# Rear Bear Vs. The Russian Bear

Discussion in 'Aircraft Design / Aerodynamics / New Technology' started by pie_row, Dec 2, 2009.

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1. Dec 29, 2009

### JimCovington

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Yes, if you call it that. It's a foot-launched glider. The carbon dragon lands on a wheel, the magic dragon (I think - it's been a while) lands on a skid. The magic dragon is lighter. You'll have to add more weight for a wheel (maybe) and more weight for engine instruments.

Think about it for a second - you're talking about removing HALF the weight from one of the lightest rigid airframes in the world. It's a VERY light airframe. This plane was planned by people who weighed each part to the TENTH of an ounce - and you're going to remove 70 lbs - ONE THOUSAND+ ounces.

The weight's just not there to remove.

You say you'll get the weight from the wing. The wing is designed to weigh 68.6 lbs. That means you can THROW AWAY THE WING from a plane that is SEVENTEEN INCHES WIDE at the seat and you STILL are over your limit. Of course, with no wing, your aerodynamic profile will suffer somewhat. :gig:

BTW, you can't just ad an engine without an engine mount. That energy has to be transmitted to the airframe somehow. Ooops, more unplanned weight!

Are you beginning to grasp just how impossible your 100lb high-AR high-performance plane is?

Again - WHAT are you removing? It's already one of the lightest airplanes in the world! You keep saying you'll "remove weight" but haven't offered anything concrete - just your opinion that skilled designers & builders in front of you have been ignoring one of the MOST important factors when building for years. I don't buy it.

2. Dec 29, 2009

### Starman

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That's right, people would pay to see it! So maybe I should go for it, I could get rich. Anyway, it's all been done before, even back as early as 1907:

Yes it's only a model, but it doesn't weigh much, and it's so obviously safe, otherwise all those people in bowler hats wouldn't be standing so close to it. You could make a larger version of the same model and add extra rockets to it so than you could light one at a time for longer trips. Change the landing gear from four wheel to taildragger, build a sling seat into it, and you're good to go, personally I would get rid of all the wires and use a cantilever wing with milled out titanium D section spar. You could use fabric for the rest of the wing so that when your speed was high enough it wold be self shedding, which would atomatically (atomically?)decrease the drag.

3. Dec 29, 2009

### pie_row

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We aren't communicating. I don't see how to show you what I'm looking at in a way that will fit into your head. I fit my turbos into your head. I can't fit my plane. I'm sorry.

Magic Dragon is this the sailplane you are talking about?
140-68.6=71.4

4. Dec 29, 2009

### Topaz

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Pie_row, one of the things you're going to have to learn in this world is how to communicate what you think and feel. Yes, I understand and sympathize that you have an extra challenge in doing that. I do understand what your particular situation entails (my girlfriend is an occupational therapist, and works with autistics every day).

HOWEVER, when it comes right down to it, your communications problems are your problem, not the world's. Several times now you've put off your difficulties in this thread as communication issues related to your Asperger's. Simply put, I don't care. Neither will your future boss, nor your future spouse. You need to earn a living and you probably want to find a mate. People can accommodate you only so far, but fundamentally the problem and solution is yours. One of the things that usually comes with Asperger's is a high degree of intelligence, which you obviously have. Put that to use on the communication problem. It'll be far more useful in your life than any engineering you could ever do. Stephen Hawking manages to communicate deepest cosmological theory to others despite his advanced disability. I'm guessing you can find a way to describe a wing structural concept to us despite yours.

Find a way to translate. Find a translator, if you must. You've got a huge challenge in this and a definite disadvantage, I understand. I feel for you, I really do. But you're going to continue to be discounted until you can clearly communicate your thoughts and ideas to the rest of us in the world. Time to stop making excuses; time to stop saying, "I can't". Your future is waiting. Don't let this hold you back.

Last edited: Dec 29, 2009
5. Dec 29, 2009

### JimCovington

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LOL - incorrect application of logic.

This is absolutely, positively, the best thing ever said in an aero engineering forum. You, sir, win one Internets.

6. Dec 29, 2009

### JimCovington

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I'm willing for you to try again. You said it would be able to weigh less than the Magic Dragon because you'd decrease the weight of the wing with reduced surface area. We agreed (I think?) that you would need to add about 30 lbs, total, (gear/engine/cowlings/prop/exhaust/engine mount/fuel systems/instruments) to a sailplane to make it a powered plane. That means you need to save about 70 lbs of weight from that design. The wings weigh less than 70lbs, which means your proposed logic for saving 70 lbs of weight in the wings is flawed.

Where are we not communicating?

Yep, that's it - a staggeringly light rigid enclosed-cabin airframe. It's the most like what you've proposed out of anything I've found flying today. If you have something you think is more similar, let me know and we can use that as a starting point.

If you say it's not like your plane, fine - but let me know why. And remember that this 140 lb airplane was built by someone who was measuring to the TENTH of an OUNCE. Every piece was weighed on a friggin postage scale. I have NO idea how you're going to build something 70 lbs lighter, and all we've heard from you is mumblings about carbon spars and weight savings. That plane uses carbon spars, and it JUST DOESN'T HAVE 70 LBS OF EXTRA WEIGHT.

Seriously, look at it! Look at the canopy cover - it's ridiculously flimsy. It doesn't even have a hinge, because a hinge is wasted weight.

We seem to agree on the facts and come to remarkably different conclusions.

7. Dec 30, 2009

### JimCovington

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So I thought some more about this, and I think I know why. It's not that you're not communicating. It's *what* you're communicating. Let me explain.

You turbo designs involve an architecture and a method for reusing exhaust gases that, to the best of my limited knowledge, is not in use today - yet is potentially feasible. That's why I "buy" the massive performance improvement - nobody else is doing it. Will it work as advertised? Hell, I dunno. But it's at least plausible that your new design - if buildable in the real world, let's not forget - *could* be a radical leap forward.

Now let's look at the airframe structure. Your various proposed construction methods (carbon spars, D-cells, glass over foam) are all relatively tried and true construction methods in use today. People use these methods daily and work hard to extract as much weight as possible. We know they're close to the edge because they occasionally push the envelope and fail. So when you say you'll make a massive performance improvement by doing exactly what everyone else is doing, but (here's the kicker) you'll do it ten times better - well, that I just can't swallow.

Like you said earlier, you need to think outside the box on this one. Your turbos are outside the box. Your airframe structure, as "radical" as carbon spars are, is plain vanilla in today's engineering world. So no, I don't think you can do radically better than today's best homebuilders in your airframe structure.

And yes, you need radical improvements. Can you find 2lbs to drop off a structure like the carbon dragon? Probably. Can you find 70lbs? Not bloody likely.

Or am I missing something? Is there an outside-the-box structure idea I'm not getting? We've already taken into account the lightweight engine & the mono-wheel gear. Is there anything else I'm missing?

8. Dec 30, 2009

### Autodidact

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Ta-da!

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9. Dec 30, 2009

### JimCovington

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10. Dec 30, 2009

### Orwasi

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@ everyone: first post, so be nice

Following this thread, I've been amazed, perplexed, confused, infuriated and puzzled (sometimes all at the same time). The one positive thing that's come out of it - for me, at least - is further reinforcement of the depth and breadth of my own igorance regarding all things aviation.

@ pie_row: I have a few comments and suggestions for you. Please don't take these as patronising or belittling, because (1) they aren't meant to be, and (2) see above paragraph re iggerence...

Don't try to build a record breaker at your first attempt. That will take too long, cost far too many , and may result in serious injury or worse. Lower your sights a little, and aim for something a little more practical.

Put the 0.5lb/hp megamonster aside for a while, and aim for something that would attract interest from the wider aviation community. Aim for a 1lb/hp ratio to start with, and once you're happy with that, move on to the bigger and better things. If you can demonstrate, for example, a 150lb engine that produces a reliable 150hp, you will get more interest and attention than you can handle. If that engine also burns an automotive gasoline / ethanol blend, interest will more than double (WAG)

However, the key word above is demonstrate. Design and build the engine, build a test rig to provide an aircraft-equivalent loading, and test it thoroughly. Don't forget durability; something that needs a serious rebuild every 100-200 hours ain't gonna cut it.

Don't worry about finding an application for your engine. If you can demonstrate it, there will be any number of people willing to apply it for you. If you must do something with it, put it in a kit car. Compared with designing and building any airplane (especially a record breaker) building a kit car is almost trivial.

Anyway, that's my $0.02, thanks for reading. Tony 11. Dec 30, 2009 ### autoreply ### autoreply #### Moderator Joined: Jul 8, 2009 Messages: 10,732 Likes Received: 2,544 Location: Rotterdam, Netherlands It's a bit more complicated than that, but the counter-torsion structure is much heavier than the whole spar is. Let's look at those remarks for a while. If you're making a claim you have to prove it, not me to disprove it. I and many others are polite enough to tell you friendly that your ideas (not all of them, but most and most combinations of ideas) are not realistic. I tell you, it's impossible to have a 16 lbs, 16 HP installed aircraft engine including prop. Glider pilots are willing to trade or compromise everything, including steep maintenance, reliability and their wives to loose weight. A turbo (30HP-ish foldable engine) is in many environments almost a requirement. Again, lower weight to whatever price and that price is very steep. So, we have a two-stroke engine plus prop, driven by a belt for a total weight of 37 kg (80lbs). That's the minimum weight, no electric starter (windmilling), no engine mounts (that's not included in the weight), no battery, just an engine, prop (fixed pitch, LIGHT) and a reduction drive. You won't get rid of it since that'll ruin your prop properties, but just assume we can ditch that weight too, that might get us to 35 kg (75 lbs). How in heavens sake are you going to scale that down to 16 lbs? I've been discussing with Autists/Aspergers a couple of times and had the pleasure (without sarcasm) to meet (some of) them in real life afterwards as well. Some are capable of more or less understanding the excellent points Topaz wrote, most don't. That majority usually ends up pretty sad "because no-one understands them" and that's a self-reinforcing attitude you don't get away with in real life. There's a good reason I've told you several times before: "go out and prove us wrong" since reality is the ultimate judge, not the way you communicate, perceive or think, or the way you type some words over the internet 12. Dec 30, 2009 ### Starman ### Starman #### Well-Known Member Joined: May 17, 2009 Messages: 2,011 Likes Received: 61 Location: High in the Andes Mountains Very good! I was thinking of a shape like this for my low aspect ratio ultralight because it's the lightest possible shape for the wing area. With this you could meet FAR103 with a 100 pound plane, not counting engine and fuel and maybe landing gear. Are we counting those things yet? The problem with that design is that there's no view of the scenery from the cockpit, the cockpit should be at the leading edge for good visibility, with the engine at the back for balance. Here's one with better visibility: 13. Dec 30, 2009 ### JimCovington ### JimCovington #### Well-Known Member Joined: Mar 30, 2009 Messages: 217 Likes Received: 0 Location: Burlington, VT There are many who think that's a highly underrated design that had the misfortune to appear at the beginning of the jet age when just about everything with a prop was considered old-fashioned. Since it required big props to neutralize the large wingtip vortices and could't be converted to a pure jet, it got left behind. Charles Zimmerman and his "Skimmer" | Flight Journal | Find Articles at BNET It was designed for a 425mph top speed and a 20!mph landing speed. That 20:1 ratio beats the snot out of the 4:1 that's the goal of many designers today. 14. Dec 30, 2009 ### pie_row ### pie_row #### Well-Known Member Joined: Nov 9, 2009 Messages: 710 Likes Received: 2 Location: salt lake city Ut You changed what you wrote and what you quoted of me after the fact. And so this statement of yours is a lie. And in doing this you abused you moderator privileges. Last edited: Jun 22, 2011 15. Dec 31, 2009 ### JimCovington ### JimCovington #### Well-Known Member Joined: Mar 30, 2009 Messages: 217 Likes Received: 0 Location: Burlington, VT Excellent! I'm really looking forward to it. There are also some basic aeroengineering programs that allow you to draw planes *and* test them. http://www.homebuiltairplanes.com/f...technology/5025-what-software-do-you-use.html 16. Dec 31, 2009 ### Mac790 ### Mac790 #### Well-Known Member Joined: Jun 22, 2008 Messages: 1,529 Likes Received: 19 Location: Poznan, Poland Theoretically it could be possible, check out this little turboprop Power 5.62KW (7.5hp) Diameter 86mm (core engine) Length 326mm (12.8in) Engine Weight 1750g (3lbs 13oz) Ancillaries Weight 200g (7oz) Propeller RPM range 1200 - 9000 RPM Wren Turbines Ltd | 44 Turboprop Seb #### Attached Files: • ###### tprop.jpg File size: 39.2 KB Views: 1,021 17. Dec 31, 2009 ### JimCovington ### JimCovington #### Well-Known Member Joined: Mar 30, 2009 Messages: 217 Likes Received: 0 Location: Burlington, VT So cute! You measure its weight in grams, its fuel flow in ounces, and its lifespan in minutes. 18. Jan 13, 2010 ### pie_row ### pie_row #### Well-Known Member Joined: Nov 9, 2009 Messages: 710 Likes Received: 2 Location: salt lake city Ut I love it when someone argues and actual believes both sides of the same argument. I really do. What a lot of people really want is a 454 chev V-8 from before emission conrtols went in. (7.5L) 19. Jan 13, 2010 ### Mac790 ### Mac790 #### Well-Known Member Joined: Jun 22, 2008 Messages: 1,529 Likes Received: 19 Location: Poznan, Poland Rather in hours, it seems that the maintenance is required after 50 hours or 500 million revolutions. Model Jet Club - Turbines. The Wren Company has more than 20 years of experience with those engines, so I think that they can build an engine which last more than few minutes, plus I really doubt that someone would pay 3000-6000$ for so unreliable engine.
Also I have more belief in those engines than in 50lbs titanium structure.

This idea isn't new.

Seb

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20. Jan 13, 2010

### JimCovington

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1) Sure people would pay that for an unreliable engine - it's going on a model airplane, after all. Crashes are a part of the hobby.

2) Their website says they've been doing it for 10 years, not 20. How many engines have they made?

3) The Wren factory site (not the distributor) says that "maintenance" may be required after 25 hours, not 50. Hmmm...your numbers aren't looking so good.

4) It's not maintenance, it's a bearing change - which is an overhaul. Changing oil is maintenance. Changing bearings is an overhaul.

So let's sum up - We have a engine that offers less time between OVERHAULS than most engines do between OIL CHANGES. It's got a TBO of 25 hours, which is 1500 minutes - less than the number of HOURS that most aircraft engine manufacturers allow.

So yes, its lifespan is measured in minutes.

And I know it's not a new idea - at least TWO!!! human-carrying aircraft have been powered by these engines. But that doesn't mean it's a practical - or even good - idea.

I am sure more airplanes will be built with these engines. But I'm also sure they'll be just novelty* acts for the foreseeable future.

*The two flying (that I know of) are novelties.

1) The jet wing requires launching from a mothership and cannot climb from sea level due to fuel/payload constraints.

2) The jet cri-cri uses almost 5lb of fuel PER MINUTE at full throttle. It's fuel load is barely FAA-legal.