I am making a para-motor rig out aluminum and needed advice

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I'm a backyard welder and never welded aluminum. I'm making a para-motor rig, I want to use aluminum to save weight. I have seen guys on Youtube using flux core aluminum brazing rods to make repairs to aluminum and i want to know if i could use brazing rods to make my rig?     I will be using a 48" propeller with a Honda GX390 motor making about 20 hp (with some mods), a gearing reduction box and a 3 1/2 gal fuel cell. Do you think that brazing is strong enough for what I want to do?  Keep in mind the para-wing is strapped to Harness(you) and cage (motor, prop. and protective cage) then the harness is strapped to cage. All said and done i want the whole to weight less than 120lb.  Or would I be better off using some 1/2" steel tubing to make my rig?Thanks in advance for you input.Last edited by tv1000s; 01-31-2011 at 01:34 AM.
Reply:This does not sound like a good idea for you to do.You get what you put in and people get what they deserve...
Reply:Even though the cage isn't holding you up, it will have a propeller spinning inside it, and an engine vibrating like crazy.  Many years ago, weldors brazed aluminum for all sorts of purposes, but along came tig welding and most people would probably prefer to have the propeller separated from their bodies by tubing that was tig welded rather than brazed.  I am not wholly convinced that aluminum can handle the vibration and stress over the long term anyway.  My instincts tell me that the whole idea of aluminum vs steel in this particular application should be researched at length before you commit... after all, there have been a lot of talented engineering people dealing with this hobby for quite a while.  Be careful.Miller Syncrowave 350Millermatic 252/ 30A spoolgunMiller Bobcat 225g w/ 3545 spoolgunLincoln PowerArc4000Lincoln 175 Mig  Lincoln 135 Mig Everlast 250EX TigCentury ac/dc 230 amp stickVictor O/AHypertherm 1000 plasma
Reply:So let me get this straight.  You want to strap not only an engine, but a big fuel tank and a large spinning object to your back?  All held together by a somewhat questionable process that has been performed by an amature?  On a material prone to fatigue cracking?  Oh, and you'll be airborne too? Congrats on your future darwin award.My name's not Jim....
Reply:Every airframe that I have ever welded on was 4130steel.  DON'T DO THIS!Non heat treated Aluminum doesn't hold up well to vibrations.Youtube is freaking dangerous..JHFC!...Buy American, or don't whine when you end up on the bread line.
Reply:You should probably listen to what everyone has been telling you. I am an Aeronautical and Astronautical Engineer and this has Darwin Award written all over it. I have had a couple aircraft that were built out of aluminum, however there wasn't one part of it that was structural that was welded. It was all held together with rivets and bolts. My specialties are in Propulsion and Aerodynamics/Design so I can't so for sure, but I think with the welding you're just asking for fatigue cracks.  I think you should buy a frame if you really want to go this route, but I hope you know about the dangers associated with these and the uncanny ability of the parachutes to collapse with the slightest downdraft.
Reply:I fly powered parachutes and while I don't fly a PPG I have friends that do and who even build them (as manufacturers, not home built). If you have to get on a forum like this to ask questions about building a PPG, you're the last person who should be building one.  Do yourself a favor -- buy one from a dealer and get yourself proper training.
Reply:Backyard welder, never welded aluminum...At least you're admitting to it. Just don't do it... l've seen similar videos to what you're talking about. They make no claims as to the structural integrity of the brazes. When you start a build like this, realize your life is riding on the competency of every person involved in every part of the aircraft. Designer, weldors, engine builder, fuel handling company, the person who helps you move it around... and the operator. It's easy for one to not see the error in their ways- which is why most insurance companies wont cover you for an ultralight.I can remember in the 7th grade my mom said "people will offer you drugs" by the 10th grade I was like, "where the hell are these people?"
Reply:Well, I give you at least -some- credit for asking the question.  But the short answer is NO.The slightly longer answer is: For a critical application, if you have to ask then it means that you don't KNOW.  If you don't KNOW the answer, then you shouldn't be doing it.Even longer answer and along the lines of what has already been said above:  Aluminum is a useful material, but it has it's advantages and it has drawbacks and it has 'quirks'.  Welding an aluminum 'airframe' by a novice is NOT a good plan at all.  The design of aluminum airframe structures is not a trivial task.  Yes, airframes are designed and made of aluminum, but they are designed and made and inspected by folks with training and experience.  The best laid schemes ... Gang oft agley ...
Reply:OP's got my vote for the Darwin Award.At least for today.  I'm sure someone else will come along though and knock him out of first place.Syncro 250 DX Dynasty 200 DXMM 251 w/30A SG XMT 304 w/714 Feeder & Optima PulserHH187Dialarc 250 AC/DCHypertherm PM 1250Smith, Harris, Victor O/ASmith and Thermco Gas MixersAccess to a full fab shop with CNC Plasma, Water Jet, etc.
Reply:Just to make th OP feel better I'd like to submit my entry for the Darwin Award.I'm attempting to build a diesel submarine. I just got me a flux-core wire feed welder from Home Depot. I've got a bunch of scrap that I've been accumulating and a alpha-1 outdrive from my dads boat (he hit a pile of rocks in the lake and messd up the fiberglas)I've got limited experience as a welder, but I lifted my bronco 8" and put sum 38''s. Any advise?thankz - Kdogbadazzbronco92To say the least, OP, you've got some cojones to be willing to set yourself up in a little aircraft... I probably wouldn't do it myself. I wish you luck with your build.Last edited by joefitz; 01-31-2011 at 01:16 PM.I can remember in the 7th grade my mom said "people will offer you drugs" by the 10th grade I was like, "where the hell are these people?"
Reply:Originally Posted by tv1000sDo you think that brazing is strong enough for what I want to do?
Reply:Originally Posted by KelvinI would probably stick with aluminum pop rivets and Liquid Nails.
Reply:Do me a favor...when you get it finished please don't fly that damned thing over my house!  I just got a new roof and I don't want to see it torn up.StephenMillermatic 251Miller Syncrowave 200Miller 30A SpoolgunHypertherm Powermax 30Etc., etc., etc.............Cancer Sucks!
Reply:I'm attempting to build a diesel submarine