Suitable airframes for industrial engines?

[aeronco]

The Aeronca C2 and C3 have remarkable performance for such low powered machines. I’ve flown several hundred hours in my C3 and have a C2 in the shop. The high aspect ratio wing is very efficient and the Aeronca E113 (or JAP J99 for an Englishman) provides honest horsepower at a sensible propeller speed. It might well only be 36 hp but is efficiently turned into thrust. The higher revving VW doesn’t provide the same efficiency. The suggestion of giving the Headwind a bigger wing is sensible as the original design is only 26 foot span; the Aeronca is 36 foot by comparison.

 

[cluttonfred]

What about some of the 1920s-1930s designs intended for use with small converted motorcycle engines. In other words, half the designs from the old Flying & Glider Manuals? Aluminum tube-and-gusset construction and other weight savings should really improve performance. I love Les Long's Longsters...no relation. ;-)

 

[Bill-Higdon]

What about some of the 1920s-1930s designs intended for use with small converted motorcycle engines. In other words, half the designs from the old Flying & Glider Manuals? Aluminum tube-and-gusset construction and other weight savings should really improve performance. I love Les Long's Longsters...no relation. ;-)

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There was a high wing Longster built as an ultralight & powered by a Carr Twin (1/2 VW)

 

[aeronco]

Lots of inspiration and vintage ultralights in this series. Don’t discount using DOM steel tube, it’s cheap, light and easy to weld with gas, TIG or MIG. The late Robert Hoover wrote an article called ‘Flying On The Cheap’, all about using mild steel DOM instead of expensive 4130. Aluminium tube and gusset construction is OK structurally but always looks like a dogs dinner of nasty sharp edges and pop rivets (just my opinion!).

 

[rv7charlie]

I don't recall any modern-day prices for DOM that are significantly different from 4130, but I may not be looking in the right places. Examples:
DOM 3/4 x .060 @ ~$4.16/ft
MetalsDepot® - Buy DOM Round Steel Tube Online!

4130 3/4 x .055 (stronger stuff) @ ~$4.55/ft
4130 ALLOY STEEL ROUND SEAMLESS | Aircraft Spruce
Note that .049 (which is likely stronger than .060 DOM) is $3.60/ft
Trickier to weld, though.
Charlie

 

[aeronco]

Having read the article again I think Hoover meant ERW. Certainly ERW is way cheaper than 4130 here in the UK and his argument was that commercial grade steels were suitable for inexpensive non-aerobatic aircraft. Obviously it isn’t as strong but for a flivver, would .049 ERW be OK instead of .035 4130? Very much an individual decision.

 

[mullacharjak]

PDQ Aircraft Products PDQ-2

en.wikipedia.org

Wayne Ison. Plans?

Aviation Plans Facebook group has got drawings for PDQ.

 

[mullacharjak]

Having read the article again I think Hoover meant ERW. Certainly ERW is way cheaper than 4130 here in the UK and his argument was that commercial grade steels were suitable for inexpensive non-aerobatic aircraft. Obviously it isn’t as strong but for a flivver, would .049 ERW be OK instead of .035 4130? Very much an individual decision.

I am also investigating the option of substitution for 4130 which is not available in my country of residence,There is lot of ERW but I think its weak. Someone suggested 201 Stainless steel being a suitable substitute for 4130.The figures on paper look promising but I have to look into it.

 

[rv7charlie]

Well, my brain took a vacation the other day when I responded. I hope that Hoover didn't mean DOM *or* ERM tubing should be used for structure. My understanding is that even the old Piper Cub-era planes used seamless tubing, in one or more of the mild steel aloys (1025 for the Cub). I've never seen anyone advocate using welded-seam tubing for aircraft. There was a local legend around my home state of a guy who built an entire a/c out of EMT (electrical conduit) but I don't think he could get the inspector to sign it off.

 

[mullacharjak]

Well, my brain took a vacation the other day when I responded. I hope that Hoover didn't mean DOM *or* ERM tubing should be used for structure. My understanding is that even the old Piper Cub-era planes used seamless tubing, in one or more of the mild steel aloys (1025 for the Cub). I've never seen anyone advocate using welded-seam tubing for aircraft. There was a local legend around my home state of a guy who built an entire a/c out of EMT (electrical conduit) but I don't think he could get the inspector to sign it off.

Forget the name now as that information can no longer be accessed on the internet.An australian builder built Early bird jenny.He used ERW 1.2mm tubing.Geo suzuki G10 /Rotax gearbox. It flew fine.

 

[rv7charlie]

My understanding is that the issue is not the raw strength of the tubing. It's the relatively uncontrolled process (meaning un-monitored for integrity) of welding the seam on the tubing. Then there's the loading on the welds, once the tubing is in service.

I have no doubt that an airframe could be built using DOM, or ERS, or even EMT, and it would fly 'fine'. Until it doesn't.

 

[TFF]

DOM starts out as ERW with one more step in the process. What ERW might do is split in a crash. As for strength, that’s math class.

 

[Victor Bravo]

The pre-war Taylorcrafts and Cubs used 1020 or 1025 I believe.

The big question is why would you want to save a small handful of money by using electrical conduit or water pipe, when it would cause two large handfuls of risk, worry, failure modes, quality control issues, etc?

 

[rv7charlie]

DOM starts out as ERW with one more step in the process. What ERW might do is split in a crash. As for strength, that’s math class.

So...Grade 5 bolts from the hardware store are OK to replace AN hardware? ;-)

 

[12notes]

So...Grade 5 bolts from the hardware store are OK to replace AN hardware? ;-)

If you design to use Grade 5 bolts, then yes.

I think some people are confusing ERW tubing with electrical conduit. While conduit is a type of ERW tubing, so is DOM. DOM is a step in the process of making "seamless" tubing.

Pretty much all commonly available tubing is Electric Resistance Welded (ERW) tubing. This can be made with cheap thin steel with little to no QC that is used for electrical conduit. Or it can be made from decent steel to make "normal" ERW tubing. Finally, ERW tubing can be Drawn Over a Mandrell (DOM) to remove the internal welding flashing and cold form to final shape to make DOM tubing. It is called seamless but the seam is still there, just smoothed over.

Aircraft should be engineered to be nowhere near the burst strength of the material in any condition anywhere close to their flight envelope. If it's properly designed for ERW tubing, then it's not going to break up in flight because of any property of the material. For that matter, you could safely design a plane to use electrical conduit, although it would likely be very heavy, as you would need to use a lot of it. In a crash, though, "normal" ERW is more likely to burst at the seam than DOM.

There are tubes that are not ERW at any point and are truly seamless, those are Cold Drawn Seamless (CDS) and Hot Finish Seamless (HFS), but they are not commonly used. It is possible, but I've never heard of it being required for any kind of homebuilt aircraft.

 

[rv7charlie]

*Nothing* is technically 'required' in homebuilts. What is prudent, or what you can get past the inspector for your a/w cert, are different matters.

I think that you will find that 4130 tubing used in certified a/c, and in all steel tube homebuilts of which I'm aware, is seamless tubing. Will you get away with using seamed tube? Maybe; maybe even probably. But seamless 4130 is the the proven standard, and never forget that a/c manufacturers are businesses, and they cut every corner they can without costing themselves money for killing people. If they thought they could safely save $2 per a/c by using seamed tubing, they'd find a way to get it past the FAA.

Grade 5 hardware is almost identical in *design strength* to AN hardware, so if the structure is designed for AN hardware, grade 5 will meet the strength requirement. But that isn't the only metric. I probably have some grade 5 stuff somewhere in the various homebuilts I've owned, but none in structural or corrosion sensitive locations (in either the bolt, or surrounding structure).

A lot (well, some) of the FAA stuff is overboard for little airplanes, and I'm sure most of us have bent some rules/recommendations on occasion, but when you're talking about structure, most of the rules & recommendations really are 'written in blood'. There are often places where we can do better, but it rarely makes sense to do worse.

Charlie

 

[Victor Bravo]

There are often places where we can do better, but it rarely makes sense to do worse.

This.

 

[TFF]

Not condoning, just acknowledging. Homebuilts are much more up scale today across the board. Not that many use to sub stuff, but there were times when homebuilt airplanes were for the scrounger who wanted an airplane because a new C150 was $7000. He could build a plane for $1500. Look at late 50s early 60s ones that don’t go to Oshkosh and they are a Johnny Cash Caddy. Most are not too bad but the craftsmanship is either stellar or whoa.

Grade 5 was the best choice for bolt in roll cages in those car classes. It’s math class, what do the numbers say? Easy to just say use aircraft hardware, I do, but like running numbers for any material Is running numbers. If it fits, it fits. Not running numbers and just using it is what most are asking the question for.

 

[Brünner]

PDQ Aircraft Products PDQ-2

en.wikipedia.org

Wayne Ison. Plans?

A Polini Thor 250 would be perfect for this.
Probably a bit more expensive than an industrial engine, but well proven.

 

[GeeZee]

I’ve been looking at DOCOL. Supposed to be 10-15% stronger than 4130. Approved for race car frames/roll cages. It’s ERW. Looks like some of its strength is from heat treat so it’s recommended to be welded with TIG or MIG only. There are some interesting YouTube vids. I haven’t checked recently but it was less $$ than 4130. To veer back closer to the OPs original question I guess the goal would be to save a little weight without sacrificing strength (and thereby maybe making a V twin a little more viable in certain airframes).

Docol® - A.E.D. Motorsport Products

www.aedmotorsport.com