Collaborative Design Challenge – Working Together to Create a Plans-Built Design

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BJC

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Yes it will help if you are experienced enough going back and forth between the real world and the CAD machine. But most people aren't. Most people have unreasonable expectations.
You guys seem to be implying that there is more to designing an airplane than simply drawing or even animating a cute little shape in a computer and calling it a design. I'm shocked! :)


BJC
 

Riggerrob

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What are the engine choices?

.........................................................................

OP suggested three of the most popular engines: 80 horsepower Aerovee (Volkswagen based), 100 hp Rotax and 120 hp Jabiru.
OP is wise to limit engine choices to popular, proven engines because that choice limits time, frustration and dollars invested in firewall-forward development.

OP has also wisely limited the mission to the that served by popular trainers made by Diamond and Cessna. Which limits it to 2 seats, side-by-side, 3 or 4 hour endurance, docile handling, decent short field performance, etc. Like most of us, he hopes to improve performance over Cessna 150 (e.g. cruise faster than 100 knots) by building a lighter, more streamlined airframe.
I tried to limit my suggestions to cockpit size and manufacturing methods that fit within OP's mission.

People, let's focus on the OP's mission and objectives.
 

autoreply

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If that's the mission; look no further. The Dyn'Aero MCR01 has done exactly that and is an all-round splendid aircraft. Works well in the real world too, including flight schools, towing gliders and rough strips.

230 kg empty, 180 mph cruise (100 hp WOT), 35-45 kts stall dependent on wing.
 

cheapracer

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OP suggested three of the most popular engines: 80 horsepower Aerovee (Volkswagen based), 100 hp Rotax and 120 hp Jabiru.

People, let's focus on the OP's mission and objectives.
<$30K is a critical objective that steers 90% of this project, that eliminates the Rotax immediately, makes the Jab very difficult to budget for and the AeroVee's 80hp not strong enough for the mission.
 

Topaz

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I'm not sure if you are responding to Bob or me, but I think you took a left turn somewhere and kept on going. This thread is about a collaboration on building an airplane for personal use. I have zero interest in starting a business selling airplanes, or anything else for that matter. But I agree, an airplane business would be a tough go.
I was expanding upon what Bob said. Given your discussions here of late, including talk of disseminating plans, production tooling that's robust enough to be used by multiple users in widely-separated geographic locations, and the poll you posted attempting to gauge interest in the airplane itself, I'd say you're setting up a program and an organization - whether you intend to take a personal income from it or not - that will be every bit as complex as running a business, with all the same liabilities and issues.

Whether you're selling the stuff or not, you're going to be dealing with most of what I listed in my post above by the time you're done. Might as well recognize that up-front.
 

mcrae0104

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<$30K is a critical objective that steers 90% of this project, that eliminates the Rotax immediately, makes the Jab very difficult to budget for and the AeroVee's 80hp not strong enough for the mission.
Perhaps the Corvair would be a contender. I know it has its detractors around here (please, let's not rehash all that in this thread) but it's more power than the VW and less cost than a Jab or Rotax.
 

autoreply

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<$30K is a critical objective that steers 90% of this project, that eliminates the Rotax immediately, makes the Jab very difficult to budget for and the AeroVee's 80hp not strong enough for the mission.
Not at all. If a 100 hp Rotax can propell an LSA with a fixed-pitch prop, the VW sure as hell can power a 480 kg lighter airframe with the same payload and a variable pitch prop. Real world performance on significantly heavier airframes on considerably less power works out just fine, as long as drag, especially induced is kept low. Plenty of LSA's that piss away 40 hp in climb to overcome drag. Halve that and 80 hp gives the same performance...
 

cheapracer

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I figure there will not be enough expertise/time/money in this program to get the compromised result pulled decently by only 80hp.
 

BoKu

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This whole thread reminds me of the best job I never had; when I got a lowball job offer from Eclipse Aviation to develop documentation for the Eclipse 500 VLJ. Unfortunately, I had to turn it down; I could survive on what they offered, but that's about it.

Vern Rayburn somehow had it in his head that Moore's Law had some sort of universal applicability, and surrounded himself with a bunch of others whom he'd so convinced, none of whom had ever run an aircraft development program of the kind of breadth and complexity commensurate with the cutting-edge nature of what they were trying to do. He thought he was going to sell 3k units a year at $ 0.88M. The which he might have done, but by the time any really went out the door the price had about doubled and the performance was much below promised.

The last straw was probably when they realized that their little Wms motors would produce the required thrust, but not while providing enough bleed air and electricity to keep the rest of the airplane and the people inside happy. T'ain't no fixing that in the software.

Thanks, Bob K.
 

WonderousMountain

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I agree,

the Suzuki 13B is a superb choice, I've owned one and researched it thoroughly. Cheapy and I are both blueprinting/building engines with different objectives.

Of course there are more traditional choices which have good safety records as well.

LuPi
 

Nims11

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To Bob and Topaz, all these comments where you elaborate on the obvious difficulty of building a lower cost airplane, what is the real purpose of it? These difficulties you are dwelling on are obvious to me, and I'm sure to anyone else with a brain (even non-engineers or experienced builders). If you focus on the difficulties as insurmountable obstacles and not problems to be solved, then progress is impossible.

Bob, let me ask you this question, as ridiculously hypothetical as it is; if your life literally depended on designing and building an airplane like I've been describing for a cost of $30k, using your obvious intelligence and experience, what could you come up with? What general direction, and potential technologies, would you point to, at least as a starting point?
 

Jay Kempf

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One must remember the premise. A group decides to build an airplane one for each member. That means the labor is free within the group and there are no overtones of building it for production is my take on it. The idea is that the group pools their knowledge, money and labor equally to achieve an airplane for each member. The reason for doing this could be a few things or a combination. One could be just getting an airplane that doesn't currently exist. Another could be making something like something that exists but for a much lower overall cost. Another could be just wanting to build vs. buy. I think the real reason ends up being somewhere in between all of them.

A The Dyn'Aero MCR01 or a Diamond DA20 are both good marks to hit. To get the same specs for $30k per member would be a reasonable goal. With good design and scrounging it can be done. Think about coordinating with people that currently have molds for wing skins, canopies, cowls, etc... and start working deals for a set of parts and design and build the rest. Get out of the box on how to make parts and molds for cheap for a few or a dozen sets of parts and solve those problems and then start filling in the blanks. All doable.
 

Nims11

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What are the engine choices?
Actually I was asking about your open source project.
But, yes engine choice is critical. In fact the more I think about it, it is the most critical thing, and maybe the focus should be not on designing an airframe at this point, but a collaboration on matching an off-the-shelf auto engine with a technology and prop that could work as a airplane power source. And I know, this has problem has been worked on for a long time.

If that's the mission; look no further. The Dyn'Aero MCR01
Thanks for pointing out this, and the Europa from another thread out as options. Both nice little planes, and it confirms for me that a plans design of a plane of this type is doable and would save cost relative to the current cost to build these planes.

Not at all. If a 100 hp Rotax can propell an LSA with a fixed-pitch prop, the VW sure as hell can power a 480 kg lighter airframe with the same payload and a variable pitch prop. Real world performance on significantly heavier airframes on considerably less power works out just fine, as long as drag, especially induced is kept low. Plenty of LSA's that piss away 40 hp in climb to overcome drag. Halve that and 80 hp gives the same performance...
True, the MCR01 uses a 80HP engine and cruises at around 180mph. Replacing the rotax with an aerovee would save 15k or so and not give up performance. The VW may not be the best engine in the world, but this just illustrates that other engine options are possible.

In terms of frame weight, Bob mentioned in another thread that carbon fiber has really come down in price. In any case, a carbon fiber frame might be best because even though it increases cost of the frame it could reduce cost in the engine because of its weight reduction. And the engine is the the lion's share of the overall cost.
 

Jay Kempf

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About 850cc dry sump twin water cooled with a turbo and EFI would be a nice little engine. About 100HP at FL10 would be nice. A belt drive PSRU or a Rotax B box would work.

How much do you think that would set you back and how much do you think it would weigh?
 

Topaz

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To Bob and Topaz, all these comments where you elaborate on the obvious difficulty of building a lower cost airplane, what is the real purpose of it? These difficulties you are dwelling on are obvious to me, and I'm sure to anyone else with a brain (even non-engineers or experienced builders). If you focus on the difficulties as insurmountable obstacles and not problems to be solved, then progress is impossible.
If I had a dime for every time someone called me, "negative", ... Well, I'd be better off than I am today. You're going to have to deal with these issues, at some point in the process of getting where you say you want to go. None of them are show-stoppers, none of them make progress "impossible", but if I also had a dime for every time I've had someone call me "negative" and say, "Don't worry so much, it'll all be fine!", only to have exactly the issues I raised at the beginning prove accurate in fact, I'd be a lot better off than I am today, too.

Your mileage may vary, but personally I'd much rather know all the possible pitfalls and issues right up front, so that I can plan and deal with them as part of my plan. My posts were intended in that spirit, not some kind of nay-saying. Best of luck to you.
 

TFF

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I think it is impossible to get a crew together unless they're close family. Too much to ask for. It's also a little sleazy to as someone to do all that work for you. Waa, I cant afford what I want. That is a lot of aircraft snobbery for not being able to contribute. Aircraft snobbery really means your not into it. You could be ripping out a Tailwind for $20,000 including a Dynon panel; wheels up. Too ugly so I won't fly at all until I get what I want exactly. Nothing wrong with dreaming big, but you have to be realistic in your world, and getting someone to 100% design and others to 100% manufacture while you are just a consumer is a joke. There are people here who are learning the math and the engineering on the side so they can build what they want. Not freeloading.
 

Rienk

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About 850cc dry sump twin water cooled with a turbo and EFI would be a nice little engine. About 100HP at FL10 would be nice. A belt drive PSRU or a Rotax B box would work.

How much do you think that would set you back and how much do you think it would weigh?
Jay, were you referring to a particular engine?
What you describe sounds very much like the Weber MPE.
Available for about $6k, plus redrive and any mods needed. Lucio at Aeroshop is building up just such an engine.

We are considering using it in our Duet (will be very similar to the Dyn'Aero MCR01, with the goal of retailing as an RTF LSA for under $60k).
But the starting engine will be a VW derivative - probably RevMaster or clone (which we would ASTM certify)
 

BoKu

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To Bob and Topaz, all these comments where you elaborate on the obvious difficulty of building a lower cost airplane, what is the real purpose of it? These difficulties you are dwelling on are obvious to me...
If the difficulties are so obvious to you, I suggest you offer us some real numbers that show how you propose to succeed at an endeavor where folks way smarter and more experienced than me have failed.

...Bob, let me ask you this question, as ridiculously hypothetical as it is; if your life literally depended on designing and building an airplane like I've been describing for a cost of $30k, using your obvious intelligence and experience, what could you come up with? What general direction, and potential technologies, would you point to, at least as a starting point?
The only possible way out that I can see requires a fundamental sea change in the way folks conceive of general aviation. Basically, you have to rejigger the relationship between society and aeronautics such that you can sell about 100k units of your design at a run rate of about 10k units/year. That gives you a total program revenue of $3B at a rate of about $300M/yr. You will have enough pull in the marketplace to get great prices in materials, and your run rate will pay for developments that will drive per-unit labor and build-hour rates down to what we see for mid-range cars.

The technologies I'd pin my hopes on are those that support autonomous flight. Basically, you drive to the airport, tell the airplane where to take you, and wait while it takes you there. No license is required.

From there, the biggest challenge is probably establishing and maintaining the required infrastructure of airports and traffic control.

Thanks, Bob K.
 

Nims11

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If I had a dime for every time someone called me, "negative", ... Well, I'd be better off than I am today. You're going to have to deal with these issues, at some point in the process of getting where you say you want to go. None of them are show-stoppers, none of them make progress "impossible", but if I also had a dime for every time I've had someone call me "negative" and say, "Don't worry so much, it'll all be fine!", only to have exactly the issues I raised at the beginning prove accurate in fact, I'd be a lot better off than I am today, too.

Your mileage may vary, but personally I'd much rather know all the possible pitfalls and issues right up front, so that I can plan and deal with them as part of my plan. My posts were intended in that spirit, not some kind of nay-saying. Best of luck to you.
I appreciate that your comments are in the spirit of pointing out potential pitfalls. But it is not simply that I think your being negative, some of your comments are gross exaggerations. Like when you said in order to copy a DA20 you would have to buy one and tear it apart. Or in this resent post where you went on about how we have to account for employ cost, sick leave, insurance, business license, marketing and advert, , bookkeeping, tax prep, legal service, cleaning service, blah, blah ,blah. We're talking about individual guys working on a homebuilt out of their garages, and collaborating remotely. Where is the employee sick leave and marketing fees in that? Even having to respond to this is tiring and counter productive. I sense that you are genuinely trying to be helpful but... I can't see it as anything but an exaggeration, or worse irrelevant.
 

Nims11

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If the difficulties are so obvious to you, I suggest you offer us some real numbers that show how you propose to succeed
I said I understand the difficulties, that does not mean I have a solution to the problem, those are two different things.
 
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