DR-1 (Sands): Builders Group - Page 203

Fokker210 · 21 February 2008, 07:44 PM

Hole saws are the way I did it as well !

CORVUS · 21 February 2008, 08:43 PM

Hi,

Thanks for the answers. I'll pick up some hole saws with fine teeth. They make those Forstner type and thought there might be a difference in the results.

Lou

gipsymoth236k · 21 February 2008, 09:05 PM

Welding advice needed:

Has anyone used mild steel of say 1020, St 35, 52 for Dr.I fabrication? I know that it is available here in the US at places like Parker Steel, and in all the original metric tube diameters and wall thicknesses:

Parker Steel- The Largest Supplier of Metric Sized Metals in North America

Is there any problem using mild steel vs 4130 for the Dr.I airframe's fabrication? Is it adequate for the purpose? Is it easier or harder to make a good weld with mild steel?

Thanks, Gary Sewall

CORVUS · 21 February 2008, 09:40 PM

Hi Gary,

I did not want to appear rude. I am going to use 4130. This is the industry standard. I'm just speculating but there might be some FAA criteria that needs to be met. At least it's something I would assume. Gulp. I hope.

Lou

acwelder · 21 February 2008, 10:54 PM

Quote:

Originally Posted by gipsymoth236k

Welding advice needed:

Has anyone used mild steel of say 1020, St 35, 52 for Dr.I fabrication? I know that it is available here in the US at places like Parker Steel, and in all the original metric tube diameters and wall thicknesses:

Parker Steel- The Largest Supplier of Metric Sized Metals in North America

Is there any problem using mild steel vs 4130 for the Dr.I airframe's fabrication? Is it adequate for the purpose? Is it easier or harder to make a good weld with mild steel?

Thanks, Gary Sewall

Highly recommend this book to anyone contemplating building a tubular steel fuselage: Construction of Tubular Steel Fuselages

and

Aircraft Welding Techniques

While mild steel was OK in WWI, in the USA today 4130 should be used. Mild steel in low stress brackets, etc. No one in the USA carries much if any METRIC aircraft grade 4130. Probably a European source, but I haven't located one yet.

Additional info:

FAQs on welding 4130

TIG WELD 4130 - Lincoln Electric

WOOD, ALUMINUM, STEEL AND COMPOSITES ... and the Properties of each

Join EAA. They have a VAST wealth of information for the homebuilder.

This Pietenpol Air Camper FAQ talks of using 1020.

gipsymoth236k · 21 February 2008, 11:15 PM

Thank you Lou and acwelder! I really appreciate your answers.

Regards, Gary Sewall

Jeff Brooks · 22 February 2008, 05:52 AM

As far as the US building rules are concerned ... if the plans call for 1025 mild steel, then it is authorized for use. All the stress testing on this plane has already been done using this material. Upgrading to a stronger material makes changes to the airplane design. Changes in weight come to mind first (for me)! Also, aircraft have a certain flexibility built into them ... making an area more rigid using a stronger materials moves the stress of flexing to an unplanned area.

I know that 4130 has become the aviation industry standard, but the correct sizes are not available. It is a known problem that the thicker wall sizes of the tubing of the tail feathers significantly affect the weight & balance of the plane. Upgrading to 4130 in this instance is not good! If I hadn't already spent a small fortune on making my tail feathers again ... I would order the mild steel in the correct tube & wall sizes, and make another set to reduce the weight on the tail!

The other question we need to ask is ... what were the tolerances of the wall thickness of the tubing used back in 1917. If the tolerances were large (sloppy) enough that substituting English measurements makes a small impact ... then it is really not a big deal. One could swap the 1025 tubes that are very close in size to 4130. Anything that is not close in size remains at 1025. The issue here is that dissimilar metal creates rust!

The fabrication process is also easier using 1025 than 4130! I watch Achim hammer those neat shapes into the steel, and he makes it look so easy. When I try the same technique using 4130 ... it is damn near impossible to get the same results! It is not as fluid, and often requires heating up the metal to get it to move the same way. Heating the metal to get that shape reduces its strength anyway ... so why not start with something easier to work with and will work harden as it moves into shape?

I have welded mild steel, and I didn't find it to be much different. You will need to change what type of filler rod you are using ... but other than, it is not that difficult at all.

I tried Parker steel, and they don't just sell to anybody. They sell to metal distributors only.

acwelder · 22 February 2008, 06:10 AM

Quote:

Originally Posted by Jeff Brooks

As far as the US building rules are concerned ... if the plans call for 1025 mild steel, then it is authorized for use.

What if the builder is using his own plans, derived from years of research studying a 90 year old German design? How does one get a design like this certified? Or do they allow a similar design a special waiver?

Don't you have to get your project inspected at certain stages of the build?

worldcrusier · 22 February 2008, 06:16 AM

The subject of steel strength has come up before in this thread. If I remember correctly, Achim supplied the typical WW1 tubing physical characteristics and the numbers showed that the Germans used tubing considerably stronger than 1025. I would not use less than 4130 unless the part was a used lightly loaded application. Another advantage of using only 4130 is that you do not have different grades of steel in inventory, reducing the possibility of accidentally using a low grade steel in a high grade application.

acwelder · 22 February 2008, 06:40 AM

While gas welding is historically correct, the results with TIG are so much better. More expensive to get started for sure, but the welds are more consistent, easier to learn, cleaner, a smaller heat affected zone, less stress and distortion in tubular frames. Rookie gas welders tend to spend a LOT of time at any given cluster allowing for a much larger heat affected area.

IMO TIG and 4130 are the way to go these days. There are many though that prefer the cheaper gas method. The debate is a continual one. Do your own research, come to your own conclusions. It is YOUR life and safety that is on the line.

The EAA offers welding workshops for those that are wanting to build a homebuilt aircraft.

Gas Welding Workshop

TIG Welding Workshop

Other Workshops

The following is taken from: Sportair Advanced TIG Welding class

"I'll try to hit the highlights here. When TIG welding thin-wall 4130 tubing, no preheating is required, other than bringing it up to room temperature and ensuring that no obvious moisture is present on the tubing. Likewise, no "post heating" or normalization is required either, but a draft-free work area is important. Keeping the weld bead as small as possible is best, in order to minimize the heat-affected zone. The best welding rod to use is ER80S-D2, ER70S-2, -3, or -6, in that order. There's nothing wrong with copper coated rod, which prevents the rod from rusting. Make sure you wipe the oils (used in manufacturing) off of the rods first. .045" diameter rod is best for thin-wall, but it's not commonly available. If you can't find it, visit Wyatt's web page at www.TigDepot.net and he'll sell you small or large quantities. (Mention you're with the EAA and you'll get a 25% discount.) Tight fit-ups are of paramount importance when TIG welding OR gas welding. The tighter the joint, the less distortion you'll encounter as the structure is welded together.

There is an age-old debate regarding which is better for welding 4130, gas or TIG. I'm here to tell you that I'll never be able to gas weld 4130 with anything near the confidence level that I can TIG it. I have no doubt that someone with years of experience can gas weld 4130 just fine, but if you want joints with the same high quality (and a smaller heat affected zone) with minimal practice, TIG is the way to go! It costs more to "get in", but it sure is easy to pick up TIG welding. There are no real variables. Just step on the pedal until it melts into a puddle, and feed it the rod. With gas welding there are so many variables. Tip sizes, oxy-acetylene ratio, etc. I never could figure it out. I proudly took an early gas attempt to the local guy that does all the certified aircraft welding for the FBOs. He just sighed and said "I'm sorry, I thought you were further along than this. You've just cooked the hell out out of it".

Much of the argument against TIG welding steel have come from the gas welding camp, who are fond of breaking TIG joints welded with "official" 4130 rod. This high carbon rod is very brittle and prone to cracking when allowed to cool quickly, as most homebuilders would tend to do when welding thin-wall tubing. 4130 steel is normalized by a carefully controlled slow-cooling process during manufacture. So when you heat it up and let it cool at room temperature, it's very strong, but far more brittle. That's why milder steel rod is best for our thin-wall application. It's far better to have a slightly weaker joint than to have a brittle one with cracks in it!"

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TIG Database

BASICS OF TIG WELDING DVD