Open Source aircraft thread #1 (criteria )

I feel that the majority of pilots are best suited by an RV, Cessna 182, Beech Bonanza,  Piper Cherokee Six,  Mooney M20, and a host of the more popular designs.  Certified or homebuilt all of these have this in common:  They are reliable, easy to build if kit build, hold at least 2 in a closed cabin, and have decent cross country capabilities.  They're also all very popular for these reasons.  The market has decided for what people have a real need in airplanes.  It is NOT what is available. 

"Fun" flying is, to some extent, a misnomer.  I for one find flying enjoyable for the precision it requires.  But then I'm more technical in nature.  Wandering aimlessly in the sky just to burn avgas doesn't make much sense to me.

 I have an idea for materials.

I have always thought wood is a great material when mated to fiberglass to form a composite. The wood of choice should be cheap and available for everyone.

Pine 2x4's are abundant and a quality lumber store can easily get #1 clear premium studs for for pretty cheap (all things considered). A wood strip boat with a layer of glass is very strong and they use cedar. Strips can be about 3/16 thick and 3/4" wide. A simple 2x4 can yield quite a few strips and the goal should always be for the common guy with a small bank account to be able to build one, I think this would go a long way towards that goal if pine was used. It just needs to be designed around the material. Obviously you cant substitute pine for sitka spruce in an existing design but if the design was based around using only pine then it becomes possible.

What do you folks think?

Just my two Yen

MJ

Well, the problem with pine is what species are you dealing with?  What is avialable at your friendly luber yard is likely Eastern White, BUT you can't always be sure.  And a lot of pine has knots and knots decrease the strength of the wood.  Then there are the checks (cracks) in a lot of the kiln dried boards....

Besides, if you're going to layup fiberglass over the wood to enhance the strength, you can use foam for the same purpose and get a lighter aircraft to boot.  The difficulty with this is that "moldless" construction is time consuming and messy.   It also causes somepeople to develop allergies to the resins and is very dusty. 

There are actually plenty of aircraft that can be built for say $30 K or less.  There's even at least one RV6 that was built for less than that.  Sure it won't win "Best of Show" but it flies straight and true.  Builders just have to be creative and scour and scavenge for parts.  In my case I have been able to collect enough parts for TWO Continental 520s for less than 6K; one of those had the turbochargers with it..  Most are in overhauled or used serviceable condition.  One set of cylinders was bought for less than $500 for the set of 6, again in serviceable condition.

You and I can both afford airplanes but that"s not what this thread is about. It's about trying to build something more affordable. The people suited to this type of project are not RV people, that's something totally different, not everybody likes RV's either. Again, this is about doing something that's never been done and it's fun to see what people come up with.

Like I said in my post, pine needs to be #1 clear and it's a premium lumber available from a lumber mill, and it's cheap. I'm not totally sold on pine either, it just an example that needs to be proven. Foam is nice and light but that's already been done.

Cedar kayaks have a ton of knots in them and they are very strong. An airplane can be made out of anything including paper if  it's engineered to be strong enough. The material really isn't the point, but rather to explore and do something different. I'm pretty sure that's what Burt Rutan did as well, he thought outside the RV box and did something totally different.

All I'm saying is an exercise like this is how things are created, not copied.

MJ

I'm not one of the RV crowd either, really.  But the fact is that economic construction has been out there for a long long time.  Many of the Fisher products (wood and fabric) can be built for less than 15K.  They won't haul much or fly very far, but they're out there, have good support and have a following if not well known.   Then there is the Bowers Fly-Baby.  All up construction with a decent little motor will be about 15K.   Again it is largely wood, fabric and Plywood.  Wrap it in fiberglass if you like, but the airplane is safe without it.

So what is the point of this effort anyway?  To re-invent the design contests of the 1960s where there were some good designs and also some very bad ones? 

As I understand the concept of "open source" (at least how it was for computers) you could mix and match components and still end up with a workable product.  it might not be a barn burner, but it worked.  It probably won't work very well for aircraft. Longitudinal, yaw and roll stabilities all have to be within decent parameters otherwise flying qualities become dangerous.  CG ranges and changes due to fuel burn have to work in unison.  There are lots of designs that didn't make it because it didn't work in the air.  That's why light aircraft all really look about the same.  The same can be said about large aircraft as well.  

What we're doing today is nibbling away at the margins.  Sure we can get anything to fly and some might be more efficient at a particular "point" in the envelope.  But in the real world airplanes are compromises.  Designers have to work withn that very narrow envelope.

Take this argument to the "What happened to wood" Post. Seems to be lots of common interests there.

I am quite interested in the concept of an open source aeroplane.  

There are quite a few projects ongoing to do an open-source car.  An aviation effort started a few years ago http://www.ligetistratos.com/  but nothing seemed to come of it. 

I have sometimes thought that an electric aircraft might be a good contender for open source collaboration.  You avoid the "ho hum, it's all been done before" way of thinking... there are some broad new horizons to seek, and some major new challenges to overcome.   It also seems like there are some very distinct specialist disciplines that are unlikely to exist strongly in a single individual and need to be somehow melded together in a team approach - energy source, software / controllers, motors,  airframe & aerodynamics, money. 

Aviation grade components are predictable as to their strength by testing and quality control.  That's why they are more expensive than hardware store and lumber yard materials.  You can design with them for structural integrity.   Wood for aircraft use is cut up differently to achieve the strongest grain profile and the plywoods have more thinner plies, the right glue and NO VOIDS.  Any aircraft that needs a certification would be unlikely to pass inspection for that purpose without approved materials.  If you are talking about an ultralight vehicle, you can use anything you are willing to bet your life on.  I wooden't!

Getting back to the general design criteria, I would suggest a very light aircraft with a less expensive powerplant, say the Aerovee 2.1 for power and weight and speed limits within the more restrictive European microlight norms (450kg/990lbs MTOW) to make it a "world" aircraft, at least potentially.

Personally I would like to see a modern interpretation of something like the old Hillson Praga (a license-built version of the Praga E-114 Air Baby) with the same thick, cantilever shoulder wing and the ability to look over or under the wing as needed.  I also think that composite construction adapted without mercy for speed and efficiency in construction, perhaps with parts cut from flat sheets, layered one on the other and interlocking like a balsa model, perhaps even fabric covered, has great potential.

Check out this site (in Russian, I mean for the photos), note the neat canopy arrangement and imagine tricycle gear if you prefer.

http://www.airwar.ru/enc/law1/e114.html

Cheers,

Matthew

I just feel I have to stick my oar in, and remind folks that A) EAA *did* have competition for an easy-to-build homebuilt, and B) The plans for this airplane are *still* available for free download by EAA members.    Start Here .

Hi Ron, thanks for the link. I actually have the original EAA book that was produced and has the plans inside it. I have always been a big fan of the Fly Baby, and that's why I'm building a Stits Playboy. The timing was right and it sort of landed in my lap. It's not a Fly Baby but it's a single seat open cockpit that's similar looking. I figured it was close enough in the type of flying I enjoy so I went with it instead of the Fly Baby. Fly Babies rule!!

What i was thinking and I think Matthew as well, was to come up with something different. I have no idea what, but I figured we could all identify problems first and start working around it.

I'll use engines as an example. I am very blessed but some folks who want to get into aviation still have a very tough time, one large expense is of course the engine. I don't know the solution to this but as long as we have certain problems we can always find a solution. Here are some of the thoughts I have on this subject:

The Briggs Vangard V twin engines are top rated. I have very influential friends at B&S and can get access to the engineers. Maybe the solution is to create a 4 or 6 cylinder using parts and components of this engine. They are available at every small engine repair shop in the country for pretty cheap. I come from a family of manufactures and have met quite a few people over the years and some of these people are in the casting and pattern business. People often times think casting an engine block is expensive but there are ways to cast it rather reasonable. I also know a forging company that makes engine parts including crank shafts etc. What I'm saying here is I can't know what the future holds but in my experience I have long held the belief that anything is possible as long as we start the process of learning. The most important thing for me is to not look at the past and just imagine in my head "what is it I want" then start creating it. Maybe the solution is to make critical components and let the builder buy the rest from a service center. I don't know but it's worth thinking about.

Hangar space is hard to afford for many people and if anybody thinks that will somehow magically get cheaper in the future their wrong. Ten years from now how much will hangar rent cost?  I bet it will leave many people out of the aviation game. I think an airplane with real folding wings could be a great solution. Maybe not either, maybe it's something that's never been created like a folding airplane or an airplane that get disassembled. Like I say I have no answer but The EAA members I have met over the years can accomplish anything and I feel a new open thread type project may supply an answer or at least spark an interest in someone to move it to the next level.

Anyhow, I thought it would be something fun.

MJ

Matthew, I agree with you about using a  standard that's good for the whole world and not just here in the States.

Are you thinking single seat or a two seater?

A single seater can make the process really easy and build it with the intent of creating a two seater in the future????

Sport pilot???

MJ

Hi.

Here are some of the design goals that I would love for this to be able to meet:

• Inexpensive to own and operate.
• Two seat.
• Able to provide both a fun local flight and reasonable cross-country performance (say 200-300 mile legs).
• Long lasting. ie: not deteriorate easily.
• Materials easily procured for reasonable prices.
• No medical required.
• Easy to work on and store.

With that in mind, what I think would meet those criteria would be:

• Motorglider.
• Folding/removable wings.
• Trailerable.
• Metal construction.
• VW/Geo type engine (or similar weight, price, performance).

Anyway, just a little fuel for the discussion.

Claude

This is my idea.

Alum. tube, pop type rivets and fabric covering. (All proven, no guessing about air worthy material.) Single place.Rotax 503 pusher, tri gear. Empty 250, gross 500.  Wing area 64 sq ft. Now for the kicker. Canard up front, bi wings in the rear with a span of 8' each.  So you would have a plane that could be flown as light sport, trailered without folding wings(how many of the folding wing planes are really taken home after each flight.)  Back the car up to the garage, hook up the trailer and pull the plane to the airport (just like pulling a boat to the lake.) Unload off trailer, pre flight and go flying! Shipping materials is also expensive, so all tubing could be 4' long. Could be the new VW of the air.  Bob

I love the idea of this thread.  IMO, there are several good "low-buck" homebuilts to choose from already.  Fly Baby, Pietenpol, Fishers, and on and on.  Personally, I've just about talked myself into putting the Ultimate on hold and building a Piet first.  What I'd REALLY like to see is an annual issue, or maybe a monthly column, dedicated to "low-buck" flying.  So many new pilots have not been exposed to the joys of low and slow and once they are...well, its pretty addictive (fortunately for me and my business).

This is my list of requirements for low buck.

2 seats, 4 cycle power, classic looks, simple construction.  Go ahead and comply w/ LSA specs too.  Very detailed plans and BUILDER's MANUAL.  Remember, many of us have never build an airplane so hold our hands and walk us through it.

Pine is not a good sub for spruce however Douglas fir is an approved substitute.  It is available at lumber stores for about the same price.  You will need to hand pick your wood to make sure the grain pattern fits requirements.  It is about the same weight as spruce and quite a bit lighter than pine.  Buy the 3/4" boards and rip to whatever thickness you need.  Roger

Engines may be one of the largest investments in this type of aircraft.  One I think is up for consideration is the Hirth.  They had some metallurgy teething problems in the early years that seem to have been worked out.  A friend of mine bought a 50 hp twin new and fitted it with a prop and ran it.  His test sequence was to let it warm up for 2 minutes and then go to full power for 4 hours.  It then was allowed to cool for 2 minutes at idle and then shut down.   The only items changed were the belts on the PSRA.  Even the spark plugs were left alone.  The engine ran for over 900 hrs and did not fail.  It just would not start at the end.  That tells me a lot.  An engine that will run at full power and almost go to TBO means an engine that should reach its advertised 1,000 hr TBO in normal usage.  At tear down it was found that the rings were gone but the cylinders nycacil was still good.  Makes me wonder what would have been the outcome if the rings were replaced at 500 or so hours.  Most certified engines have a TBO of 2,000 hrs.  Most will need attention well before then with either rings or valves replaced in the engines and at a lot higher price.  It may be a 2 stroke but it has my attention right now for a worth while power plant for my own project.  Roger

Douglas Fir is ~25% stronger than Sitka Spruce but ~29% heavier for the same dimensions.  Do the math but if you only want to duplicate the strength, there is a minor weight penalty for using Doug Fir. 

Home Depot sells "Green Doug Fir" dimensional lumber for very little compared to Sitka (~$2.40 for a 2x4 by 8ft).  The equivalent Sitka Spruce would run ~$64, but it would of course be clear.  The wood plane I'm working on came with much of the Sitka (wing and ribs), but I still needed to get additional wood for other structure.  I found that selected green Doug Fir air dries to proper moisture content in only a few days after ripping, and by scarfing and laminating with T88 I can get any desired thickness and length.  Weight is a consideration, but at most for my plane I'm looking at a 10 lb penalty even though I'm using the same wood dimensions for the major structural pieces.  The cost however is ~5% even though I end up making a lot of sawdust.  FWIW. 

Dale O.

If you're scarfing and laminating you could probably put a lighter piece of wood in the middle to more nearly match the properties of the spruce, though you'd have to think about loads and orientation carefully first.

Although I'm not sure an open source airplane is feasible, I think some of the issues kicked around here are interesting.

One goal might be something like a VP-2 but enclosed. It may be that some of the newer materials, not necessarily the ones we think of as high tech, might enable something that hasn't been done before.

It ought to be possible to make an airplane that will fly quite well on only, say, 30 or 40 hp. Probably needs a long wing. Those Briggs engines can probably be fiddled with to get some good results. I recently saw a page someplace where they're selling 35 and 40hp (originally in the 20's) Briggs converted with PSRU's, etc. About 4k in Euros, but I don't know the conversion rate these days. The French Luciole uses a similar engine. I suppose the more reputable VW engines are the other viable alternative, as long as they're not pushed too hard.

I think another barrier, besides cost, for people is the amount of labor required to build a plane. Anything that can simplify that and still get good results is probably helpful. On the other hand, by now maybe everyone has watched so much TV that they won't go for anything that's not cool and sexy.

Using wood probably requires a skill that needs to be carefully developed before one picks out something for an airplane. I think there IS some nice wood available occasionally, though it's hard to find. I saw some Port Orford Cedar not so long ago that looked very nice.