Mini or Full Size?

[sprzout]

This is a question my dad asked me the other day while perusing the Flite Test speed build kits:

"Which is more stable in flight, a bigger plane with a big wing, or the smaller planes?"

My thought is that the smaller planes, like the Duster or any of the Mini series, are going to be snappier, more responsive, but require more stick input to keep it level than the larger planes, but then I started thinking about scale, and maybe it just breaks down to the shape of the wing and how the plane is built?

I ask this because I'm starting to think about designing my own plane, and I'm trying to think about the wingspan and fuselage size so that 1) I can build it out of a couple sheets of foam board, 2) keep it to a size that will actually fit in my car, and 3) keep it to a size that doesn't make the wife toss it out because it's taking up too much room.

Are there any recommendations for videos/articles here on FT that I can refer to in helping me to decide? I feel like there's an ocean of knowledge out here, but it's so much I don't know where to start!!!

 

[Hai-Lee]

Larger planes are easier and more predictable to fly for 2 reasons. Greater mass means greater inertia and so they tend to be less effected by wind gusts and the like. As the plane size is increased the wings become more efficient because the air does not scale and the change in reynolds number means that more lift is generated per unit of wing area.

Bigger does not mean less nimble or less aerobatic but just more efficient. My own rule is that wing spans below 1 metre fly less efficiently and as the wing span decreases from there the efficiency drops almost exponentially. Wingspans below 500 mm are only for the brave and the indoor fliers.

The biggest failing in most smaller planes is that the setups for control throws are far too great and the Expo setup is insufficient both lead to an overcontrol situation which in turn leads to a pile of FB and electrics trying to dig a hole in the flying field.

As for fitting larger planes into small car spaces the normal method is to have wings that detach for transport and storage. You can also have fuselages that breakdown into two pieces, (see FT Explorer). Mind you do not ignore the flying wing and tailless designs as they can be great fun, easy to transport, and have a lower parts count.

Finally you could always get a dedicated trailer for your plane transport or even storage if garage space is available. Failing that a roof topper for the car can increase the available carry space and give plenty of room for complete aircraft around the 1 metre wingspan.

Just a few thoughts!

Have fun!

 

[sprzout]

Larger planes are easier and more predictable to fly for 2 reasons. Greater mass means greater inertia and so they tend to be less effected by wind gusts and the like. As the plane size is increased the wings become more efficient because the air does not scale and the change in reynolds number means that more lift is generated per unit of wing area.

Bigger does not mean less nimble or less aerobatic but just more efficient. My own rule is that wing spans below 1 metre fly less efficiently and as the wing span decreases from there the efficiency drops almost exponentially. Wingspans below 500 mm are only for the brave and the indoor fliers.

The biggest failing in most smaller planes is that the setups for control throws are far too great and the Expo setup is insufficient both lead to an overcontrol situation which in turn leads to a pile of FB and electrics trying to dig a hole in the flying field.

As for fitting larger planes into small car spaces the normal method is to have wings that detach for transport and storage. You can also have fuselages that breakdown into two pieces, (see FT Explorer). Mind you do not ignore the flying wing and tailless designs as they can be great fun, easy to transport, and have a lower parts count.

Finally you could always get a dedicated trailer for your plane transport or even storage if garage space is available. Failing that a roof topper for the car can increase the available carry space and give plenty of room for complete aircraft around the 1 metre wingspan.

Just a few thoughts!

Have fun!

Hai, thanks for the info on the wing size. That's pretty much on par with what I was guessing; I just needed someone with a better understanding of aerodynamics explain it to me. Thanks!

As for the size issues, unfortunately, there's not a whole lot I can do there unless I get a different vehicle. I currently have a Ford Mustang GT, and can BARELY fit my Sea Duck in it with the seats laid down; my wife's vehicle is a Mini Cooper; it is roomy inside, it's true, but then I have to wrestle the keys away from her and that generally does not go well.

As for the trailer idea, I like it, but I am an apartment dweller, and we do not have space to store a trailer onsite. I'll just have to see about something like a station wagon that might work. I'd love to have a Ute like what you Australians have down under, but sadly, the States don't offer anything like that - we have huge SUVs.

 

[Hai-Lee]

Pity! As for the local Utes they are very cheap on the second hand market here as our gas prices are high. The ones I refer to are the ones which share parts with the "Factory Seconds" we sold in the US. (Factory Seconds because the steering wheel was on the wrong side).

To own an Aussie style Ute all you need is a second hand body, (plenty around here), and a Pontiac GTO. With some effort and funds you could have a Ute of your own (though we race them here as V8 BrUtes).

Have a good look at flying wings though as the ones I fly take little space and I can fit 3 in a passenger side foot well without issue.

Have fun!

 

[sprzout]

Pity! As for the local Utes they are very cheap on the second hand market here as our gas prices are high. The ones I refer to are the ones which share parts with the "Factory Seconds" we sold in the US. (Factory Seconds because the steering wheel was on the wrong side).

To own an Aussie style Ute all you need is a second hand body, (plenty around here), and a Pontiac GTO. With some effort and funds you could have a Ute of your own (though we race them here as V8 BrUtes).

Have a good look at flying wings though as the ones I fly take little space and I can fit 3 in a passenger side foot well without issue.

Have fun!

I'm definitely considering a flying wing...They look like they're easy enough to fit several into the trunk and would be great for combat events! Only issue I have is that I've never flown one; I'm sure I'd be able to pick it up really quickly, but it's just a matter of adjusting for a different type of aircraft.

 

[Hai-Lee]

I actually found that when I started to fly them that they were easier to fly. My best performing wing is actually a tailless design which can top 100 KPH on 120 Watts and a 1300 3S. If you keep them light they can just about float in to land My first wing was a KFM4 wing listed on the FT site and it is still flying without any damage.

Actually come to think of it since starting on the flying wings I have not had a crash and I fly lots of different craft nowadays.

Have fun!

 

[rockyboy]

Wings are tons of fun to fly - once the CG is right I find they do better in windy situations than almost anything else. Less vertical surface area for cross winds to kick around. And they also pack and store super easy!

 

[JimCR120]

On size, I like the example of balancing a pencil on a finger conpared to balancing a broomstick on your finger. Dimensions and mass make a difference.

I'm a fan of flying wings. I'm planning on another when my project list shrinks. The thing with them is when you set up the mixing and the throws, you might find as I did that (depending on the geometry) you'll find it's slower to roll and quick to pitch requiring a softening of the pitch control. I think mine is 50%. Yaw is another issue I hope to improve with a twin version and differential thrust.

Back to size... I like small because I can fly in smaller areas. I like big because it's easier to see at a distance. There are more trade-offs to be considered such as the electronic requirements, cost of outfitting, safety, transporting, etc.

I hope this helps. Enjoy.

 

[sprzout]

On size, I like the example of balancing a pencil on a finger conpared to balancing a broomstick on your finger. Dimensions and mass make a difference.

I'm a fan of flying wings. I'm planning on another when my project list shrinks. The thing with them is when you set up the mixing and the throws, you might find as I did that (depending on the geometry) you'll find it's slower to roll and quick to pitch requiring a softening of the pitch control. I think mine is 50%. Yaw is another issue I hope to improve with a twin version and differential thrust.

Back to size... I like small because I can fly in smaller areas. I like big because it's easier to see at a distance. There are more trade-offs to be considered such as the electronic requirements, cost of outfitting, safety, transporting, etc.

I hope this helps. Enjoy.

Completely understand being able to fly in smaller areas - I've got 2 quadcopters in addition to my Sea Duck. The quads, I can fly them at the baseball fields across the street (when nobody is there, of course; I try to be safe and also avoid the ire of people who think I might be "spying" on them since I'm flying FPV), but the Sea Duck requires more room for takeoff/landings, and a cleaner area where there's not so many trees, light poles, backstops, etc. that I can run into.

I have a feeling that I'll be building either an FT Versa or an Arrow in the near future - I just need to research matching up motors, props, and ESCs so that I can get something that's 1) fast, but not so fast it's out of control for me, and 2) that won't run so hot the wing catches on fire or melts.

 

[Beavis]

My opinion changes every month or so. Mini's are so portable, fly in smaller spaces, and posses a greater strength to size ratio. I've plowed a few into the ground, and was amazed how well they held up. The big ones? Not so much...

As already stated, the big ones are less twitchy, somewhat more forgiving, and easier to see. But they also break apart much more spectacularly when they crash.

Most of the FT models I've built have oversized control surfaces. This creates less stability, and makes overcorrection and crashing much more likely. Simple Scout and Sportster are cool planes, but the aileron surfaces are too much. Spitfire was pretty decent (for as little as I flew it before blowing it apart), as is the Mustang. I run ailerons on the lowest servo arm/horn settings possible, fly on 70% low rate selected, AND use 30% expo, just to get to a low panic flight experience. It makes things more scale, as well as more enjoyable, yet still has enough control attitude to do all the aerobatic silliness I want.