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Thread: Relative safety of various construction materials

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    Relative safety of various construction materials

    Hello,
    I am looking at building a new kit, and considering my options there is one piece of information I would love to have, but don't find readily available. Wood is my preferred material to work with, since I have a very complete shop. In the event of an accident, or forced landing, how does it compare to aluminum or cloth and tube? Are there any definitive studies, or at least compelling anecdotal and engineering evidence?

    Thanks in advance for the help,
    Ward

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    Re: Relative safety of various construction materials

    Aluminum airplanes don't do well in some crashes, true. An engine out crash causing damage has more to do with math than it does material. A wood Pietenpol is a "low and slow" type airplane so it just barely kills you in a crash. Lol. A engine out over a plowed field with a stall speed of a 100 mph can be a nightmare regardless of material used. Physics.

    I feel tube and fabric is the strongest but wood is a amazing material as well.

    I'm not sure of any documentation of material characteristics because there's a ton of variables to consider. If you Google a design and accident and click images you can see the aftermath.

    Of course, the goal is not to crash, learn to fly and be prepared at all times. If you like wood I think you'll discover it's a great material in which to build a airplane.
    Last edited by Little Scrapper; January 6th, 2017 at 08:44 AM.

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    Re: Relative safety of various construction materials

    Quote Originally Posted by wardo View Post
    ... Wood is my preferred material to work with, since I have a very complete shop. In the event of an accident, or forced landing, how does it compare to aluminum or cloth and tube...
    Regardless of construction materials employed, the entire objective is to maintain deceleration of the delecate pink bodies inside at a survivable rate. If the entire airframe is crumpled like a beer can and consumed in the crash event but allows the people to live, thats far better than a hell for strong structure that survives intact, but forces the occupants to withstand deceleration in isolation.

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    Re: Relative safety of various construction materials

    It is going to be dependent of design, but they are going to be close to the same. Lots goes into thinking about crashing but planes are really designed to keep flying not crashing. That is the first protection of crashing. Nothing wrong with wood.

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    Re: Relative safety of various construction materials

    My view on which material set to build in is all wrapped around materials you can communicate in and like to work in. Building an airplane is a huge thing, and if you do not love it, you will never fly it.

    Safety is largely a matter of flying the airplane well, making good decisions, using good judgement. If awful things result in a forced landing, be proficient in landing under control and at minimum speed.

    That being said, I think that if you select an airplane with a good safety record and without major issues, build it to the plans, and then get fully proficient in flying before you start flying it, you will have seriously stacked the deck in your favor.

    Billski

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    Re: Relative safety of various construction materials

    Quote Originally Posted by wardo View Post
    In the event of an accident, or forced landing, how does it compare to aluminum or cloth and tube? Are there any definitive studies, or at least compelling anecdotal and engineering evidence?
    Without regard to construction materials, installing basic safety equipment to properly restrain and support the pilot's torso when subjected to deceleration forces will give the best opportunity in an accident. I would not at all be concerned with wood as a building material.
    “The only difference between reality and fiction is that fiction needs to be credible.” - Mark Twain

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    Re: Relative safety of various construction materials

    Quote Originally Posted by wardo View Post
    Are there any definitive studies, or at least compelling anecdotal and engineering evidence?
    Some thoughts elated to your question can be found here: https://flycorvair.net/2012/11/17/st...mph-accidents/
    ​simplify.

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    Re: Relative safety of various construction materials

    Since the early days of aviation it was known that wood sticks can snap and impale the pilot. They tried wrapping the longerons with fabric, which helps a bit. The real solution was plywood sheathing in the cockpit, pioneered by Dehaviland.
    Metal yields (bends and absorbs energy) which is ideal in a crash. But wood and composites can be engineered for crush loads.

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    Re: Relative safety of various construction materials

    Don't crash, Had a friend with a Lohl 5151 and he crashed it twice (three if you count a ground loop after a rudder cable snapped), last one all he got was a bruised butt and it was close to destroyed , damn if he didn't rebuilt it as a razorback looks better too. aluminum and wood disposal can heat a camp fire or buy beer and pizza after your done, plastics tend to require special handling to get rid of....No mater what material you pick I bet it will fly just fine.

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    Re: Relative safety of various construction materials

    Quote Originally Posted by BBerson View Post
    Since the early days of aviation it was known that wood sticks can snap and impale the pilot. They tried wrapping the longerons with fabric, which helps a bit. The real solution was plywood sheathing in the cockpit, pioneered by Dehaviland.
    Excellent point !

    You could possibly use Kevlar thread to wrap the longerons and cross members in an "open frame" design, and the Kevlar would prevent the sticks from snapping. The Kevlar thread weighs almost nothing, and is fairly inexpensive too.

    However, if there are plywood sheet structural materials that are glued to the sticks as part of the design, the Kevlar thread could interfere with proper bonding between the sticks and the plywood. You'd have to have somebody look into that before you put that thread in as part of the glue joint. May be a deal-breaker.

    A layer of thin Kevlar cloth on the inside of the structure would surely add a lot of crash safety, but this has far more weight, cost, and complexity than wrapping sticks.
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    Re: Relative safety of various construction materials

    Any construction material can be made "relatively safe" in a crash. Design for crashworthiness is more about design and much less about materials.

    Quote Originally Posted by BBerson View Post
    Since the early days of aviation it was known that wood sticks can snap and impale the pilot. ...
    If cockpit structure is being deformed to the point of failure, there are much larger crashworthiness issues with the design than what material was chosen. The cockpit should provide a "secure cage" capable of withstanding the design crash loads without significant deformation. Otherwise, all the other crashworthiness measures are for naught.

    Quote Originally Posted by Turd Ferguson View Post
    Without regard to construction materials, installing basic safety equipment to properly restrain and support the pilot's torso when subjected to deceleration forces will give the best opportunity in an accident. I would not at all be concerned with wood as a building material.
    Yes. Also, keeping the pilot's extremities (including the head) from flailing into hard or sharp features in the cockpit. Either put the stuff out of "flail range" (there are actual numbers for this, with the usual percentile ranges for pilot size) and/or make sure everything within that range is either soft, padded, and/or given rounded corners or edges.

    Quote Originally Posted by wsimpso1 View Post
    My view on which material set to build in is all wrapped around materials you can communicate in and like to work in. Building an airplane is a huge thing, and if you do not love it, you will never fly it.

    Safety is largely a matter of flying the airplane well, making good decisions, using good judgement. If awful things result in a forced landing, be proficient in landing under control and at minimum speed.

    That being said, I think that if you select an airplane with a good safety record and without major issues, build it to the plans, and then get fully proficient in flying before you start flying it, you will have seriously stacked the deck in your favor.

    Billski
    This is the best route. Established designs with a big enough history can be seen to have good or poor crashworthiness characteristics. Choose the airplane, not the material, build in a material you enjoy, and stick to the plans. Best way to "come out good" in the end.


    The best reference on general-aviation crashworthiness design that I've found is here: http://www.niar.wichita.edu/agate/Do...034043-036.pdf
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    Re: Relative safety of various construction materials

    All planes in similar categories with the lowest injuries/fatalities are composite airframes...for good reason.

    High-end racing... same reason.

    A bad airframe design will make a far bigger difference though.
    Last edited by autoreply; January 6th, 2017 at 02:45 PM.
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    Re: Relative safety of various construction materials

    Thanks everyone for all the input. It was most helpful. Of course not crashing should always be your first line of defense, but I like to consider the planned and unplanned outcomes. I owned and flew an RV-4 for a few years, and the unexpected never showed up. The years I spent racing a rally car are another story....

    Ward

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    Re: Relative safety of various construction materials

    Quote Originally Posted by mcrae0104 View Post
    Some thoughts elated to your question can be found here: https://flycorvair.net/2012/11/17/st...mph-accidents/
    That link directly addresses a number of relevant issues. I am also an Embry-Riddle grad, so I guess I should give the author extra points for that as well.

    Thanks,
    Ward

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    Re: Relative safety of various construction materials

    The link looks very promising, but it is going to take me a few minutes to wade through the 414 pages!

    Thanks,
    Ward

    Quote Originally Posted by Topaz View Post
    Any construction material can be made "relatively safe" in a crash. Design for crashworthiness is more about design and much less about materials.



    If cockpit structure is being deformed to the point of failure, there are much larger crashworthiness issues with the design than what material was chosen. The cockpit should provide a "secure cage" capable of withstanding the design crash loads without significant deformation. Otherwise, all the other crashworthiness measures are for naught.



    Yes. Also, keeping the pilot's extremities (including the head) from flailing into hard or sharp features in the cockpit. Either put the stuff out of "flail range" (there are actual numbers for this, with the usual percentile ranges for pilot size) and/or make sure everything within that range is either soft, padded, and/or given rounded corners or edges.



    This is the best route. Established designs with a big enough history can be seen to have good or poor crashworthiness characteristics. Choose the airplane, not the material, build in a material you enjoy, and stick to the plans. Best way to "come out good" in the end.


    The best reference on general-aviation crashworthiness design that I've found is here: http://www.niar.wichita.edu/agate/Do...034043-036.pdf

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