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Thread: Welding vs triangulated brackets with rivets

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    Welding vs triangulated brackets with rivets

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    Alan Waters

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    Re: ON NETFLIX NOW. PLANE RESURRECTION

    I reviewed the second episode which was the rebuilding of the Hawker Hurricane. My attention was directed toward the lack of welding in the airframe. Starting at 29.22 on the tape counter and freezing the tape in various places I was unable to see much weld. There was some but by in large in the limited area we can see the tubes are fastened with riveted triangulated brackets. Round tubes have been squared up on the ends and others are square all or most of the length. This should be of interest to our builders who do not weld. I am a retired welder and have welded on airframes and it is of great interest to me. Welding on CM airframes is not easy. Well.... the weld itself is not that hard, it is getting into the position which allows you to weld that causes the grief. I may go out on a limb and say one could build an entire airframe with no weld. The BELITE aircraft may have already done this.

    Max. takeoff on the Hurricane is 8,710 lbs and I suppose could take all the g's a pilot could supply and stay awake. So, is it not reasonable to think the constructions methods used would work as well on a 1320 lb aircraft? Most of which will likely never see more than 4 or 5 g's.


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    Re: Welding vs triangulated brackets with rivets

    Its not that it can be done, the BD4 and some other Bede fuselage designs are like a Hurricane. It is just leaving a lighter weight plane off the table. The Hurricane was meant to be field repairable by low end personnel with out a lot of training. While some of that may be applicable, as a hobby its not life or death to get the plane built. A builder has other paths to get the welding done. Build a small plane 50 lbs heavier and you gave up 8 gallons of gas or some other necessity. 50 might be extreme but 10-20 easily.

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    Re: Welding vs triangulated brackets with rivets

    The current LightFighter P-36 we're building is basically this way. Aluminum tube subframe, skin on the outside. It was this way because we were going to a Hurricane style fabric covering over part of the fuse. Just turns out we ended up with the whole thing metal-covered.

    The weight penalty is about 15-20lbs over what we'd have if we went with a semi-monocoque version of the same. It isn't optimal, but it's part of our concept to have the one frame and cover it depending on the look one is going for.

    It looks to me, having done it the riveted tube truss way and then doing a sheet-metal riveted box with angle longerons, for making a sub-frame under the skin (in either case not the optimal stressed-skin method) they seem equally capable of supporting the required loads. The box style seems like it should be slightly lighter than tube truss, and is easier to assemble from parts (less parts) but if one doesn't have a magic CNC machine or a pre-cut kit, the tubes are really nice as it can all be done by hand and a template pattern and the result is quite sturdy.

    That said, I'm definitely starting to wonder how much is saved in either design time or engineering analysis by going with a common structure and there might be diminishing returns. We want to be able to replicate dozens of aircraft which means individual analysis isn't ideal but also you end up with more and more cases that aren't a perfect fit so you end up needing more and more custom cases anyway as more designs are considered. Somewhere is a sweet spot.

    But yes, overall, it's totally viable. People will nitpick the weight but if analyzing a truss seems like a safe bet, the penalty isn't crippling. It's the compromise you make for simplicity or speed.
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    Re: Welding vs triangulated brackets with rivets

    Are you asking about steel tube or aluminum?
    I think the Hurricane used all steel tube. Perhaps it was very high tensile tube and they didn't want to weld it.
    I think some photos are in a thread somewhere.

    Click image for larger version. 

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    Last edited by BBerson; January 9th, 2017 at 01:50 PM.

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    Re: Welding vs triangulated brackets with rivets

    It was a fad of British aircraft design at the time. I'm not sure of the origins but it's an industrial production technique to reduce the amount of precision hand work.

    The Wellington bomber us a good example with the visual treat of being geodetic. It's a transition from wood frames & fabric - to aluminum monocoque technology. IIRC it was used from the late 1920's through the 1950's.

    http://www.nationalarchives.gov.uk/t...rkers_week.htm

    Airdrome airplanes uses this tech with aluminum tubing. http://www.airdromeaeroplanes.com/
    The result is an air frame kit that needs few tools to build.

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    Re: Welding vs triangulated brackets with rivets

    In aluminum, riveted gussets are the way to go. In steel tube, welding allows round tubes and usually a significantly lighter structure. I am sure Hawker had very good reasons to do what they did, most likely a combination of rapid scale up of the workforce and less training required to get good quality. Other pro factors likely are speed of production and ease of field repair.

    It has a down side in that it makes the primary structure susceptible to water in the joints and subsequent corrosion, but, quite frankly, no one was expecting Hurries to live very long in combat, and combat was iminent.

    The Hurricane was a very successful fighter and close air support airplane, but I would not do steel tubes with gussets and rivets in a LSA category or lighter plane- too much weight. Pick between welded steel tube or riveted aluminum or wood or maybe composite if you are aimimg for the high airspeed end of the spectrum.

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    Re: Welding vs triangulated brackets with rivets

    Guess what I was doing today ...

    Click image for larger version. 

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    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: Welding vs triangulated brackets with rivets

    The question is not what you are doing with your design, Cheapracer. We want to know the penalties for using it. Many people may want easier to build, your way, but what, would a 4130 frame doing the same thing weigh, is how we want to grade easy to build. If you give up too much utility just to say you have an airplane, do you really have a useful airplane?

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    Re: Welding vs triangulated brackets with rivets

    Not sure if that's fair. If I don't want to build a plane out of napkins & honey, for any reason including I don't like sanding or the epoxy makes me stop breathing, does that make my hypocritcal ( for example ) sheet metal airplane not useful?

    Folk famously build CH-850s in mud huts with solar panels charging their electric drill batteries.

    The question "We want to know the penalties for using it."???? is the relevant one. There's always a compromise.

    The steel tube and stamped gusset system seems to be gone as a modern production method. I assume there is just not that much demand for fastest possible production of 1930's designs in the face of imminent invasion as there used to be.

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    Re: Welding vs triangulated brackets with rivets

    Type certificated Super Cub clones, including the Husky, plus Pitts, Extra, Maule, and several ag planes, not to mention many HBA designs, continue to be built with steel tube fuselages. Sometimes it is best for the mission, sometime wood, composite, aluminum semi-monoque, aluminum tube or FRP is better.

    Select a material for your HBA just like you picked your wife.


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    Re: Welding vs triangulated brackets with rivets

    Quote Originally Posted by BJC View Post
    Type certificated Super Cub clones, including the Husky, plus Pitts, Extra, Maule, and several ag planes, not to mention many HBA designs, continue to be built with steel tube fuselages. Sometimes it is best for the mission, sometime wood, composite, aluminum semi-monoque, aluminum tube or FRP is better.

    Select a material for your HBA just like you picked your wife.


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    Re: Welding vs triangulated brackets with rivets

    Quote Originally Posted by TFF View Post
    If you give up too much utility just to say you have an airplane, do you really have a useful airplane?
    If you need to ask then you probably have high expectations, next question is do you have the cash to meet those expectations.

    I'm building to a criteria that demands I use local source'able, cheap materials and methods, welded 4130 tube frames do not fit that criteria (locally for me, as it might be vice versa for others).

    For sure I would be slightly heavier than an equivalent 4130 tube frame, I don't think there's enough in it to ruin your day though, prob 15 to 20lbs as someone mentioned above.

    Anyway, I was just co-incidentally doing the same type of gusset today as shown here, had no other meaning.



    Quote Originally Posted by BJC View Post

    Select a material for your HBA just like you picked your wife.

    .. so many answers, so little time ...
    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: Welding vs triangulated brackets with rivets

    Quote Originally Posted by cheapracer View Post
    Guess what I was doing today ...

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    Practicing building a Hurricane!

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    Re: Welding vs triangulated brackets with rivets

    Welding steel tube isn't the only way. Before welding, builders of Heath, Pietenpoll and others used flattened end tubes and bolts. The flattened end worked well for steel when heated red with a simple torch.
    Should be considered for those shy of welding.
    It would be especially good if thinner wall steel tube was found. Welding super thin tube is tricky, no problem for bolts or rivets.

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    Re: Welding vs triangulated brackets with rivets

    [QUOTE]
    Quote Originally Posted by Aesquire View Post
    It was a fad of British aircraft design at the time. I'm not sure of the origins but it's an industrial production technique to reduce the amount of precision hand work.

    The Wellington bomber us a good example with the visual treat of being geodetic. It's a transition from wood frames & fabric - to aluminum monocoque technology. IIRC it was used from the late 1920's through the 1950's.

    http://www.nationalarchives.gov.uk/t...rkers_week.htm
    Absolument remarquable! thank you for posting that movie!

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