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Old Sep 14, 2012, 02:31 AM
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davereap's Avatar
Ashford. Kent. England
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all good stuff that realy deserves a build thread of its own..
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Old Sep 14, 2012, 02:53 AM
Lets break some props :D
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United Kingdom, Liverpool
Joined Jun 2008
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good idea Dave, plans can be ready soon too.
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Old Sep 14, 2012, 03:07 AM
flyin' fool
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Vancouver Island, Canada
Joined Jul 2003
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Quote:
Originally Posted by vinnieg View Post
I finally made the flat wing version of the Underball. I just had the maiden flight this morning and it was awesome!
Congrats, nice effort. That idea was pioneered by the designer of the Warp 9, the late Jef Raskin. Maybe you could call it the 'NineBall' in his honor.

And yes, it works amazing well, even as a cardboard sloper trainer, as it was originally designed.
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Last edited by goldguy; Sep 16, 2012 at 04:41 PM.
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Old Sep 14, 2012, 07:49 AM
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Liverpool, UK
Joined Jul 2006
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Quote:
Originally Posted by joseico90 View Post
I must say it has put a smile on my face to see you reproducing my Underball (thought flat) concept, you're going to love it .

I was amazed to see how well you've followed the lines

Work permitting I'll soon finish a Mark II version and do more videos with my existing one.

As you said..low and slow is what it does best, and ..for me.. not having to worry about damaging anything on it on crashes is a BIG bonus, this thing just bounces and keeps going, motor-prop always safe back there

http://www.youtube.com/watch?v=SfVD9D4gIRA
looks like otterspool?
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Old Sep 14, 2012, 08:27 AM
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United States, NJ, Edgewater
Joined Feb 2012
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My fun with the flat wing underball came to an end yesterday. The 5gram hextronik motor stopped spinning and now jitters back and forth. I assume one of the fragile wires broke. Looks like it's going to be pain to try to fix it.
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Old Sep 14, 2012, 08:33 AM
Lets break some props :D
joseico90's Avatar
United Kingdom, Liverpool
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Originally Posted by mudcow007 View Post
looks like otterspool?
yes!
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Old Sep 14, 2012, 09:44 AM
Lets break some props :D
joseico90's Avatar
United Kingdom, Liverpool
Joined Jun 2008
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Quote:
Originally Posted by vinnieg View Post
My fun with the flat wing underball came to an end yesterday. The 5gram hextronik motor stopped spinning and now jitters back and forth. I assume one of the fragile wires broke. Looks like it's going to be pain to try to fix it.
Wish you good luck with that, I used a short piece of shrink tube to hold the wires against the motor's rear tube.

Had a look at the comments on HK about the 10 gram motor, folk thrust figures are of over 4oz on the same 5x3 prop, SO

Time to swap motors and see, maybe MK2 will have a 10grm motor, I mean the 5grm is adecuate with my AUW for my flying, but won't hurt to try with more power.
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Old Sep 14, 2012, 10:53 AM
Lets break some props :D
joseico90's Avatar
United Kingdom, Liverpool
Joined Jun 2008
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Ok,

So.. I get 100grms thrust with the new 10grm motor,

The 5gram one gave 70grms

Both with the same prop GWS 5x3

now the AUW is 61 grams.

Should go vertical no problem, can't wait to fly it, strong winds out there at the mo.

UPDATE.

Flew today with the 10gr motor..

Observations..
-Silly vertical, more (to me) power that it needs at this weight.
-Torque does indeed flex the EPP at the mount, can be fix with a strip of carbon, easy but won't bother.
-The extra few 6 or so grams make it more steady on wind and model "seats" better on flight.
-I noticed loss of control when model beyond say 20 meters and pushing hard on the throttle, didn't do this with the 5gr motor so could be a kind of brown out?
-As expected shorted flights from the 180mAh 2s packs

In short, I'll be reverting back to the 5gr motor, I like it better.
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Last edited by joseico90; Sep 15, 2012 at 04:07 PM. Reason: Update
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Old Sep 16, 2012, 02:38 PM
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Central Florida
Joined Dec 2008
62 Posts
Just wondering how the stability of the Underball compares to that of the Nutball with the original dihedral (about 24). If it's close, how does it get that stability... something like a pendulum effect? Would more weight at the very bottom of the thing make it more stable?
Thanks, just curious. I like the simple construction of this Underball a lot. I may try building one about 24" to 26".
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Old Sep 16, 2012, 04:23 PM
flyin' fool
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Vancouver Island, Canada
Joined Jul 2003
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A history lesson............

The Warp 9, designed by Jef Raskin, was the predecessor to the NutBall for a rudder and elevator design that offered silly fun and flyability in a super simple package. But, with a difference. It's side area and rudder were on the bottom and the wing was flat. It was published in MAN as a 'slope trainer' and re-introduced about 10 years ago here on RCG by GPW as a powered foamy.

GPW's comments on his new discovery were.........'it's very stable, loops, rolls, is a hover machine and can do VOTs'. I can attest to that, plus it flies inverted and can do weird silly stuff like the NutBall.

Now, those of us that have been playing around with foam for the last decade or so have discovered, for whatever reason, that the round wing platform seems to have distinctive advantages over other shapes.

So in round it should be better.
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Last edited by goldguy; Sep 16, 2012 at 11:48 PM.
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Old Sep 16, 2012, 09:37 PM
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vinnieg's Avatar
United States, NJ, Edgewater
Joined Feb 2012
200 Posts
I replaced the broken 5 gram motor with the 10 gram hextronik 1811. My underball is back in service! I'm still running the GWS 4025 with the the 10 gram motor. I prefer the slow flights with longer battery life.

14" flat wing nutball RC plane (3 min 42 sec)
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Old Sep 16, 2012, 09:58 PM
flyin' fool
goldguy's Avatar
Vancouver Island, Canada
Joined Jul 2003
7,290 Posts
[QUOTE=Redbird1;22749268]If it's close, how does it get that stability... something like a pendulum effect? Would more weight at the very bottom of the thing make it more stable?[/QUOTE

There's your answer to the pendulum effect.

A picture is worth..................
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Old Sep 16, 2012, 11:40 PM
chuck
santa barbara, CA
Joined May 2009
4,182 Posts
after watching the latest underball vid i am reminded of my cool surfer dude which flys w/ the same pendulum affect. it was originally designed for elevon but i used rudder / elev w/ the rudder under as an oversized surfboard fin. the rudder is incredibly effective and the whole silly thing is unbelievably stable.

one thing i did learn that may transfer to this one is that just a small amount of dihedral was very effective for increase in roll rate and maybe overall stability. the design is similar to the nut ball w/ a elevator all across the aft so what i did was to put a few degrees of dihedral in at the nose and it just peters out to 0 at the elevator. the rudder is small and the thing will do rolls like mad.

chuck.
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Old Sep 16, 2012, 11:54 PM
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Oklahoma
Joined Aug 2008
670 Posts
Here's my recently completed NutBall, a photo and short video to go with it. Its a 20 inch diameter with a 20 degree angle on each side. Dollar Tree foamboard construction, Firepower motor and HURC ESC from Heads Up RC, HiTec HS-55s with a Hobby King receiver, all up weight less than 15 oz including 3S 1300 battery. My clubmembers who have seen it went NUTS over it and have asked about how to build it!

NutBall (3 min 39 sec)
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Old Sep 19, 2012, 10:46 AM
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India, West Bengal, Kolkata
Joined Apr 2012
28 Posts
The lightest electronics I have is around 330 gms(~12oz) providing a thrust of about 1000gms (~35oz) swinging a 9" prop at 1100kV(Turnigy 2836_8 on 1.6Ah 3s). I am a beginner and only flew in the simulator. As I cannot get foam here in India I have to use 3mm coroplast (550g/m^2). What span should I go with to get a very slow and stable flight characteristic?
Thanks!!
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