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Thread: Relative safety of various construction materials

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    Re: Relative safety of various construction materials

    Hi Ward. What airplane are you considering?

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    Re: Relative safety of various construction materials

    Quote Originally Posted by Little Scrapper View Post
    Hi Ward. What airplane are you considering?
    It all kind of depends on what happens with my medical, which I lost 18 years ago on a technicality. I am working on getting it straightened out, which if that happens I am looking to transition to an LSA license. If not, maybe an Belite ultralite or glider, my understanding is that it is really hard to get wood to fit within the ultralight weight limits. On the two place front, I have looked at a few different things, but the Fisher line and the new Mini-Max Epic hold interest. After reading the links others have provided, I am wondering what is available with a steel tube fuse and wooden wings and tail feathers.

    Thanks,
    Ward

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    Re: Relative safety of various construction materials

    Quote Originally Posted by autoreply View Post
    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.
    Composite is probably the one material I am not interested in working with. I've done a good bit on scratch built R/C gliders, and don't really enjoy the work and the amount of waste generated really bugged me.

    Thanks,
    Ward

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    Re: Relative safety of various construction materials

    I build and teach building of acoustic guitars so naturally I'm drawn to the wood aircraft designs... composite anything looks too slippery to me. For myself I look at performance, low and slow being my preference. Low (25 to 30 mph stall) and nice glide ratio. But in an ultralight I prefer the combination of would and steel like the Legal Eagle. But don't forget the smile factor... almost nothing brings one to my face like opening my Pietenpol plans for the Sky Scout... or the seemingly vast array of Flying Fleas... just my 2 cents..

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    Re: Relative safety of various construction materials

    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.
    Yup, sure is.

    My beast is light aluminium, but tied at all corners and relevant places with steel to stop it tearing apart and spread the loads, and a strong steel roll cage. Weight is not the enemy when things go wrong, just a few pounds can make a huge difference to survival.

    I'm currently hoping to get it into a car manufacturer's high end crash software to see what it does.


    Quote Originally Posted by Topaz View Post


    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.
    Yup.

    This video has slow-mo of what is a slow impact, yet see how far and the directions they travel from the forces (cuts and bruised but otherwise ok by the way), people should take this very seriously ...

    Quote Originally Posted by BoKu View Post
    The vast majority of engineering failures are the results of failure of imagination rather than failure of calculation.

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    Re: Relative safety of various construction materials

    Quote Originally Posted by wardo View Post
    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
    Safety in the event of an accident is a factor of design. First, I would strongly recommend ignoring advice which seems to believe that accidents only happen because of some form of mental deficiency. Making sure that you build, operate, and maintain an aircraft safely is always a good idea, but it this will not eliminate the possibility of mechanical failure (you may be relying on a 12 year old kid working a 16 hour day having put that piece into the carburetor properly) is never non-zero, and the possibility of somebody else making a mistake and causing you to crash is also non-zero. And, of course, nobody is at 100% all of the time.


    What you need to do is to have a strong enclosure around you and your passengers, structure designed to have the distance and structural properties to keep accelerations in the survivable range. This can be done with wood, metal, or composite structures, but has to be done during the design phase; it is very difficult to impossible to tack it on after the fact. Do a search similar to "crashworthy design of general aviation aircraft" on NTRS and Google, then find a good library, with an EBSCO subscription, and then see how various designs compare to crashworthiness guidelines.
    Last edited by Swampyankee; January 7th, 2017 at 12:56 PM.

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    Registered User cheapracer's Avatar
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    Re: Relative safety of various construction materials

    Quote Originally Posted by Swampyankee View Post
    , I would strongly recommend ignoring advise which seems to believe that accidents only happen because of some form of mental deficiency. .
    Exactly.

    An "accident" is an unforeseen and unexpected event and it doesn't matter how much maintenance you have applied, and how well trained you are, no one is immune from it.
    Quote Originally Posted by BoKu View Post
    The vast majority of engineering failures are the results of failure of imagination rather than failure of calculation.

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    Re: Relative safety of various construction materials

    Quote Originally Posted by wardo View Post
    It all kind of depends on what happens with my medical, which I lost 18 years ago on a technicality. I am working on getting it straightened out, which if that happens I am looking to transition to an LSA license. If not, maybe an Belite ultralite or glider, my understanding is that it is really hard to get wood to fit within the ultralight weight limits. On the two place front, I have looked at a few different things, but the Fisher line and the new Mini-Max Epic hold interest. After reading the links others have provided, I am wondering what is available with a steel tube fuse and wooden wings and tail feathers.

    Thanks,
    Ward
    I have over a hundred videos on YouTube showing step by step how to build a legal eagle fuselage. You are absolutely capable of building that, there's no doubt in my mind at all. You just need to decide that welding is a skill you will have fun learning. Who doesn't love to learn?

    I love the Pietenpol and the minimax line. The Fly Baby also holds a special place in my heart.

    If you were considering a true 2 place scratch built that's easy to fly efficient and can still.go cross country with the Sport Pilot cert I'd look at 2 airplanes.....

    1.) WagAero Wagabond. This is a replica of the Piper Vagabond. Not only are the plans great and it's simple but you truly have a budget airplane with a phenomenal track record. You can also buy parts if you don't want to build certain things.

    2.) Wittman Buttercup. The Buttercup is a delightful design by a legendary designer and racer..the plans are great as well.

    I sat in the Earl Luce replica and boy is it nice! Earl is a top notch guy.

    If you want to have fun with an ultralight I can't imagine a better idea than a Legal Eagle or a Minimax.

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    Re: Relative safety of various construction materials

    Quote Originally Posted by wardo View Post
    Composite is probably the one material I am not interested in working with. I've done a good bit on scratch built R/C gliders, and don't really enjoy the work and the amount of waste generated really bugged me.

    Thanks,
    Ward
    Then for you, composite will be the ultimate safe airframe. (Since you'll never finish the build if you don't enjoy it)


    Sounds like a cheap pun, but there's more to it. Other factors play a much bigger role in how likely you are to die or get serious injuries.

    Assuming decent flying characteristics, flaps-up stall speed shows by far the highest correlation to crash survivability, though when they get below the 40-50 kts range, the correlation drops of.

    Why flaps-up? Planes with very efficient flaps like some microlight here have a 35 kts stall with the double-slotted Fowler flaps down, but will still stall in the 50 kts range flaps up. Consequently, take-off and landing speeds are about as high as planes with simple plain flaps and a clean stall of 50 kts. I believe this was the chief reasoning behind the LSA rule.
    Last edited by autoreply; January 7th, 2017 at 02:35 PM.
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    Re: Relative safety of various construction materials

    Quote Originally Posted by Little Scrapper View Post
    I have over a hundred videos on YouTube showing step by step how to build a legal eagle fuselage. You are absolutely capable of building that, there's no doubt in my mind at all. You just need to decide that welding is a skill you will have fun learning. Who doesn't love to learn?

    I love the Pietenpol and the minimax line. The Fly Baby also holds a special place in my heart.

    If you were considering a true 2 place scratch built that's easy to fly efficient and can still.go cross country with the Sport Pilot cert I'd look at 2 airplanes.....

    1.) WagAero Wagabond. This is a replica of the Piper Vagabond. Not only are the plans great and it's simple but you truly have a budget airplane with a phenomenal track record. You can also buy parts if you don't want to build certain things.

    2.) Wittman Buttercup. The Buttercup is a delightful design by a legendary designer and racer..the plans are great as well.

    I sat in the Earl Luce replica and boy is it nice! Earl is a top notch guy.
    Great choices. I'd also consider the Bearhawk LSA.

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    Re: Relative safety of various construction materials

    The good news is that I know how to weld, but I would need to improve my technique. To date I've built a trailer and the usual farm items. Thanks for the suggestions.

    Ward
    Quote Originally Posted by Little Scrapper View Post
    I have o6ver a hundred videos on YouTube showing step by step how to build a legal eagle fuselage. You are absolutely capable of building that, there's no doubt in my mind at all. You just need to decide that welding is a skill you will have fun learning. Who doesn't love to learn?

    I love the Pietenpol and the minimax line. The Fly Baby also holds a special place in my heart.

    If you were considering a true 2 place scratch built that's easy to fly efficient and can still.go cross country with the Sport Pilot cert I'd look at 2 airplanes.....

    1.) WagAero Wagabond. This is a replica of the Piper Vagabond. Not only are the plans great and it's simple but you truly have a budget airplane with a phenomenal track record. You can also buy parts if you don't want to build certain things.

    2.) Wittman Buttercup. The Buttercup is a delightful design by a legendary designer and racer..the plans are great as well.

    I sat in the Earl Luce replica and boy is it nice! Earl is a top notch guy.

    If you want to have fun with an ultralight I can't imagine a better idea than a Legal Eagle or a Minimax.

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    Re: Relative safety of various construction materials

    Thank you everyone for all the great input. Your well thought out answers are incredibly helpful.

    Thanks,
    Ward

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    Re: Relative safety of various construction materials

    Mild steel has a surprisingly high energy absorption to weight ratio, composites also do well, and are generally better shaped. I don't know how wood compares. As others have said, stall speed makes the biggest difference.

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    Re: Relative safety of various construction materials

    Quote Originally Posted by autoreply View Post
    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.
    The "good reasons" being that composite structures need to be actively designed; it's quite easy to design a typical steel tube or semi-monocoque or wooden fuselage by looking at practice from the 1930s or 1940s. You can't do that with composites.

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    Re: Relative safety of various construction materials

    Quote Originally Posted by wardo View Post
    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
    Hi Ward. In your thread I get the notion your looking for what type of build is the best. Like you I prefer wood to other types and I feel that a landing is a controlled Stall. In a crash I don't think it matters much on what the craft is built of, it's more the speed and angle of attack you hit the ground. What I've seen and read about is the safety item's installed on your craft is your best bet for survival, rather it's a parachute or 4 point harness, good roll over protection. I like to keep in mind stuff like, C.G. shift with fuel burn off, Trim abilities on the control's. If you like wood for your build go for it, All types of build's will come home in about the same size pile after a similar crash. I say think of what can be done to make the craft survivable "BEFORE" such an event. IMO
    KR-2, Taylor Mono,

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