Fuselage Frame Construction

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Im researching several plane kits and wanted to ask the pros out there what they think abt the dff types of frames made. By pros I mean the guys/girls working in the profession. Welders and metal workers and instructors.One aircraft fuselage is built from rivet fastened sheet aluminium. The rest is also. See attached pic.The other one uses 4130 Alum tubing welded together. See - http://www.bearhawkaircraft.com/Tour/TourFuseJig.htmlhttp://www.bearhawkaircraft.com/Tour/TourFuselage.htmlhttp://www.bearhawkaircraft.com/Tour/TourWelds.htmlWhat im after is an answer to the question, : Which method of fuselage construction you consider the most stable/strong, crash resistant and which would you prefer if you were buying the plane?thanksBlueraven Attached Images
Reply:I would say the rivet one is more forgiving to novice builders via the lack of knowledge required to assemble. Clamp, drill, rivet, etc.  Welding a entire alluminum frame will require some skill to not have a fatigued mess on your hands.Millermatic 251Century 180 migSpectrum 625 Syncrowave 250DX
Reply:CK,I guess i needed to say, the frame of the welded one is done at the factory and you can get the riveted one done at the factory also. BR=================
Reply:I'd say both are amazingly strong for thier weight.  My introduction to airframes was about a year ago - and was serious crash course!  I ended up on an episode of monster garage that consisted of making a 3500lb sportscar fly.  Another guy and I got to build the "roll cage" around the car and the tail boom.  The tail boom was 1" and 1/2" .o49 wall cromoloy tubing and all had to be tig welded together.  I had never worked with cromoly before, and was thoroughly amazed at how strong that tail boom turned out.  BTW - I'm assuming that is a typo where you mentioned "4130 alum"?  That stuff is definitely a steel alloy...Here is a pic of the flying car - tail boom looks smaller than it is there:
Reply:Pano,Yea your right it is  typo, it is steel .. There are 26 different sizes ranging from 3/8 x .035 to 1.125 x .065.thanks for the eye..
Reply:There's a lot to be said about the differences between steel and aluminum, but it should suffice to say that both can be used to good effect to manufacture a fuselage.  If you're concerned about strength and protection, I would assert that the largest differentiating factor will be the design itself.One difference is the fact that an aluminum airframe will have a limited service life relative to a steel airframe.  I'm not sure if this has any practical impact, but it is true that aluminum will eventually suffer from metal fatigue.  Steel will not if the yield stress is never exceeded.-Heath
Reply:First of all let me point out i have no=0 airplane experience but i have had the fortune and privledge of working with someone who was a cert. aircraft welder.I salute ya for going the way way of a kit(personal dream...not first on list but its up there lol).It means that you are very cofident in ur skills and your ability to make something that truly works so as far as im concerned its at the top of the list as to a truly remarkble project.( I know I can put a bike or car together and would trust it with my or anothers life but 20-40,000 feet adds another dimension).From some wisdom gleaned from someone I respect there is very little welding done that is post factory.most things if in need of repair is a rivet or replace function.That is of course not including peices that have welding done as part of a finished sub assembly.That said(basicaly cause if in unknown territory I tend to go towards the safe zone)I would buy either from a very well known company but rivet from a relative newcomer company.This is very relative, if that new company has examples(several) that they can physicaly convince you that they have a clue then go for it.However,being in the bike buis for a little bit,i can tell ya right now that some of the advertised companies have little to none in the way of product testing and development!That translates into a massive outlay of time and money on anyones part even in a relatively safe bike let alone something that will definetaly maim or kill if something goes wrong.Basicaly it comes down to who and what your willing to bet not only your life on but also any freinds or family(or even strangers) on.Justr because it worked once or twice does not make it ideal...thats a shear number game that few very small manufactures can tackle.Best bet is to see if ya can talk to the people that actualy did the work.If its just a distributer or sales then i would pass simply because they can not give ya any real data or info.!!!!!!!!!!SAFETY,FUNCTION,FORM,In that order or find someonelse!!!!!!!!!!
Reply:Panozeng, got an email address I can write you at?JohnnyWeld
Reply:Panozeng,Yeah, that JJ guy is dumb as a rock. Could not be a better example of lots of dollars, and no cents (sense).I bet that was a fun project though.
Reply:I wonder how he acquired all those dollars?  It must have been in spite of his intellectual failings.-Heath
Reply:I know a few really dumb people that have a quite alot of  money. I also know lots of very smart and talented people of modest means. If you get in the habit of assuming that all people with money are smart, you'll wind up dumb yourself. We don't want that now do we?
Reply:Hello all, this is my first post to the forum.I figured I'd start here since I happen to work on large Aircraft for a living at a major airline and most of my experience is with big iron and not puddle jumpers so I will saw this...there is no safe fusealage frame to keep you from killing yourself, mother earth and speed turns airplanes into very small pieces.When you can plant a DC-9 in 3ft of water and can't see any wreckage from thae air or a B767 in a field and all you see is a hole.Airplanes are built to fly not be crash resistant, there's not an airbag in the world that is going to protect the human body when it slams into the ground at 500mph and higher.If you want to build with economy in mind then 4130 tubing and dope and fabric is your airplane otherwise aluminum or composite structure.
Reply:Archer,Thanks for your reply.What i was asking is which fueslage type wld absorb the most energy in the same type crash. The welded 4130 frame or the stressed-skin, semi-monocoque construction alum frame?I was thinking the steel but now thinking the alum. there's more alum to deform than the steel and hence the frame will be able to absorb foreces from many diff directions.BR.
Reply:Aluminum construction will absorb the most energy but in a small plane your still sitting in the ft. right behind an instrument cluster, a firewall and a motor... there is no crumple zone.
Reply:check out www aircraftspruce.com