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Little Scrapper

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Those are some pretty cool videos!! I do really like a couple of those planes....but, for some reason the sonex really appeals to me.
The aaron videos are great!!! Exactly what i can envision me doing.. hahaha
It's an amazing airplane!

Studentofbudo

Member
It does look pretty cool. Seems pretty robust.
I think i read were it can be made to be able to remove the wings pretty easily... or, maybe i was hoping thats what i read.. haha

Little Scrapper

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We had like 7 Sonex in our EAA chapter, lol. The wings come off pretty easy but not something you want to do daily.

Bang for the buck it's very very hard to beat the Sonex.

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Fun machine.

Little Scrapper

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Probably my favorite Sonex video for some reason, not sure why, just a cool video.

Studentofbudo

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That, seriously, is a killer video!!
I get more and more excited to get into this hobby the more i read and learn!!

Little Scrapper

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So, I have this buddy in the Philippines. He's a A&P mechanic for a big US company. On his lunch break and evenings he makes Sonex parts from scratch. When he gets a box of parts made he ships them to his other home in the USA. The prints are exact, so if you make them per plans they will all go together eventually. In like 2 years he's almost done with parts and ready to assemble. If you have patience making the parts from scratch is very very easy......and fun. Start with simple little aluminum parts the size of your hand and work your way to more complex parts. For literally $20 you can make multiple airplane parts. Studentofbudo Member Im pretty excited about that... simply because of my profession snd where i work, i can buy material at a much lower price than standard retail. Little Scrapper Well-Known Member HBA Supporter Log Member Here's a couple shots from my Sonex plans. The parts in the above photos are dead simple to make from scratch with simple tools. Guess what, all the parts are this simple, there's just a lot of them. Sonex let's you buy the kitsor the individual parts or you can scratch build. I have 4 buddies who are scratch building and all of them are really having fun because the parts don't take up much space. A sheet of .040" aluminum 2' x 4' pre cut from Aircraft Spruce Company is about$20. You don't even need to buy the big 8' or 12' sheets to start with. Start small and humble with a file and snips and a cheap little sander from Harbor Freight. That's it. Grow your tools as you mature in the project.

This is a Sonex stabilizer spar I cut as an experiment using a hand saw and a file. It started out as a 2" x 2" angle stock. I just wanted to see how doable it is by hand. I have a lot of power tools but I was curious so I tried it.

I put a dial caliper along the edge down the length of this spar and it's within about .015" total runout before filing and blocking. Think about that for a second, this wasn't cut on a table saw or bandsaw, I cut it with a hand saw. That's a little extreme of course but the moral of the story here is aluminum is so easy to work with there's no reason not to make parts......if you have time and patience.

lr27

Well-Known Member
I hope that guy with the Sonerai had the tail fastened down somehow. Otherwise an oops could have been really expensive.
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There are quite a few homebuilts that use VW engines. If there was a redrive*, you could even fly a Pietenpol Air Camper! If you haven't run across it yet, one of the most popular is the Volksplane. Since your on the small side, you probably have a lot more choices of designs than I would.

One thing to understand with the VW is that higher RPM's aren't always better. For the same amount of power as a slower turning engine, you will have to use a smaller prop, or maybe just tolerate a lot more noise from the prop. If you get close to Mach 1 tip speed, your prop will be both noisier and less efficient. For a 6 foot prop, Mach 1 would be around 3,500 rpm. Slower, larger airplanes are generally going to be happier with larger props.

*Reduction drive. I don't know if there is, I understand there's some kind of problem with doing that on a VW. An Air Camper is slow, and I expect it would need considerably more thrust than a Sonex. Which means a larger prop, most likely. But I guess if you like the Sonex, you wouldn't like a Piet.

Hi; hope you love your new hobby. In regards to making more HP it takes roughly 4 times the HP to go twice as fast, most of additional HP goes to rate of climb performance (generally). snip
Actually, 8 times. 4 times the drag, but moving twice as fast.

Probably my favorite Sonex video for some reason, not sure why, just a cool video.
I wonder what the folks on the ground thought of it when he was low? OTOH, the two times I remember being buzzed by full scale airplanes, I enjoyed it. Once by a single place RV. The other time, some years ago, by a single engine jet, possibly an F-86. Low enough that I could see the pilot over the nose. Loud!

Studentofbudo

Member
Hey, thanks for all that info!
I have been reading on that the speed of props and such. I do understand the concept of needing as much torque and such as possible close to 3500. Dynamic compression, static compression, ignition amd cam timing all play a pretty hefty role in achiving all that. Static compression is pretty much constant, but dynamic compression changes with altitude. My goal is to achieve 180-200hp with a dynamic compression of 8.0 to 1 at sea level and 6.5 to 1 at 8500 (would translate to about 100hp). With adjustable timing, this is completely feasible.

Seriously?! All the parts are really that easy? Well, i do have a lot of tools myself from being a machinist...and a hobby mechanic... oh man! I cant wait to start building one!!!

lr27

Well-Known Member
Typical airplane engines would be in the 2,000 to 2,500 rpm range, I think. Maybe 2,800?

How do you get that much power without blowing up or melting the engine?

Studentofbudo

Member
Timing, appropriate dynamic compression, extra oil cooling and using ALL the tin work. VWs are actully quite good at cooling themselves...if...AND ONLY IF, all the tinwork is used and appropriately placed.

RetardedTiming and a lean burn together will explode one of these little things extremely fast... found that out years ago! Haha... average hp at 3500ft was 140ftlb of torque at 3800. This was repeated 4 times in a row on engines ive built. Again, im reading and doing my research as i havent built one to travel at 8500... so, i do have alot to learn in that regard.

Studentofbudo

Member
I say 3500-4000 as all the engines im seeing... including the aerovee is running at that RPM for cruuse and takeoff... am i misunderstanding what they are stating?

TFF

Well-Known Member
Different world than drag racing. First thing is propellors dont work well spinning fast . Diameter of the prop matters on how fast you can spin one and about 3800 rpm is as fast as a VW can spin one and 3200 rpm is really the sweet spot. Max hp is not important, sustainable max hp is. Swinging a prop, over 80 hp and you will break cranks in direct drive and they will start running hot. Remember this is not a 7 second engine; it is an engine that needs to run two hours at a time 500 times with no sweat of blowing up.

lr27

Well-Known Member
I'll bet none of those 3,500 to 4,000 rpm engines are swinging anywhere near the size prop an A-65 (i.e. conventional aircraft engine) would. So I imagine that there aren't many large, low powered airplanes using the VW. I also imagine that very few of those VW powered planes are STOL unless they're very light.

https://en.wikipedia.org/wiki/Continental_O-170#Performance

Little Scrapper

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For decades now people have been building VW engines for airplanes. No point in trying to figure this out by experimenting, just follow the time tested proven methods that work, then go flying.

Dana

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...My goal is to achieve 180-200hp with a dynamic compression of 8.0 to 1 at sea level and 6.5 to 1 at 8500 (would translate to about 100hp)...
If you can get 180-200 reliable HP out of a VW aircraft conversion then all the world will hail you an engine genius and beat a path to your door. The fact that nobody has done it yet, and there are a lot of smart people building aircraft conversions, should tell you something.

When a race engine blows up, you pull over to the side of the track and you don't win. When an aircraft engine fails, you land, right now. If you do everything just right and you have a good place to land, you might save the airplane. In a worse situation, you might die. That puts a light on the required reliability, doesn't it?

There are two main design points for an aircraft engine. The first is takeoff power, WOT for a certain time. Max power gets you off the ground in the shortest possible time and above the surrounding trees and hills. Some engines have a 2 or 5 minute max power time; most can sustain it for much longer than that. Then there's cruise power; typically 70-80% which is still a very high power setting by automotive standards; it has to be able to sustain that pretty much forever.

Few if any aircraft engines use any kind of variable timing because it's really not necessary; the two rpm points I mentioned above are too close together for it to be much advantage. Ignition timing is usually fixed at somewhere around 30°BTDC, though aircraft magnetos often have an impulse coupling or other arrangement to retard the spark for starting.

But keep your enthusiasm up; just because 200HP is unrealistic doesn't mean there isn't room for improvement.

Dana

Studentofbudo

Member
noted...
thank you all for your statements. i appreciate all of your opinions and thoughts. will definitely take them into consideration.

Little Scrapper

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Horsepower and reliable horsepower are two different things. Reliability in the air is different than reliability on a drag strip.

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