any aviation experts/enthusiasts here?

Alexia

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i decided to build a plane for a winter project. i imagine it can't be much harder or any different than building an RC model on a bigger scale. i mean, the laws of aerodynamics are exactly the same for wound rubber toys, RC models, and the big jumbojets.

i thought the best way to start my project is to go all the way back to square one and study the Wright brothers' planes.
all three of their early functional prototypes used a 12hp piston engine that weighed over 200kg which brought the weight of the whole plane to around 450kg and it still flew.

that was all the way back in 1903 when internal combustion engines were weak and heavy, but these days even a simple lawnmower has an engine that outputs 5hp and weighs less than 20kg. there's also a lot of light materials that didn't exist back then so i could reduce a lot of weight.

so in theory: two lawnmowers match the power of the Wright plane engine with 5x less weight, modern materials make a lighter frame which means the whole thing will have equal or higher power with less weight.

it all adds up on paper but i'm still curious about some secondhand opinions because i couldn't find any useful information on google
 

Traemo

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Some things that jump out at me:
You're basically right that the basic laws of physics don't shift between the scales you're discussing; the square-cube law still applies though.
The Wright Brothers designs' use a very unintuitive and exhausting control system, something to keep in mind
Aeronautical Engineering is a complex discipline, likely why you're not finding much on Google
If you're really set on trying to build a plane, see if you can your hands on one of the kits for that or at least some designs - from scratch will more than likely take you a few years
 

LittleSissieJolie

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China makes Wankel motors in all sizes including rc planes. Can't import them to the U.S. but Mexico would. MAYBE Canada, but our current Commander in Thief calls the economy "his". The RC plane market had the only permission to ship to the U.S., and it's why junkyards won't sell Mazda motors for cars. you have to buy the whole vehicle. The RC ones are less than half a kilo and put out 5hp. I was being optimistic a few years ago about getting the British Patent Ministry to have available schematics for the Sopwith Camel but 1) I didn't have the bread and 2)couldn't find it. Now, THAT'S a project. Substitute aluminum tubes, fiberglass floor and panel and nylon instead of wood and linen components... keep the motor under 20hp and register it as a motorized kite or ultralight. Alas I can't afford the down payment on a parking space to go to any company selling the components, so I'm in the Snoopy Flying Doghouse class.
 

Llayden

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I spent 14 years building, maintaining, and testing jet engines with the Air Force. I got my Airframe and Power-plant license and have been working on some small aircraft to help fund my schooling. I am an engineering major and have had a few internships as well.

Models can be exceptionally helpful, but they don't necessarily scale (as Traemo states), especially when dealing with fluids. How a small scale model interacts with fluids is very different that a full size or large scale model. This issue is that while the model scales the fluid does not.

I don't think your idea of using lawnmower engines would work either. The issue isn't necessarily horsepower, it's torque. You won't have enough oomph to much air, or to move it very quickly.

However, if you're very interested in this (or things like this) I highly suggest pursuing the knowledge. Pursue a career path in aviation, aviation maintenance, or engineering. Find a local aviation club and see if anyone is building anything in their garage. Try your hand at building a few flying models, the more complicated the better. You have some interesting thoughts. The more interesting way to answer them is to try some of your ideas for your self. Build a small scale replica of what you're thinking. Or, even build a full size of your proposed power-plant (be very careful!) and see for your self if you can generate enough torque to move a prop, or get the prop up to sufficient speeds.
 

Elenwen

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I'm kind of interested in this, but, unfortunately, when it comes to engineering, I don't understand anything... I once participated in a project of recreating a "mehve" from "Nausikaä of the Valley of the Wind" as a sort of a designer and I must say, that while the model flew pretty well, the first trial of a full scale carcass failed magnificently. Can't say, whether there was some mistake in building or something, but the project didn't go any further... I guess the person, who had this idea freaked out and everything stopped...
 

Alexia

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I don't think your idea of using lawnmower engines would work either. The issue isn't necessarily horsepower, it's torque. You won't have enough oomph to much air, or to move it very quickly.
the thing is that i have a very tight budget so i can't afford a rotax engine or a double jet. but you seem to know a lot about this so maybe you could give me some answers that i couldn't find on google.

the only somewhat useful information i found online was about the prop speeds. according to what i read, the tips of the blades should never break the sound barrier because that would cause some sort of an interference with the airflow and heavily decrease the thrust. the optimal speed, according to google, is 2700rpm on the prop.
that's where i was left confused: if the airflow is all that matters and if the best prop speed is 2700rpm, then why can't i just use a gearbox to properly transmit the power of a smaller engine? once the engine gets up to speed there won't be any interference that would cause it to lose power. on a same note, what's the purpose of an engine with more power if it doesn't use that power to spin the prop faster? where does all this extra power go? it just doesn't make any sense to me.

so a lawnmower engine won't do it. then what about a 200cc motorcycle engine? it has plenty of torque and horsepower. the way i imagined that to work is to have the engine in the middle of the fuselage and use a transmission to spin two props. same thing that the Wright brothers did on their planes. a lot of pioneers successfully used motorcyle engines all the way back in 1920's so i can't see any reason why it wouldn't work
 

Traemo

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. . . the tips of the blades should never break the sound barrier because that would cause some sort of an interference. . .
In a way, the more likely result is that the blade destroys itself. The sound barrier (defined as Mach 1 local) really is something of a physical barrier - at that point the object is moving precisely at the speed of sound so all the air along the leading edge just keeps building up.
 

Hababhi

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I have x plane 10(a flight sim similar to FSX) and have flown planes like the Cessna and such.
 

dogboy

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My dad flew and I used to fly with him. There's a lot to know concerning flying such as aerodynamics. I think before you start, you should take a beginner course on flying and see if you like it. It will also allow you to weigh the risks. As was suggested, if you want to build a plane, buy an ultra-light kit. In the long run, it should save you a lot of money rather than a piecemeal approach and you would have the correct engine for the size of your plane.
 

Alexia

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I think before you start, you should take a beginner course on flying and see if you like it. It will also allow you to weigh the risks. As was suggested, if you want to build a plane, buy an ultra-light kit. In the long run, it should save you a lot of money rather than a piecemeal approach and you would have the correct engine for the size of your plane.
i already know how to fly and all the risks that come with it. the whole reason why i decided to do this (besides the fact that i always wanted to have my own plane) is so i can finally redeem myself for all of my failed projects and experiments. that's why pre built kits are not an option here. i want to use my own design with a fully enclosed cockpit and yoke control. it's all part of the challenge that i set for myself. if i just bought the whole thing i wouldn't acomplish anything.

the biggest challenge right now is getting the engine and all the remaining moving parts. i just can't find anyone who'd sell me just the engine without the rest of the machine
 

LittleSissieJolie

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the biggest challenge right now is getting the engine and all the remaining moving parts. i just can't find anyone who'd sell me just the engine without the rest of the machine
Gracious. Learning flight is something I've procrastinated away for the past 40 years. But I did find out from my grandpa a couple of engineering headaches... one is that the Wankel engine was made first for the Luftwaffe and... resizing solid components is a real female dog. Later I found that Wankel motors could come to the States In A Mazda or in a model aircraft kit and now even the latter is on hold. Because it's made in China. The EU refuses Mazda because of the German patent, and the Chinese versions are not very welcome in the West. Except, perhaps, Mexico. They don't care about EU patent laws. Next best is Yamaha makes a racing dirt bike, 2 cycle, you can swap the top-end from 350cc all the way to 650cc without destroying the center of gravity. I've been working on that to motorize another bicycle. Here in Colorado you can have a 49cc motor without a license. for bikes of any kind...but nobody actually checks. Non-standard vehicles is a passion of mine. Also the FAA now wants to license drones, and already have licensing issues with ultra-light fixed wings and gyrocopter craft... And with all the military bases around the Air Farts have a lot of regulations. No Fly Zones. Even hang glider use has restrictions. I'm rooting for you.
 

Alexia

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wankel engine is completely out of the question for this project. i just don't have the budget to buy a whole car just to get the engine. besides, mazda RX-8 is a damn nice car so i really wouldn't want to dismantle it.

anyway, i just remembered that my dad's car mechanic is also an aircraft mechanic and a helicopter pilot which means he definitely knows how to get the stuff i need. we're seeing him next week so maybe i'll finally make some real progress on this project. i'll certainly post some pictures once i move from the drawing board to the workbench
 

Musashi

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I've only had 3 or 4 hours of flying a Cessna 172. It was stall training.

However I prefer to fly in x-plane, that's where I learned some autopilot rf landing through the uk dude on youtube.
 

WildBlueCrinkle

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that's why pre built kits are not an option here. i want to use my own design with a fully enclosed cockpit and yoke control. it's all part of the challenge that i set for myself.
I know a lot of guys (they've all been guys) who built their own planes. Including the guys who designed and built SpaceShipOne. All of them started with kits. Every single one.

The questions you're asking here suggest you're not ready to design and build a plane, frankly. For instance, horsepower. The plane I fly has a 5.9L 200-horsepower Lycoming IO-360. That's 200HP at sea level. By the time I hit 12,500' I'm lucky to make ~55% of that power, spinning my two-blade scimitar prop at 2700 rpm (for climb, but leveled off, probably closer to 2500 depending on the mission). And yeah, once the propellor tips go transonic (which isn't exactly RPM-specific, but a function of length + RPM; most GA planes are using 74" props which have an effective operating range up to around 2700 rpm, some engines (Continental IO-360-ES) are spec'd to run to 2800, which might work if you're spinning a smaller, multi-blade prop...), the prop's efficiency drops precipitously, because it's basically doing nothing but churning the air.

You asked why a smaller engine couldn't spin a prop with a gear box. They do. The Rotax engines (912, 914, etc) do just that, operating in the 4700+ RPM range but turning a prop around 2500 rpm. But that's more noise, more vibration, more maintenance, more weight, etc. So most planes don't use a gear box. Cessna tried combining a traditional aircraft engine with a gear reduction box on the 177, and it was kind of a disaster (though a lot of that was pilot error).

Anyway. I digress. For your first effort, pick up the plans for a KR2 or somesuch and get to building. Get an engine meant for aviation purposes. Do it right. Learn a lot. There's always time enough to build your own plane, when you understand fluid dynamics properly, etc.

Oh, and, AircraftSpruce is your friend. I make a pilgrimage there regularly (they have a shuttle that will pick you up from Corona Airport).
 

WildBlueCrinkle

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Also:

http://www.redddit.com/r/homebuilt

Here's an RV-7 that broke up mid-air because it's highly experienced ATP certificates pilot exceeded the Va speed; how will you determine the safe maneuvering, etc speeds of your bespoke design? https://generalaviationnews.com/2017/12/05/rv-7-breaks-up-inflight/

And, look at all the service bulletins from Vans on their ubiquitous, professionally designed, homebuilts: https://www.vansaircraft.com/public/service-rv7.htm

This stuff ain't as simple as it looks...
 

Slomo

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Also:

http://www.redddit.com/r/homebuilt

Here's an RV-7 that broke up mid-air because it's highly experienced ATP certificates pilot exceeded the Va speed; how will you determine the safe maneuvering, etc speeds of your bespoke design? https://generalaviationnews.com/2017/12/05/rv-7-breaks-up-inflight/

And, look at all the service bulletins from Vans on their ubiquitous, professionally designed, homebuilts: https://www.vansaircraft.com/public/service-rv7.htm

This stuff ain't as simple as it looks...
Agreed, actual airplanes are not only far more expensive, they are that more dangerous as well. Hence why I keep on recommending Alexa shoud try building an ultralight.
 

Alexia

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as i already said, i can't afford a kit and/or a proper engine. i also know enough about structural integrity to design a frame that won't collapse under load so there's no need to doubt my abilities. but a sturdy frame is still just a brick without the engine and that's why i'm kinda at the point where i feel like giving up.

the only option i see here is to forget about the engine and a proper cockpit, increase the wing area, and end up with a glider that i'd launch from a nearby hill. that'd be extremely lame compared to my inital plan but it seems like it's the best i can do in this situation.
but then again, even the Wright brothers built a few gliders before their motorized prototype was ready. i could probably still bolt a couple of chainsaw engines on it and see if they have enough power to do anything useful
 

ade

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....even the Wright brothers built a few gliders before their motorized prototype was ready.
The Wright's Flyer was launched by catapult, ultimately destroying the airframe, so you need to factor in the cost of that, if you're using the Wrights as your sole inspiration.
Also, the oft quoted $1000 cost of The Flyer is over $28k in today's money (keeping in mind that the Wrights had their own factory and craftsmen and engineers in their employ); a 1978 reproduction from the original plans cost over $11k in today's money.

The cost of a modern kit compares favourably with the cost of The Flyer. Mark Evans' A Plane is Born, available on YouTube, goes through that process (his helicopter one is also worth watching).

I'd planned another reply, few days ago, but wasn't sure if you weren't still sore from all the other negative replies, and at that time saw that a Rotax 447 and a suitable propeller were available on eBay for a total cost of around $900.
Not sure if the engine was just bare-bones or included fuelling and electrical systems.
Props are readily available from the US, sourced mainly as old barnstormer parts turned into decorative ornaments. Whether they'd be airworthy or not is another matter.
On a similar airworthiness note, any land engine will need to be made airworthy, probably running into hundreds of dollars to make so.

You said originally that the numbers add up, but of the numbers that you've so far provided, they don't.
Obviously, I don't want to kick you while still down [about this], but I still do think that you need to have a rethink about the project.
And we've not even got onto construction methods and materials; btw, Wikipedia's page on the dehavilland Mosquito goes into a fair amount of detail about wooden airframe construction.

And with my earlier hint of radio control, I wasn't talking about a scale model, just more of not wanting to hear about you burning to death at the bottom of some field.
 

Llayden

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i also know enough about structural integrity to design a frame that won't collapse under load so there's no need to doubt my abilities.
I think (for those of us that have formal training and experience with this/engineering) this is what makes us uneasy. It makes me uneasy. You haven't really shown much proof of understanding static or dynamic loads, much less anything to do with power transmission. You could help all of us by sharing your plans? Show us your idea, show us your design and planned building materials.
 

Alexia

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i never intended to replicate the Wright flyer. it's a terrible design. i just thought that if they could build a flying machine all the way back in 1903 i should be able to do the same since i have a lot of better materials available.

as i already said, any rotax engine is completely out of the question for this project. if i had the funds for it i wouldn't even be writing here right now.
i kinda already gave up every last bit of hope to build something that'll take off under its own power so i'm going with something that i'll launch from a hill. i would make it remote controlled but i thought i already made it clear that i can't afford it.

You could help all of us by sharing your plans? Show us your idea, show us your design and planned building materials.
i don't have any drawn plans so far. the whole design will completely depend on the engine i'll end up getting and i currently have no idea what that'll be. my plan is basically to first get the engine then build the whole thing around it.

however, i do know what kind of materials i'll use. assuming i'll get a heavily underpowered engine i'm planning to use plywood or pvc tubing and foam boards for the sake of weight reduction. since i won't have anywhere near enough power to do a barrel roll or anything else that'd stress the frame i'm very confident it's all gonna hold together
 
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