Help with UL design, need plywood

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skyguynca

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Lots of people building ul and exp planes have used exterior grade luan door skins in place of 1/8 aircraft birch ply.

Does anyone know where to find these? Lots of posts say lowes, homedept or wood supply places...I can only find interior, not water proof.

Help?

David
 

Richard MacCrone

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I know this is an older post but thought I'd answer it as it may benefit someone else with the same idea. I have never seen Luan plywood that was built with waterproof glue. All I have ever used had voids and plugs everywhere, nowhere need the quality required for an aircraft. A fellow did build the Home Depot Special on a lark but after it's initial appearance it disappeared. If you are building an aircraft with wood the added expense of AC grade wood is money well spent.
 

Victor Bravo

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Sorry to pee in the pool here, but the computer nerds have a saying that is equally accurate for an airplane... "garbage in, garbage out".

Build an airplane with crap quality material, you will get a crap quality airplane that might hurt you.

I'm not saying Luan is crap, I'm sure that you can possibly design a safe structure using Luan. But poorly made Luan plywood with knots or bad glue or cracks or whatever is not something you can design around.

So I am guessing you can use 'aircraft quality Luan" if you design for it, and have a place where you can buy it. I doubt Lowe's is that place.
 

skyguynca

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Wow, I don't recall ever saying I would be using crap or garbage.
There is plenty of Luan AA/AB that contain no voids or knots with waterproof adhesive. I was asking for a better source.
Also Okoume plywood because if exterior grade is it cheaper and every bit as strong as mil spec plywood at half the cost.
Your right though, NO ONE SHOULD EVER FIND ALTERNATIVES.

Forget about receiving wood that is certified for use in an airplane. The only grading that occurs at the mill is done to meet Mil-Spec-6073 but in no way will they tell you that the wood is aircraft quality.

So VB, what factory built airplane do you fly because homebuilts are not certified parts, therefore not aircraft quality stamped approval.

Also let me clue you in, In AC-43 Acceptable Methods and Practices, it lists plenty of alternate materials that CAN be used that ARE NOT STAMPED "AIRCRAFT GRADE OR AIRCRAFT QUALITY". In fact that 2024-t3 and 6061-t that Cessna, Gruman and Piper use does not have a stamp like that anywhere on it or on its production paperwork, just an ASTM number verifying is process of production.....in fact you can order that through your local metal supplier without it ever going thru AC Spruce or the like.....Done it way too many times to save money.

Also before you start attacking with more home grown BS....I have been both military and civilian helicopter and fixed wing mechanic my entire life, since high school where I attend OT Autry Vocational Center in OK for A&P school, then on to Ft Rucker and Ft Eustis for military aviation schools for UH1H, UH-60 and CH47 to include sub shops ratings for turbine engine, prop and rotor and sheet metal. also added parachute rigger, also pilot.
I am not the smartest person in the world, but I know I don't want to die a painful scary death either.

So now if you would like to rephrase your response to take the superior tone out of it, and totally remove that garbage claim, we can talk.
 
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skyguynca

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You know VB, a better response should have been,

David try finding ANC-19 on the internet. It is an old military publication that talks about the proceedures for grading and building wood aircraft and how to inspect them. ? You should also try getting AC-43, it is an FAA publication that talks about that acceptable methods and practices used in the repair and modification of certified aircraft, it also contains chapters that discuss alternate materials for the substitution of mil spec plywood and spruce. Both are really informative and will help you in your selections of your materials in a safe manner......................

Yep, you never thought of that did you?
 

patrickrio

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Wow, I don't recall ever saying I would be using crap or garbage.
There is plenty of Luan AA/AB that contain no voids or knots with waterproof adhesive. I was asking for a better source.
Also Okoume plywood because if exterior grade is it cheaper and every bit as strong as mil spec plywood at half the cost.
Your right though, NO ONE SHOULD EVER FIND ALTERNATIVES.

So VB, what factory built airplane do you fly because homebuilts are not certified parts, therefore not aircraft quality stamped approval.

Also let me clue you in, In AC-43 Acceptable Methods and Practices, it lists plenty of alternate materials that CAN be used that ARE NOT STAMPED "AIRCRAFT GRADE OR AIRCRAFT QUALITY". In fact that 2024-t3 and 6061-t that Cessna, Gruman and Piper use does not have a stamp like that anywhere on it or on its production paperwork, just an ASTM number verifying is process of production.....in fact you can order that through your local metal supplier without it ever going thru AC Spruce or the like.....Done it way too many times to save money.

Also before you start attacking with more home grown BS....I have been both military and civilian helicopter and fixed wing mechanic my entire life, since high school where I attend OT Autry Vocational Center in OK for A&P school, then on to Ft Rucker and Ft Eustis for military aviation schools for UH1H, UH-60 and CH47 to include sub shops ratings for turbine engine, prop and rotor and sheet metal. also added parachute rigger, also pilot.
I am not the smartest person in the world, but I know I don't want to die a painful scary death either.

So now if you would like to rephrase your response to take the superior tone out of it, and totally remove that garbage claim, we can talk.
Hey SkyGuyNCA,
Victor Bravo is sometimes the resident Comedian, and as you spend time here you will see his humor better and laugh with everyone else.

I can tell you for sure that nothing was written to offend you (at least not you specifically!!).

His comment on the appropriateness of Luan sheets from Lowes is likely in the area of accurate. Reputable contractors often find the material quality found at Lowes or HD wanting. Wood used in airplanes usually needs to be several quality grades better still.

when you build an aircraft from wood, you are usually counting on using wood substantially nearer it's structural limits than you would in home construction. As a result, Glue defects, knots (and knot splices), voids etc. are much less acceptable for airplane construction purposes. Wood grain direction and thickness is also very important in airplanes and not so important for homes.

You MIGHT find good wood materials for airplanes at Lowes or HD, but you will likely sort through stacks of materials to do so. You also should REALLY know your wood if doing this type of searching/sorting... a mistake can actually be fatal.

A better choice for most people with less wood evaluation skill is to buy from a source that consistently supplies suitable wood materials. It costs more but takes less skill on your part.
 
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TFF

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I think without backstory sometimes it sounds like a prank with odd requests.

I think I have what you are really trying to find. No you will not find Luan you can build an airplane from home depot, you know that. If anyone on the internet says they did, don’t stand under their plane when they fly over. Now if they used Lauan plywood, that makes a difference. Lauan the non junk version of Luan, can be bought as marine plywood. Normally we see it called Meranti.
 

patrickrio

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Oh, Also there is an overall swift and severe response to anyone who suggests doing something that sounds like it might result in a dangerous airplane.

NOBODY wants information written here to influence others to make dangerous choices so the first response is likely to be very short and fast when you suggest something that might be dangerous. Their first concern will often not be politeness.
 
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Richard MacCrone

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You know VB, a better response should have been,

David try finding ANC-19 on the internet. It is an old military publication that talks about the proceedures for grading and building wood aircraft and how to inspect them. ? You should also try getting AC-43, it is an FAA publication that talks about that acceptable methods and practices used in the repair and modification of certified aircraft, it also contains chapters that discuss alternate materials for the substitution of mil spec plywood and spruce. Both are really informative and will help you in your selections of your materials in a safe manner......................

Yep, you never thought of that did you?

Wow, lets all step back a bit. VB did not attack you but did state a valid point. Your initial post specifically mentioned Luan door skins. I have NEVER seen Luan door skins that would pass a boil test. I too have experience, PP license in 1969, A&P in 1979 (did time is SE Asia in between), Master Parachutist (D-19258), Senior Rigger, and Electrical Engineer. You can build anything you want out of anything you want, it's your call. It is after all experimental aviation. Don't fool yourself though, there is no grade of luan plywood that is anywhere near the quality of birch, mahogany, meranti or Okoume plywood (given the same dimensions). BTW, I never said anything about "stamped" wood. I said aircraft grade, although they are not mutually exclusive. Take care skyguynac, and lighten up a little
 

skyguynca

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I think without backstory sometimes it sounds like a prank with odd requests.

I think I have what you are really trying to find. No you will not find Luan you can build an airplane from home depot, you know that. If anyone on the internet says they did, don’t stand under their plane when they fly over. Now if they used Lauan plywood, that makes a difference. Lauan the non junk version of Luan, can be bought as marine plywood. Normally we see it called Meranti.
yep, both names are used it meets BS1088
 

Victor Bravo

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I can't vouch for anyone else's airplane, but the old 172 I currently fly definitely has mill stamps on the aluminum. And on the "master data list" which the TCDS is based on. I believe all of the factory production airplanes have mill stamps, but there are many far more experienced repairmen and inspectors here who would know that better than me.

For the record, I am no stranger at all to the "aircraft parts aisle" at Lowe's and Home Depot. 4 of the experimentals I've had used a combination of un-certified stuff and certified stuff. The other 4 were factory built overseas and used stuff that was certified in their country of origin.

My intent was to say that if you use door skin wood from a door skin store, the odds are that most responsible builders would not consider them wing skins. I stand by that thought. On the other hand, Lexan and Plexiglas sheets from the door skin store have been used by me on windshields and windows with absolute confidence. Same with some of the glue I bought at Home Depot. I've even used plenty of pop rivets, screws, and other "crap" stuff from those stores, because I was matching the quality of the fastener/hardware with the specific use on the aircraft. All aluminum cheap pop rivets to hold silicone baffling strip in place... no problem. Same rivets on a sheet metal repair... no.

I have never said that nobody should find alternatives. I've found alternatives to a lot of things in aviation, including an FAA approved "Alternate Means of Compliance" for a flight safety AD on antique airplanes.

Thank you for signing up and being willing to walk into harm's way in the military. People like you gave me my freedom to spout off homegrown BS. I'm in your debt.
 

skyguynca

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NOPE, no American is ever in my debt, My service was a labor of love for my home and my extended family. After serving all over this planet, being in 39 different countries, this is by far the best. No matter who many people try to tear it down.

As far as you speaking your home grown BS, that is every man's and woman's right given by god and can never be taken away.

I never said mill stamp I said "aircraft quality" stamp. I did say they were stamped with the ASTM which would be the ASTM number like B233 which would mean extruded, I forget what drawn is right now, and then the batch number and the type like 6061t3 or maybe 6061t4 or even 2024t3 etc.
 
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TLAR

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David
Would you be willing to share a little information about the ultralight you are designing?
Maybe I have made an incorrect assumption, but I am interested in any design cooked up by a welder and machinist!!
I am just a lowlife 11Bulletstopper with a chute on my back and a rucksack hanging out front hoping no other grunt steals my air by going under me, you can’t see it coming at night 😂
 

skyguynca

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Been there done that.

no one who serves is a low life. honor go with all who sacrifice. 11BangBangs are always out front.

I have built several planes, a few gyrocopters and a helicopter....anything I come up with is with years of experience and from other aircraft. It is really hard to come up with something new in this day and age.......believe it or not most of the current ideas are just rehashes of the great minds of the 1950's and 60's. Those guys were absolute geniuses.
 

wktaylor

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The guys of the 1950s and 1960s were WWII and Korean war era aircraft designers-builders under pressure of war-time to git-er-done. Lessons were learned the hard way... but then most of aviation was still in relative infancy with lots of learning to do.

Often the 'grand wartime achievements' came a price of build-fly-test-field... and a then do a lot of 'aw-****' mods and new-models... to 'clean-up messes' in the hundreds of major and minor mechanical-structural-weaponry-operational problem areas... each system.

As a USAF general stated recently about [high-tech] R&D in this new era of rapidly technology and emerging-threats... and [backward descriptive] applicable to WWII & Korea era aviation developments... "...we are building the bicycle as we're riding it."
 
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