light bulb was installed. Sliding plywood over that light box will reveal inside structure of the plywood...such as gaps voids, resin pockets, knots... All these lower the strength of the plywood.

When these areas are found, mar ktme by pencil and avoid these areas when making parts.

But it is always better to use aircraft or marine grade plywood as one already select best material for you in the making.
 

Abraham Leket

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Try to imagine yourself at 3000 feet when the vertical web ply that holds your main spar straight under pressure -is acting up..
Get the real thing at Spruce Aircraft or Wicks- and save your life-its only $800-$1000 bill of material.
 

Turd Ferguson

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Is it possible to build a structurally sound airframe from furniture grade plywood.

The "grade" should be based on appropriate type veneer, appropriate number of piles, appropriate orientation, appropriate type glue. While plywood for building a plane may meet the grade for building furniture, plywood for building furniture may not be appropriate for an airplane. Has to be evaluated based on what it is, not what it's for. Have seen plenty of "aircraft grade" plywood I wouldn't trust past a static model. Just because it comes from Wicks or Spruce is no guarantee either.
 

ultralajt

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Some years ago I purchase set of 3 and 2 seat chaise. After some use, internal structure starts to fell appart. Unfortunately I realize that item was made in China and sold by Harvey Norman too late. I open the chair and found 12mm thick "plywood" that was in stage of "delaminating.."
A "plywood" was made of outer plies similar as white poplar, but inside plys were made with some stuff similar to paper!!!

I replace all damaged wood with PROPER plywood and now the furniture will last soem years more.

I was very surpriset what sh*tty material was used for the basic structure, that must carry some brackets screwed on. Screws were just fell out as there was almost noething firm to grab on.

So, I am doubt in quality of the furniture grade plywood since then, specially if came eastern of my country.

I believe in Finnish birch plywood, and a little less on mahagony marine...
 

WonderousMountain

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Before aircraft ply was defined and standardised, furniture grade lumber was used. This was partly a misnomer because the early pioneers would instruct the furniture manufacturer what they needed often.

Cabinet grade is better, but be aware marine uses more hydrophobic glues, and treats wood different.

I understand north and south India is not the same.
Delamination is probably the big danger, so look into glue as much as wood, and do not seal in any cavity, moisture will get in.

LuPi
 

JamesG

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Well... Not really. It can be difficult to decern the differences between various alloys of aluminum without complicated tests. The old saying of "you get what you pay for" is (sadly) especially true in aircraft. Aerospace suppliers get to charge their premium because they are supposed to verify and assure the quality of the materials they provide (and assume the liability there of). When you source your materials from "lesser" suppliers, then you take on the responsibility of doing your own quality control.
 

Lucrum

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Canton, GA
Hi everyone,

I had a question about plywood construction:
Is it possible to build a structurally sound airframe from furniture grade plywood.
(by that, i mean non-marine, non-aircraft grade plywood you can access in any carpenter or furniture store.)
Has anyone built a functional light airplane/glider using this material?
What would be the tradeoffs with regards to weight and strength.
These are the specs I had in mind:
Size and weight in the same class as the Volksplane or Flybaby or Legal Eagle.
never exceed speed: 100 kts
It's doable but not really advisable. Reminds me of an experimental built from Home Depot supplies. The wing separated 1st time the plane was loaded to 1.3G. There is a youtube video on it I think.
Is it also possible to use aluminum for spar material and wood for the ribs at the same time?
Please forgive me if these are stupid questions.
As I understand it the biggest issues with using such different materials in a structure is attaching them to each other. Different rates of expansion and contraction with temp changes.
And the materials having different physical properties, making proper design more complicated.
 

dcstrng

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In a pinch I might try genuine marine grade (like aviation grade there is a schedule of glues, veneers, allowable "patches" etc) since it is a known quantity (typically slightly heavier strength for strength as marine doesn't always use the lightest), but furniture grade, exterior, construction grade, etc, have deteriorated into mostly marketing terms these days ... and not terribly confidence inspiring as what means one thing from one supplier may or may not mean the same from the wood-peddlers down the street...

I've tried box-store construction grade ply in marine applications, but usually go up a thickness or two... wouldn't consider it in any aircraft I planned to put my family in...
 

rbrochey

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It's worth the money to get the right wood. Really, don't scrimp on safety to save a few bucks. I do a fair amount of building in wood and lately supposed really high grade plywood is more like some GMO product... plywood off the shelf behaves more like waffer board. When in doubt, don't. :)
 

Vipor_GG

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There is the Home Depot plane. Will it fly? I've never seen it off the ground. Would I fly it? Not on a bet!
[video=youtube_share;1Q-8TilAluQ]http://youtu.be/1Q-8TilAluQ[/video]
 

JamesG

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I'd like to see THIS HD Special fly. (advance to 2:00 to see it, or watch to get a sense of the context of the builder).

[video=youtube_share;1V8quR2P7lw]http://youtu.be/1V8quR2P7lw[/video]
 

hopeless_dreamer

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Feb 11, 2013
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Delhi, India
Based on the responses i have seen, it seems getting reasonable quality wood is getting harder and harder even in the states. doing it on this side of the puddle is going to be virtually impossible, given how much even inferior quality wood costs over here.
 
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