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Thread: Bolted steel tubed fuselage?

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    Registered User Mac790's Avatar
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    Bolted steel tubed fuselage?

    I've seen many bolted/riveted aluminum fuselages, and it doesn't surprised me at all. Everybody with a little knowledge about alloys, knows why it's better/easier to bolt aluminum fuselage rather than try to weld it.

    But I was doing a little bit research about steel fuselages, and I found a Hawker Hurricane steel fuselage, it's bolted fuselage (pic1,2), I said ok I can understand it, this plane took off (if I remember correctly) for the first time in 1935, but I was a little bit surprised when I saw a Hawker Tempest fuselage pic3,4. The front section is build from steel tubes, the rear section is aluminum monocoque, of course the front steel tubed section is bolted again.

    Probably they decided to use this method because they were familiar with it (they designed Hurricane a couple of years earlier), but I'm still surprised about it, there were other planes with steel fuselages like Yak's family but those planes had welded fuselages.

    I was thinking about a potential advantages of this method, simpler manufacturing (questionable), easier maintenance (maybe), no problem with alloy changing properties? (I don't know proper English term for it) due to the heat/welding.

    Any opinions about it?

    Seb
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    Last edited by Mac790; April 30th, 2010 at 04:16 PM.
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    Registered User Autodidact's Avatar
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    Re: Bolted steel tubed fuselage?

    I am very interested in this type of construction. I like the idea of being able to fabricate a strong and durable aircraft structure using minimal tooling and a little more work. A drill press, a bandsaw or hacksaw, some kind of facing tool for the drill press to set the length of the spacer tubes that the rivets or bolts will go through...

    The welding process is simpler and more elegant, but the tooling and skills are more complex, I would want to do it with TIG and that is some cost there; it would be nice to be able to accomplish a similar end with tools that I mainly already have.
    As many takes as it takes.

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    Re: Bolted steel tubed fuselage?

    Quote Originally Posted by Mac790 View Post
    I was thinking about a potential advantages of this method, simpler manufacturing (questionable), easier maintenance (maybe), no problem with alloy changing properties? (I don't know proper English term for it) due to the heat/welding.
    To what I recall, one of the major reasons to choose it was English Engineering which has a reputation for being different and sometimes not the most logical approach, based on techniques they used before.

    That's probably not a very useful answer to you (in terms of arguments against or in advantage of this technique), but it might give you some insight in the why

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    Re: Bolted steel tubed fuselage?

    I recently learned to weld and preferr it to bolting. However, as mentioned the tools required of metal fabrication are numerous and expensive. Bolts if properly fit and there's no serious deformation of tube don't significantly affect the strength or weight of the aircraft. The only concern would be to slop from wear around the bolt holes. Probably less of a concern in steel, due to it's greater hardness, but this is more of an assumption.

    A lot would depend on the gauge of tube and method of connection.

    As always,

    Good luck and godspeed.


    Wonderous Mountain

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    Re: Bolted steel tubed fuselage?

    I see only two advantages to bolted steel: It doesn't require welding (which shouldn't be an issue for an aircraft manufacturer that can hire a welder), and damaged parts can be easily replaced. Perhaps that's what Hawker was thinking: easy to repair battle damage. A third advantage might be that you can use heat treated tubing without having to worry about subsequent heat treating (welded steel fuselages are heat treated, so there's no weakening from the weld as in aluminum).

    But in the end, unless it's heat treated and you can thus use lighter sections, the bolted structure will be heavier than the welded by the weight of the bolts and gusset plates... which could be significant. Plus bolt holes can wear oversize... gussetted and riveted might be a better choice than gussetted and bolted if repair isn't a major concern.

    My biplane project will have either a welded steel or gusseted and riveted or bolted aluminum fuselage. I'm leaning toward the former but my welding skills aren't up to it (I'm a hack welder with a torch but my skills are nowhere near the level of an airworthy airframe). Still, other homebuilders have learned to weld so I guess I can too.

    -Dana

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    Re: Bolted steel tubed fuselage?

    The big thing is unskilled labor can put the thing together. You can have a small group of fabricators making the bits and then pass it on to the assymbler who can be a task taught person instead of having all the workers be highly skilled which may be in short supply in war time. The Spitfire required a bunch of skilled labor to make which ended up killing Supermarine in the 50s; their engineers relied on the skill of the fabricators to fix the details and when the jet age hit the need for getting it right at the drawing board took its toll. Monocoque construction is the same; riviters can be taught pretty easy; the guy doing the layout and cutting of the aluminum is the skilled guy.

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    Re: Bolted steel tubed fuselage?

    Quote Originally Posted by Mac790 View Post
    Probably they decided to use this method because they were familiar with it (they designed Hurricane a couple of years earlier), but I'm still surprised about it, there were other planes with steel fuselages like Yak's family but those planes had welded fuselages.
    On and off I've been helping a gentleman build a Bristol Bulldog bipe, which included a fairly good look at British aircraft industry practices pre and post war. The Bulldog had a very complex fuselage, an aspect that wasn't helped by the fact that the whole thing was bolted together with myriads of these relatively intricate joints (either cast or machined). Looking at the background of the industry, the reason for the process was two-fold: First, the British were very slow in accepting any practice that they themselves didn't develop. They knew about welding practices across the pond but despite that they still didn't believe in them and so decided to go with what they knew. This attitude was maintained 'till well past WWII.

    Furthermore, welding was considered as too efficient. With the British socialized form of labor, it was (and still is) considered more important to keep a bunch of people "employed" rather than producing an optimized product at an efficient rate. As such, efficient newer technologies were rarely incorporated into production since it was seen as an attempt to reduce the labor force, which was of course unacceptable.
    "To live is to learn; to learn is to live" (author unknown)

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    Re: Bolted steel tubed fuselage?

    Quote Originally Posted by orion View Post
    Furthermore, welding was considered as too efficient. With the British socialized form of labor, it was (and still is) considered more important to keep a bunch of people "employed" rather than producing an optimized product at an efficient rate. As such, efficient newer technologies were rarely incorporated into production since it was seen as an attempt to reduce the labor force, which was of course unacceptable.
    I believe it. Some years ago I was designing automated production machinery for 3.5" floppy disks. We had built several of the systems, which assembled basic components (the plastic shells, liner, the disk itself, the stainless steel shutter, and a spring) into the complete assembly, at about 40 per minute. A British firm wanted us to quote a system that did the same things, but took some minimum number (I forget exactly) of people to run it. Kinda missing the point as automation not only reduces labor but improves product quality; machines are more reliable than people. We quoted a set of semiautomatic systems, where the operator put the parts in one at a time and the machine fastened them together, but on one Friday afternoon we got crazy suggested to our boss a machine identical with the ones we'd already built, automatic controls and all, but with a light and a lever replacing each air cylinder... when the light comes on, the operator has to pull the lever...

    -Dana

    Why did the chicken cross the Mobius strip? To get to the other, er, um....

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    Re: Bolted steel tubed fuselage?

    I hope you didn't go through with that. It's cruel. Plus, likely to raise trouble with labor. Can you imagine your state of mind after 8 hours of doing that? Bad enough spending 8 hours loading the machine.
    Quote Originally Posted by Dana View Post
    snip
    but on one Friday afternoon we got crazy suggested to our boss a machine identical with the ones we'd already built, automatic controls and all, but with a light and a lever replacing each air cylinder... when the light comes on, the operator has to pull the lever...

    -Dana

    Why did the chicken cross the Mobius strip? To get to the other, er, um....

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    Re: Bolted steel tubed fuselage?

    No, it was just one of those Friday afternoon bull sessions. As I recall, we never sold them anything, though we built some semiautomatic assembly tooling for some other customers in South America.

    -Dana

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    Re: Bolted steel tubed fuselage?

    The average hunter gatherer works 3-4 hours a day.

    I worry that future jobs may all break down to machine sitting, and service to the machine sitters. Job creation and destruction is a touchy subject. I've been in towns where plants move and shut down either because of new processes or cheaper labor elsewhere. It's a crazy and sad thing when half a town is out of work.

    Yet the standard of living I accept as an American by birth is good because we do things the cheapest we possibly can. As an unemployed american in a time of financial woes the question is very poiynant. The bottom line is you can never forget the human toll, or you are it.

    Godspeed to all the crazy crafters out there that help me be lazy!

    Wonderous Mountain

    P.S. Go with bolts; when the taxman comes you can undo everything and say, "oh that, it's just a pile of scrap, probably never get off the ground"

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    Re: Bolted steel tubed fuselage?

    Hello all,I'm most a reader here,I read somewhere that they used high carbon alloys tubes,not weldable,thath was the reason of this kind of truss structure construction.

    Regards

    JC

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    Re: Bolted steel tubed fuselage?

    Quote Originally Posted by orion View Post

    Furthermore, welding was considered as too efficient. With the British socialized form of labor, it was (and still is) considered more important to keep a bunch of people "employed" rather than producing an optimized product at an efficient rate. As such, efficient newer technologies were rarely incorporated into production since it was seen as an attempt to reduce the labor force, which was of course unacceptable.

    Here I have to chime in and voice my dissent to that opinion:

    Orion, I have a lot of respect for your technical knowledge, but on this point you are completely off the mark.

    Anything and everything that ever came out of Britain has had the label"socialized" tacked onto it by Americans, usually meant in a somewhat derogatory way. (Incidentally, nobody outside the USA even uses that word.)

    There was nothing "socialized" about the British aircraft industry; all of them were private companies, founded and funded privately and through public share issues. They did not receive money from the government except through the form of government contracts which were earned, just like in the USA, through competition with other manufacturers. And just like in the USA they spared no effort when it came to designing and building state of the art aircraft for the military, at a time when the national security was not just a vague concept, but a real problem. To suggest they employed less efficient methods in their aircraft production or design just keep people employed is ludicrous.

    I have stacks of books behind me about the British aircraft industry of the 30s and 40s and have personally known a great many people employed in the industry, from shop floor workers to design apprentices. From Supermarine, Hawker, Airspeed , Miles and many others. (Did I mention I met and talked with T.O.M. Sopwith when he was 90something years old once...?) Sadly most have now passed away.
    All these companies were very concerned with making profit, just like in the best capitalist tradition. They had to produce first class products at a reasonable price. To do that and employ people just to "give them jobs" was a concept as foreign to them as it is in the USA. (Sure, you had trade unions, but so does the USA, that has nothing to do with government subsidized "socialized" labor.) When it came to civilian aircraft, welding was employed to larger extent and yes, they were wary of the process. Not because it was "too efficient", but because of concerns about quality control and because when it came to top of the line military aircraft, they could afford to design structures far advanced beyond welded tube. They perfected the science of working with incredibly high strength steels and got amazing buckling stress limits out of them through the careful and clever use of corrugations and fluting of the extremely thin material which they developed to almost an art form. Of course, such steels cannot be welded without losing its strength and clever bolted and riveted joints had to be designed - labor intensive and costly, yes, but worth it to produce extremely light and efficient airframes to win government contracts. It is the same here and today in the USA - manufacturers trying to produce state of the art military aircraft put cost on a lower level of importance than efficiency and performance. Back then British companies had to balance books and advance technology on their own, just like any American manufacturer, with no government subsidies. Many companies went under; if you want to know how hard it was to make an aircraft company work and pay, read Nevil Shute's account of how he and some others founded Airspeed in the book "Sliderule". They lived from week to week trying to make ends meet but kept the company running and eventually started making a modest profit, but only after years of struggle. There was nothing "socialized" about the system and the only government money was received through contracts which were won in fair competition with other manufacturers. Need I repeat it - just like in the USA.

    There is no doubt that the welded tube structure is cheap and practical and fairly efficient. But the structures developed by Bristol were simply more efficient, even if only by a few percent. In age age when aircraft were obsolete in a matter of three years and there was a real threat to the national security, a few percent might make all the difference.

    There is a blueprint above my desk right now of the Bristol Bulldog - I still marvel at the elegant engineering - this was state of the art technology making use of the most modern materials and methods to produce the most efficient machine to defend the nation - it had absolutely nothing to do with "socialized" labor or keeping people in jobs.

    End of rant and back to topic.....
    "Aeronautical engineering is highly educated guessing, worked out to five decimal places. Fred Lindsley, Airspeed."

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    Super Moderator orion's Avatar
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    Re: Bolted steel tubed fuselage?

    That's more words than it's worth - although the term "socialized" was not used in the text (hence my term for it), the intent or practice of the type of program and/or labor organization I refer to was actually published in the very historical texts the gentleman showed me. Several of them as a matter of fact, most written and published by British historians of the era. Furthermore, when discussed previously on this forum, several have responded on the forum and privately that this type of practice is still very much alive in England, one very reason that so very few things get actually manufactured and exported from that country, especially airplanes.
    "To live is to learn; to learn is to live" (author unknown)

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    Re: Bolted steel tubed fuselage?

    Very interesting technical account, but, to me, after reading the news for several decades, your faith in the US military acquisition system seems misplaced. Anyone notice all those obnoxious Boeing tanker ads?

    Quote Originally Posted by PTAirco View Post
    snip
    There was nothing "socialized" about the system and the only government money was received through contracts which were won in fair competition with other manufacturers. Need I repeat it - just like in the USA.
    snip

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