It's a NUTBALL!

[C140]

What's super cheap, super round and super fun? A Nutball of course! These things are great. I just built my first to use some spare parts and I must say, it's pretty amazing. It's a circle, mine happens to be 17" across, and it weighs 6 ounces. I maidened it today with the wind sock straight out, 15 knots, and it flew great. I couldn't believe it. It can actually get up to a good clip, but slow down enough to walk with it. The planform kills me. I couldn't stop laughing watching a circle fly, and fly well I might add. Anyone else build one these?

[wingspann]

Originally Posted by Crash&Burn(Often)

Anyone else build one these?

Yep! I've built a couple of them, and they are a hoot to fly! (Less fun when they're stuck in a tree)



The motor shaft makes a nice spike for storing your NutBall in a tree! I managed to jiggle it loose with a long PVC pole, no damage to plane or motor shaft.

John

[philipa_240sx]

Reviving an older thread....

I just built one out of FFF, 20" dia, 1300kv Blue Wonder, 9047 prop, 6.5-7oz AUW (depending on pack size).

I agree, it's a hoot to fly! Prop hangs with little effort and does all sorts of interesting maneuvers. It is a bit pitch sensitive but not bad. I've also flown it indoors (single basketball court)... high alpha flight is easy. I would build it with EPP like the original for crash resistance however.

Next mod is to add skiis (and insulation to keep the lipo warm) so I can fly off snow this winter!

[Billmanak]

Anybody got a link to a build thread with plans?

[Wildflyer]

As a percentage of diameter, how far back from front of circle,is the balance point.

Thats all I need to build one of any dia.

Thank you

[philipa_240sx]

You can find plans here:

http://www.rcgroups.com/forums/showt...=836389&page=2

There isn't dedicated a build thread... nor is one really needed as it's a very simple build.

A couple of tips:

- The plans can be scaled up from the stock 17". I went to 20" to decrease wing loading with the gear I was using. I have seen upwards of +30".
- EPP will require CF or bamboo reinforcement. If you look carefully at the pics on pg1 of the thread, you will notice the 2 spars under the wing.
- Once the fuse is built, mount the motor but temporarily tape everything else in place (servos, esc, battery, rx) and check CG. Move the components around until the CG is correct (approx 25% chord or 'diameter' from the LE).
- Use a velcro mount for the battery to allow for field adjustment of CG.

[philipa_240sx]

Originally Posted by Wildflyer

As a percentage of diameter, how far back from front of circle,is the balance point.

Thats all I need to build one of any dia.

Thank you

About 25%. On my 20" version I used 5.5". Moving the CG back makes it more twitchy but high alpha and prop hangs are reportedly easier to do. I made my battery adjustable with velcro so I can play with CG at will. I also top mounted the battery... it was just easier due to the motor mount I used.

[philipa_240sx]

Pics of my FFF Nutball 20".

- 2712-12 1300kv Blue Wonder from HeadsUpRC
- GWS EP9047 prop (The EP9047 is prone to breaking despite the prop saver. I would consider a cut down EP1047 or APC TE prop for more strength)
- 10A Power Up ESC from HeadsUpRC
- 9g servos
- 800mAh 2S or 350mAh 2S lipo. I use the lighter pack for indoors.
- Dubro hardware: 1.5" wheels, micro2 horns, EZ connectors, EZ Links
- AUW: 6.5oz with the 350mAh pack, 7oz with the 800mAh
- CG: 5.5" from LE (27.5%)
- Wing loading: 2.97oz/sqft with 350mAh battery
- Motor thrust angle: Approx 3deg down and 3deg right thrust. (The design calls for 5deg down thrust which will likely be better as mine climbs straight up under WOT.) The prop shaft center line is 1/8" below the lower wing surface
- Control surface throws: Rudder: Low 5/8", High 1.5" (with 75% expo), Elevator: Low 5/8", High 1.5" (with 75% expo)

Ignore the masking tape on the tail... it broke shortly after the maiden. I'm replacing it with an EPP tail for better crash resistance as it seems I end up landing mine upside down.



Not shown in the plans are the tail skids. I went for 'dual fins' cut from a 3" dia circle of FFF cut in half.



I tried a somewhat 'flexible' motor mount to keep the FFF from shattering on impact. A stick mount glued to thin ply, layer of 6mm EPP, then glued to fuse. I use PU (Gorilla) glue for the motor mount. Landing gear slips into place using laminated thin ply to create a 'slot' on each side of the motor mount.

If you are going EPP, use the firewall mount the designer suggested and used. Apparently it's far more forgiving in crashes.



Servos are mounted in a cutout and held with a few drops of hot melt glue. I add thin ply squares to my control horns to prevent tearing out. PU (Gorilla glue) is used to glue the servo horn mounts for strength. I used homemade 1.5mm CF pushrods for strength and they did not require any supports/guides.

The 'slanted' cut at the bottom of the rudder is not shown in the plans but is visible in many of the pics.
If you want more elevator throw, you will have to play with the rudder placement and/or cut the rudder to gain more clearance.

Here is a strong method of forming the wing dihedral without cutting the FFF:

- Strip the plastic covering from the FFF 1/4" either side of the dihedral bend.
- Use a pizza cutting wheel to 'compress' the foam along the bend line, then bend the wing tips up to 30 deg or so.
- Cut a couple of wedges of foam at the required dihedral angle of 24 deg, then tape the wedges in place to hold the wing tips at the correct angle
- Run a thin bead of hot melt along the bend line and use a damp finger to smooth out. Voila, dihedral bends formed in FFF. The foam will break long before the glue joint fails.

[Wildflyer]

Thanks I got to try this, I've got a large building available, for indoor

[aramid]

Philipa, that's a very clean-looking NutBall.

I've been thinking about building one of these myself, but I would scale up to at least 25", possibly even 30". The lightest equipment I have is a TowerPro 2409-12 and a 1000 mAh 2s. Even with those heavy parts, I figure a 30" model will come out around 10 oz, which ought to be pretty decent indoors.

The huge pack of pink FFF in the corner is beckoning...

[philipa_240sx]

Originally Posted by aramid

Philipa, that's a very clean-looking NutBall.

Thanks! I built mine using the scrap ends of FFF that get dinged up on the outside. It turned out better than expected. I may even give her a paint job now.

Originally Posted by aramid

I've been thinking about building one of these myself, but I would scale up to at least 25", possibly even 30". The lightest equipment I have is a TowerPro 2409-12 and a 1000 mAh 2s. Even with those heavy parts, I figure a 30" model will come out around 10 oz, which ought to be pretty decent indoors.

Nice thing about the Nutball is wing surface area goes up almost exponentially with radius. My little 20" version has 2.2 sqft of wing area! A 30" Nutball would have nearly 5sqft. If you can keep it under 10oz, that would make for some very light wing loading... under 2oz/sqft.

Here is the latest pic with the EPP vert stab. Increased the surface area by 20% and extended the bottom front edge forward to give me more gluing surface and a more 'curved' shape. I used the hot melt glue hinge method and a small piece of CF taped along the hinge to increase rigidity.

[philipa_240sx]

Originally Posted by aramid

The lightest equipment I have is a TowerPro 2409-12 and a 1000 mAh 2s.

If you keep the pitch speed down it should be OK.... maybe 1047 or 1147 prop?. The motor setup should be high thrust and low speed.

I just had mine outdoors today in the backyard (45'x70'). Unfortunately I nosed in hard twice and broke a couple of props including an APC! . Maybe the cold -8C (17F) makes the prop brittle? The good news is the prop saver did it's job (mostly) and saved the motor shaft. Motor mount has been rock solid too.

The BW seems to be a great motor for this foamy. At 11oz thrust with a 9047, it has lots of power to punch out of prop hangs, etc. However mine still wants to nose over backwards... maybe a CG adjustment or moving the battery below the wing? In hindsight a firewall mount would have been even better as I could adjust the thrust angle using washers under the screws/bolts.

[aramid]

Originally Posted by philipa_240sx

If you keep the pitch speed down it should be OK.... maybe 1047 or 1147 prop?. The motor setup should be high thrust and low speed.

Yeah, my normal setup on that motor and battery is a GWS 1060 DD. I think that's about 21 oz of thrust and 38 MPH pitch speed, which would definitely work but is probably a bit excessive for a NutBall, particularly if I want to fly indoors. I might have to pick up a 10x4.7 and an 11x3.8 to test. I'm a bit concerned about the torque from an 11-inch prop on a plane with no ailerons, though - my StevensAero SportStik runs an 1147 on about the same total power, and requires a fair bit of aileron trim to counteract the torque.

[philipa_240sx]

My second build attempt of the Nutball. This time with full EPP foam:

- 6mm EPP Foam
- 20" diameter
- CF support rods 1.5" from LE and along elevator hinge line
- triangle shaped 'under' fuse
- APC 9x4.5 prop
- AUW: 6.7oz, 190g

[weathervane]

Oh, how cool. I have got to build one of these. I might build 2 or 3. thanks for sharing them.
-Andrew

[Azarr]

I've build a few of them, Fun planes. The rudder is surprisingly effective.

Azarr

[philipa_240sx]

Nutball v2 completed with graphics:

[philipa_240sx]

Originally Posted by Azarr

I've build a few of them, Fun planes. The rudder is surprisingly effective.

Azarr

Absolutely. I've added a bit more height to the rudder as it seems you cannot have too much area! It's quite easy to turn within it's own length.

If I were to build another, the only thing I would change is extend tail skids rearward in line with the TE (you can barely see them in the white EPP version above). Not only will it add some protection to the elevator, you can support the plane vertically on it's tail using the skids and rudder. Makes vertical takeoff's a blast!

The BlueCore/FFF version I posted earlier has been retired. It would be fine for outdoor flight but it took a beating indoors... I snapped the rudder off once, tore the control horn out of the elevator (tail first crash), and the motor mount had started to weaken. The upside is FFF is more readily available and does not require reinforcements unlike EPP.

A few more hints:

- Tape the 'leading edge' with filament tape (fiber reinforced packing tape) to protect against prop strikes.

- Use a prop saver. I experimented with a prop adapter at first and tore the motor mount clean off the plane on the first crash. It was repairable, but have since went back to the prop saver.

- Make the battery position adjustable using velcro to allow for changes to the CG. CG @28% from LE is fairly tame. Once you 'warm-up', move it back to 35-40% and she will prop hang easier but is far more pitch sensitive.

- Use a low kV or a geared setup to spin a big prop (9-11" range would be fine). Lots of prop wash over the control surfaces is a necessity for hovering... just like a 3D ship.

- The only reinforcements I used which gives enough flexibility to shrug off crashes but makes it stiff enough for flying:

1) 'V' shaped central fuse made from EPP
2) Forward CF spar (2-3" from LE, spanning the wing between the dihedral bend in the wing tips)
3) Rear CF spar along the elevator hinge line
4) Short CF spar along the rudder hinge line.

I think both the original 17" and my 20" version are perfect for both indoor and outdoor flight. Just keep her light and have fun!

[philipa_240sx]

The EPP version suffered it's first major crash.

I was unhappy with the prop saver and APC prop combo so I switched to a collet style prop adapter. I would live to regret it... one good smack with the floor tore the motor and mount clean off.

While I was fabricating a new motor mount, I was also able to build in a bit more right thrust. A bit of glue and an hour later she was fixed. I swapped back to the better fitting GWS 9047 and prop saver combo and off I went. The CG also changed but that was simple to fix by moving the battery.

The increased right thrust (almost 5 deg) eliminated most of the tendency the plane had to turn left. It also improved right hand turns. Hovering has become easier as I no longer have to fight the motor torque as much. The motor shaft does have a slight bend in it. Not too much vibration to notice, but I ordered a replacement shaft to be sure.

I'm happy again. My Vapor has been out of commission with another busted motor mount so the Nutball is definitely making up for it. I would go as far to say the it's even more fun to fly! Makes me want to build another... maybe a lightweight 15" version?

[cisc0box]

haha! These things look great.

Wonder how much these cost to make .... I'm interested and am on my way to look for videos of these.

LOVE the LED one .... very cool.

[philipa_240sx]

Originally Posted by cisc0box

Wonder how much these cost to make ....

Build cost is about $70 not including the receiver:

Components from HeadsUpRC

2712-12 Motor - $11.95:

http://www.headsuprc.com/servlet/the...lectric/Detail

10A Power Up ESC - $16.95:

http://www.headsuprc.com/servlet/the...OWER-UP/Detail

GWS 9047 Props - $6.90

http://www.headsuprc.com/servlet/the...rs-FIVE/Detail

Prop saver - $2.95

http://www.headsuprc.com/servlet/the...r-3.0mm/Detail

2x SG90 Servos - $11:

http://www.headsuprc.com/servlet/the...sh---9g/Detail

800mAh 2S Lipo - $9.95

http://www.headsuprc.com/servlet/the...y-7.4v-/Detail

EPP Foam - Approx $10 for a 24x36" sheet.

Misc Hardware: Pushrods, control horns, wheels: $10

[jclassic1]

Over the last few years I have built a number of nutballs from 17" upto 32" Octagon.They are all great fun to fly but for me the 32" is the best of the lot.
You really can rely on a nutball to deliver the goods.
Just fitted some skis on my 32" octagon nutball to fly from my grass field.It is starting to look more like a snowball now.

John

[C140]

I had an extra one of those 2410-09Ys with an 11x7 prop hanging around, so I built another one. It's 24" diameter, made out of EPS, and weighs in at 14.5 ounces. Naturally, I added a large Cessna tail like its sibling. For the power, I think it's a little small, but the higher wing-loading makes it real smooth for flying outside in the wind. I haven't got much above half-throttle yet. I'm afraid I might blow something off. It's amazing how this design still flies good whether it's super light or a lead sled. Nutballs are cool.

[Major Danger]

Now these look like unlimited backyard fun. ....but on floats?
http://www.vidoemo.com/yvideo.php?i=...ball-on-floats

[philipa_240sx]

Floats? Why not!

Mine's getting skis come winter... and turn into a snowball.