Wooden aircraft and crash safety

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Dan Thomas

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Yes, most lumber found in lumber yards is fast growth intended for general framing.
Not in western Canada. A bit still comes from old-growth forests, most now from forests that were burned a century or two ago. All-natural wood, no plantation stuff. Not fast-growth, so the rings are tighter. But so much of it is small trees, maybe only five or six inches in diameter, and they're run through a machine that, in one pass, makes a couple of 2 X 4s from it, hence the bark on two corners sometimes. The waste is chips for the pulp mills. Lumber like that has its grain in a tight radius; try making anything useful from it, especially with all the knots along its entire length.

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A stack of 2 x 4s. Look at that mess of grains. Very few with any edge grain, almost none with the requisite 8 grains per inch. Small-radius curved grain, indicating that the source is small trees. Knots in evidence, plenty of checking as well. Too much heartwood. If we pulled out the nicest piece, what would the faces look like? Knots? Yup. sloped grain, outside the max slope of one in 15? Yup. I wouldn't get into any airplane built with any of this stuff, any more than I would get into an airplane built with 5052 aluminum instead of the specified 2024 and 6061. Or a tube-and rag airplane built with electrical conduit instead of 4130 tube.

"Natural-growth wood" reminds me of a funny story. A gas station operator in BC had bundles of firewood for sale at his station. All split ready for the campfire, with some kindling bundled with it. It sold to the tourists for $7.95 per bundle. When he went to the supermarket to get groceries, he saw all this "organic" food, grown without chemicals. All-natural. Much more expensive than the fertilized and pesticized stuff. So he went back to his station and made a separate pile of firewood bundles, labelled them as organic firewood, since it all had come from natural-growth forests anyway, and asked $11.95 per bundle for it. Couldn't keep up with the sales on it, with uninformed city people eagerly buying it up for their "natural" campfires.
 
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wren460

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I could post images of DF furring strips I've selected from home depot with grain much closer than aircraft grade spruce and grain slope that meets the criteria but there would be no point.
 

TFF

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It all depends on location. I just bought 350 spruce 2x4s for walls for my house. I have touched each one myself. One was the unicorn and close. I have four others that I set aside for sections. That’s it out of $3500 of wood. Some of the pine 2x8-10-12 are pretty nice. Not airplane wood but not junk. Some of it was cut during the sap season. They are heavy.

Picture of the unicorn board.
 

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Dan Thomas

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It all depends on location. I just bought 350 spruce 2x4s for walls for my house. I have touched each one myself. One was the unicorn and close. I have four others that I set aside for sections. That’s it out of $3500 of wood. Some of the pine 2x8-10-12 are pretty nice. Not airplane wood but not junk. Some of it was cut during the sap season. They are heavy.

Picture of the unicorn board.
The larger boards (2x8, 2x10, etc.) come from larger trees. Larger trees are taller, and have no branches in their lower lengths. In the forest, it's dark under the tree canopy, so the trees don't bother growing branches down there, since the needles wouldn't be productive.

Edit: No branches means no knots.

Nearly 40 years ago my Dad called me from the lumberyard. Said he had a new lift of 8' 2x8s that looked really good. I rushed over and bought a bunch of them. Most of the ones I picked were clear, close- and straight-grained, some with edge grain. All spruce, likely Englemann rather than Sitka, but equal in strength. Very unusual to find wood like that in a pile of construction lumber. I was building a wooden airplane at the time. These would have been useful for crosspieces and wing ribs, shorter stuff.

But then our son was born and Mom stayed home to look after him, and expensive projects got put on hold. That nice wood was turned into toys for the boy. Dandy toys.
 
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Dan Thomas

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I could post images of DF furring strips I've selected from home depot with grain much closer than aircraft grade spruce and grain slope that meets the criteria but there would be no point.
There would be the point of proving to us that such lumber exists in lumberyards. Please post a picture.
 
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Pops

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When I built my first house in 1970 I hand picked the lumber. All the wood at that time can't be found at any box store today. The walls and roof was sheeted with 1"x12"x 16' with zero knots. 16 cents a board foot.
 
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TFF

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The forest industry around here is all fast growth pine now. My wife’s relatives on the other side of the state are all in that line of work. Unless you order something specific, houses are built with local wood. Most people think they see an old forest from the roads because all they see is trees. Most of them are from the 50s at latest. They stripped all the Cypress on the Tennessee Kentucky border by 1900, some of those threes looked like redwood forest trees that they cut down. We pretty much live in the aftermath of the strip harvesting. Anything good is because they missed it the first time. I bought my big orders from a place that specializes in builders. I have filled in with the box stores. I’m paying about 20% more than HD. The wood is better quality and I haven’t had to reject a dozen of the stud’s. That’s what I payed for. 20% better, I don’t know. I am an amateur so I need help I can get.
 

speedracer

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One Sky Dog, what you described is exactly true for something like a Mignet Pou-du-Ciel. In that case, it can be a benefit in that it provides a way steepen the glide path on demand in a plane that cannot slip or spin. It does mean the pilot must learn *not* to land with full back stick and instead push forward to a less extreme angle to avoid a hard landing. That inability to control the glide path is something that David Thurston highlights as a pitfall of two-axis designs like the Ercoupe in his book Design for Safety. I suspect that the EZ is set up so that it never goes down the drag bucket, but that's why it needs the belly air brake and, IIRC, the ability to splay the rudders out as well for additional air brake function.
Long EZ's slip just fine, but even slipping and with the speedbrake (landing brake, belly brake) down it still glides better than most cleaned up spam cans. Unless it's really windy and gusty all my landings are at idle starting abeam the numbers on downwind. Great dead stick landing practice. Back to wooden airplanes: A couple decades ago I had the hots to build a wood airplane (I have a cabinet shop). I dropped two 20" diameter hem fir trees, cut off the (branchless) butts at 16' and used a come a long to haul them into my pickup pulling from the lumber rack. I took them to a mom and pop sawmill and had them cut up. It broke my heart to see that all the lumber had small knots. I believe they'd still be OK to use with composite reinforcement. I still have that lumber and I'm still thinking about doing it after the third EZ (not for me) is out of my shop. And BTW, I cut up the rest of those trees for shop firewood.
 

don january

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With my all wood Taylor-monoplane the ability to survive a crash is a very big concern for me because the fact it's a all wood plane. I started by addressing the roll over problem at low speed with the vertical stabilizer and roll over protection at seat back. But lets face it guys not all emergency's end in that format. What will make it more survivable in a stall spin at 100 AGL and 65 mph ? As a rule the engine will hit first or a wing tip and a cartwheel is induced. If your lucky enough to get the plane level before impact and your in a off field situation most the time your gear will cause a flip onto your back but if not like my fathers crash in a Piper Pawnee the gear folded up and his seat bent down the lower longarons and broke his back and no wood in that plane. So I ask myself would it have been better if the gear self sheared on impact and took out some of the energy? As bizarre as it may sound I would like to have the bottom of my wing just a couple inches from the ground and have the wing bottom take the impact in a crash but the thinkers haven't came up with a working gear to address the flip over problem on either a low wing or high wing to stop those dreaded flip over incidences. My old man asked me once if I had a power failure over water in a biplane would I fly it level to impact or would I invert the plane and take impact that way?? So rather wood or metal plane I believe he was trying to take my mind out of the box of normal flight rules and expand my abilities for survival in a non normal way.
 

TFF

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Inverted water landing is not necessarily a bad idea if it’s going to flip. It would put you upright.
 

WonderousMountain

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So I ask myself would it have been better if the gear self sheared on impact and took out some of the energy? As bizarre as it may sound I would like to have the bottom of my wing just a couple inches from the ground and have the wing bottom take the impact in a crash but the thinkers haven't came up with a working gear to address the flip over problem on either a low wing or high wing to stop those dreaded flip over incidences.
Yes,
I agree with this line of reasoning, retracts & landing skids will be a last ditch solution, not knowing your wing attachment, I'm not sure if inches lift is a pragmatic thing.
 

don january

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Yes,
I agree with this line of reasoning, retracts & landing skids will be a last ditch solution, not knowing your wing attachment, I'm not sure if inches lift is a pragmatic thing.
Taylor-mono has been built with retracts and a skid in retracted position would/could be a a life saver in a off field landing.TAYLOR MONO #1.jpg even a permanent skid under belly would be doable tho you may lose a prop.
 

Ava

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Junior, ask for more $$$. One of the Grand Canyon Airlines airplanes (5-AT-74) is (or was recently) for sale... $1,400,000.00

tri-motor.jpg
I bought a copy of this off eBay. Oh... my... God! It's about the greatest book ever. In 120 pages it basically assumes that you are some rich person who had a spare $100,000 lying around in 1929 and thought aviation was the next "big thing" even though you knew nothing about it. Step-by-step it explains how to select a piece of ground and build a well drained grass aerodrome; how to organize an airline; how to assemble a Ford Tri-motor from the shipping crates it would be delivered in-- one per major assembly; what tools you will need to assemble and maintain it; how to rig the airplane; how to hire employees; how to fly the airplane; and how to inspect and maintain it. Because some rich person could actually do all that with $100,000 in 1929-- of course back then middle-class people made $50- $150 a month and a Model T cost $260 (open-top flatbed farm truck) to $745 (four-door touring sedan).

Edit: The Stock Market Crash was pointed out to me-- but publication of this book preceded October 29, 1929, known as Black Tuesday.

 
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Dan Thomas

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Belly skids and the like assume that you'll always have a nice smooth field to land in. How often is that true? Maybe if you live in an area where there is nothing but hayfields. There are crops that are dense enough to flip your airplane. Canola is a tangled mess that will definitely flip you. Logging clearcuts are horrible: infested with stumps. Some open areas are choked with rocks. Other areas are covered with trees. Mountainous areas are mostly vertical real estate.

You'd be better off with a ballistic parachute, except that at low altitude like takeoff and landing, they're useless.

Pilot training, proper maintenance, and careful construction go MUCH farther to reduce accidents than any crashworthiness efforts. Read the accident reports sometimes, and see why they happen. It's educational. With homebuilt airplanes themselves, it seems to be systems failures (fuel supply, venting, or something like that). Some of the accidents are due to a low-time pilot, or a rusty pilot, trying to fly an airplane that's beyond his skills. With any airplane, a VFR pilot flying into IMC is a common way to die. And carb ice gets a lot of inadequately-trained people. They don't know enough about it. Then there are the loss-of-control factors, one of the biggest of all. Getting too slow in the circuit, or low flying, or showing off, or complacency during critical phases of flight like takeoff and landing.
 

Pops

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Belly skids and the like assume that you'll always have a nice smooth field to land in. How often is that true? Maybe if you live in an area where there is nothing but hayfields. There are crops that are dense enough to flip your airplane. Canola is a tangled mess that will definitely flip you. Logging clearcuts are horrible: infested with stumps. Some open areas are choked with rocks. Other areas are covered with trees. Mountainous areas are mostly vertical real estate.

You'd be better off with a ballistic parachute, except that at low altitude like takeoff and landing, they're useless.

Pilot training, proper maintenance, and careful construction go MUCH farther to reduce accidents than any crashworthiness efforts. Read the accident reports sometimes, and see why they happen. It's educational. With homebuilt airplanes themselves, it seems to be systems failures (fuel supply, venting, or something like that). Some of the accidents are due to a low-time pilot, or a rusty pilot, trying to fly an airplane that's beyond his skills. With any airplane, a VFR pilot flying into IMC is a common way to die. And carb ice gets a lot of inadequately-trained people. They don't know enough about it. Then there are the loss-of-control factors, one of the biggest of all. Getting too slow in the circuit, or low flying, or showing off, or complacency during critical phases of flight like takeoff and landing.
If WV was spread out flat, it would be bigger than TX. :)
 
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